Good news: the follow-ups to this video hav arrived! Still confused about how the ground can be accelerating up? We now take a deeper look into this concept in our new videos, "The Sky Is Falling Up" and "The River Model of General Relativity". Check them out!
There's nothing "confusing" about it. Is only as confusing as learning a rectilinear uniform motion undergoing an opposing friction force is also "accelerating" in classical mechanics. The surface of the planet is accelerating (when we choose a certain frame of reference) because is impeded to follow a geodesic in the 4d spacetime manifold going to the center of Earth. ¯\_(ツ)_/¯ You are the confused one @Dialect. And Veritasium explains it beautifully (and even shows you the equation to understand that your acceleration is merely to keep you in place as it cancels out the curvature of spacetime that would lead your geodesic straight down to meet the center of Earth) Around mark 8:50 ruclips.net/video/XRr1kaXKBsU/видео.html
I've known this was true for 10 years, but nobody has put it to words for me. I love you, man. Thank you for explaining everything. Can you go through the math in another video, please?
Isn't this argument circular? If gravity causes time dilation, doesn't the whole argument assume gravity exists, that it causes time dilation, and then time dilation causes gravity? Or to put it another way, why not assume gravity causes gravitational attraction without the added step of time dilation in between?
Hey Dialect, I made a video myself on general relativity recently (most recent video on my channel) and if you have time I’d like to know your thoughts on it. I don’t want to be spreading misinformation so if there’s something wrong in my video I’d like to be able to correct it - thank you!
This kind of response is an all-too-common response that science communicators receive from scientists. You _think_ your issue with my video (and other similar videos) is that the physics is wrong, but that's not the case. You're just offended by an approximation/analogy I used because it ignores some detail that you _personally_ feel is vital to the topic. When you're a science communicator, you have to consider your audience. Where are they currently in their understanding of the topic? What ideas are they going to accept or immediately reject? A fully detailed explanation of general relativity is going to be pretty abstract and full of jargon, which is unapproachable for most viewers. Teaching is the art of knowing exactly what details you can leave out while still communicating the topic. I'll admit that if you leave out too much or make it seem like nothing is missing, then you're just wrong. However, if you watch the cold open of my video, I clearly stated I was about to explain the gravity humans experience here on Earth. In jargon terms, that's the weak-field approximation. I'm saying the analogy I'm about to use is limited. It's not meant to give someone a deeply detailed understanding of gravity. It's just meant to take them a little outside their comfort zone and give them an idea of how spacetime can cause the motion that non-physicists attribute to gravity. By using the weak-field approximation, it allowed me to ignore space and focus on time. The fluid analogy then makes the idea of time more tangible and familiar. Things like approximations and analogies are perfectly fine as long as you're open about it. The other issue is language. Are the words I use in my videos following the strictest scientific definitions of those words? Absolute not. In fact, if I'm going to use a strict scientific definition, I usually make a point to explain that strict definition within the video. Otherwise, I'm likely using a more common definition for that word. In the video you're referencing, I'll admit I'm pretty lax with my use of words like "gravity" and "curvature." Again though, I wasn't teaching an upper-level physics course on GR. I made an educational video for a general audience. Saying I'm "100% unequivocally wrong" or "all wrong on all counts" is too harsh. I just took some educational liberties you don't like. Personally, the "ground is accelerating upward" explanation bothers _me._ Is that explanation mathematically true? Kind of, depending on your definition of acceleration, but I also wouldn't say it's "100% unequivocally wrong" because that's too harsh. Different explanations make sense to different people. We're all trying to educate here. You don't have to be so divisive.
As someone watching this back and forth that is trying to get an actual understanding of GR, do you have any resources you can point to that don't take educational liberties in trying to explain how GR works? If it's one of those situations where you can only truly understand the theory if you understand the math and that requires a 10 hour lecture to understand, then I'm fine with that.
Thank You for responding here. The explanation you gave left me with questions, pointing me in directions I could work with. This did much the same, but left me disoriented and less likely to follow my questions. I am less interested in things I need to grasp all at once. I build a frame and use that frame to add new understanding to, even when that requires some reorganizing backward sometimes. He did nt seem interested in my learning about the reasons for the puzzles he put out. You do not do that. T.Y.
@@amentrison2794 The actual papers from Einstein are still publicly available and in English translation, and his thought experiments are for a general audience. Some people learn better from textbooks. Nick has one, and the Gravitation textbook from Misner, Thorne, and Wheeler is usually considered the gold standard for GR. There's also the GR lectures at Stanford from Leonard Susskind available on RUclips. He has a detailed explanation of the Equivalence Principle and how to distinguish uniform gravitational field (accelerated frames of reference) from spacetime curvature and tidal forces. Regardless, it's going to take years to learn Newtonian Mechanics and General Relativity and just be at an elementary level of understanding. It's worth the time because you'll have a new level of respect for Isaac Newton and Albert Einstein. It will make understand why physicist call it "the most beautiful theory in science."
You quoted and showed animations from my video, but what you didn't mention is that my video also included statements such as "This visualization does not accurately represent the full picture, since a point particle of zero volume would still follow the exact same path." With regards to where I got the idea for my visualization, this did not come from any other RUclipsr, but from Einstein's Field Equations. I have another video explaining the mathematics of Einstein's Field Equations, which is what one needs in order to get the full picture. (Your video doesn't explain the full picture either.)
@@ytdpaul well I am actually reading a book on general relativity, what about you? There is a difference between the Newtonian limit and black holes, I agree. But what are you talking about earth accelerating outwards? Where did you read that? The only variable on earth gravitational field is time, not space curvature Smh? What's wrong with you are you Einstein himself? I correct myself: I agree with most you are saying now, but do not agree on dismissing the Newtonian perspective as irrelevant
Hey Eugene, thanks for watching. One might wonder, if your visualization didn't "accurately represent the full picture" why you would have shared it in the first place, or why you are unable to explain to any of us what exactly the "full picture is". Of course, the truth is that your video isn't even a partial picture of what is correct; it is simply a wrong picture. As ScienceClic, Veritasium, and others have already done videos about, the traditional notion of a gravitational field is a fictitious one, a relic of being in an accelerated frame of reference. It is the tidal forces (spacetime curvature) which are truly responsible for the attraction between bodies, and your interpretation of time-dilation as a significant causal agent is a misinterpretation of the first-order approximation of the theory, in which the potential gradient of a uniform gravitational field is associated with the time-dilation gradient. But this is nothing more than restatement of the fact that a uniform gravitational field is an accelerating frame of reference. Of course, we understand that from your likewise deeply-flawed twin paradox video that you have not yet grasped the distinction between general covariance and the general principle of relativity, and so you still likely believe that acceleration and gravitational fields are interchangeable, "relative" phenomena. Unfortunately, it is enough to look at the observer-independency of the four-acceleration to know that this is not the case, moreover since apparent gravitational fields can be made to vanish instantaneously, they stand clearly in violation of the principle of local action and cannot be regarded as "real". Our next video in this series will treat more on the topic. We're sure you'll stay tuned.
@@Robinson8491 Maybe you should read your textbook a little more thoroughly before jumping to conclusions. He’s saying that the four-velocity of objects without proper acceleration will have only a time component in its four-velocity IN ITS OWN FRAME. However, the four velocity of the object in the other frames can have components of space and time mixed. But these are coordinative space and time - which is the whole point Dialect is making. These other channels don’t understand the difference between proper and coordinative time and space. The metric of a locally free-falling object doesn’t differ from a Minkowskian metric - they’re locally equivalent, that’s the whole equivalence principle. It only differs in how you express the coordinates, but that’s observer dependent. Either you read Rovelli wrong or he was imprecise enough as to leave out the necessary qualification that the components of the metric will change dependent on the observer.
@@se7964 he uses the earth as example. This is misleading, as only time is a variable here. Then talk about black holes (or mercury) instead if you want to be correct, or am I misunderstanding the situation here? Also you speak of others frame of reference where time and space curvature in the four-vector in acceleration is of an issue: but isn't this Special Relativity you're talking about and not General Relativity? They are seperate situations. Would love to hear your comment
he couldn't@ died in darkness. In 1952 he rejected his own (false) 1918 article (in his friend R.Schlegel's books) although he "smelled" the problem without knowing the answer - a quite simple for the REv.Philophers, semantic realists. Sorry, u will not find the answering textbooks and youtube.ps.the key problem: Ein.The theory is a field theory,then...use your Holy Spirit in u have it]
PhD physicist here. I am not exaggerating when I say that I don't understand 90% of the popsci videos/articles about physics, of topics I have a good grasp of. I just don't understand what they mean and oftentimes, it sounds like gibberish to me. I can't imagine what the layperson understands from them. It's probably worse than not understanding. No wonder we have so many misconceptions about science going around.
Modern science has gotten themselves hopelessly loss in the realm of nonsensical mathematics. That's why the lay person doesn't understand physics. I was watching a few of Sabine's videos on RUclips. I thought she was a fence sitter when it came to understanding the nonsensical nature of relativity. Nope. She talked about clocks but never once explained that clocks are instruments specifically designed to measure acceleration in space. The cesium-133 atom is chilled to absolute zero (cryostasis) and shielded from electromagnetic interference.(UV rays cause premature skin aging). Is the observer afforded the same environmental conditions? Then she discussed the twins journey in the Twin Paradox. Not once was it mentioned that an astronaut's heart rate is in an accelerated state during lift-off and returns to normal in zero gravity. Not once in all of these Twin Paradox videos is that simple fact addressed. Where did this time-dilation nonsense originate from? Where is the evidence that acceleration in space equals deceleration in time? The infamous Hafele-Keating experiment is often referenced but if you look at the data, it clearly shows no difference in the amount of force (energy/battery drain) between stationary and moving clocks. And as discussed earlier, the caesium-133 atom is prevented from being accelerated time (change in mass), when a force is applied. So when you plug the data into the proper formula, F=ma, the defacto law of motion/acceleration/physics, the only difference is in acceleration. Now the tricky part is determining of it went into the space frame or the time frame or both. What is aging? A change in mass? Radioactive decay? What is it that is being inferred when a physicist says that mass is being accelerated in time. A biologist would say that entities lifespan. A chicken going from an embryo to market weight. A plant going from seed to physiological maturity/fruit production. For a physicist, wouldn't acceleration in time be radioactive decay? In the Breakthrough Starshot experiment, it's evidently clear that inorganic objects accelerated in space are also accelerated in time (radioactive decay of the mass). So where does this time-dilation/increase in mass postulate of relativity originate from? I can find no evidence to support relativity. In fact, all evidence is contrary to relativity. And yet, here we are, a century later, still worshipping at the alter of relativity. You have to completely ignore the laws of physics to get relativity to work. That's not science. That's religion. The fact that they use science to promote their religious nonsense and are funded by the taxpayers is utterly appalling. Nothing is going to be done until the physics students start demanding answers instead of accepting their shut up and calculate (Sabine) attitude.
Great point. Most of this stuff sounds interesting on the surface but seems to lose me in the summations. What makes more sense to me is that the source of gravity is the quantum wave form collapse which constantly creates matter and (I believe) is directionally biased towards a lower state of entropy. This directionality is what we call gravity. The rate of collapse is altered by the amount of entropy and this is what we call time and hence time dilation occurs in the presence of different states of entropy. Just a thought. $.02
This problem needed to be addressed, it is indeed a wrong explanation for general relativity. It is, in my opinion, a really wrong explanation, since in reality things are the other way around : it is gravity that causes a difference in time dilation. And more precisely it is the fact that the person on Earth has to constantly accelerate upwards, to compensate the curvature of spacetime, which causes the gradient in time dilation. However I don't think any RUclipsr is to blame since I have also seen this explanation told by physicists themselves, such as Carlo Rovelli who sometimes wrote in his books that "gravity is the tendency for objects to go where time slows down". It is similar to how misconceptions about black holes spread : some of them were popularized by physicists themselves. It is then pretty difficult knowing what is right and what's not. For instance, another example is the fact that one would see the universe accelerate to infinity as one would cross the horizon of a black hole. This is completely wrong, but this explanation shows up all the time and it is sometimes told by physicists themselves. ---------------------------- I want to clarify my point of view. There are two distinct phenomena that one could call "gravity" : 1. First one is the fact that when we drop an apple, it seems to accelerate towards the ground. This is a matter of kinematics, apparent movement. The apple seems to experience a "force", which we could call "gravity". 2. The second one is the fact that when we drop an apple, the distance between the apple and the Earth becomes smaller : the apple moves closer to the center of the Earth. This is a different kind of observation, not linked to kinematics this time, but to geometry : we look at the distance between the two objects. This could also be referred to as "gravity" : it is the fact that massive bodies seem to mutually attract each other. It is important to note that there is a clear distinction between both phenomena : The first observation depends on the observer. A free-falling observer would not see the apple experiencing any acceleration, since from their point the view the apple seems to float, weightless, as they both fall. This first notion of "gravity" is "observer-dependent". In particular, in a free-falling frame of reference, this type of "gravity" disappears (this is the equivalence principle). The second observation however is not observer-dependent : all observers will agree that the apple and the Earth tend to move closer to each other (and eventually collide). This notion of "gravity" is "absolute". If I understood correctly, what Dialect and myself consider to be "true gravity" is the second observation : the fact that massive objects attract each other. In this case, it is impossible to explain this phenomenon with a time dilation gradient. Why? Because the gradient of time dilation is observer-dependent : a free-falling observer doesn't measure any gradient ! However the phenomenon of gravity (the apple coming closer to the Earth) is still there, it is not observer-dependent. The explanation comes from the fact that this second notion of "gravity" is fundamentally non local. (mathematically, it is of "order 2", it involves how the gradient of time dilation itself changes from place to place). What explains this type gravity (i.e. the fact that massive objects attract each other) is the curvature of spacetime. And indeed, curvature is not observer-dependent, all observers, even the free-falling one who doesn't observe a time dilation gradient, will still agree that spacetime is curved. So to sum up, the gradient of time dilation is linked to the first type of "gravity". Which, more simply, is explained in general relativity by the fact that the ground constantly accelerates upwards (and inside an accelerating frame, you will indeed observe a time dilation gradient, whether you are on Earth or in a spaceship, whether you are in curved spacetime or not). That's the key point : the gradient of time dilation is not linked to "gravity", at least not directly, it is actually more general, and is present in all accelerated frames of reference. So, also in your car when you accelerate, or in a spaceship with fake/artificial gravity. The curvature of spacetime on the other hand is ONLY present when there is "true gravity", in the sense that two massive bodies attract each other. In other words, there is "true gravity" only when the gradient of time dilation is not the same everywhere in space. Or yet in other words, there is "true gravity" only when there are tidal forces.
Wow, thank you for putting the final pieces of the puzzle together for us! Your clarification is immensely enlightening. Next time we'll make sure to consult you before we put up our videos 😂. Indeed, we figured this explanation had to have come from somewhere outside of RUclips, and we did finally realize that what it was describing was the potential gradient of a classic gravitational field. When we first comprehended that this explanation was wrong, we felt immensely betrayed by these channels. We had placed a great deal of trust in these videos when we were younger, back when we had no knowledge of the theory itself. We believed them at the time, and that belief fundamentally inhibited our ability to progress in our understanding of the theory for a number of years. So are they to blame? That's a difficult question to answer. Eugene Khurtoryanski, Science Asylum and PBS Spacetime all acknowledged in their videos that there was something lacking to their explanation, but how was the naive viewer like ourselves supposed to know that this could imply that time dilation didn't cause gravity, since that was the entire purpose of their making the video? If these channels knew something was off, why didn't they look into it more deeply? Why did they never follow-up with a fuller explanation? This is where we feel a level of blame lies, and that a desire to profit off an explanation that sounded super-cool overcame their mission to instruct and teach. We understand everyone makes mistake; undoubtedly we will get many things wrong if we continue down the path of attempting to understand General Relativity. And if any of these channels acknowledged that they had made a mistake, or like yourself clarified that it was mis-interpretation of a first order approximation of the theory, we would happily eat our words! Otherwise, we feel that it is our duty to warn others to not approach such channels uncritically. Certainly, they are not nearly as concerned with precision and clarity as channels such as yours or Eigenchris'.
@@dialectphilosophy Excuse me for asking, but how much of GR do you know yourself? Surely everyone who knows their GR will realize where the explanation outlined by these other content creators arise from the grand scheme of GR (as briefly presented by scienceclic)? This is a genuine question, not meant to be insulting or anything.
@@WSFeuer I think you are entirely mistaken here, I'm afraid. I am confident that these RUclipsrs know all of this themselves. Pbs spacetime, for example, have some older videos where they go more into detail on geodesics and spacetime curvature, and I believe Science asylum also have videos that have at least mentioned the full geodesics equation and Einstein field equations. Thing is, when you are going to try to explain GR to a wider audience, especially one that isn't otherwise into physics that much, then you have to make shortcuts to make the explanation at least somewhat understandable. That is going to make it at least somewhat inaccurate. Most people only have experience with the "everyday" kind of gravity; that when you drop something, then it accelerates down at 9,81 m/s^2. Therefore, you are going to have to explain how geodesics and spacetime curvature give rise to that experience; and as it turns out, the fictitious "force" given by the geodesic equation in this scenario is related to the gradient of the g_00 component of the metric tensor, which again is related to gravitational time dilation. Of course this is not all that the geodesic equation can predict; in general, this picture is wrong. But it is one that is accurate for this "everyday" kind of gravity, and it shows how geodesics may give rise to an apparent force like this. Now, I am indeed confident there's better ways to explain how GR really works. But whatever choice you make, it is a tradeoff between making it accurate, making it somewhat short (ie. resist making it hours long) and making it understandable/relatable to the audience.
@@frede1905 Go rewatch those videos. Each one of them contains numerous unfactual statements. If they truly understood GR like ScienceClic or Dialect, why wouldn’t they have just straight-up said that the explanation came from a first-order approximation meant to replicate the potential gradient of an observed gravitational field (which in General Relativity is a pseudo-fictitious field and therefore not gravity at all.) You can even find Eugene’s response in the comment threads below where he STILL can’t explain to Dialect what his video supposedly meant. Reading your comment and listening to you try to rationalize a completely unfactual explanation makes you sound simply biased, like you think because these channels are popular it’s okay for them to not be honest or right. The truth is PBS Spacetime and Eugene and the others aren’t really intelligent or great physicists, they’re just good at capitalizing off of their viewer’s naivety and presenting digestible sound-bites that sometimes are passable physics.
@@frede1905 Re-reading your comment I see now that you, like the videos you are championing, have failed to distinguish the difference between spacetime curvature and observed gravitational fields. The “everyday” gravity of an apple falling to the earth is explained by the fact that the earth is accelerating upwards. It has nothing to do with spacetime curvature. This is not a disputed fact, you can find it discussed on many other videos and in many other sources. (Did you even watch Dialect’s video?) Now that I see you don’t understand General Relativity yourself, your championing of these videos becomes less disingenuous, although your intelligence and the merit of your opinion has rather sank.
It would be nice to see a straightforward video just laying out your theory with less drama and personal attacks punctuated with giant text. Sometimes in life people have to eat their own words, and big bold text can be hard to swallow. Let your work stand on its own. Be humble.
I was thinking the same thing: better to be careful not to give people an excuse to throw away an obviously rigorous and thoughtful work. Don't get in your own way with sarcasm, or other trite drama. If you are interested in getting to deeper understandings, you have to maintain your (what seems to be normal) thoughtful, polite, skepticism. People might still disregard what you write, but you will not have pushed them away.
Completely agree. Reading the comment from Eugene (above) and tgen reading the replies the conversation quickly devolved into petty "I'm right, you are wrong" thing and people becoming "fan-boys" over the RUclipsrs they follow. Science does not need this drama.
I’m fairly certain this video could have been done in a more polite manner. Sometimes on your journey North, you end up going East because you don’t yet have the strength to plow through a mountain. These concepts are not easy for the non-scientific person to understand. The other explanations, wrong as they may have been (East), still took us in the right direction (North) without overwhelming us with concepts that we’re not familiar with (the mountain). Thanks to them, I was able to understand your video more easily than I would have with my layman’s blank slate. I think, rather than being a stab at the other channels, you could have treated this video as “the next step” in the layman’s journey to understanding gravity. Even Newton’s explanation, wrong as it is, is a good stepping stone to understanding Einstein’s explanation. Maybe I’m wrong, but that’s my two cents.
I can somewhat understand the creators frustration as there are certainly a lot of "wrong" explanations on this topic in general on RUclips. That being said, maybe its not the best idea to expect to learn one of the most complex and unintuitive topics of modern physics on RUclips and then blame other creators when they use approximations or even "wrong" explanations to make the topic even remotely accessible to a wider audience. Its amazing that you point that problem out and make a video about it but dude chill
I like exploring this topic but frankly this video is more about “I’m right and they’re all wrong” than actual education. You could have given a better presentation without making it so personal.
@@EDITᲽ its fine to call it out but he was doing it every 2 minutes with their faces and stuff. That much frequency and emphasis stops being a simple calling out incorrect data and starts becoming more toxic/egotistic sounding. At least in my opinion. I wouldnt have done it in such a sledgehammer approach
@@EDITᲽThis guy spreads more misinformation than any other science channel out there. He acts like he knows Relativity in and out, but then he completely fails at grasping the most fundamental concepts.
@@EDITᲽ Yea and this guy made general relativity about his ego. I'm more focused on how much I hate him rather than his correction, and I'm sure everyone else is
My problem with this video is the general message that is conveyed. In particular, while Dialect attempts to make a 'fuller picture' of gravity, it seems the main point is to actually put down other physics content creators for what Dialect deems as wrong. The ending completely rubbed me the wrong way, and is harmful to the physics content space. ScienceClic has been brought up a couple times in the comments, and I think their channel is the perfect example of how Dialect should've communicated this video. Instead of focusing on other content creators---and in certain cases making a straw man of their videos--the focus should be on the actual physics and the creativity of how Dialect wants to communicate such physics. Not to say that Dialect doesn't include a lot of physics in this video, but I believe the tone of this video is not effective. I'll end this by saying; if Dialect believes they have a better point/visualization/explanation to make than what is currently on RUclips, then they should make a video solely on that. Believe me, if their video is well-made and does the physics service more than other content creators it will get praise. However, the only takeaway I can get from this video is a sad attempt to recruit viewers and gain popularity by putting other content creators down. In such a small space as physics visual education, it is sad to see a video such as this.
I think you are incorrect here. The problem with having such a small education-space is that no one wants to admit their own mistakes. This doesn’t only apply to youtube physics videos, but science as we practice it today. I think you’re right in saying if you’re correct and making better content, then you can out-compete the worse content. But this is a function of quality and doesn’t tell us anything about being right or wrong. Think about when the Catholic church didn’t want to admit that Galileo was right about a heliocentric world, the correct information was essentially suppressed by the power of the masses of people who follow the Catholic church. So I agree with Dialect saying that the larger channels need to admit their mistake. If they don’t, the masses of people who follow them will find strength in their numbers and suppress the information that is more correct. That is, until they can all be proven wrong though experiment, instead of competition of quality.
The reason why I even met this channel is exactly because I was unsatisfied with the answers to the Twin Paradox on RUclips. So I can't exactly agree with you considering that's how I came to know him. If it wasn't for that I would never watch a single one of his videos even if they showed up to me.
This was an ambitious video, but unfortunately it falls a bit short off of its goal. There are several wrong statements made herein, though not all of them terribly impact the topic at hand, but being a type of fact-checking video it's not a pristine look. For instance, the narrator asks with incredulity whether the travelling spaceship creates curvature as it passes through space, ending with the statement that this would be absurd. But it's really not. Any stress-energy tensor creates curvature wherever it exists, so a spaceship moving through spacetime will most certainly create curvature, and the faster it moves, the more kinetic energy it has, meaning it creates more curvature at higher speeds. A collection of photons would create curvature - hell, you could in theory create a black hole out of nothing but photons. Another example is the spacetime diagrams vs. spacetime segment, where the narrator seems to disregard the geodesics explanation. It's unclear what they really meant here, but it's uncontested fact that objects *do* follow geodesics - geodesic trajectories map to Newtonian trajectories so closely that they're nigh indistinguishable - so it's unclear what the real objection here is supposed to be. The narrator also doesn't discuss the relationship between geodesics and observed time dilation (I'll return to that topic later on), which is the thing that is the real "cause" of these videos they're trying to debunk, contrary to the explanation they're giving about misunderstanding a coordinate translation. It also rather seems that the narrator didn't fully understand the point made in the videos he's attacking. At the heart of the presented argument is that matter alters the flow of time (putting a dent in local spacetime), and the altered flow of time is then what causes the realization of why an object moving through that field seems to change directions. It can't be the space component, because if it was only the space component then gravitational pull wouldn't create inertial trajectories, objects of all velocities would follow the same path. What they are referencing here is Einstein's gradient for how proper time evolves in a gravitational field - and it does so in a manner that maps to the evolution of the geodesic. So what they are *really* saying, is that gravity in non-relativistic frames of reference occur because *time* is curved (space is also curved since it's a part of spacetime, but the curvature of the space component is irrelevant for macro objects and indeed with a velocity not approaching c), and it's uncomplicated to show why that must be - I'm sure there's an equal explanation in GR, but it's much easier to realize that special relativity basically says so without any complexity at all. Under SR, basically all macro objects move more in the time component than they do the space component - significantly more so - so any curvature strong enough to affect them in the way we see has to arise in the component their delta is large in. Meaning the time component, because the space component delta is disappearingly tiny in comparison. To go from all of this to "gravity is caused by time-dilation", is a little bit of a leap... I'll give the narrator that. It's not a strong explanation, but it's also not nearly as wrong as the narrator is trying to make it out to be in this video, certainly far from being "100% unequivocally wrong".
I agree with you. I think the narrator misinterpreted some words physicists in these videos spoke, but it is also true and understandable that they may not have been 100% clear for everyone, which is an extremely hard thing to do, giving the very complex topic of these videos. Either way, I found this video to be too focused on criticizing the others rather than focusing on giving better and more clear explainations. I would say no one here is really wrong, but I feel like the narrator wanted to point out and make a big thing out of these "not entirely clear explanations" which feels, speaking as a physicist myself, totally uneccessary and a bit "unpolite" (at least in the tone the video has).
The author is correct that the other videos are wrong. But as you stated, he himself made a few incorrect statements, such as the Earth accelerating up in all directions 24/7 as the cause for gravity. The other videos are saying time dilation causes gravity. Matter and energy in the presence of space-time is the cause, and space curving (gravity) and time being stretched (time dilation) are both effects. Cause and effect. To say time dilation causes gravity is like saying a fever causes a runny nose. A fever and runny nose are effects. The cause is an infection from a virus or bacteria. The bottom line is mass and energy distorts space-time, causing BOTH gravity (via space curvature) AND time dilation (via stretching of time). Gravity doesn't create time dilation and time dilation doesn't create gravity.
I would be cautious with certainty. General Relativity is very difficult, I've studied it myself and at university and have become quite familiar. But every so often I encounter a situation that you'd think is quite simple, but turns out to have a lot of nuance I had missed before. Given that the theory explicitly demands that there is no privileged coordinate system, we know that there is a huge amount of flexibility in how we can describe any given spacetime and I would argue that disentangling those features which are absolute and "real", from those which are artifacts of a given description, is a very difficult task. At the end of the day, we still need to use the coordinates, we can't analyse a spacetime without them, but you cannot just look at a metric and know immediately what's real and what's subjective. It takes a lot more work than that. If your view is that anything less than an unabridged explanation of GR that is then fully absorbed by the layperson audience, is misinformation, then I'm afraid you haven't met enough people to gauge how unrealistic that is
As a professional AIA architect I use a 3D relative Cartesian and polar coordinate system on the computer to map out the curvature of space between and around large bodies. I discovered the missing variables in Einstein's field equations on gravity back in 2004. He and Newton neglected to address the action causing gravity in their equations. Their equations perfectly explained the motion and orbits of small bodies like planets and moons but failed miserably when trying to describe or predict the motion and orbits of stars and galaxies. The fix to their equations was so simple. I can't believe no one else realized what was missing. Now their equations are able to accurately describe the motion and orbits of all the stars in galactic disks, without having to resort to using wildcard variables like dark matter. The equations also explain why space is expanding and why it expands exponentially with great distance. There is no missing mass in the universe. There is no missing energy in the universe. The equations of relativity and laws of motion need to reflect what's happening inside of large mass, which then causes space to react. The action causing gravity in all large mass is over-unity of energy. Energy is constantly being added to the universe via the nearly perfect spherical shape of all large bodies. I tried to publish a paper to peer review several years ago and instead of calling it dark energy I referred to this action as over-unity of energy. They denied my publication. They do not want to believe that Einstein was wrong or the possibility that energy and matter can be created. Gravity is a constant. The creation of energy and matter then is a constant too. It explains so much. Good-by big bang. Just by adding in over-unity of energy to their equations everything changes. Instead of nothing is able to escape a black hole because of their gravity, nothing is able to fall into them because of the amount of energy they radiate. The black hole is not black because light cannot escape. The black hole is black because the energy they radiate is so energetic it goes beyond the visual spectrum of light. So the massive star looks black to an optical telescope. Yet they stick out like a sore thumb when studying them with radio telescopes. The visible light becomes invisible to optical telescopes when the star's energy output reaches that of a black hole. Nothing can fall into or collide with a black hole because of the amount of energy they radiate. I wrote and published a series of 6 books about this theory last year, starting with Gravity and the last book in the series called Over-unity. Get this, the only way galaxies can move away from us in every direction faster than the speed of light is if an infinite amount of energy times and infinite amount of energy is constantly being added to the vacuum of space between us and said distant galaxies. As gravity is produced an equal opposite amount of energy is created. This energy adds space around the large mass because energy is something new, it is being created. Matter is not converting into energy. This one action causes a reaction of motion to all the mass in the universe. When energy is applied to mass suspended in the vacuum of space by magnetic fields energy is created. Much more energy radiates away from mass than the energy that absorbs into it. This is true for all spherically shaped bodies not grounded out.
The first explanation of how gravity works that I truly understood was that mass warps the spacetime around it. It makes it so that a straight line going only in the time direction (i.e., an object at rest) will go toward the mass. How true is this explanation?
@@ronaldkemp3952 you might have more issues than that going on here my man. Can you not discuss it with other people in the field? Try to find any holes in the theory you may need to patch? I’d argue that almost 100% of new ideas in physics need peer-assisted revision before they become rigorous enough to really turn heads. If you’re the only one who’s completely convinced of your claim, chances are something is wrong with it- not the consensus understanding of nature. You should never be completely convinced of anything anyway, especially your own work, since you’re already going to be biased towards ignoring problems rather than revising your ideas accordingly.
@@alexweschler9470 I realized that energy can be created but it cannot be destroyed. That's why the universe is expanding exponentially with distance and why it grows over time. Energy is being created by large mass that takes on a spherical shape. When energy enters the universe it produces all the reactions referred to as motion of mass. It is not gravity causing all the motion. It is energy constantly being added new to the universe everywhere as an equal opposite counterpart to gravity. Every ounce of gravity that is produced accompanies an equal amount of energy that radiates out into space. When that energy interacts with mass it causes motion. Space is constantly increasing in the volume of energy it contains. When energy comes to the extents of the EM field it cannot be destroyed. So, it converts into elementary particles per the pair producing theory. So not only is the universe increasing in energy it is increasing in matter too. There is no such thing as a static universe. The laws of conservation between matter and energy, and the laws of thermodynamics is incorrect assuming matter and energy cannot be created. They are right to claim energy and matter cannot be destroyed. The universe is slowly growing in both energy and matter over time. The same action causing gravity in all large bodies is the same action causing all the motion that occurs to large matter. The reason why peer review did not accept this postulate or theory was because I claimed energy and matter can be created, over unity of energy. Seeing how the predictions I've made about gravity and many other observations has come true, this postulate should be called a theory. I even came up with the plans to a device which would create more energy than what is input into the device (over-unity). I suspect the entire reason why academia frowns on the idea energy can be created is because of their fear that we would no longer need to rely on corporations to supply our energy. Maybe they think it will cause an economic collapse? I may be wrong or I may be right. There is no in between. Seeing how every one of my predictions about gravity has come true, I have to believe I'm most likely right. Thank you for you're kind response.
My head hurts when I watch this. My head hurt 45 years ago when I took relativity at Uni despite being good at maths & theoretical Physics. The maths is hard, and I think all kinds of issues arise when people try and make the explanations simple - perhaps simpler than possible. I would no more uncritically trust your explanation than the other RUclipsrs without being able to verify against the maths, and I'm too old to do that now.
1. at 23:07 Why is mass accelerating outward from the rest of the other masses? What causes the internal pressure (if there is any)? 2. at 23:23 What causes THIS space-time curvature AND WHY?
Someone can correct me if wrong but as i understand it: 1. it is not in freefall towards to center of mass, so it is being accelerated. As explained earlier, the object falling is actually not accelerating, the earth is moving towards it, but when they meet, the earth accelerates it away from its freefall path along whatever geodesic it was following through spacetime. Electrons provide pressure in the same way that makes it so you dont fall through the floor. 2. Presence of matter and energy warps spacetime, which defines what the geodesics through that spacetime would be. WHY is a fundamental question im not sure has been answered yet, at least intuitively.
1. Electromagnetic force of the atoms in exactly the same way as when you push against a wall the wall pushes back. Newton's 3rd. Being in constant motion and being at rest are equivalent. So the falling apple is at rest and you are accelerating. That's why a falling person is weightless, there are no forces. Two parallel lines on the surface of a sphere will converge without any force and atoms their bodies will push them apart. 2. Because of the fixed speed of light. It cannot be otherwise. It is geometrically impossible for spacetime to be flat and for the speed of light to be fixed. First, there's no absolute coordinate system. Position and motion is only defined in relationship to other things. Also, information isn't passed instantly. The earth is orbiting where the sun was ten minutes ago. If you're on a train and you fire a gun the bullet goes faster shooting forwards than backwards from the perspective of an observer in the ground. Not so with information. Always at the same speed to every observer. A flat coordinate system won't work for that. Think about it, I fire a bullet at 1000m/s on a train moving at 100m/s and it's still going at 1000m/s to all observers regardless of which direction I'm firing it. Impossible, right? Just like three 90 degree turns making a triangle is impossible. Except on a sphere, then it *must* be like that. So speed is time and distance, right? Just stretch and squeeze them until everything fits the speed of light is the same for everyone. Hey presto: curved spacetime.
@@davidmurphy563 1. Newton's laws are incompatible with relativity and quantum mechanics. Two magnets attract. Where is the opposing outward force? I'm pretty sure the falling apple FEELS acceleration instead being at rest. I'm pretty sure the Earth striking the apple after accelerating towards it would have a different effect than the apple striking the Earth after accelerating towards it. 2. Space being curved doesn't logically follow from the speed of light being fixed to all observers. You are begging the question. The connection takes more rigor (detailed proof). Plus you have to define what "curved" and "flat" means precisely.
@@h1a8 1. Newton's 1st, 2nd and 3rd are alive and well. Especially the 1st, that's a restatement of the Galilean Principle of Relativity. Also a restatement of the Conservation of Momentum. Perfectly valid statements with great utility. Even the Law of Gravitation is still valid when gamma = 1 and given a series of caveats. Obviously in the hundreds of years since Newton our knowledge as expanded and there's more to add but the statements still have true and utility. I mean, the Ideal Gas Law is valid and that never ever occurs in nature. Hell, there are no right angles in nature but Pythagoras still gets used to normalise vectors! 2. It was a layman's explanation in order to give some intuition on the matrix transforms at the heart of GR. Of course it's not complete. In fact I leaned on SR as it's conceptually simpler. That's what Einstein did after all. Plus, there are no formal proofs in science and anyway, how would a page full of maths be helpful to the man? Why don't have a crack at it?
@@davidmurphy563 1. What about my magnet example? Falling Apple rebuttal? Author states that mass is accelerating outwards (doesn't explain why) and space is curving to compensate. You stated newton's 3rd law which would be compensated for the electromagnetic force, not space curving. You two are using different rationale. 2. You argue something you first must define it. Curved and flat space needs to be defined. Then you must logically connect fixed light speed for all observers implies space is curved. Can that be done without any intense mathematics without any question begging?
This reminds me of the time when I was an instructor for the USAF. I noticed that some of my fellow instructors would change some of the well written systems explanation to try to make them easier to understand for their students. In that attempt they taught some things wrong. I don't think that they understood the subject either. Fortunately it was a rare event that a good understanding of systems operation and purpose was required to fix the airplanes we worked on.
In the Navy Electricity and Electronics Training Series, module 10, section 1.12.2, it seems that the left hand rule is mistakenly used in place of the right hand rule?
@@ic7481 I have never needed to use that rule in my forty years of airplane fixin. I did use the knowledge that wires have capacitance and that water can act as a dielectric once to figure out an intermittent problem that affected several helicopters on damp mornings. A twisted pair of rate gyro signal wires (Kapton) were getting noise induced into them from the gyro motor power wire when they were damp. It had to be capacitance because no conductance was measured with an ohmmeter.
@@jnbfrancisco That's interesting. The relative dielectric constant of water is 80, so can definitely cause problems, especially for high frequency signals. I recently designed a specialised capacitor assembly, and the material used had a dielectric of about only 2! I guess this is also a problem for 50/60Hz, which is why undersea links are DC.
In my view, It helps explain why Neil Armstrong was so good. Maybe it’s the number one principal I respected Dr. Feynman for. He always desired to understand the most fundamental concepts or aspects of a system and wouldn’t put up with any nonsense. It seems human beings in general are satisfied living in ignorance and I’ve never understood it. But who am I to judge that.
@@ic7481 It's been almost 20 years since my last advancement exam, but offhand (no pun intended), I'd say it's because the Navy teaches electron flow. For hole flow, that'd be the right hand
I understood the arguments against other RUclips channels, but didnt understend his explanation about thr real cause of gravity. ScienceClick and Veritasium did this same explanation.
Here are my issues with your further reflections: 1. (@4:14) Yes there is a force holding atoms together, it's called the electromagnetic force. Electron and Ion-bonds are studied in chemistry. In cosmology there exists a term "Roche limit" and it's the distance at which a heavier celestial body can disintegrate a lighter celestial body if it's held by it's own gravity alone. You can think of this "flow of time" becoming too great for one part of the body. One real-life example of this would be comet Shoemaker getting fractured during it's collision course with Jupiter. 2. (@6:11) You are drawing comparison between Newtonian gravity and General relativity. Why bother? We already know Newtonian mechanics does *not* describe the universe accurately. 3. (@6:42) You are saying apparent gravitational attraction is not gravity but Einstein does make a point of there being no difference whether you are in a gravitational field (curved spacetime/time flow gradient) or undergoing acceleration (in flat spacetime). Undergoing acceleration does not mean spacetime gets curved. Why are you trying to draw that analogy? Undergoing acceleration means spacetime is squeezed in front of you and stretched behind you. You don't have curvature, you have spacetime elasticity in a plane perpendicular to the direction of your acceleration (including the opposite direction). This elasticity has no gradient, it just depends on your acquired acceleration (compared to your state before the acceleration). The gradient is in the acceleration accumulation. Your mass does *not* change because of your acceleration, so your gravity well remains the same as before you started accelerating. Only your clock ticks at a slower rate (compared to your clock rate before undergoing acceleration). You are not stretching or contracting the universe for everyone else, it just appears so from your point of view, because your clock ticks slower and you have a direction of relative motion compared to the rest of the objects in the universe. 4. (@9:30) In your example here, distant clocks (in the direction of your acceleration) would seem to tick at different rates only if you continue accelerating (at the same rate) until you reach them. This is because while you are accelerating your clock would continually slow down compared to those distant clocks. In reality all the clocks in front of you tick at the same rate, and only if you continue to accelerate the clocks would seem to tick faster (because your own clock is slowing down, again compared to your state before undergoing acceleration). If you stopped accelerating, all the clocks would tick at the same rate, because your own clock is no longer slowing down. 5. (@10:05) Just because you are accelerating doesn't mean you are curving space time. The equivalence principle states the effect would be the same for the body undergoing the acceleration, not of the bodes at rest which are observing the acceleration. While you are accelerating, spacetime sure looks curved (sloped) to you. 6. (@10:33) Nobody said curvature (spacetime elasticity, in the case of accelerating bodies) is observer independent. You just had a false premise that an accelerating body would create spacetime curvature that is observer independent. What an accelerating body does is just alter the speed at which it's clock ticks. That again is observer dependent though because for each observer no matter the frame of reference, time flows at the same rate (the speed of light, but in the time direction). 7. (@10:45) All observers can only agree that certain regions of space have more mass/energy than others. They can't agree on how much exactly this energy is or when exactly is it at a certain location. When you accelerate away from a star, it's energy appears to become less than before. Energy is conserved only in it's own frame of reference. 8. (@10:54) A uniform gravitational field does not have a curvature, but it *does* have a slope. That's why it *is* equivalent to an accelerated frame of reference. If you want to imagine it as time flows, then the time between clocks changes in a linear fashion (the rate of change is constant). 9. (@11:43) There is gravity on the surface of the earth because there is spacetime curvature or difference in clock speeds. It doesn't matter if the curvature is linear (as in the case of uniform gravitational field), it's there and it's causing the attraction force. 10. (@11:57) Assuming you are accelerating towards the apple is just equivalent to spacetime being curved and time flowing at different rates and even to spacetime flowing towards earth. None of this contradicts the time flow assumption. 11. (@13:06) -Yes in the frame of reference of the apple it's clocks will tick at the same rate- , but from the apple's frame of reference the Earth's clock would seem to speed up the close it gets to the ground. So again it's the same picture as the couple looking at different clock flows depending on the distance from the ground. Your example is *not* contradicting the point of view of the couple on the ground. *EDIT:* Actually since the apple has volume and is on a space time slope, the lower part will be more attracted to the ground compared to the upper part. If the atomic bonds are strong enough the acceleration experience by the lower part of the apple will propagate through the EM force through the top part and fall as an apple on the ground. If gravity is strong enough to overcome the the electromagnetic force (as in the vicinity of a black hole), then the apple will break apart. The situation is the same if you apply to much acceleration, the apple will be squished and the top and bottom parts will meet. 12. (@19:06) You are comparing spacetime an uniform gravitational field with a non-uniform one (the slope gets less steep the further from Earth it is). This just means gravitational attraction becomes weaker at higher distances. It would be the same as saying the rate of change of the flow of time is smaller the farther you go from Earth. None of this contradicts the time flow assumption. 13. (@19:37) I can appreciate the effort of trying to trace the origin of some suspicious source of information. 14. (@20:09) If the time flow assumption is just a simple coordinate transformation, you should know it's as true as the original theory itself. You are just doing calculations differently. This finding is a contradiction to the point you are trying to make. 15. (@21:15) Time dilation has a lot to do with curvature. You can't have curved spacetime and not have time dilation. Even more the extent to which time is dilated depends on the extent to which spacetime is curved. Even when you undergo acceleration, from your point of reference, the universe is curving (stretching and contracting around you), again the stretching depends on the amount of acceleration you experience and the tick rate of your clock also depends on the amount of acceleration you experience. 16. (@25:15) Would you acknowledge your own mistake?
about 6:42 he is exactly NOT drawing that analogy. He explicitly said that the problem of that analogy would be that, if true, an accelerating body is wrapping spacetime all across the universe and then when it stops all universe reshapes 'at rest' position. And he called that nosense.
@@enricobelvisi3880 Yes I tagged the wrong timestamp, the author of the video actually draws the analogy at 10:00 onwards. So either he doesn't have a good grasp on general relativity or the equivalence principle or maybe he was just confused at this point (for example if he was making the video late at night after a heavy workday). And why state what he did at 6:42, none of the other videos he's quoting imply that. Seems to me this is how Dialect thinks the other videos were trying to portray things. At 6:42 is just the first time he comes with this false premise, that spacetime elasticity due to acceleration should be reference frame invariant.
@@lamcho00 I think he mean that if you define time dilation as cause of Gravity (NB that he is defining as equivalent to ST curvature), as some of those videos have done, you are impling that your acceleration is causing ST curvature, and viceversa is causing ST flattening when you decelerate, instead of being only 'apparent' observer-dependent phenomenons. But rereading your comment I would say the point is that Dialect (if I understand his thought correctly) thinks we are accelerating on a flat ST instead of being at 'rest' in a curved ST IN THE NEARBY of the Earth's surface, supporting this view with the parallel geodesics observation- i would like to know by you if this observation is really so unequivocable sign of flat ST, cause I'm not an expert on this point. And so he derive that other videos are saying: you accelerate in flat ST-->you get Time Dilation-->this change other obj motion in TS. While those video could also be saying: you are in curved ST-->you get Time Dilation-->this change other obj motion in TS. And in the end, he would state that (if his assumption of being accelerating in a flat ST is correct) if you are accelerating and for example an apple is at rest (free falling) you don't need Time Dilation as a cause to explain the phenomenon, it's almost classical motion. But if his assumption is wrong then his explanation doesn't hold. I find difficult to accept the Time Dilation story, cause to me this seems only an apparent pheonomenon, but also accept that is not the ST curvature generated by gravity to 'produce' gravitational forces is a bit uncomfortable. One thing I am thinking is that Dialect idea of flat ST nearby the Earth surface could join with the idea that the geometry of ST could allow globally curved ST shape but locally flat ST shape (as in a minimum of a really big parabola), I don't rememeber where I listened to this idea but is a possible one. So even if we are at rest in a globally curved ST, locally we are in a flat ST (but accelerating? that's the part maybe doesn't fit to mix the two ideas) . Still confused thoughts....
@@enricobelvisi3880 In a way acceleration is causing spacetime curvature, but only in your immediate vicinity. That's how you get relativistic length contraction. When you accelerate you actually look like you are getting squeezed to the stationary observers. Why call this "apparent" observer dependent phenomenon? It's just how the universe works. Why assume there is a deeper root cause? Where is the evidence? It's not in the video. You can have flat space time, but still get gravitational attraction. Imagine you have a piece of paper and this piece of paper represents spacetime. If you lay the piece of paper on a table it's flat and if you put a grain of sand on it it'll stay where you put it. In this case space if flat like a dash "--" and there is not space or time dilation between different points on the piece of paper. We can say there is no gravity there. Now imagine you glue the lower two of the corners to the table and grab the upper corners and lift them at some height wile pulling away from the glued end. Then you again have a flat piece of paper, but now it's on an angle like a slash "/". If you take a point near the top and another near the bottom there would be a difference in potential energy, or in the case with spacetime it would be a difference in time flow rate and space dilation. Again the piece of paper is flat, but if you put a piece of sand on it, it will roll down to the glued end to the table. This is how spacetime is flat near the surface of the Earth. It's wrong to say there is no gravity there, because while being flat it's flat in a different way. The flatness here refers to the rate of change between equally separated points (from the top and bottom part of the paper). The higher the change the closer the angle between the paper and the table is to 90 degrees. If you want to think of it like a parabola, you are not in the maximum or minimum, you are on the steep slope, but you are looking at such a small part of the parabola that it looks like a straight line (flat). Much like how Earth's surface looks flat to us, because we are so small compared to the radius of the Earth. In both cases you have flat paper (spacetime). And in both cases you can draw geodesics and they'll remain parallel, because the rate of change between points is linear. But in the second case "/" you definitely have gravitational attraction. I think Dialect doesn't differentiate between the two cases and that's one of the reasons why he's wrong. The idea about flat spacetime is true, but different than how you describe it. I did some reading some years back and it turns out the maximum of Earth's gravitational field is under the surface of the Earth, so there is where you get the global maximum and the flat part (flat like a dash "--" part). It's not even in the center of the Earth, it's a zone between the center and the surface and it makes a surface of an irregular sphere on which you'll feel 0g acceleration due to Earth's gravity. The center of the earth will be a local maximum where you again feel 0g acceleration, but spacetime is not that stretched as in the case of the surface of the sphere mentioned above (time flows at a faster rate). Just because you'll be at the bottom of spacetime well and feel 0g doesn't mean time will flow at the same rate as in flat space in intergalactic space for example. To reach the bottom of Earth's gravitational well you've acquired acceleration and this means your clock ticks at a slower rate, compared to before reaching that point. NOTE: I'm not a physicist myself, physics is more of a hobby for me, and not every aspect of general relativity is clear to me either. So take my explanations with a grain of salt. But even with my limited understanding I can see the flaws in Dialect's arguments. I've done some Lorentz transformations and other GR derivations myself so I'm not a complete novice either.
You lost me at 10 minutes - the accelerating fighter jet analogy - it doesn't work. In the case of the accelerating jet, there is no curvature in time and the clocks would not be advancing at different rates according to their distance. The difference in the rate of time would only relate to the difference in speed between the jet and the clocks, not the distance of the clocks. The G-force felt is local only, being caused by the acceleration which is the result of a force acting on the jet. Likewise, the curvature of time around a massive object, such as the Earth, is only apparent to an external observer - it is not apparent or measureable/observable to a body in freefall or in orbit, and the only reason it is curved is because the Earth is spherical. If the Earth's surface were flat and infinite, there would be no curvature, only the gradient. When no force is acting on a body, it is in an intertial frame of reference. A body in an intertial frame of reference has a constant speed through space and time. Therefore, if there is a gradient in time, a body in an intertial frame of reference must change its course in in order to maintain its speed through time. This means accelerating towards the mass, where the rate of time slows. On Earth's surface, as in the case of the fighter jet, the G-force experienced is because you are not in an intertial frame of reference. The presence of the ground prevents this and the result is exactly the same as accelerating at 1G.
@@narfwhals7843 What is the equation to calculate the time gradient based on the acceleration? Because such an equation does not exist for a gravitational field.
@@narfwhals7843 The Rindler effect is the metric seen relative to other accelerating objects, not all of spacetime or objects in non-accelerating references. It can't be used to claim a time gradient in spacetime is observed, as it only applies to objects in the same accelerating reference frames, and spacetime is not an accelerating reference frame. Also, you can't calculate your absolute time dilation using acceleration. You must have your velocity.
The acceleration outwards of every mass being magically balanced by curvature is causeless physics and circular logic. I love this channel, really one of the best content out there. Please don't fall short of what you stand for. Stay rigorous, consistent, logical and mechanical. If humans have not reached a meaningful understanding of gravity yet, and you have nothing to propose, please state those limitations or explain how are we accelerating upwards, mechanically, and what causes space to shrink and counter that accelerating expansion. How can space have elastic properties? What constitutes that elasticity? What material is it made of? How does mass and energy cause such phenomena? If time dilation and space contraction cancel out for moving observers, can we state these are artifacts of our measurement methods (apparent) and not actual physical effects? If that is so, could we say that special relativity is a theory of how the finite speed of light skews our measurements, not implicating on the nature of reality itself? Please don't stop.
Our wording was a little awkward there, the above commenter is correct. As to space "elasticity", our leading theories of dark matter have space constantly stretching and appearing out of nothing, so you'll have to take that idea up with them until we can get a better grasp on the philosophy of what space actually "is".
@@dialectphilosophy If we discover what space actually is, we will discover what matter is, beyond or instead of our present ``understanding`` of it being excitations in fields.
13:09 while what you said is true so far, I believe this is wrong. Gravitational time dilation is something all observers agree on. Someone far away from earth is inertial and sees the time dilation. It is true space is locally flat, but this doesn't mean clock tick at exactly the same rate. Just minor difference between the ticks.
Tell us how do you check "gravitationnal Time dilation"? By supposing "gravitationnal Time dilation" between clocks that are "gravitationaly distant" from one another ? Or by an unknown trick of infinite speed exchange of intengled information between those two clocks appart ? Curious to hear about your "Magic method". Or is it more likely just empty words of wind blowing thoughts in the chimeric empire of fairy tails ungrounded beliefs
23:02 I completely disagree, there's not some magic force pushing outwards on every body, that's a reaction force due to gravity, like if I tried to squeeze a ping pong ball in my hand. The force it exerts on my hand isn't the cause of the squeezing, it's vice versa - just the same as the acceleration outwards isn't inherent, it's a reaction force due to gravity. If we could "turn gravity off", a large metal sphere wouldn't just fly apart, it would still remain in one piece, right? I'm glad you could correct the time dilation mistake made by other RUclipsrs, but this is either a gross misrepresentation or just plain wrong, and in a video where you're trying to "fix mistakes" too.
The videos you attack are correct. As other respondents have indicated and as emphasized by Thorne, Schutz, and other leaders in the field, curved spacetime has a time component which dominates in certain conditions - weak gravitational field and viewed at low velocity. (Like an apple falling from a tree, as opposed to starlight bending around the sun.) It is called the Newtonian limit. The Einstein equation reduces to Newtonian gravity in everyday life situations where only time curvature (otherwise known as the time dilation gradient) applies. The curvature of space in these conditions is de minimis. Narrowly defined, the Newtonian limit is uncontroversial. It is explicit in the math and in Einstein's explanations of general relativity and universally recognized. The dispute among experts and groupies alike is about physical intuition and is due to systemic pedagogy failure and a philosophical prejudice that both go back to Einstein. When Minkowski introduced spacetime, Einstein famously quipped that since the mathematicians got a hold of it, he no longer understood his own theory. His reputation for abstract thought notwithstanding, Einstein was most at home with imagined concrete events and bridled at the ontological weight Minkowski attributed to the most ethereal of abstractions: spacetime. At this time, Einstein was just starting to work on gravity and it took him several years before he reluctantly conceded the power of a modified version of Minkowski's scheme ( a pseudo-Riemannian manifold) to get him to his destination. But way before the curved spacetime breakthrough, Einstein did develop a picture of a gravitational time gradient causing the bending of starlight around the sun. Your presentation indicated that you pursued the provenance of the ideas in the target videos and the trail goes cold a few years ago. Please. That's off by about a century. The real source is a 1907 breakthrough memorialized in Einstein's 1911 "On the Influence of Gravitation on the Propagation of Light". According to this paper, the range of differences in time dilation at different points on the radial axis causes gravitational attraction. This is what we now call time curvature. When he later nailed the new theory of gravity at the end of 1915, this model of time curvature was subsumed into a more complete model of curved spacetime - a phrase he himself assiduously avoided, even though it would have elegantly explained why his earlier deflection prediction was short by half. Here was his unfortunate description of the separate elements involved: "...half of this deflection is produced by the Newtonian field of the sun, and the other half by the geometrical modification ("curvature") of space caused by the sun." This startling quote exposes the gulf between his reliable spacetime math and his resistance to embracing the intuitions implicit therein. It's as if he is propounding a system of mere curved space (not spacetime) and then attempts to coax an exhausted Newton into what should have been an unnecessary assist.
I just reread this for the fifth time and it explains a lot. I remember reading about Einstein's initial gravity estimate being off be 1/2, but I did not understand why. Thanks for at least providing some insight into what happened. Would really like to see this described in a video with space-time diagrams. It does not seem that hard to explain that "gravity" (the attraction of two objects) is caused by multiple things and then explain the differences between the various causes and under what conditions one or the other dominates. This would be extremely interesting. The term "curvature" is not well defined in my opinion, and the idea of space flowing into a massive object is also somewhat unclear. Why does space flowing into an object create any type of force or action if an object traveling through space is not slowed down? Space does not create 'friction' when it passes over an object, right?
Thanks for the note and for the Gravitational Velocity pitch on your site! I vote for Eugene Khutoryansky to make the suggested video and here are a few proposed script elements: Before you even get into Riemann and curvature, spend a few minutes on Minkowski. After all, this is where Einstein stumbled early, and he was smarter than us. To construct, or as we Platonists would assert, to reveal spacetime, Minkowski uses -c to normalize his dimensions. He converts time into a fake fourth spatial dimension. The result is a matrix with wildly counterintuitive proportionality. We remove the third spatial dimension so we can visualize a cubic section of spacetime. A cube might measure 300 million meters by 300 million meters by one second! It just doesn’t sound like a cube. I would spend some time trying to visualize this in the video. Then when you add warping, your video might help brook resistance to the dominance of time curvature in low velocity moderate gravity circumstances. Then the three examples of the relative weight of time and space would be 1.) All about time: Newton’s apple drops on his head. And close to Newton’s solar system except for Mercury to a small extent. 2.) Time effect matched with space: The starlight passing the sun. When Einstein finally got space curvature down, he correctly doubled his estimate of the effect on the apparent star position. An earlier attempt to verify his incorrect prediction was thwarted by WWI. This protected his reputation and paved the way for later stardom. 3.) Space dominates: Life near a black hole - or so I hear.
Wow, great idea for a video. I had a slightly less thought out idea of comparing the calculations of a plain newtonian orbit vs the calculation of a relativity affected orbit (such as mercury) in a simplified manner. There must be a way to show at least some of the extra terms used to calculate the orbit of mercury (and why they are not material for the other planets) but so far no physics educator/popularizer has picked this seemingly low hanging fruit!
Thanks for the note. Einstein's "On the Influence of Gravitation on the Propagation of Light" is worth reading to get some insight into this elusive subject. I am not having any luck finding it for free online, but it is a section in a little indigo-covered paperback called "The Principle of Relativity" which includes pieces by Lorentz and Minkowski that might also help you. Let me give you an overview of the time dilation argument that may help with some of your questions and please tell me if you think it is of any use. There are several steps to the argument so bear with me. First, we don't live in a world of space and time. It is spacetime. This is not wordplay. Nor is it a simple truism to the effect that you cannot arrange a meeting with a friend for beer without designating both the time and place. It is, according to Herman Minkowski in 1907, (and shortly afterwards according to everyone in physics) the logical consequence of Einstein's relativizing of space and time as separate measurements in his two revolutionary 1905 papers known to us as the theory of special relativity. It is the mathematical means by which objective reality is rescued from the perspectival nature of space and time separately apprehended. How does it work? Minkwoski converts time to a fake fourth spatial dimension. The conversion factor is minus c where c is the speed of light in a vacuum. If I take my X-15 hypersonic plane out of mothballs to illustrate what a path through spacetime might look like I might fly one mile from point A to B in one second. This is very fast. Yet by six orders of magnitude the displacement is through time as opposed to space. The total spacetime distance is the square root of the sum of the following squares x y z -ct. My plane traveled one mile in space but the equivalent of minus 186,000 miles in time. This exotic four-dimensional system provides us a measurement of the distance between events upon which all non-accelerated observers can agree. Objective reality is restored. But confidence in our experience of space and time as we perceive them separately is forever damaged. We are being asked to take a mathematical model more seriously than our direct experience. As the old joke goes: "Who do you believe? Me or your lying eyes?" As I indicated in my post above, Einstein understandably hated this at first. but he eventually required a warped and warbled version of this construction to solve gravity. His early tentative step in that direction is in the "Influence..." article. Here Einstein invokes Huyghens who had explained how lenses change light direction by a varying effect on velocity. Einstein thinks this is a good metaphor for the problem at hand. It's just a metaphor and you have to imagine this in a version of Minkowski spacetime where the passage of an object through time is very much like movement through a fourth spatial dimension perpendicular to the other three actual space dimensions. As you "travel" through time your passage is retarded the closer you are to a gravitational source, the way a piece of glass of varying thickness ( a lens) retards the transmission of light to varying degrees along an axis more or less perpendicular to the rays of light - thus altering their trajectory. The light bends towards the direction of retardation (Huygens). And equivalently, the apple falls to the ground as it traverses the very subtle time gradient that is the gravitational field. (Time is passing slightly slower as you approach the gravitational source and the apple is proceeding through time at right angles to the time gradient at the equivalent speed of 186,000 miles every second so even the subtle gradient has a powerful effect.) There's much more to the story. For purposes of concentrating on your question I am ignoring curved space which comes into play in extreme gravity or velocities approaching that of light. Einstein's original prediction of curvature of starlight near the sun was off by half because he was only taking into account this time effect - not space curvature. Bad weather and WWI thwarted the eclipse observation and thus conspired to keep his reputation intact. I hope this helps. @@johnnysilverhand1733
Saying those other videos got it wrong seems to be uncharitable. I'd be willing to concede that the explanations leave something to be desired, but not that they're outright incorrect. That said, this video leaves a lot to be desired as well. Without explaining tensor calculus, no explanation will do the subject justice.
No clue what this video was about. It had spent the first 7 mins arrogantly shitting on other You Tubers when I turned off. All I know is we're all travelling in a straight line through spacetime at the speed of light. Mass curves spacetime, so we're drawn together, that's gravity.
22:50 This reasoning makes absolutely no sense to me. There is no acceleration that an apple feels as it falls to the ground?? How can the entire surface of a spherical object at every point experience outwards “acceleration” If at the same time gravity crushes it into an equilibrium? What you are explaining must be the pressure of the body of matter itself battling that of the acceleration of gravity. This video provides me with many more questions than answers. I have a hard time believing in time dilation being the cause for gravity either. If time dilation directly causes gravity then what about light? Light allegedly does not experience time according to all of these youtube scientists yet we clearly see the bending of light due to extremely powerful cosmic phenomena like black holes don’t we? This hurts my brain
Yeah, that just came out of nowhere with zero explanation except as a fix for the clock. If he didn't spend sooo much time explaining the "wrong" ways, he might have thought of explaining that
Well, i think that is very good question. Probably frame of reference. If you are stationary in place where spacetime is curved, you need to compensate it's curvature moving you to the center. Came here because was not agree with above comment, but now completely agree, electromagnetic interaction keeps you stationary
The earths surface is pushing up on you at the same rate that an object falls. Therefore due to the Equivalence Principle this the same as you accelerating outwards st that rate.
couple of questions with the video at 12:42 1.) “…observing the clocks, while on the ground accelerating” is this now real/actual acceleration? because earlier at 6:08 you said “gravitational attraction is only an apparent phenomenon” 2.) is time dilation merely apparent with respect to the accelerated observer on the ground? then the difference of time dilatation with same spacial displacements of the clocks would be linear (because the acceleration of 9,8m/s^2 remains the same, no matter how far the clocks are away). But I learned that time dilatation depends on the gravitational potential, which would increase/degrease exponentially with same distances. how does this fit? 3.) free falling apple: although both states are inertial, does it make a difference, if it just started falling or gained already a velocity with respect to the surface (e.g. escape velocity)? or would both see the same time rates on all clocks (i.e. only the fact of free fall matters)? 4.) time dilatation of an orbiting satellite consists of both factors, velocity (SR: time ticks slower for the satellite) and gravitational potential (GR: time ticks faster for the satellite). overall there is a total/net time dilation (TD), where the TD of velocity cancels the gravitational potentials’ TD out and has the higher impact. But thinking of a free fall, which is the same for a satellite as for the vertical falling apple, according to your video, gravitational potential does not matter hence all clocks tick with the same rate for the satellite (except that all tick faster due to the kinematic TD). So eventually only special reality (SR) would apply, where both, the observer on the ground and the satellite, cannot agree on who is ageing faster. Something seems not consistent, either in my head or in your video.
At that point I thought this was satirical video by a purported flatearther. But by the end he goes on claiming things are constantly accelerating towards other masses in the universe, but spacetime itself around masses is constantly curving inward masses to balance this out...
Anyone who says that something is “100% unequivocally wrong” in this high end level topic that is still being studied is a narcissist who doesn’t understand anything.
Facts aren’t relative bro. They’re either unequivocally right or unequivocally wrong.” Don’t get mad at Dialect just cause you got fooled by a wrong explanation
@@se7964 I’m actually a physics major studying to be a theoretical physicist, and I’m deriving general relativity right now. So no, he is not right. I’ve still yet to see any qualifications for what he’s saying.
@@se7964 When did I admit that I didn’t understand the topic? I literally claimed that I did understand it. And again, I’ve yet to see his credentials that prove he understands it.
@@maxwell8758 you admit that you don’t understand the topic because you’re scrolling through RUclips trying to learn GR from pop-physics videos. My advice is to remember that the components of a four-velocity are not real, and can be interchangeably mixed bwtn time and space depending on the coordinate transformation. These other videos don’t understand the difference bwtn coordinative time and proper time
@@se7964 Your logic is so bad. I don’t know relativity because I’m watching this video? By that logic, you don’t know it either. I always watch videos about science because it’s interesting. I never said I was trying to learn it. I’ve already done this before. And I’m literally also doing it right now! I have a better understanding. This video is needlessly superficial and argues based off of different definitions than truth.
When you said "100%, unequivocally, completely wrong", I think you could've done a better job of driving home the point that other channels are wrong. Maybe add a few more adjectives? Like "100%, unequivocally, decidedly, undoubtedly, utterly, completely wrong" would've been better. Plus you could've put flame effects around the "WRONG" in red text to hammer your point into the viewers' heads. In your next video, make sure to leave no stone unturned in putting down other science channels 😊
20:35 Both explanations work, there's no ultimate coordinate system. You can technically switch between some of them and remain accurate like Nick from The Science Asylum did. Also tracing circles and drawing lines isn't wrong, it's literally what a parabola (or any curved line) is: an infinite amount of infinitely tiny straight lines connected together.
Flow=gradient They are the same thing. Relatively different coordinate systems. It's like asking two people facing each other, what direction is forward...
Disagree with “infinite straight lines” as a premise for curves. Infinite straight lines only makes sense if you stop at a level of precision and think “eh, close enough” It’s infinite points along the curve, almost zero size, but completely precision dependant, which makes those “infinite” lines the closest approximation to curves - which is not the same as “literally what a parabola (or any curved line) is” by definition, as it’s a closest approximation
@@bowkenpachi7759 well, if we're nitpicky af we could try to warp OP's words to make a statement that is correct. A curve can be composed by an infinite amount of lines if we're considering an infinite set of tangent lines lol, so the curve would be described by the infinite amount of points from those tangent lines that contain the curve, but thats obviously not what OP meant, not to mention its not really a good way to describe curves since we still need to obtain its points from the tangents so it doesnt really make sense to describe it like that, but still, a silly little dumb way to try to justify OP's lines comment.
Not really. Time dilation doesn't cause gravity, it IS gravity. Gravity is caused by the warping of space and time. Saying that the warping of time causes the warping of space is incorrect
I think you're overstating your case here. Yes, saying time dilation 'causes' gravity is wrong in the purely scientific sense of gravity being defined as curvature in spacetime. But in the sense of gravity acting like a force in everyday interactions, the idea of 'time dilation gradient = gravity (as an accelerating force)' is a perfectly valid one especially for the lay audience of these youtube videos. Your point about a guy standing on the surface of a planet not being inertial is a good one, but it ignores the fact that if we shift our perspective to the most comparable inertial reference frame (i.e. an observer at the center of the planet, with no net acceleration required to remain at rest with the overall planet), they STILL see the time dilation gradient for the falling apple, and can use it as an explanation for the apparent acceleration - no non-inertial reference frame required. This means the connection between the time gradient and acceleration cannot merely by a trick of a coordinate transform, and is in fact much more fundamental. If anything then both your video and theirs are understating the connection between time dilation gradients and apparent accelerations. In the end, both accelerating frames of reference AND intrinsic spacetime curvature can cause time dilation gradients, which always result in apparent accelerations relative to the observer. In a very real sense then those gradients can be said to 'cause' the accelerations we see between objects (the lay meaning of 'gravity'), even as both are in turn merely outcomes of some more fundamental theory in which 'gravity' is equivalent to intrinsic curvature, and time dilation gradients are the result of gravity, and not the cause.
Yes, his argument is pure semantics, and while wording is extremely important in science, none of the people who made those videos misunderstand GR or SR. He's annoyed that instead of saying "time dilation is the cause of apparent gravitational attraction" they said "time dilation causes gravity". Nick, Matt, and others know very well time dilation isn't the source of "gravity".
@@SolidSiren is time dilation the cause of apparent gravitational attraction though? If so, how does a photon, which doesn't experience time at all, experience gravitational attraction?
18:40 of course there would be no change in distance, because spacetime is always LOCALLY FLAT, that means that for small regions arround a point, we can aproximate it by a tangent flat space time, meaning that for small motions there would be no significant deviation from a straight geodesic
I must say, I was very surprised at 23:18. Part of me suspects that you have a very specific interpretation for what is happening with spacetime when it curves in the presence of mass-energy. I've never seen that animation of spacetime "flowing into" a body to counteract an outward acceleration before, though I have heard Leonard Susskind use that analogy before when discussing black holes. To be fair, that is an intuition I almost can't even picture, because a "true" picture of it would be in four dimensions - something we can't visualize - and it would be static. Though, to preface, I happen to believe in the B-theoretic interpretation of time, in which the flow of time is an illusion. But, of course, mathematically speaking, that should ideally be beside the point. I think the biggest confusion everyone's having here might be, at rock bottom, linguistic. Relativity is, even for most experts, really fucking hard to comprehend. We're forced to resort to constructing analogies and intuitions to guide us through its complexities. I've used the analogy of temporal gradients before because one can mathematically show - in the weak field limit - that the g₀₀(x) component of the metric tensor is overwhelmingly the largest contributor to a weak gravitational field and can be identified - in that limit - with the scalar potential in Newtonian gravity. For whackier gravitational fields and funky frames of reference, this analogy breaks down, but it's a way to illustrate that, without time being included, general relativity couldn't possibly work. I still need to wrap my head around that intuition you presented at 23:18. I'm still learning - and will hopefully never stop learning -about relativity. But my initial impression is that, while you may have added some nuance, you also could take a step back and recognize that many of the analogies we use hold some truth. There are some truly piss poor analogies out there, in my view (the trampoline analogy comes to mind). Others, though imperfect, may represent aspects of the theory. But I think the degree of "wrongness" you've so confidently attributed towards many RUclipsrs, some of which are very smart physicists, was overstepped. Most of them likely know that mass-energy is the source of curvature and that uniform accelerations can be removed. We're just trying to drudge through this beautiful and horrifically intricate theory as best as we can. So, take it easy 👍
@pyropulse You have several misconceptions, which I'll try to address here as succinctly as I can: 1) "We can always transform to a frame that eliminates an object's acceleration." That can only be done locally, that is to say, at a single point. The metric can only be made flat generally at a point; this obstruction indicates curvature. 2) "The error comes from thinking a mathematical association to 'real space' means that real space is actually curving; that literally makes no sense; you cannot curve nothing." Spacetime is not "nothing." I don't know where you got that from, but to call something with such a rich differential structure "nothing" is at best a vague description, and at worst blatantly false. 3) "I did physics, and I aced every exam with no effort, getting a 4.0 gpa with skipping lectures and just figuring out the exam problems when I showed up; and I would finish my final in 25 minutes when I had 3.5 hours, and got a 98% on it, while next highest was a 72% (UC Berkeley). I only say this because my abilities and understanding are clearly superior, so why should I trust nonsensical nonsense just because inferior people tell me that is how it is?" The fact that you think spacetime curvature is not only impossible, but not even a sensible concept, disproves the hypothesis that you somehow possess "superior" abilities. Moreover, your need to explain your superiority invalidates you right from the off. If you have you display your virtue in order to get people to notice it, then you never even had the virtue in the first place. 4) "To demonstrate my point, there is a curved spacetime in a purely Newtonian framework, called Newton-Cartan theory." That theory is a reformulation of general relativity in a language that makes its connections to Newtonian gravity more easily visible. It is a mathematical rewording of the same theory, if you will. It does not demonstrate that spacetime doesn't curve.
@@jmcsquared18 This nickname piss-marked every comment thread by replying to every single comment with similar nonsense. Kudos to your patience and your answer! It made me grin like 😁!
@jmcsquared the channel Science Clic also presented the intuition at 23:18. He talks a little bit more about it, but, doesn't give a full on explanation, if I remember correctly.
I've seen a similar representation of with spacetime flowing into the body in a ScienceClic video called "A new way to visualize General Relativity", though he seems to have more videos on GR as well that I haven't yet watched. I'm still trying to wrap my head around all of it too.
I'm an avid follower of all channels mentioned and admittedly learned a lot of physics from them in combination with personal study. They're not "unequivocally wrong", perhaps some technicalities yes, but imo it kind of felt like this video was putting them down to draw attention to this channel. Your videos are brilliant in their own right. And everyone here has the same passion; to investigate and evaluate a more complete view of the Universe. No individual person knows everything about everything. Humans are like bees. We all have our slice of expertise that serves the greater species and genius emerges from each of us sharing ideas and why we believe them. It's ok to elaborate on ideas of others and refine them towards a greater truth, but we should learn to be humble and realise we are all searching for the same thing on the same journey. Having said all that, you do have a good point distinguishing between curvature and constant velocity motion. @10:49 this is describing a Minkowski Spacetime. Time Dilation is still relevant as the Rocket is an inertial reference frame, only experiencing motion through time, but everything else in the Universe is comparatively percieved as being time dilated. What all these channels neglect to explain is what a slow moving clock even means to an observer, and where the term Spacetime originates from. Time Dilation is looking at another moment within the history of the Universe. The past and future existing simultaneously. And this is where the term Spacetime comes from; Space and time forms a single overarching entity. A block timed Universe. The first step to understanding gravity is to understand a geometrically coordinate equivalent block time, then introduce the scewed geometry of the time coordinate components towards mass.
@@narfwhals7843 Ahh true. The vid does say it's an accelerated reference frame. However, acceleration works perfectly well within Special Relativity (meaning not considering curved time). "there is no truth to the rumor that SR is unable to deal with accelerated trajectories, and general relativity must be invoked", Sean Carroll. An Introduction to General Relativity, Spacetime and Geometry (2003). Cambridge University Press (2019). pp. 11. This makes sense as acceleration should not have any impact on perceived time dilation other than an increasing affect as velocity increases.
I was going to leave a response to this video but in in scrolling thru, I found yours and the points you make were similar to mine. So, I will simply say - well done) 🔲
No I think his criticism is valid. The other channels claiming certain effects are "caused by" other things is not reasonable. Namely the claim that gravitational attraction is caused by a time dilation field. A gravitational attraction effect IS necessarily going to go hand in hand with a "time dilation" effect, in order to uphold the laws of thermodynamics. However, it's kind of like claiming that rain is caused by a lack of blueness in the sky. Yes the sky generally isn't going to be blue when it is raining, but it is entirely unreasonable to claim that is the underlying cause of the rain when they are both artifacts of the water in the air condensing into droplets.
I believe one should be quick to jump on people for giving bad reasons for things that are true, they do an enormous amount of harm, perhaps even more than those that say things that are untrue, because it gives more credibility to those saying falsehoods than anything they themselves could say. It's like the Piltdown man. It's like the Piltdown man. That was a fraudulent fossil of a hominid. Ultimately it provided fuel for young Earth creationists to claim as dirt they dug up on the theory of evolution. False claims undermine the credibility of everything else you've ever said.
9:35 no. the equivalence principle is valid in a constant gravitational field. Observers ALL in a constant g.field will observe clocks ticking at the same rate. The reason objects in space tick at different rates is because the curvature is less the further away from earth. So the Jet flying at 9:39 will see clocks everywhere tick the same if he is indeed accelerating in flat spacetime.
Thank you for this necessary video! But I have a question. If I've understood you correctly, you're saying that the time dilation gradient observed on the ground can't be the source of true gravity (the curvature of space-time) because this gradient depends on the observer. An observer in freefall does not observe a time dilation gradient, but he does observe that he is getting closer to the Earth. This time dilation gradient is due to the fact that the ground is accelerating upwards, and due to this acceleration, we observe a time dilation gradient. But at 2:52 we see in the PBS spacetime diagram a time dilation gradient on a much larger scale: on a scale where the curvature of spacetime is not negligible. So this time there's a time dilation gradient that's not due to acceleration, but to the curvature of spacetime caused by the Earth. But the time dilation gradient caused by curvature doesn't depend on the observer, does it? Because this time it's due to the curvature and not to the acceleration of observers on the ground. So how do we show that this explanation is wrong in this case?
He made a huge mistake in singling out PBS Space Time and The Science Asylum, both are run by actual physicists and only try to explain current theories. they never say that any of the theories are the answer. This really bothered me and too bad, I had been enjoying his videos.
@@bobinmaine1 if the theory is the answer isn’t really the question here. They are all talking about general relativity and trying to explain that theory. But dialect disagrees with their interpretation of the theory.
I had this same question, and after some probing to get some clarification, I finally arrived at this essential part of the explanation. The issue is, that acceleration in general relativity doesn't mean the same thing as acceleration in kinematics. In kinematics, it is the rate of change in velocity (a = dv/dt) In general relativity, it is the net force per unit mass, not counting gravity as a force. (a=Fnet/m) The equations a=dv/dt and a=Fnet/m are interchangeable ways to define acceleration, as long as you treat gravity as a force, and relativistic effects are negligible. But the problem is, that these are profoundly different when relativity comes in to play.
@@carultch So he is using something also called acceleration but that is not really acceleration to state a fact about the REAL acceleration of Earth. Let's zoom it out for a bit and double check the variables we should have defined ( or take for granted). Earth is spinning around its own axis at (on average) 1,669.8 km/h; around the Sun at (on average) 107,278.87 km/h; The Solar System as a whole is orbiting Sagittarius A (the Black Hole at the Center of the Milky Way) at around (on average) 220 km/s; The Milky Way itself is very likely orbiting a larger object (or 'attractor') , e,g., the mass center of the 'Local Group'... and then it all must orbit something else, but wait... the Universe as we state...I mean, as we know doesn't really have a center. Does it? Now, ask yourself again what 'accelerating in all directions' mean. Tks.
@@thesecondslit1710 Allow me to clarify this. When your environment accelerates due to gravity alone, the two effects nullify each other in terms of your ability to feel either one. You cannot tell the difference between being in free fall nearby a planet, and being in deep space moving at a constant velocity away from all sources of gravity. Because force of gravity is proportional to mass, and because force needed to cause acceleration is proportional to mass, the two factors act uniformly on every kilogram of your body, and no constraint force is required. This is apparent weightlessness, whether it is zero gravity or not. You don't feel gravity; you feel constraint forces.
@@thesecondslit1710 That being said, the gravity due to outside astronomical bodies also nullifies this way. This is why we don't feel the Earth's acceleration due to orbiting the sun, or due to orbiting the center of the galaxy, or due to any galactic motion we have. The only gravity due to outside astronomical bodies that plays any significant role in governing actions on this planet, is the tidal forces, which are only significant due to the sun and moon. The moon, moreso than the sun. The tidal forces are on the scale of nanonewtons for a human body, which is why they are only significant when applied across the ocean that spans a vast distance to different parts of the moon's gravitational field. That really only leaves the acceleration due to the Earth's own rotation to explain, and this one is easy. Calculate the force needed to accelerate with the Earth's rotation, and it is 0.334 Newtons/kg. Use the speed of 1669.8 km/hr translated to m/s, and the radius of Earth in meters, 6.378e6 meters, and the equation v^2/r, and that's what you'll get. Notice that this is nowhere near Earth's g of 9.8 N/kg. All this ends up doing is making gravity slightly less than what it is at the equator, which is measurable. There are other ways we can measure this as well, such as the Eotvos effect.
@@thesecondslit1710 The "acceleration" that he's using in this video, is not the same thing as the kinematic acceleration due to changes in velocity as you would measure in simple Euclidean spacetime, like you are accustomed to doing at an introductory level. But in the spacetime distortions caused in general relativity, there is an acceleration when you are at rest on this planet. You are accelerating against spacetime collapsing in on itself, nearby the source of a gravitational field. The normal force from your seat stops you from free falling, and the structural forces of this planet stop it from collapsing, following the collapsing spacetime. The idea in GR is that gravity is "not a force", but is a body's natural nature to follow the path governed by spacetime. Constraint forces stop you from doing this, so that you can be at rest in Euclidean spacetime in the Earth's surface's reference frame.
21:43 Time dilation comes from the line element ds, which is derived from the metric tensor guv, which is found using the Einstein’s field equation. The Einstein’s field equation deals with curvature of space time using the Riemann curvature tensor Ruv, which is just a compactified block of a bunch of metric tensors. The sourcing term in the equation is mass, but time dilation and length contraction are still from the curvature in spacetime. At least in Einstein’s general relativity.
No, the time dilation appears because of accelerating frames of reference, which are constructed via special relativity, then imported to General Relativity via the equivalence principle. And yes, they are associated with the metric, but they are a consequence, not a cause of it.
@@dialectphilosophy time dilation comes from the curvature of space time and as well acceleration, I made no claim of time dilation causing any of the above. Edit: acceleration as in deviation from geodesics. In special relativity, time dilation is a consequence of Lorentz shifts, which is velocity dependent and frame dependent, it doesn’t need to come from acceleration.
@@dialectphilosophy This is not true in the case of objects near massive ones. You can orbit a black hole while the theta coordinate changes without altering altitude. This state is called free-fall, where you still experience time dilation from the metric.
Deflection from time dilation is still a thing, at least correct in terms of gravitational lensing and Shapiro delay. The explanation of gravity is due to time dilation isn’t complete, but it’s not wrong. Since any deflection comes from the geodesic equations which depends on the metric which depends curvature tensor which depends on energy momentum tensor, the curvature of space time in some cases looks like a curvature in time. Your explanation of everything accelerating outwards isn’t wrong either, it’s not going to explain anything regarding to tidal forces. Tidal forces comes from geodesic converging at the centre of mass of the massive body (in case of a planet), which comes again from curvature. Edit: the tidal force part I mean if we take the frame of two objects falling, they should get closer together in a point sourced gravity field, but for a expanding sphere in flat space, this doesn’t happen in the object’s frame. You need to improve the condition that all distances in sphere is constant while the sphere expands, which is equivalent to saying space time curvature.
There is no such thing unfortunately as "curvature in time" which is another popular fallacy of general relativity. There is only curvature of the spacetime manifold, which can be sliced such that, according to a particular observer, the curvature will not appear in the spatial subslice but only the temporal one. However, a different observer can always slice the manifold in a different way, meaning there is never a unified sense of "time curvature". Time dilation as a causal agent of gravity is one-hundred percent factually inaccurate, and a misunderstanding of both the nature of gravity and coordinative time dilation.
@@dialectphilosophy you are talking about space time foliations, the time curvatures in that case is a gauge condition, taking this gauge to 0 causes problems such as geodesics colliding and falling inside the event horizon when doing simulations. The idea of time “curvature” is flawed, as in speaking of space and time separately without constraints is flawed, but it is a interpretation in some gauge. Edit: I guess it’s really “time dilation can look like the cause of gravity, if you transform your coordinates.” As in case of Shapiro delay, it looks like the wave in the inside gets squished from being “slower”.
@@dialectphilosophy And hilariously enough, the "particular observer" for whom only the temporal curvature will be apparent was the only observer ScienceAsylum was referring to in his video -- and he specifically explained that. He was saying that for that "particular observer" on earth, only the time slice of the spacetime manifold will seem to be affecting gravity -- and therefore, in that frame of reference, the "cause" is predominantly the curvature of the time slice of the spacetime manifold. If you missed that in his video, then perhaps the problem here is your inability to understand the English language -- and your inability to understand basic philosophy (which is shocking for a channel named "dialectphilosophy"). Even though he didn't say all the words that I just did, everything I just said was clearly implied to anybody with a command of basic common ordinary language. So, admit defeat and go home.
So, are you asserting that there IS an ether - spacetime, I guess, and suggesting that Einstein thought so too - or just that everything - absolutely EVERY SINGLE THING - is in an accelerating frame of reference? Or have I got it all wrong? I've laid awake at night for years trying to figure out what it is about two masses that draws them towards one another. If spacetime curves, cool, but why? If mass - the concentrated binding & kinetic energy of (mostly virtual) quarks jiggling about in a nucleon - is what curves spacetime, why? Is it that certain masses end up in one place that creates the curvature, or that the existing curvature - the whole CMBR ripples thing(?) - is what agglomerates the mass? I found the river/waterfall analogy compelling - and it helps resolve the counterintuitive notion that we're rushing upwards at 9.8m/s2, but then, water is water, spacetime is spacetime, ether is...? What exactly? I was always taught that transverse waves didn't need a medium... If particles are excitations in quantum fields, are quantum fields the ether? I was intrigued by your comment that literally every piece of matter in the universe is 'rushing towards every other piece of matter.' I kinda thought years ago that what we perceive as attractive gravity could actually be repulsive - in the sense that the universe is rushing away from itself as fast as possible (C) in every direction and that agglomerations of (observable) mass are really just localised, almost foamy, versions of that - bottlenecks of accelerating boats as you show it(!) - and really tiny ones, at that - stars are so, so far apart that even large masses are relatively puny on a cosmic scale. But at the end of the day, and if, say, the universe consisted of two nucleons only, how would they curve spacetime in order to rush away from, or toward, each other & why? (indeed, would there be any spacetime for them to curve?) Your videos are very interesting & a slightly different take on PBS et al. Confused as ever, but still curious. Dominic
Hey there, thanks for watching! As to the question -- why do two masses attract one another? Unfortunately none of our modern theories come close to answering that question -- it's as mysterious as when Newton first postulated it. In this video we were concerned with differentiating cause and effect as the theory of GR views it, in which the apple does not fall to the earth, but the earth accelerates towards the apple. (However, indirectly one can still blame the apple falling on spacetime curvature, as spacetime curvature causes the "river of space" to converge in towards the center of various masses, and thus produces the outward acceleration of the earth.) GR takes a very substantial, ether-like view towards space itself, which Einstein himself confessed in 1920, and in that manner, is actually quite at odds with the philosophy of special relativity.
I don't think those videos made the mistake of equating gravity with gravitational acceleration. It seemed clear to me that they were using "gravity" as shorthand for "gravitational acceleration", which, after all, is what most people call "gravity".
This really should have been handled like how ElectroBoom and Steve Mould and Veritassium had and settled their disputes. Shoutouts to their respective channels by the way. Their exchanges about the mould effect and about the nature of how electricity flows through wires were civil, respectful, fun, and just as informstive as entertaining and didn't have this air of putting either of them down even when one of them was wrong about something or learned something new. That should be like the gold standard of disputing another creator and holding a debate or exchange, especially since it seems like the issue could have been resolved with a conversation with them, and in the comments, it even seems like there's very interesting details to clarify and dig into that would be more informstive. However, I can definitely understand a disdain for oversimplified explanations they lead to faulty understandings of concepts that are born from "dumbing it down" too much in the attempt to make the knowledge more digestible to a key person. At a certain point it is very challenging and even crushing to have to do what feel like butchering a concept in an attempt to communicate it to someone who doesn't have the background to understand it or relate to it. It's very easy to then get a sense of harsh superiority with the "right" way of doing or understanding the concept. I get it, I've been there. I've been they person who would just insist that if someone wants to truly understand they unavoidably have to apply themselves and engage with the material. The thing is, expecting everyone to do that isn't sustainable and it limits how far knowledge can go. It is unfortunate that in your case these oversimplified models hindered your progress, but you must take the time to appreciate how far that communication got you in the first place and others like you, and how it gives people who have only a casual interest in science something they can handle. It's so easy to take for granted that they make graduate level topics easy to understand and relatable to engage with. The value in this cannot be denied. But regardless, this is a good thing as it promotes everyone to be vigilant of where they get information from and to not blindly accept things as doctrine but to always cross reference and seek to know for oneself to the best of one's ability. That is a good takeaway, along with the intellectual content if this video.
Rinkamime, sometimes it's just as simple as 'wrong is wrong', and there is NOT value having a whole bunch of profiteers pretending to be at a level to teach something they really don't understand. It's dishonest of you to portray those wrong videos as merely "oversimplified", so you can make your point they still have value. They don't. You said it's unreasonable to expect everyone "to apply themselves and engage with the material", but he's not expecting everyone, just those who want cross over and claim they can TEACH a subject, then yes it is definitely reasonable to expect those who teach (and/or profit from pretending to teach) to understand what they are teaching.
@@Grrrnthumb Did you read the comments of the channels called out posted to this video, ie PBS Spacetime and Scieny Asylum? I'm of the impression that this very much is a misunderstanding, and in.many instances they even outright say in their videos that they are simplifying the subjects. And there definitely is value in what they've done. Like are yours eripusly going to say that people who don't have a background in calculus but have an interest in science being introduced to the scientific concepts on a level they can engage with at their level (ie, they aren't just gatekept out of it all together) is not a net plus? The guy said in his own video that it was videos like there's that held his curiosity about science and fueled his enthusiasm. Sure *he* encountered issues where the way he learned things were a road block for him, but like, he's speaking for himself here. I personally can attest to how videos from the channels he mentioned actually got me *ahead* in a lot of my science classes and I went into those classes primed on certain topics. Sure I didn't know everything, but there were lots of rewarding profound times when I'd witness so ething "click" where the stuff I'm learning reminds me of a video I watched and then it all makes sense and is infinitely more meaningful. It also felt good to be the one answering questions preemptively with wyd I knew, and having my background knowledge, being able to apply what all I learned from those channels in new ways as I problem solve In other words, speaking for myself, I most definitely benefitted. I was watching videos like this since middle school so by the time I was on college so many things were a breeze and just rehashes of things I generally knew, just with the mathematical rigor added into it once I was prepared for it. But as I said, I've been on the giving end of this attitude to, where I'd just get impatient with people and be like " okay no I can't simplify this anymore, google it or get a text book or something." It takes character to amdit that that is a failure, but I'm not a teacher xD Cosndier the words of Feynman where I think he said that if you *can't* communicate a concept in terms that let people can grasp it, you yourself don't understand it well. This is a real art qbd it has very real value. Now like, if you want to go intellectual edge lord and be like "well ACKSHUALLY it's really like this" for everything they say in every one of their videos then by all means, but at least do so knowing that, it is definitely a good thing to be able to communicate these topics in ways let people can grasp well, and that they do well in my experience and humble opinion. And again, read their comments and you'll see really clearly they all of this is really just either a misunderstanding, or at worst, is a video made out of spite and frustration.
@@occultninja4 Yes I've seen all those & read most of the comments. You're being dishonest on at least 3 things: 1) That the author of this video left any possible room for a "misunderstanding". Did you even pay attention to this one? Either he's plain wrong or they are, no middle ground possible here. 2) You're dishonest in your implication that you understand the underlying facts enough to claim there could be a gray area/misunderstanding on this issue. 3) It's dishonest to use fake debating techniques like restating the author's view in crazy, false, exaggerated ways like implying he (or I) want to 'ackshually be an intellectual lord and correct every point on every one of their videos'... clear sign you care more about winning a debate than finding truth.
@@Grrrnthumb I don't get where you're coming from with the dishonesty thing. But whatever, let's just agree to disagree. We have different views on this. I'm fine leaving it at that xD Evidently we aren't seeing eye to eye on this and if youve actually read the threads of the other content creators and still don't understand where they are coming from, it's a lost cause. It should be pretty clear cut to understand I'd imagine, or at least, to be able to relate to without assuming foul play or malicious intent. But maybe you're just not convinced and if so, that's you I'm not pressing you. My limited free time isn't going to be sucked up in an internet argument xD I've stayed my stance and opinion, and Lile, bare minimum, I adamanelty hold to my original commebt that the way this video was aimed could have been done more constructively. But I'll unconditionally respect your opinion though!
23:36 so is spacetime kind of constantly flowing into the center of a mass? Now a black hole also makes more sense, as things seemingly flow into it, because they are "stationary" on that path? Where the mass is accelerating.
Question: why would an outside acceleration be the cause of an apparent attraction between masses if it is balanced by spacetime curvature? Answer: it isn't. The explanation of those RUclipsrs is actually closer to the truth than you realize, but you need to look at the falling apple (or squirrel) from the point of view of a hypothetical observer at the center of the Earth. At the center of the Earth, you're surrounded by an equal amount of mass in all directions, so you're not attracted towards any particular direction, so you're just floating inertially. If you were to carry an accelerometer, it would show 0 in all directions. If you look at an apple near the surface of the Earth falling towards you, you can draw the trajectory of that apple through time and distance and find it curved. In this scenario, you're actually looking at space time curvature, as your time axis is a geodesic - and so is the time axis of the apple [if it were to carry an accelerometer, it would show 0 in all directions as well]. And indeed, the curvature of the apple's time axis is the only possible explanation why it would fall towards you, because neither you nor the apple experience any acceleration. Observers at the surface of the Earth make a similar observation as our observer of the center of the Earth, because they're not moving inertially [which would mean that we just fall through the surface towards the center]. Our being accelerated upward is the explanation *for us* why *we* see things falling down: the acceleration just keeps us stationary with respect to an inertial frame that is the key to understand the cause why the apple falls. You're correct in pointing out that clocks ticking at different rates isn't the cause of the phenomenon called gravity. But surface acceleration isn't the causal answer, either [it only explains why we're stationary with respect to the center of the Earth]. Curvature is the true cause, when understood appropriately. And to play your game now: Now the question is if you can acknowledge your mistake. You've been fooled by the word "acceleration" into thinking that this somehow translates to an attraction between massive objects. I'm relying on the readers of this comment to bring this to Dialect's attention and make them publicly apologize.
@@marope I'm not sure why the creator felt the need to attack other videos, under the guise of properly applying Einstein's Equivalence Principle and explaining the cause of apparent gravitational attraction, but anyone serious about learning relativity and gravity, wouldn't solely rely on a single RUclips video. I don't think any of the videos intentionally mislead anyone into believing that something other than the energy/momentum density of matter is the cause and source of gravity. The confusion comes from the different terminologies used in _Newtonian_ Gravity, _General_ Relativity, and _classical_ mechanics. The definition and descriptions of tidal forces/acceleration, gravitational attraction, gravitational field, and spacetime curvature have all changed since Einstein's paper on _General_ Relativity was published.
I don't think you can use the center of the earth as a reference frame to locate objects that are falling towards the earth. In general relativity, reference frames are only valid locally, due to the curvature of space-time. As the objects falling towards the earth are actually very far from the center of the earth, more than 6,000 km away, you can't use the reference frame at the center of the earth to locate falling objects, or to measure their acceleration. The ground accelerating upwards is indeed the reason we observe objects falling to the earth's surface, because if the ground didn't accelerate and followed its geodesic in space-time, then it would move closer to the center of the earth due to curvature, and the earth would collapse on itself into a black hole. And so the distance between the ground and an object above it would increase over time, instead of decreasing as we observe it. To counteract this collapse, the ground is forced to accelerate outwards so that the earth remains constant in size.
I confused by questions like “does gravity cause warped time” or “does warped time cause gravity.” It’s like asking do “trees cause forests” or “forests cause trees.”
Trees cause forests because you first need trees to have a forest but you don't need a forest to have a tree. It's a bad analogy but it's good because it shows how most analogies in natural sciences are wrong and do nothing to make things easier to understand.
Actually, both are wrong. It's like saying fevers cause coughs, or coughs cause fevers. Both are effects/symptoms of the real issue: an infection. Matter or energy warping space-time is the cause. Gravity and time dilation are the effects, or the children. You can't say child A caused child B. The cause/creator is the mom.
I'm wondering where is that point where the distance between geodesics begin to grow? Were they really exactly the same before that point, or the difference being so tiny we couldn't measure it before? Thank you! (in reference to the video at ~19:00)
While I respect this channel’s contribution to the subject, I don’t think slamming other channels attempts to contribute WRONG in such an arrogant manner. Particularly due to the simple fact that even this channel’s “ABSOLUTE” is predicated on General Relativity. The entire question stems from the original (GR) breaking down. The person responsible for figuring out how to merge physics into microphysics, where the math complements the subatomic structure of the “microverse” will be responsible for defining the next phase of humanity. This will require people presenting radical ideas and thinking outside the box. The box in this case being general relativity. Dialect needs to remember that everything is wrong until proven correct.
What causes the space to bend into the condensed energy? It's easy to explain gravity by making such an assumption, but to understand the true cause, it would be more interesting to understand the cause of spacetime curvature. And if the the ground has been constantly accelerating up for billions of years relative to space moving down through it, does that mean space is now moving down through the earth at billions of times the speed of light?
You can say that space is falling. But from my understanding of GR, a "falling space" is not accurate. It's just the solid surface on earth keep accelerating upward in its own (local) frame of reference, and when you look at that frame "from afar", it doesn't move. It is important to state that a global frame of reference does not make sense in GR.
@@longhoacaophuc8293 saying the volume between geodesics shrinks to keep the entire planet in the equilibrium stage while every section of the planet is accelerating outward are more accurate.
@@longhoacaophuc8293 My issue with the provided explanation is that it starts by saying the ground is accelerating up, and then it says spacetime curvature opposes it, keeping it from expanding outwards. But what causes the upward acceleration to begin with? I find it makes more sense to start by saying spacetime curvature brings the material of the earth closer together. When the atoms that make up the earth collide, the repelling forces between them start to oppose the spacetime curvature. These repelling forces are what drives the grounds upward acceleration, doesn't this make more sense? (No physics background here, I could be missing lots of stuff x) ) I think starting the explanation with "the ground accelerates up" is a bit counter intuitive.
@@japar107 yes, the pressure caused by the internal interaction from the material that make up the earth is the cause of the net acceleration on the surface since gravity is no longer a force.
The issue I take with Relativity is its inability to explain how gravity is an energy source. I say that because the heat energy released during precipitation isn't like some battery that has stored evaporation heat energy, which is traceable to a conversion of mass into energy like fusion or oxidation. If gravity causes things to accelerate in a way that adds heat, then that additional energy requires the acceleration is kinetic energy being converted into thermal energy. What is implied by that gets into other issues, but I have my own thoughts on what it is on my channel if anyone is curious.
Gravity doesn’t cause things to accelerate. Things accelerate due to their own mass, and gravity responds to that by curving spacetime to compensate. Gravity is just the curvature of spacetime. It can’t cause anything to accelerate. Acceleration is caused by a force. The appearance of gravity causing things to accelerate is a misunderstanding about our own acceleration, when we think we are at rest. We see something in free fall, moving inertially, but we perceive it as accelerating, because we are seeing the differential with our own acceleration, and an optical illusion caused by the misconception that we are at rest.
@@douglasmurdoch7247 I'm fully aware of Relativity's definition of gravity. I have a hard time accepting it. First off, the violation of the conservation of energy that's required for the CMB to remain unaffected by the uneven expansion of spacetime, while all other sources of radiation are redshifted. Second, it can't explain the rotation curve of galaxies without and the lensing of galaxy clusters without leaning onto Dark Matter as a crutch. That, and the intricate structures within galaxies themselves as they aren't basic spirals no more than a smiley face would resemble any one man. Then there's the infamous oil and water relationship that Relativity has with Quantum Mechanics. Furthermore, the superluminal movement of galaxies has to be assumed to be expanding spacetime without any ability to confirm that independently, which would falsify Special Relativity, and open up a can of worms in physics that makes such an assumption desirable. Then there is the acceleration of water molecules moving against the atmosphere during evaporation and precipitation phases due to the effect of gravity that is dissipated as heat. Such heat is not traceable to fusion from the Sun or oxidation from a campfire.
@@Hydroverse I fully agree that dark matter is a crutch. I have a deep seated instinct that dark matter isn’t real, and that it’s a stop-gap to glue together our flawed math.
It's amazing to me people accept "gravity is fake!" as an answer. That's bullshit, it's a real force. It's way more likely gravity is an electromagnetic effect somehow than that Einstein is right about "spacetime curvature."
These RUclipsrs you reference definitely helped my understanding of gravity and the physics of spacetime. And you have also helped shaped my understanding. At this point, my layperson's view of gravity is that it is like a "current" flowing towards the centers of massive bodies. A falling apple is just caught in the "current" towards the Earth's center of mass. Standing on the surface of the Earth is like standing under a waterfall of spacetime and any loose object above you will move towards the center of mass at the rate of the "current" which on Earth is 9.8 m/s2. This helps simply explain how we can be "accelerating" while standing still on the surface of the Earth.
That was my thought before I watched Science Asylum's video and I was happy because that "flowing" spacetime makes no sense to me - where does it go in the center of the mass? That time explanation got rid of all of that, which was great! My explanation for now is the difference in spacetime distortion between two objects. For example, the distortion of earth's spacetime is just "closing" the distortion of an apple, which "accelerates" the apple. Like if you have a ball in a hose and push it forward by compressing the hose behind it. Since it is spacetime itself that is changing, no actual acceleration of the apple takes place. Once the apple hits the ground, the constant pressure against the ground makes it effectively accelerating upwards.
@@Korbin0815 Re. your last sentence. At 9.81 m/s^2 ? Is that where it's coming from? I watched his (Science Asylum) video, back when it came out. I am lost at "the ground goes towards the falling object" explanation but his assumption that there is a time gradient really sounded, for me as a person with biology background, plausible and at least understandable.
@@Korbin0815 could it not just be that the centripetal force of the earth as it rotates through space produces the force we feel as gravity? We’re so small relative to a planet, we’re essentially a spec on the surface. Earth is a rocket ship. It’s accelerating though space in different frames of motion while spinning. Essentially imagine a car with a tennis ball, but then that car driving is inside another huge car that is also driving. It makes sense to me that we’re just being pushed inwards due to how the forces of motion operate, but at a planet, solar system, galactic scale.
12:00 If the ground if rushing upwards to meet the apple, if we drop an apple from two opposite poles of the Earth, then earth will explode since the grounds on the opposite poles is rushing in opposite direction? Or atleast since the Apple does not have much mass, the earth will get stretched\ expanded due to the trying to rush towards the two apples?
amazing video! this is the best video. as you could see, coordinate-free mathematics will be highly required for true research of Gravity. it is really absurd to see how many wrong interpretations have been spread out by pseudo-physics youtubers
@@se7964 : Here we are on a channel that at least claims to have a scientific interest. If that were the case, then personal insults would generally be forbidden. In fact, I regularly experience personal hostility when I express criticism. It seems to be more of a religious community than people who are genuinely interested in science. The author of this channel is waging a campaign against the understanding of special relativity. His ideas about it are simply not accurate. Apparently he doesn't even understand what an inertial system actually is. In this respect, I actually can't take his well-crafted videos seriously and you should also be a little more critical.
the issue of GR is just how hard to visualize it without simplifying it to the point where you end up not understanding what you are trying to do anymore.
Yet we can easily visualize many God entities and their intentions, their thoughts and desires toward us and the world... ( the hubris in those religious preachers heh, 'believing in something you don't understand isn't the problem, the problem is to be Sure to understand about something you don't know ;) The real issue is simply failing to understand the easy basics and as long as we won't understand them, we will be like those kids who wonder about something so far away in their mind and mystically incomprehensible while you are just explaining them simple addition. We are mystified by General Relativity like those kids are mystified by additions.
After all that build up I was waiting for what the correct explanation is and all I got is “you are accelerating towards the apple”. That explains less than any of the other videos. Its about equally useful to saying “gravity makes objects accelerate downwards” Why am I accelerating towards the apple? What causes that? Curvature? Well why would curvature cause that? (Unless there is a force involved?) and what causes such a force? I started questioning myself if I stumbled on flat earther youtube. Also ends with “granted, this is a very abbreviated explanation”. Which is what you just accused the others of doing.
Devil's advocate: the reason you would be accelerating towards the apple is the same reason that the pieces of an object accelerate away from the center of the object: the normal force, caused by the fact that matter can't be less than a given distance away from itself (which in turn is cause by the other 3 fundamental forces). This, however, leaves the central question unanswered: why does spacetime curve towards mass?
What is the “shortest path between coordinate grids”? 15:01 the world line on the Spacetine diagram will be curved if the object wants to take the shortest path between coordinate grids.
Brilliant. Not sure I get even 50% of it but my intuition maybe gets another 40% or so... the last 10% I reserve for healthy skepticism in case some part of this excellent video isn't quite right. I too very much appreciate the work that it took to sort out the complicated RUclips science pedagogy mess and present it in such clear, graphic terms. Does anyone know if the Veritasium video "Why Gravity is Not a Force" gets it right, or at least more correctly, like this one here? In any case, this is fantastic investigative science journalism. Many thanks!
Well done, except no one is right. This kind of videos are all metaphors for the real thing, you can't really explain to someone a coordinate transformation and so on in a single video, I believe the less you actually dive in theory and maths of the models, less accurate is your analogy. Folks from Scienceclic did the same analogy, but with a whole series on GR an even that is incomplete. Lay people won't leave any of these videos with a degree, they have their purpose on motivating a spread of science to uninvolved people. The only way to really grasp what is gravity is from a "full" course (with real math), like Eigenchris' series on tensors (algebra+calculus) and general relativity, or a book, like Gravitation from Misner, Wheeler and Thorne, or maybe the hardest way, going to an university
Then you get lost in the math / MODELS and don't even pay attention to physical reality. Our universe does not have 4 dimensions. It doesn't have curved space. Those are observed facts.
@@paulthomas963 the problem is that "reality" is just a layer of existence, our models compile a set of phenomenology in a way that is understandable and workable to us. Math is a language taylored to try to code nature's observable (or possible) behavior, many times proven right, some times proven wrong, what really matters is if a mathematical code happens to be numerically right (at least to 95% confidence) and mostly conceptually coherent within itself and other areas of Physics. To that point, light might behave like waves in a puddle or little pebbles throw at each other, it can also change frequency or bend in vacuum as if there is refractive media there, so choose your favorite mathematical narrative and defend it with actual research using it. I think that somewhere along the path perceptions change and models adapt.
PBS Spacetime is known for stating a positive for the title. Part of their style to assume the affirmative, while always adding the nuance. I consider this video to be a bit of a cheap shot. Especially knowing there's a Nobel Prize waiting for you if you're able to connect the dots on the actual nature of gravity, I think it's good to stay highly sceptical of people posing an absolute truth claim, without the nuance other channels might add.
12:00 So if the Moon moves in space around the speed of the Earth, it should have the same gravity? And the apple on the side of the Earth, that looks the opposite direction from the Earth's movement should not fall down, but up?
Interesting to say the earth is moving up to meet the apple, however that can't be right because what if we had 2 apples falling, from opposite ends of the Earth eg North and South. This implies the Earth stretches. In reality different objects accelerate in various directions at the same time. The general relativity explanations work when look at one object but seems to fail for multiple objects at the same time in different locations. Also one of the principles of relativity is invariance so it should not matter which frame of reference you are observing from. So equally the apple is considered as falling to Earth. General relativity still fails to explain the true cause of gravity. It is just a series of paths that are followed - but why exactly, what makes it that way? It's like space is a set of rail tracks and masses must follow that track, why?
@@Nygaard2 The problem is when you try to be very clever and you produce a very confusing argument (like this video). General relativity is based in tensors and differential calculus, that are quite difficult to explain in layman words. In reality the explanation given by those other channels, explaining the time dilation, etc, is just a simplification, an analogy so people can understand the basics. And I don't think it's a bad analogy. The equations Einstein wrote relates the presence on matter (actually something more general described in the energy-stress tensor) with the local geometry of Space-Time, there is no a single parameter called gravity in the whole system of equations. The only thing you can argue is that the curvature of space-time is the cause of the phenomenon that Newton described as the force of Gravity, but that's it. Only "one part" of this distortion of the space-time is felt a dilation of the time measured by a clock following a "free movement" trajectory, that is the base for the explanation used in those videos the author doesn't like. And to answer the question, one analogy that is sometimes useful is thinking of space-time like a body of water, and instead of a mass, you have a sink in this body of water. Around the sink the liquid moves toward the sink, pulling everything suspended with it. Stuff suspended in the liquid, lets say little wooden beads, that don't move with respect the liquid are equivalent to inertial systems, and don't feel any "gravity force". Beads that move with respect of their surrounding water are like objects accelerating in real space, and "feel" forces. Indeed, the water around will try to stop them. If you put some strainer around the sink that stops the beads, the beads will feel a force pushing them against the strainer, the strainer would be the analogy of a planet surface, and the force the beads feel is an analogy of the gravity force. In this analogy the beads at the strainer surface are accelerating, because they do not move at the speed of the surrounding water, so the strainer surface, although stationary, is also accelerating!, but going nowhere because is the water what is moving. When they say the surface of the earth is accelerating is in a similar sense of the strainer, but the thing that is "moving" is not water, but space-time. Well, this is just an analogy, useful for visualizing the concepts, but that is it, for the rest, you need the equations. I hope my clumsy explanation has helped.
I liked your video. 1) why: because you spoke slowly allowing me to sort and comprehend each point. I still prefer reading as I can take as long as I need to comprehend each point. An appeal to Authority fallacy is always possible. That’s why complicated ideas are built up one by one. Sometimes, initial ideas are not entirely correct, but more like observations with more and more details added. For example, Newtonian physics isn’t wrong. It works perfectly well in many cases. What Einstein did was to refine it through a more detailed, and different point of view. The maths ARE the physics. Our words and diagrams are only representations of the Maths. For example, music. The notes on the paper are equivalent to the math. They ARE the music. What we hear is an interpretation of of the notes, which are not perfect. There is always difficulties with trying to explain complex ideas with words, written or spoken. Our brains evolved to survive nature. Not to accurately perceive it. Anyone reading this should be familiar with the concept. That is why we can visualize 3D objects but not 4D, 5D......etc. our brains have not evolved to do so. But the maths enable us to accurately describe any n- dimentional object. As we have seen through this video, even with educated people trying to explain phenomena, there are differences. Knowing this, we should see how less educated people fall for ideas such as the Earth is flat. They don’t have the requisite knowledge, and critical thinking skills to even comprehend their mistakes. I like the vast majority are always victims of Dunning-Kruger. Perhaps even Ed Whitten is....
I would argue that if you think that notes on the paper are the music then you have done very little music. Notes are a handy tool to describe music but they are NOT the music. If they were then every performance by every performer would be the same and that just isn't true. If the problem is that people get caught up in simplifications and mistaking them for the real thing then you are not to that effect either.
Those videos you mention had been very puzzling to me for a long time. I'm a nuclear engineer, not a physicist, but I have studied enough of General relativity (granted, a long time ago!) to doubt these explanations. What had me questioning this is that the internal forces that would leave the squirrel unchanged should be on the same order of magnitude as the gravity, i.e. not small and actually measurable, which is not the case. Indeed, the phenomenon they are describing is spaghettification, the effect of which is not overall movement but dismantling of the body. It appears in intense gravitational force gradients, such as the one encountered at the horizon of a black hole, not on Earth. I think the confusion comes from an oversimplification of the equivalence principle. What it states is that for an observer with a constant acceleration in outer space (curved trajectory in a flat spacetime) everything outside behaves as for a free falling observer in a gravitational field (straight trajectory in a curved spacetime). What this really means is that the effect of gravity is homogeneous to acceleration, i.e. it can be expressed as a second order derivative of the metrics, i.e. gravity is curvature. But those two situations are really different, as spacetime curvature due to gravity is observer independent and free fall referential is inertial, whereas an accelerating referential is by definition not inertial. What happens to both experimenters is of very different nature.
You need to read An Engineering Model of Quantum Gravity. Then you might understand that gravity, time dilation, length contraction, and space-time curvature are all observables resulting from the damping of the quantum harmonic oscillations that make up matter, not space-time, due to the local mass/energy density "in the way". Time is what is measured with a clock. Space is what is measured with a ruler. These tools are variables in the quantum vacuum.
So, if one were plopped outside of space-time (and no other phenomena occurred), one would expand (explode) because there is no space-time to counter (annihilate) the mass' outward acceleration?
All those other videos are analogies, just as GR is a mathematical analogy - nothing wrong with that as far as the average Joe is concerned. But your analogy is actually misleading and flat out wrong while pretending to be above the rest. Bottom line, I have not seen one person who understands gravity on a fundamental level; and maths is not understanding if you cannot explain it to a barmaid. Everybody knows that GR is incomplete, hence one should not think of it as the final word but a challenge to build on it.
I'm all for hearing another equivalent explanation, but you mostly provided an exercise in semantics. I was never confused by what you call "gravity" vs "apparent gravitational attraction." On the other hand, you did get me to watch your entire video, so maybe you win.
If the entire Earth is accelerating to meet falling objects, then why doesn't the Earth develop a measurable change in its size? His point doesn't make any sense.
@@carultch If I remember correctly, he was fuzzy there. Something about the curve being exactly shaped to hold Earth together. However, gravity is equivalent to acceleration (roughly speaking). Earth is accelerating, often imperceptibly, towards objects, but also towards its own center. It is definitely accelerating towards the Sun, but keeps missing. :-) Many forces, or accelerations, cancel out.
@@carultch Publisher of this video is kind of just semantically gaslighting everyone, I agree. Ultimately, he is speaking about observational orientation in the fourth dimension. Like, if we could step out of our dimensionality to observe what is happening in the fourth, this is what we would see... So in terms of a simpler explanation, it's absolutely not. Seeing as he spends half his time trying to use the failed analogies he argues fall flat, to explain his reorientation for it to not stick in anyone's mind. In terms of it being more correct... that has no merit in a system created to be "relative" to the specific observer being invoked. His arguments about not being gentle to children with information they have no conceptual framework for handling, is whatever you want to interpret it as. I know how I do...
@@Robert_McGarry_Poems I feel like the publisher of the video could do a better job with explaining what he means by "acceleration". Most of us learn this term as a kinematics concept, which is clearly different than what he has in mind. What he seems to have in mind as his meaning of the word "acceleration" is the net non-gravitational force per unit mass. So in the simple case of an apple in a tree, that's the tension in its stem divided by its mass. How this is a kind of acceleration, is something he could do a better job of explaining.
@@carultch I very much agree. Language is even more complex than GR, or we couldn't use it to explain GR. Having that said, he switches between conventions as a matter of fact, as opposed to... As my teachers used to say, showing his work. That is, unfortunately, not great. Conventions allow us to use the insights of those whose shoulders we stand on. If we go mixing and matching parts of random conventions together, I want to see the translation... Otherwise, how do we know what rigor might actual exist in any alleged insights?
Outstanding!!! I have seen all the RUclipsrs shown in this video. They trace the misconception back to Edward Current! I remember when he first uploaded that video and was blown away at how I could finally understand (misunderstand) what gravity really was.
It's easy to see those youtubers are not that wrong: free falling objects follow geodesics, then you just look at the geodesic equation and see which factors influence it the most near a slow massive object, you find it's the time gradient in the metric tensor. The rest is pure geometry.
My understanding from the other videos is that we are constantly moving at the speed of light through space time, the majority of that movement is through time as the speed we move through space is very slow. Mass bends space time & its these geodesics that cause gravity. I'm definitely more confused after this video.
@pyropulse you are using the word "speed colloquially". Speed through time is not dx/dt. It's a ratio between time and proper time. "Do you feel like you are moving the speed of light" is the type of argument a flat earther would use.
Noooooooooooooooooo. Moving at the speed of light? Dude, are you on a new stuff in market(don't take it as offensive). 😂 We are definitely not moving at the speed of light. Anything with mass needs infinite amount of energy to be accelerated at the speed of light.
@@TheKingBeyondEverything bro, it's C through time, not space over time. Your Worldline is a 4-vector that has a conserved speed through spacetime. The colloquial speed of light is a 3-vector that is a quotient of space over time.
@23:30 Where does space go? Space is visually represented as moving inward toward the center of a gravitational mass, so what happens to space when it gets to that center? @dialectphilosophy
But the more you live, the more you learn you have even more opportunities to be wrong then you previously thought ;) Einstein : As our circle of knowledge expands, so does the circumference of darkness surrounding it
15:41 thank you for posting this video. The subject matter to a certain portion of us out here :-) never gets tiring… I do have to agree with some of the comments as I have read them; it would help tremendously in your presentation to be mindful of conjecture. Everything is theory until proven . As an example, regardless of what your degree path is, we all have to take the arts, so I had to take an English literature class, which was being conducted by a gentleman who had gotten his doctorate interpreting Shakespeare . On the very first day of class, he would pull lines from the plays, and tell us precisely what Shakespeare meant; point being if you did not agree with him, you were not going to pass his class, and that was rather obvious and I quit that first day. the information you have presented is fascinating, and very informative, but to postulate that you are right and everyone else is wrong betrays true science. From a Laymans perspective, for example, one has to immediately conclude from your argument that gravity is a constant. the way gravity behaves does indeed suggest your interpretations but if we know that gravity varies, depending upon mass that would have to appear that objects would therefore overtake each other depending on mass. Again, from a Laymans perspective in order for your theorem to be functional one can only conclude that space, and time are expanding at the same rate.
No offense, but saying something like "Everything is theory until proven" is truly cringy and only reveals you don't have a rudimentary understanding of how Science really works (don't worry, neither do many "scientists"). There is NO SUCH THING as "scientific proof"! Proofs only exist within the domains of Mathematics and Logic, in closed systems in which all variables are known (which is NEVER the case in Science). You can only ever DISprove a theory, never prove one. A theory is nothing more than a more or less plausible (and incomplete) EXPLANATION of observed phenomena that can only ever be replaced by a more strongly supported theory. It is exceedingly ignorant to employ the false reference to "scientific proof", and it is this very misuse of language (the mind shaper) that contributes to people being so confused about such matters.
12:00 If we are accelerating and we reach the falling object in space, and acceleration has to have a direction as well. So 180 degrees apart, when two objects fall in the opposite sides of Earth, how are we accelerating simultaneously to both of them? I know you can answer this but point is each video I see in youtube about gravity confuses me more than earlier, though I get some additional information each time.
Relativity is based on acceleration. These so-called scientists are either parrots mimicking what they are told or outright charlatans peddling the physics of a fake universe. And they have the nerve to degrade flat Earthers. You relativists need to take a look at your own physics before you criticize someone else's.
Why can't gravity be a force similar to buoyancy? In water, a balloon released under water is repelled upwards with a force that is dependant on how much water it displaces. (the bigger the balloon, the more water is displaced.)This happens because air is less dense than water. Why couldn't the same (or opposite) principle be applied to space? Mass displaces empty space, which somehow disrupts the equilibrium. This somehow causes mass to attract other mass with less density.
_"This happens because air is less dense than water. Why couldn't the same (or opposite) principle be applied to space?"_ Because there is more of a gravity source for water to be pushed to the center of the earth than the air that weighs a lot less to be pushed to the center of the earth. _"Why couldn't the same (or opposite) principle be applied to space? "_ Because there is no earth out in space.
Interesting stuff. I've been thinking about the topic for a long time and had questions about the time curving to velocity claims. So space is flowing into mass?
Flow=gradient If something goes from not flowing, to flowing, then the concentration of that something must change. I.e. it's instantaneous density. Whether or not that resembles mass density is another topic all together. But, you can't make an argument about flow without the consequences of that flow. An equivalent statement to pressure can be made about how gradient density causes what can be perceived as motion along that flow. Or, relatively speaking, from the point of view of inanimate objects like particles, the cause of inertial acceleration. I'm confused on how this is considered two different things...
@@Robert_McGarry_Poems I've kind of worked through the fact that flow is not really feasible based on the fact that what we see is not a flow into a gravity well but rather an acceleration. But evidently the Schrodinger equation says that there is a contraction of space and time as one approaches a BH. It appears that space expands where there a low quantity of mass/energy and contracts in inverse circumstances. I find spacetime to be a fascinating topic and suspect there's a lot there that we're not seeing.
@@Eric-Marsh it's all relative to the question you are asking, what reference frame, and therefore framework answers the question best for your given instantaneous moment in spacetime. But you still need to build a sharable convention for translating that to other people. 😊 Cheers.
Yes it flows and "accelerates" due to the inverse square law in a gradient. Earth's surface it flows in at 9.8mps²^ that for 6.000km from the centre of earth, 12.000km from the earth's centre gravity is quarter'd due to the inverse square law so it's 2.7mps²^. And everything in-between and beyond is in a gradient. It doesn't move twitchy like an old Pac-Man arcade game, it's goes in smoothly hence we use the word flow.
Ok now I am REALLY confused about this whole idea of space time, gravity, relativity. Specially after reading some of the comments below to try to get a better grip on this. I'm an Electrical Engineer by training and always thought I was fairly intelligent. I also try to be a lifetime learner. But this just blows everything I thought I new into deep space and I am now a blithering idiot. Thanks for all to trying to explain it from your point of view in the video and responses, but at times it appears to be a pissing contest to be blunt. It makes no sense to me that the earth is accelerating up to an apple "falling". So if two apples are "falling" from opposite hemispheres then the earth should split in half and move towards the apple in my mind. Do this simultaneously all over the sphere of the earth with "falling" apples and the earth explodes. YES I do NOT get the explanation here. Not say its wrong cause I'm NOT a physicist and only studied under grad physics.
Network Engineer checking in; Im in a similar boat to you Tim. Unfortunately, I don't think this video or the comments are going to give us the answers we desire because, as you aptly said, there is a pissing contest going on. It seems that no matter where you look, no one can agree 100% (let alone 50%) on this topic which tells me that there's more to this than any of us know.
I like to think about it like space time is "falling" into the center of the mass and in doing so it drags down whatever is not subjected to any other force.
@@107thFruit Yep I had thought that both objects were attracted to each others mass, with each "moving" proportionally award the other. Ie for all piratical purposes the earth doesn't move. So sounds like a bunch of Post Hole Diggers arguing.
To clear your mind from all this Einstein mess, you will have two Come back to Poincaré wisdom that stated since 1885, alike Kant, that nor "Space" nor "Time" are physical observable. What could be thoughts as observable is thé "distance" for instance between two objects. But not even, since the way to measure such thing IS by using a spectromètre that gives you SPECTRAL RAYS DATA. That is the only certainty WE have : SPECTRA. The rest is theoric CONVENTIONAL reconstruction of what could explain such SPECTRA. And IS what we call MODELS. There is several. Curved metric as in GR is not the only one, nor even the best. Not even correct... Thus a clear step forward out of this Einstein mess of entengled confusions, is to upgrade to SPECTRAL GEOMETRY developed by Alain Connes and GEOMETRIC ALGEBRA developped by Hamilton, Grassman, Clifford, Hestenes. These are général frame works in which the hall picture of facts, not arbitrary asumptions and ungrounded dogmas, can be more clearly unified in order to clear this century mess
I think you are missing the fact that they are performing a perfectly legitimate Lorentz transformation to show that the curvature of spacetime (not perceivable to the standard observer) is what causes the effect we attribute to gravity, and if you combine that with Quantum Field Theory you have the reconciliation of Relativity and Quantum Physics. I also was wondering, when you are talking about the ground accelerating upward and engaging the SR equivalence principle, the there wasn't going to be a flat earth reference in there. It's perfectly acceptable to have your inertial frame of reference where the universe distorts because of your velocity. That's what special RELATIVITY is.
I think we shouldn't point fingers at other people being wrong, provocatively. We all need to contribute by referencing thoroughly and remember to link to full publications. In the 45 years since I've been around, there have been a lot of conflicting viewpoints, but until there is some kind of overwhelming agreement, everyone's contributions should be appreciated and argued professionally. I do like the arguments posed here. The 2-way speed of light assumption argument about moving references and the speed of 1-way light being different that than the reverse speed at the same reference speed, really opened my ideas. Thanks for the discussion.
Someone complains about the trashing other videos in this one about true nature of gravity. If Dialect didn't do so, I wouldn't be able to make a comparison by myself. It would be just another brilliant explanation among many. But who is right then? Sometimes it's necessary to point out where others are wrong. It's a huge help. I had watched all the videos mentioned in here, and I felt very confused at the time. This one helped me to understand. Who cares about not being "p.c." if it's for a good cause.
This is a very good video. I would add that a bit more explanation that gives an intuitive understanding of what "upward acceleration at the surface of the Earth really is" would be good. The "curved space" description at the end is adequate for someone who has already studied GR a bit, but is probably impossible to understand if you have had no physics beyond SR. To be fair, I'm still trying to figure out what this explanation would entail so this is not a criticism...it's more a request.
You're completely right and your feedback is definitely appreciated. We really struggled with what to include in this video; we knew the main bulk of it needed to debunk the bad physics in the other videos, but unfortunately that didn't leave much time for the more accurate explanations. We will be addressing these ideas more in our upcoming videos though, so stay tuned!
What I also find a bit strange is that among my hundreds of posts a month here or on Facebook, I sometimes only get one thumbs up. Have you all become puppets because you are all not allowed to comment on the fifth dimension???
Because you released a follow-up, YT started promoting this one again. Nice. Now, at 12:55, I have thought about that for quite some time. However, if the apple falling shouldn't see the time gradient, how come GPS satellites experience a quantifiable time dilation? They are also in free fall, right? Also, Kip Thorne himself calculated the time ratio between the ship and the planet in Interstellar, when around the BH. Aren't all these orbits equivalent? Thanks
Gravity: Imagine a sheet called space moving through a 4th dimension where the 4th dimension was called time. The fabric’s direction of travel is from a place we call the past to a place we call the future. The surface of the sheet is what we will call the present. This 4th dimension is not the same as our ordinary experience of time but is related to it. If you put a lead ball on the moving fabric the ball would resist the movement so as to cause the fabric to deform. The ball and the fabric pushing the ball would lag behind the rest of the fabric. According to our definitions, the ball could be said to be in the past. If another ball were put on the fabric it would deform the fabric too. If the two balls were close together they would approach. The balls would seem to be attracted to one another but in reality, the same place is moving toward the both of them. When you fall the Earth is moving toward you.
You know what this was probably the most informative thing of this whole video, and comment section on gravitational curvature.You just opened my mind to visualise the bending of a space time curvature.
"When you fall the Earth is moving toward you" Then answer me this. Every country(plus 2 jumpers on the poles) on Earth places one of their citizens to do a skyjump. They all get to their planes and when they are at, let's say 10 000 ft. They check their watches, and then, exactly at the same time all the skydivers around the world jump off their planes. Towards which jumper the Earth moves?
@@nudestoteles The Earth is moving toward all of them at the same rate but it is only moving toward them in the fourth dimension. Think of a water glass moving through space. There are stationary marbles around the rim of the glass. Because the glass is moving past the marbles the bottom of the glass is moving toward all of them at once. From a two-dimensional standpoint, the marbles are opposite one another but from a three-dimensional standpoint, they are all in a line. In the same way, the jumpers are opposite one another from a three-dimensional standpoint but from a four-dimensional standpoint, they are all in a line. The center of gravity of the Earth is the bottom of the glass. The center of gravity is the furthest back in time and is moving toward all the jumpers at the same rate. The closer the jumpers are to the center of gravity the further back in time they are.
Instantaneous moments sliced up into infinitesimal branes which flow together creating our perception of a 3+1 spacetime. But what, other than our convention to label it that way out of convenience, causes the smoothe interaction of these branes from one instant to the next? What, if not our failed observationally built model of entropy driven thermodynamics, is that fourth dimension people are so quick to invoke but never define? Kind of like a gradient or a flow of density. Almost as if language is recursive and we need to agree on the relative starting point of the labeling to be in convention with one another. Almost as if starting your explanation with a holographic simplification, and then switching convention mid step to 4D talk is bad language form. Logarithmically speaking, base and order are pretty important concepts.
maybe, are you trying to stir up controversy(for clicks) where it's a bit fuzzy? I don't know that your explanation was more edifying than the others, since you're both using abstract visualizations to represent these ideas. It seemed more like a dig at the other channels rather than just trying to communicate science effectively.its okay to have a desire for your pedagogy to be integrated with the mainstream but you honestly seem hositile. You explained it differently but we still don't really know that's the "best explanation." I'd rather see an experiment to demonstrate the concept than a visualization to become convinced. I'm not sure you're doing any more good than the other videos, except at stirring up contempt. If you really want me to agree with you you should try and contact those other channels and get them to address your concerns, maybe they will agree with you if you make a persuasive argument?
Interestingly enough, we wrote to each channel featured in this video weeks before we put it out. Very politely and in a non-crackpotty way we put forward our case, and asked if those channels would give us a comment/response/rebuttal or further clarification for our video. None of them did. Only Eugene responded to us, and only after the video came out, but he declined to clarify his explanation any further. (You can see his answer in the comments). This video was intended for an advanced audience; we didn't expect it to go as viral as it did. The layperson's explanation is given in our follow-up "The Sky is Falling Up" which we'd recommend you watching if you have confusions still.
@@dialectphilosophy I think you did a well enough job showing that it is mistaken to simplify apparent gravitational attraction as being caused by time dilation. However the video spent an inordinate amount of time dunking on the other creators ; whereas the alternative explanation of apparent gravitational attraction given at the end of the video felt rushed and incomplete. Your perspective on general relativity and the explanations of the metric tensor have been excellent, and even the explanation of time dilation not being the cause of apparent gravitational attraction was very clear. This video was a bit of a low point in the overall momentum of the channels explanations on this topic. Im watching all your videos in order, so i am excited to see the direction you take in future videos from this one.
I agree that the tone was off-putting and somewhat hostile , and i agree that the alternative explanation given at the end was lackluster. That being said its pretty clear that the general point of these videos he mentioned-that time dilation CAUSES apparent gravitational attraction-is based upon a misinterpretation of the geodesics. Whats telling is that technically none of these videos are well backed by recent scientific papers and are basically reinventing the wheel by recapitulating stuff from the days of Newton , Mach , and Einstein. String theory is pretty silly oftentimes, but all five of these videos had extremely non-useful explanations of gravity. Thankfully most people don’t actually have to “use” gravity or gravitational effects in their day to day life, making it fairly harmless popular science. Additionally, very few people talk about it, but observational phenomenon that are agreed upon by physicists can nevertheless have competing philosophical interpretations as to the meaning of these observations without technically violating any of these observations. I see Dialect as a channel that is more focused on providing alternative interpretations to the accepted math of general relativity. So long as an interpretation doesn’t violate the observations of the phenomena, it is technically speaking philosophically valid and potentially “more accurate” than other interpretations. As you mentioned it would be interesting to see some sort of experiment designed to elucidate any physical differences between these explanations-for example, an experiment that confirms observationally that time dilation is a second order effect rather than a first order cause.
23:41 "because every single mass in the universe is literally accelerating towards every single mass" even distance galaxies? so can we just assume the Hubble Constant(the rate of the expansion of the universe) is just the true gravity(the curvature of space) over powering the acceleration of local frames or reference?
Good news: the follow-ups to this video hav arrived! Still confused about how the ground can be accelerating up? We now take a deeper look into this concept in our new videos, "The Sky Is Falling Up" and "The River Model of General Relativity". Check them out!
There's nothing "confusing" about it.
Is only as confusing as learning a rectilinear uniform motion undergoing an opposing friction force is also "accelerating" in classical mechanics.
The surface of the planet is accelerating (when we choose a certain frame of reference) because is impeded to follow a geodesic in the 4d spacetime manifold going to the center of Earth. ¯\_(ツ)_/¯
You are the confused one @Dialect.
And Veritasium explains it beautifully (and even shows you the equation to understand that your acceleration is merely to keep you in place as it cancels out the curvature of spacetime that would lead your geodesic straight down to meet the center of Earth)
Around mark 8:50 ruclips.net/video/XRr1kaXKBsU/видео.html
I've known this was true for 10 years, but nobody has put it to words for me. I love you, man. Thank you for explaining everything. Can you go through the math in another video, please?
Isn't this argument circular? If gravity causes time dilation, doesn't the whole argument assume gravity exists, that it causes time dilation, and then time dilation causes gravity? Or to put it another way, why not assume gravity causes gravitational attraction without the added step of time dilation in between?
If two apples fall simultaneously from opposing trees one each on the other end of the diameter of the earth, your video does not make sense.
Hey Dialect, I made a video myself on general relativity recently (most recent video on my channel) and if you have time I’d like to know your thoughts on it. I don’t want to be spreading misinformation so if there’s something wrong in my video I’d like to be able to correct it - thank you!
This kind of response is an all-too-common response that science communicators receive from scientists. You _think_ your issue with my video (and other similar videos) is that the physics is wrong, but that's not the case. You're just offended by an approximation/analogy I used because it ignores some detail that you _personally_ feel is vital to the topic.
When you're a science communicator, you have to consider your audience. Where are they currently in their understanding of the topic? What ideas are they going to accept or immediately reject? A fully detailed explanation of general relativity is going to be pretty abstract and full of jargon, which is unapproachable for most viewers. Teaching is the art of knowing exactly what details you can leave out while still communicating the topic.
I'll admit that if you leave out too much or make it seem like nothing is missing, then you're just wrong. However, if you watch the cold open of my video, I clearly stated I was about to explain the gravity humans experience here on Earth. In jargon terms, that's the weak-field approximation. I'm saying the analogy I'm about to use is limited. It's not meant to give someone a deeply detailed understanding of gravity. It's just meant to take them a little outside their comfort zone and give them an idea of how spacetime can cause the motion that non-physicists attribute to gravity. By using the weak-field approximation, it allowed me to ignore space and focus on time. The fluid analogy then makes the idea of time more tangible and familiar. Things like approximations and analogies are perfectly fine as long as you're open about it.
The other issue is language. Are the words I use in my videos following the strictest scientific definitions of those words? Absolute not. In fact, if I'm going to use a strict scientific definition, I usually make a point to explain that strict definition within the video. Otherwise, I'm likely using a more common definition for that word. In the video you're referencing, I'll admit I'm pretty lax with my use of words like "gravity" and "curvature."
Again though, I wasn't teaching an upper-level physics course on GR. I made an educational video for a general audience. Saying I'm "100% unequivocally wrong" or "all wrong on all counts" is too harsh. I just took some educational liberties you don't like. Personally, the "ground is accelerating upward" explanation bothers _me._ Is that explanation mathematically true? Kind of, depending on your definition of acceleration, but I also wouldn't say it's "100% unequivocally wrong" because that's too harsh. Different explanations make sense to different people. We're all trying to educate here. You don't have to be so divisive.
As someone watching this back and forth that is trying to get an actual understanding of GR, do you have any resources you can point to that don't take educational liberties in trying to explain how GR works? If it's one of those situations where you can only truly understand the theory if you understand the math and that requires a 10 hour lecture to understand, then I'm fine with that.
Thank You for responding here. The explanation you gave left me with questions, pointing me in directions I could work with. This did much the same, but left me disoriented and less likely to follow my questions. I am less interested in things I need to grasp all at once. I build a frame and use that frame to add new understanding to, even when that requires some reorganizing backward sometimes. He did nt seem interested in my learning about the reasons for the puzzles he put out. You do not do that. T.Y.
Excellent response and very classy, Nick!
@@amentrison2794 The actual papers from Einstein are still publicly available and in English translation, and his thought experiments are for a general audience.
Some people learn better from textbooks. Nick has one, and the Gravitation textbook from Misner, Thorne, and Wheeler is usually considered the gold standard for GR.
There's also the GR lectures at Stanford from Leonard Susskind available on RUclips. He has a detailed explanation of the Equivalence Principle and how to distinguish uniform gravitational field (accelerated frames of reference) from spacetime curvature and tidal forces.
Regardless, it's going to take years to learn Newtonian Mechanics and General Relativity and just be at an elementary level of understanding. It's worth the time because you'll have a new level of respect for Isaac Newton and Albert Einstein. It will make understand why physicist call it "the most beautiful theory in science."
Make another video on general relativity that clears everything without any approximation no matter general audience understand it or not.
You quoted and showed animations from my video, but what you didn't mention is that my video also included statements such as "This visualization does not accurately represent the full picture, since a point particle of zero volume would still follow the exact same path." With regards to where I got the idea for my visualization, this did not come from any other RUclipsr, but from Einstein's Field Equations. I have another video explaining the mathematics of Einstein's Field Equations, which is what one needs in order to get the full picture. (Your video doesn't explain the full picture either.)
@@ytdpaul well I am actually reading a book on general relativity, what about you?
There is a difference between the Newtonian limit and black holes, I agree. But what are you talking about earth accelerating outwards? Where did you read that? The only variable on earth gravitational field is time, not space curvature
Smh? What's wrong with you are you Einstein himself?
I correct myself: I agree with most you are saying now, but do not agree on dismissing the Newtonian perspective as irrelevant
Hey Eugene, thanks for watching. One might wonder, if your visualization didn't "accurately represent the full picture" why you would have shared it in the first place, or why you are unable to explain to any of us what exactly the "full picture is". Of course, the truth is that your video isn't even a partial picture of what is correct; it is simply a wrong picture.
As ScienceClic, Veritasium, and others have already done videos about, the traditional notion of a gravitational field is a fictitious one, a relic of being in an accelerated frame of reference. It is the tidal forces (spacetime curvature) which are truly responsible for the attraction between bodies, and your interpretation of time-dilation as a significant causal agent is a misinterpretation of the first-order approximation of the theory, in which the potential gradient of a uniform gravitational field is associated with the time-dilation gradient. But this is nothing more than restatement of the fact that a uniform gravitational field is an accelerating frame of reference.
Of course, we understand that from your likewise deeply-flawed twin paradox video that you have not yet grasped the distinction between general covariance and the general principle of relativity, and so you still likely believe that acceleration and gravitational fields are interchangeable, "relative" phenomena. Unfortunately, it is enough to look at the observer-independency of the four-acceleration to know that this is not the case, moreover since apparent gravitational fields can be made to vanish instantaneously, they stand clearly in violation of the principle of local action and cannot be regarded as "real". Our next video in this series will treat more on the topic. We're sure you'll stay tuned.
@@Robinson8491 Maybe you should read your textbook a little more thoroughly before jumping to conclusions. He’s saying that the four-velocity of objects without proper acceleration will have only a time component in its four-velocity IN ITS OWN FRAME. However, the four velocity of the object in the other frames can have components of space and time mixed. But these are coordinative space and time - which is the whole point Dialect is making. These other channels don’t understand the difference between proper and coordinative time and space. The metric of a locally free-falling object doesn’t differ from a Minkowskian metric - they’re locally equivalent, that’s the whole equivalence principle. It only differs in how you express the coordinates, but that’s observer dependent. Either you read Rovelli wrong or he was imprecise enough as to leave out the necessary qualification that the components of the metric will change dependent on the observer.
@@se7964 he uses the earth as example. This is misleading, as only time is a variable here. Then talk about black holes (or mercury) instead if you want to be correct, or am I misunderstanding the situation here?
Also you speak of others frame of reference where time and space curvature in the four-vector in acceleration is of an issue: but isn't this Special Relativity you're talking about and not General Relativity? They are seperate situations. Would love to hear your comment
@@Robinson8491 read the ScienceClic comment pinned at the top. He explains it perfectly. Rovelli is misinterpreting a first order approximation.
I wish Einstein was still alive and had his own RUclips channel to clear this all up.
To be fucking real.
He already commented
"Since the mathematicians have invaded the theory of relativity, I do not understand it myself anymore."
Don't you worry. There will be a new Theory of Relativity soon in the market, replacing Einsteins Relativity. (Either in 2022 or in 2023)
What did Einstein say when 100 physicists joined to disprove his Theory of Relativity?
.. "Why hundred, if I'm wrong, one is enough"
he couldn't@ died in darkness. In 1952 he rejected his own (false) 1918 article (in his friend R.Schlegel's books) although he "smelled" the problem without knowing the answer - a quite simple for the REv.Philophers, semantic realists. Sorry, u will not find the answering textbooks and youtube.ps.the key problem: Ein.The theory is a field theory,then...use your Holy Spirit in u have it]
PhD physicist here. I am not exaggerating when I say that I don't understand 90% of the popsci videos/articles about physics, of topics I have a good grasp of. I just don't understand what they mean and oftentimes, it sounds like gibberish to me. I can't imagine what the layperson understands from them. It's probably worse than not understanding. No wonder we have so many misconceptions about science going around.
Modern science has gotten themselves hopelessly loss in the realm of nonsensical mathematics. That's why the lay person doesn't understand physics. I was watching a few of Sabine's videos on RUclips. I thought she was a fence sitter when it came to understanding the nonsensical nature of relativity. Nope. She talked about clocks but never once explained that clocks are instruments specifically designed to measure acceleration in space. The cesium-133 atom is chilled to absolute zero (cryostasis) and shielded from electromagnetic interference.(UV rays cause premature skin aging). Is the observer afforded the same environmental conditions? Then she discussed the twins journey in the Twin Paradox. Not once was it mentioned that an astronaut's heart rate is in an accelerated state during lift-off and returns to normal in zero gravity. Not once in all of these Twin Paradox videos is that simple fact addressed.
Where did this time-dilation nonsense originate from? Where is the evidence that acceleration in space equals deceleration in time?
The infamous Hafele-Keating experiment is often referenced but if you look at the data, it clearly shows no difference in the amount of force (energy/battery drain) between stationary and moving clocks. And as discussed earlier, the caesium-133 atom is prevented from being accelerated time (change in mass), when a force is applied. So when you plug the data into the proper formula, F=ma, the defacto law of motion/acceleration/physics, the only difference is in acceleration. Now the tricky part is determining of it went into the space frame or the time frame or both. What is aging? A change in mass? Radioactive decay? What is it that is being inferred when a physicist says that mass is being accelerated in time. A biologist would say that entities lifespan. A chicken going from an embryo to market weight. A plant going from seed to physiological maturity/fruit production. For a physicist, wouldn't acceleration in time be radioactive decay? In the Breakthrough Starshot experiment, it's evidently clear that inorganic objects accelerated in space are also accelerated in time (radioactive decay of the mass). So where does this time-dilation/increase in mass postulate of relativity originate from?
I can find no evidence to support relativity. In fact, all evidence is contrary to relativity. And yet, here we are, a century later, still worshipping at the alter of relativity. You have to completely ignore the laws of physics to get relativity to work. That's not science. That's religion. The fact that they use science to promote their religious nonsense and are funded by the taxpayers is utterly appalling.
Nothing is going to be done until the physics students start demanding answers instead of accepting their shut up and calculate (Sabine) attitude.
layperson here. can't understand anything of popsci videos, but that also applies to this video.
Great point. Most of this stuff sounds interesting on the surface but seems to lose me in the summations. What makes more sense to me is that the source of gravity is the quantum wave form collapse which constantly creates matter and (I believe) is directionally biased towards a lower state of entropy. This directionality is what we call gravity. The rate of collapse is altered by the amount of entropy and this is what we call time and hence time dilation occurs in the presence of different states of entropy. Just a thought. $.02
Thank you.
@@HowardRorkegravity is the acceleration of mass to a null-point between masses. Mass is simply a charge
This problem needed to be addressed, it is indeed a wrong explanation for general relativity. It is, in my opinion, a really wrong explanation, since in reality things are the other way around : it is gravity that causes a difference in time dilation. And more precisely it is the fact that the person on Earth has to constantly accelerate upwards, to compensate the curvature of spacetime, which causes the gradient in time dilation.
However I don't think any RUclipsr is to blame since I have also seen this explanation told by physicists themselves, such as Carlo Rovelli who sometimes wrote in his books that "gravity is the tendency for objects to go where time slows down". It is similar to how misconceptions about black holes spread : some of them were popularized by physicists themselves. It is then pretty difficult knowing what is right and what's not.
For instance, another example is the fact that one would see the universe accelerate to infinity as one would cross the horizon of a black hole. This is completely wrong, but this explanation shows up all the time and it is sometimes told by physicists themselves.
----------------------------
I want to clarify my point of view. There are two distinct phenomena that one could call "gravity" :
1. First one is the fact that when we drop an apple, it seems to accelerate towards the ground. This is a matter of kinematics, apparent movement. The apple seems to experience a "force", which we could call "gravity".
2. The second one is the fact that when we drop an apple, the distance between the apple and the Earth becomes smaller : the apple moves closer to the center of the Earth. This is a different kind of observation, not linked to kinematics this time, but to geometry : we look at the distance between the two objects. This could also be referred to as "gravity" : it is the fact that massive bodies seem to mutually attract each other.
It is important to note that there is a clear distinction between both phenomena :
The first observation depends on the observer. A free-falling observer would not see the apple experiencing any acceleration, since from their point the view the apple seems to float, weightless, as they both fall. This first notion of "gravity" is "observer-dependent". In particular, in a free-falling frame of reference, this type of "gravity" disappears (this is the equivalence principle).
The second observation however is not observer-dependent : all observers will agree that the apple and the Earth tend to move closer to each other (and eventually collide). This notion of "gravity" is "absolute".
If I understood correctly, what Dialect and myself consider to be "true gravity" is the second observation : the fact that massive objects attract each other.
In this case, it is impossible to explain this phenomenon with a time dilation gradient. Why? Because the gradient of time dilation is observer-dependent : a free-falling observer doesn't measure any gradient ! However the phenomenon of gravity (the apple coming closer to the Earth) is still there, it is not observer-dependent.
The explanation comes from the fact that this second notion of "gravity" is fundamentally non local. (mathematically, it is of "order 2", it involves how the gradient of time dilation itself changes from place to place). What explains this type gravity (i.e. the fact that massive objects attract each other) is the curvature of spacetime. And indeed, curvature is not observer-dependent, all observers, even the free-falling one who doesn't observe a time dilation gradient, will still agree that spacetime is curved.
So to sum up, the gradient of time dilation is linked to the first type of "gravity". Which, more simply, is explained in general relativity by the fact that the ground constantly accelerates upwards (and inside an accelerating frame, you will indeed observe a time dilation gradient, whether you are on Earth or in a spaceship, whether you are in curved spacetime or not).
That's the key point : the gradient of time dilation is not linked to "gravity", at least not directly, it is actually more general, and is present in all accelerated frames of reference. So, also in your car when you accelerate, or in a spaceship with fake/artificial gravity. The curvature of spacetime on the other hand is ONLY present when there is "true gravity", in the sense that two massive bodies attract each other. In other words, there is "true gravity" only when the gradient of time dilation is not the same everywhere in space. Or yet in other words, there is "true gravity" only when there are tidal forces.
Wow, thank you for putting the final pieces of the puzzle together for us! Your clarification is immensely enlightening. Next time we'll make sure to consult you before we put up our videos 😂. Indeed, we figured this explanation had to have come from somewhere outside of RUclips, and we did finally realize that what it was describing was the potential gradient of a classic gravitational field.
When we first comprehended that this explanation was wrong, we felt immensely betrayed by these channels. We had placed a great deal of trust in these videos when we were younger, back when we had no knowledge of the theory itself. We believed them at the time, and that belief fundamentally inhibited our ability to progress in our understanding of the theory for a number of years. So are they to blame? That's a difficult question to answer. Eugene Khurtoryanski, Science Asylum and PBS Spacetime all acknowledged in their videos that there was something lacking to their explanation, but how was the naive viewer like ourselves supposed to know that this could imply that time dilation didn't cause gravity, since that was the entire purpose of their making the video? If these channels knew something was off, why didn't they look into it more deeply? Why did they never follow-up with a fuller explanation? This is where we feel a level of blame lies, and that a desire to profit off an explanation that sounded super-cool overcame their mission to instruct and teach.
We understand everyone makes mistake; undoubtedly we will get many things wrong if we continue down the path of attempting to understand General Relativity. And if any of these channels acknowledged that they had made a mistake, or like yourself clarified that it was mis-interpretation of a first order approximation of the theory, we would happily eat our words! Otherwise, we feel that it is our duty to warn others to not approach such channels uncritically. Certainly, they are not nearly as concerned with precision and clarity as channels such as yours or Eigenchris'.
@@dialectphilosophy Excuse me for asking, but how much of GR do you know yourself? Surely everyone who knows their GR will realize where the explanation outlined by these other content creators arise from the grand scheme of GR (as briefly presented by scienceclic)? This is a genuine question, not meant to be insulting or anything.
@@WSFeuer I think you are entirely mistaken here, I'm afraid. I am confident that these RUclipsrs know all of this themselves. Pbs spacetime, for example, have some older videos where they go more into detail on geodesics and spacetime curvature, and I believe Science asylum also have videos that have at least mentioned the full geodesics equation and Einstein field equations. Thing is, when you are going to try to explain GR to a wider audience, especially one that isn't otherwise into physics that much, then you have to make shortcuts to make the explanation at least somewhat understandable. That is going to make it at least somewhat inaccurate. Most people only have experience with the "everyday" kind of gravity; that when you drop something, then it accelerates down at 9,81 m/s^2. Therefore, you are going to have to explain how geodesics and spacetime curvature give rise to that experience; and as it turns out, the fictitious "force" given by the geodesic equation in this scenario is related to the gradient of the g_00 component of the metric tensor, which again is related to gravitational time dilation. Of course this is not all that the geodesic equation can predict; in general, this picture is wrong. But it is one that is accurate for this "everyday" kind of gravity, and it shows how geodesics may give rise to an apparent force like this. Now, I am indeed confident there's better ways to explain how GR really works. But whatever choice you make, it is a tradeoff between making it accurate, making it somewhat short (ie. resist making it hours long) and making it understandable/relatable to the audience.
@@frede1905 Go rewatch those videos. Each one of them contains numerous unfactual statements. If they truly understood GR like ScienceClic or Dialect, why wouldn’t they have just straight-up said that the explanation came from a first-order approximation meant to replicate the potential gradient of an observed gravitational field (which in General Relativity is a pseudo-fictitious field and therefore not gravity at all.) You can even find Eugene’s response in the comment threads below where he STILL can’t explain to Dialect what his video supposedly meant. Reading your comment and listening to you try to rationalize a completely unfactual explanation makes you sound simply biased, like you think because these channels are popular it’s okay for them to not be honest or right. The truth is PBS Spacetime and Eugene and the others aren’t really intelligent or great physicists, they’re just good at capitalizing off of their viewer’s naivety and presenting digestible sound-bites that sometimes are passable physics.
@@frede1905 Re-reading your comment I see now that you, like the videos you are championing, have failed to distinguish the difference between spacetime curvature and observed gravitational fields. The “everyday” gravity of an apple falling to the earth is explained by the fact that the earth is accelerating upwards. It has nothing to do with spacetime curvature. This is not a disputed fact, you can find it discussed on many other videos and in many other sources. (Did you even watch Dialect’s video?) Now that I see you don’t understand General Relativity yourself, your championing of these videos becomes less disingenuous, although your intelligence and the merit of your opinion has rather sank.
It would be nice to see a straightforward video just laying out your theory with less drama and personal attacks punctuated with giant text. Sometimes in life people have to eat their own words, and big bold text can be hard to swallow. Let your work stand on its own. Be humble.
I was thinking the same thing: better to be careful not to give people an excuse to throw away an obviously rigorous and thoughtful work.
Don't get in your own way with sarcasm, or other trite drama.
If you are interested in getting to deeper understandings, you have to maintain your (what seems to be normal) thoughtful, polite, skepticism.
People might still disregard what you write, but you will not have pushed them away.
Completely agree. Reading the comment from Eugene (above) and tgen reading the replies the conversation quickly devolved into petty "I'm right, you are wrong" thing and people becoming "fan-boys" over the RUclipsrs they follow.
Science does not need this drama.
Ever heard of Aristotle, Socrates, Plato? Morons! 😂
Human nature wants drama. Emotions carried with knowledge might make certain kinds of people to remember things better.
That's social media for you. Drama sells.
I’m fairly certain this video could have been done in a more polite manner.
Sometimes on your journey North, you end up going East because you don’t yet have the strength to plow through a mountain.
These concepts are not easy for the non-scientific person to understand. The other explanations, wrong as they may have been (East), still took us in the right direction (North) without overwhelming us with concepts that we’re not familiar with (the mountain). Thanks to them, I was able to understand your video more easily than I would have with my layman’s blank slate.
I think, rather than being a stab at the other channels, you could have treated this video as “the next step” in the layman’s journey to understanding gravity. Even Newton’s explanation, wrong as it is, is a good stepping stone to understanding Einstein’s explanation.
Maybe I’m wrong, but that’s my two cents.
You are absolutly right but sadly this Kind of presentation gets more people engaged and the algorythm favors „engageing“ content.
Right on! Well said!
I can somewhat understand the creators frustration as there are certainly a lot of "wrong" explanations on this topic in general on RUclips. That being said, maybe its not the best idea to expect to learn one of the most complex and unintuitive topics of modern physics on RUclips and then blame other creators when they use approximations or even "wrong" explanations to make the topic even remotely accessible to a wider audience. Its amazing that you point that problem out and make a video about it but dude chill
I made it to 9:54 and then I said WRONG. I love the appeal of the argument, but it was at that moment when I realized it was no longer cogent.
This was too true
I like exploring this topic but frankly this video is more about “I’m right and they’re all wrong” than actual education. You could have given a better presentation without making it so personal.
My thoughts exactly. Comes across a little egotistic
yeah but they also made millions of people belive wrong things
@@EDITᲽ its fine to call it out but he was doing it every 2 minutes with their faces and stuff. That much frequency and emphasis stops being a simple calling out incorrect data and starts becoming more toxic/egotistic sounding. At least in my opinion. I wouldnt have done it in such a sledgehammer approach
@@EDITᲽThis guy spreads more misinformation than any other science channel out there. He acts like he knows Relativity in and out, but then he completely fails at grasping the most fundamental concepts.
@@EDITᲽ Yea and this guy made general relativity about his ego. I'm more focused on how much I hate him rather than his correction, and I'm sure everyone else is
My problem with this video is the general message that is conveyed. In particular, while Dialect attempts to make a 'fuller picture' of gravity, it seems the main point is to actually put down other physics content creators for what Dialect deems as wrong. The ending completely rubbed me the wrong way, and is harmful to the physics content space.
ScienceClic has been brought up a couple times in the comments, and I think their channel is the perfect example of how Dialect should've communicated this video. Instead of focusing on other content creators---and in certain cases making a straw man of their videos--the focus should be on the actual physics and the creativity of how Dialect wants to communicate such physics. Not to say that Dialect doesn't include a lot of physics in this video, but I believe the tone of this video is not effective.
I'll end this by saying; if Dialect believes they have a better point/visualization/explanation to make than what is currently on RUclips, then they should make a video solely on that. Believe me, if their video is well-made and does the physics service more than other content creators it will get praise. However, the only takeaway I can get from this video is a sad attempt to recruit viewers and gain popularity by putting other content creators down. In such a small space as physics visual education, it is sad to see a video such as this.
This. The video sets a really bad tone. If anyone wants to see how flaws are respectfully pointed out, Veritasium has done that a couple of times
Literally all of his videos are like this... Just plain unprofessional
I think you are incorrect here. The problem with having such a small education-space is that no one wants to admit their own mistakes. This doesn’t only apply to youtube physics videos, but science as we practice it today.
I think you’re right in saying if you’re correct and making better content, then you can out-compete the worse content. But this is a function of quality and doesn’t tell us anything about being right or wrong.
Think about when the Catholic church didn’t want to admit that Galileo was right about a heliocentric world, the correct information was essentially suppressed by the power of the masses of people who follow the Catholic church.
So I agree with Dialect saying that the larger channels need to admit their mistake. If they don’t, the masses of people who follow them will find strength in their numbers and suppress the information that is more correct. That is, until they can all be proven wrong though experiment, instead of competition of quality.
The reason why I even met this channel is exactly because I was unsatisfied with the answers to the Twin Paradox on RUclips. So I can't exactly agree with you considering that's how I came to know him. If it wasn't for that I would never watch a single one of his videos even if they showed up to me.
💯!
This was an ambitious video, but unfortunately it falls a bit short off of its goal. There are several wrong statements made herein, though not all of them terribly impact the topic at hand, but being a type of fact-checking video it's not a pristine look.
For instance, the narrator asks with incredulity whether the travelling spaceship creates curvature as it passes through space, ending with the statement that this would be absurd. But it's really not. Any stress-energy tensor creates curvature wherever it exists, so a spaceship moving through spacetime will most certainly create curvature, and the faster it moves, the more kinetic energy it has, meaning it creates more curvature at higher speeds. A collection of photons would create curvature - hell, you could in theory create a black hole out of nothing but photons.
Another example is the spacetime diagrams vs. spacetime segment, where the narrator seems to disregard the geodesics explanation. It's unclear what they really meant here, but it's uncontested fact that objects *do* follow geodesics - geodesic trajectories map to Newtonian trajectories so closely that they're nigh indistinguishable - so it's unclear what the real objection here is supposed to be. The narrator also doesn't discuss the relationship between geodesics and observed time dilation (I'll return to that topic later on), which is the thing that is the real "cause" of these videos they're trying to debunk, contrary to the explanation they're giving about misunderstanding a coordinate translation.
It also rather seems that the narrator didn't fully understand the point made in the videos he's attacking. At the heart of the presented argument is that matter alters the flow of time (putting a dent in local spacetime), and the altered flow of time is then what causes the realization of why an object moving through that field seems to change directions. It can't be the space component, because if it was only the space component then gravitational pull wouldn't create inertial trajectories, objects of all velocities would follow the same path. What they are referencing here is Einstein's gradient for how proper time evolves in a gravitational field - and it does so in a manner that maps to the evolution of the geodesic.
So what they are *really* saying, is that gravity in non-relativistic frames of reference occur because *time* is curved (space is also curved since it's a part of spacetime, but the curvature of the space component is irrelevant for macro objects and indeed with a velocity not approaching c), and it's uncomplicated to show why that must be - I'm sure there's an equal explanation in GR, but it's much easier to realize that special relativity basically says so without any complexity at all. Under SR, basically all macro objects move more in the time component than they do the space component - significantly more so - so any curvature strong enough to affect them in the way we see has to arise in the component their delta is large in. Meaning the time component, because the space component delta is disappearingly tiny in comparison.
To go from all of this to "gravity is caused by time-dilation", is a little bit of a leap... I'll give the narrator that. It's not a strong explanation, but it's also not nearly as wrong as the narrator is trying to make it out to be in this video, certainly far from being "100% unequivocally wrong".
Why don't you do a video to explain your idea with graphics?
I agree with you. I think the narrator misinterpreted some words physicists in these videos spoke, but it is also true and understandable that they may not have been 100% clear for everyone, which is an extremely hard thing to do, giving the very complex topic of these videos. Either way, I found this video to be too focused on criticizing the others rather than focusing on giving better and more clear explainations. I would say no one here is really wrong, but I feel like the narrator wanted to point out and make a big thing out of these "not entirely clear explanations" which feels, speaking as a physicist myself, totally uneccessary and a bit "unpolite" (at least in the tone the video has).
The author is correct that the other videos are wrong. But as you stated, he himself made a few incorrect statements, such as the Earth accelerating up in all directions 24/7 as the cause for gravity. The other videos are saying time dilation causes gravity. Matter and energy in the presence of space-time is the cause, and space curving (gravity) and time being stretched (time dilation) are both effects. Cause and effect. To say time dilation causes gravity is like saying a fever causes a runny nose. A fever and runny nose are effects. The cause is an infection from a virus or bacteria.
The bottom line is mass and energy distorts space-time, causing BOTH gravity (via space curvature) AND time dilation (via stretching of time). Gravity doesn't create time dilation and time dilation doesn't create gravity.
@@StefSubZero270 Agreed!
I would be cautious with certainty. General Relativity is very difficult, I've studied it myself and at university and have become quite familiar. But every so often I encounter a situation that you'd think is quite simple, but turns out to have a lot of nuance I had missed before. Given that the theory explicitly demands that there is no privileged coordinate system, we know that there is a huge amount of flexibility in how we can describe any given spacetime and I would argue that disentangling those features which are absolute and "real", from those which are artifacts of a given description, is a very difficult task. At the end of the day, we still need to use the coordinates, we can't analyse a spacetime without them, but you cannot just look at a metric and know immediately what's real and what's subjective. It takes a lot more work than that. If your view is that anything less than an unabridged explanation of GR that is then fully absorbed by the layperson audience, is misinformation, then I'm afraid you haven't met enough people to gauge how unrealistic that is
As a professional AIA architect I use a 3D relative Cartesian and polar coordinate system on the computer to map out the curvature of space between and around large bodies. I discovered the missing variables in Einstein's field equations on gravity back in 2004. He and Newton neglected to address the action causing gravity in their equations. Their equations perfectly explained the motion and orbits of small bodies like planets and moons but failed miserably when trying to describe or predict the motion and orbits of stars and galaxies. The fix to their equations was so simple. I can't believe no one else realized what was missing. Now their equations are able to accurately describe the motion and orbits of all the stars in galactic disks, without having to resort to using wildcard variables like dark matter. The equations also explain why space is expanding and why it expands exponentially with great distance. There is no missing mass in the universe. There is no missing energy in the universe. The equations of relativity and laws of motion need to reflect what's happening inside of large mass, which then causes space to react.
The action causing gravity in all large mass is over-unity of energy. Energy is constantly being added to the universe via the nearly perfect spherical shape of all large bodies. I tried to publish a paper to peer review several years ago and instead of calling it dark energy I referred to this action as over-unity of energy. They denied my publication. They do not want to believe that Einstein was wrong or the possibility that energy and matter can be created. Gravity is a constant. The creation of energy and matter then is a constant too. It explains so much. Good-by big bang.
Just by adding in over-unity of energy to their equations everything changes. Instead of nothing is able to escape a black hole because of their gravity, nothing is able to fall into them because of the amount of energy they radiate. The black hole is not black because light cannot escape. The black hole is black because the energy they radiate is so energetic it goes beyond the visual spectrum of light. So the massive star looks black to an optical telescope. Yet they stick out like a sore thumb when studying them with radio telescopes. The visible light becomes invisible to optical telescopes when the star's energy output reaches that of a black hole. Nothing can fall into or collide with a black hole because of the amount of energy they radiate.
I wrote and published a series of 6 books about this theory last year, starting with Gravity and the last book in the series called Over-unity.
Get this, the only way galaxies can move away from us in every direction faster than the speed of light is if an infinite amount of energy times and infinite amount of energy is constantly being added to the vacuum of space between us and said distant galaxies. As gravity is produced an equal opposite amount of energy is created. This energy adds space around the large mass because energy is something new, it is being created. Matter is not converting into energy. This one action causes a reaction of motion to all the mass in the universe. When energy is applied to mass suspended in the vacuum of space by magnetic fields energy is created. Much more energy radiates away from mass than the energy that absorbs into it. This is true for all spherically shaped bodies not grounded out.
If I had called the action causing gravity Dark Energy I believe now the journal would have allowed my publication.
The first explanation of how gravity works that I truly understood was that mass warps the spacetime around it. It makes it so that a straight line going only in the time direction (i.e., an object at rest) will go toward the mass. How true is this explanation?
@@ronaldkemp3952 you might have more issues than that going on here my man. Can you not discuss it with other people in the field? Try to find any holes in the theory you may need to patch? I’d argue that almost 100% of new ideas in physics need peer-assisted revision before they become rigorous enough to really turn heads.
If you’re the only one who’s completely convinced of your claim, chances are something is wrong with it- not the consensus understanding of nature. You should never be completely convinced of anything anyway, especially your own work, since you’re already going to be biased towards ignoring problems rather than revising your ideas accordingly.
@@alexweschler9470 I realized that energy can be created but it cannot be destroyed. That's why the universe is expanding exponentially with distance and why it grows over time. Energy is being created by large mass that takes on a spherical shape. When energy enters the universe it produces all the reactions referred to as motion of mass. It is not gravity causing all the motion. It is energy constantly being added new to the universe everywhere as an equal opposite counterpart to gravity.
Every ounce of gravity that is produced accompanies an equal amount of energy that radiates out into space. When that energy interacts with mass it causes motion. Space is constantly increasing in the volume of energy it contains. When energy comes to the extents of the EM field it cannot be destroyed. So, it converts into elementary particles per the pair producing theory. So not only is the universe increasing in energy it is increasing in matter too.
There is no such thing as a static universe. The laws of conservation between matter and energy, and the laws of thermodynamics is incorrect assuming matter and energy cannot be created. They are right to claim energy and matter cannot be destroyed. The universe is slowly growing in both energy and matter over time.
The same action causing gravity in all large bodies is the same action causing all the motion that occurs to large matter.
The reason why peer review did not accept this postulate or theory was because I claimed energy and matter can be created, over unity of energy. Seeing how the predictions I've made about gravity and many other observations has come true, this postulate should be called a theory.
I even came up with the plans to a device which would create more energy than what is input into the device (over-unity).
I suspect the entire reason why academia frowns on the idea energy can be created is because of their fear that we would no longer need to rely on corporations to supply our energy. Maybe they think it will cause an economic collapse?
I may be wrong or I may be right. There is no in between. Seeing how every one of my predictions about gravity has come true, I have to believe I'm most likely right.
Thank you for you're kind response.
Alesandro Russel did a great job explaining gravity in his videos, which I really recommend to watch.
But he also says that is the time component that cause gravity.
@@FelipeSJardim No he does not. You can read his comments and replies in this very video.
My head hurts when I watch this. My head hurt 45 years ago when I took relativity at Uni despite being good at maths & theoretical Physics. The maths is hard, and I think all kinds of issues arise when people try and make the explanations simple - perhaps simpler than possible.
I would no more uncritically trust your explanation than the other RUclipsrs without being able to verify against the maths, and I'm too old to do that now.
there is no math in any of the theories of gravity except for the original Newtonian formula of gravitation force.
@@KronStaro
That's... false.
Amazing story bro
The real problem is trying to explain "simpler".
Instead, they could try to explain the basic math of the relativity.
The best answer is we don't know, but since we know this, we are searching for answers.
1. at 23:07 Why is mass accelerating outward from the rest of the other masses? What causes the internal pressure (if there is any)?
2. at 23:23 What causes THIS space-time curvature AND WHY?
Someone can correct me if wrong but as i understand it:
1. it is not in freefall towards to center of mass, so it is being accelerated. As explained earlier, the object falling is actually not accelerating, the earth is moving towards it, but when they meet, the earth accelerates it away from its freefall path along whatever geodesic it was following through spacetime. Electrons provide pressure in the same way that makes it so you dont fall through the floor.
2. Presence of matter and energy warps spacetime, which defines what the geodesics through that spacetime would be. WHY is a fundamental question im not sure has been answered yet, at least intuitively.
1. Electromagnetic force of the atoms in exactly the same way as when you push against a wall the wall pushes back. Newton's 3rd.
Being in constant motion and being at rest are equivalent. So the falling apple is at rest and you are accelerating. That's why a falling person is weightless, there are no forces. Two parallel lines on the surface of a sphere will converge without any force and atoms their bodies will push them apart.
2. Because of the fixed speed of light. It cannot be otherwise. It is geometrically impossible for spacetime to be flat and for the speed of light to be fixed.
First, there's no absolute coordinate system. Position and motion is only defined in relationship to other things. Also, information isn't passed instantly. The earth is orbiting where the sun was ten minutes ago.
If you're on a train and you fire a gun the bullet goes faster shooting forwards than backwards from the perspective of an observer in the ground. Not so with information. Always at the same speed to every observer.
A flat coordinate system won't work for that. Think about it, I fire a bullet at 1000m/s on a train moving at 100m/s and it's still going at 1000m/s to all observers regardless of which direction I'm firing it. Impossible, right?
Just like three 90 degree turns making a triangle is impossible. Except on a sphere, then it *must* be like that.
So speed is time and distance, right? Just stretch and squeeze them until everything fits the speed of light is the same for everyone.
Hey presto: curved spacetime.
@@davidmurphy563 1. Newton's laws are incompatible with relativity and quantum mechanics. Two magnets attract. Where is the opposing outward force?
I'm pretty sure the falling apple FEELS acceleration instead being at rest. I'm pretty sure the Earth striking the apple after accelerating towards it would have a different effect than the apple striking the Earth after accelerating towards it.
2. Space being curved doesn't logically follow from the speed of light being fixed to all observers. You are begging the question. The connection takes more rigor (detailed proof). Plus you have to define what "curved" and "flat" means precisely.
@@h1a8 1. Newton's 1st, 2nd and 3rd are alive and well. Especially the 1st, that's a restatement of the Galilean Principle of Relativity. Also a restatement of the Conservation of Momentum. Perfectly valid statements with great utility. Even the Law of Gravitation is still valid when gamma = 1 and given a series of caveats. Obviously in the hundreds of years since Newton our knowledge as expanded and there's more to add but the statements still have true and utility.
I mean, the Ideal Gas Law is valid and that never ever occurs in nature. Hell, there are no right angles in nature but Pythagoras still gets used to normalise vectors!
2. It was a layman's explanation in order to give some intuition on the matrix transforms at the heart of GR. Of course it's not complete. In fact I leaned on SR as it's conceptually simpler. That's what Einstein did after all.
Plus, there are no formal proofs in science and anyway, how would a page full of maths be helpful to the man?
Why don't have a crack at it?
@@davidmurphy563
1. What about my magnet example?
Falling Apple rebuttal?
Author states that mass is accelerating outwards (doesn't explain why) and space is curving to compensate. You stated newton's 3rd law which would be compensated for the electromagnetic force, not space curving. You two are using different rationale.
2. You argue something you first must define it. Curved and flat space needs to be defined.
Then you must logically connect fixed light speed for all observers implies space is curved.
Can that be done without any intense mathematics without any question begging?
This reminds me of the time when I was an instructor for the USAF. I noticed that some of my fellow instructors would change some of the well written systems explanation to try to make them easier to understand for their students. In that attempt they taught some things wrong. I don't think that they understood the subject either. Fortunately it was a rare event that a good understanding of systems operation and purpose was required to fix the airplanes we worked on.
In the Navy Electricity and
Electronics Training Series, module 10, section 1.12.2, it seems that the left hand rule is mistakenly used in place of the right hand rule?
@@ic7481 I have never needed to use that rule in my forty years of airplane fixin. I did use the knowledge that wires have capacitance and that water can act as a dielectric once to figure out an intermittent problem that affected several helicopters on damp mornings. A twisted pair of rate gyro signal wires (Kapton) were getting noise induced into them from the gyro motor power wire when they were damp. It had to be capacitance because no conductance was measured with an ohmmeter.
@@jnbfrancisco That's interesting. The relative dielectric constant of water is 80, so can definitely cause problems, especially for high frequency signals. I recently designed a specialised capacitor assembly, and the material used had a dielectric of about only 2!
I guess this is also a problem for 50/60Hz, which is why undersea links are DC.
In my view, It helps explain why Neil Armstrong was so good. Maybe it’s the number one principal I respected Dr. Feynman for. He always desired to understand the most fundamental concepts or aspects of a system and wouldn’t put up with any nonsense. It seems human beings in general are satisfied living in ignorance and I’ve never understood it. But who am I to judge that.
@@ic7481 It's been almost 20 years since my last advancement exam, but offhand (no pun intended), I'd say it's because the Navy teaches electron flow. For hole flow, that'd be the right hand
22:20 -24:07… By what mechanism does spacetime curvature respond to the outward push of mass to hold it in place?
I understood the arguments against other RUclips channels, but didnt understend his explanation about thr real cause of gravity. ScienceClick and Veritasium did this same explanation.
ScienceClic's video has been very convincing for me.
ScienceClic made EXACTLY the same analogy used in the videos attacked here. Which makes his support for this nonsense extremely disappointing
We don't know the real cause of gravity.
At 12:11 if we are rushing upward to meet the apple what about the people on the other side of earth?
Good question, this guy is a flat earther in a way
He literally explains that here 22:53
@@kimtheguy this guy explains it very well. ruclips.net/video/k5H7UwSjdek/видео.html
Here are my issues with your further reflections:
1. (@4:14) Yes there is a force holding atoms together, it's called the electromagnetic force. Electron and Ion-bonds are studied in chemistry. In cosmology there exists a term "Roche limit" and it's the distance at which a heavier celestial body can disintegrate a lighter celestial body if it's held by it's own gravity alone. You can think of this "flow of time" becoming too great for one part of the body. One real-life example of this would be comet Shoemaker getting fractured during it's collision course with Jupiter.
2. (@6:11) You are drawing comparison between Newtonian gravity and General relativity. Why bother? We already know Newtonian mechanics does *not* describe the universe accurately.
3. (@6:42) You are saying apparent gravitational attraction is not gravity but Einstein does make a point of there being no difference whether you are in a gravitational field (curved spacetime/time flow gradient) or undergoing acceleration (in flat spacetime). Undergoing acceleration does not mean spacetime gets curved. Why are you trying to draw that analogy? Undergoing acceleration means spacetime is squeezed in front of you and stretched behind you. You don't have curvature, you have spacetime elasticity in a plane perpendicular to the direction of your acceleration (including the opposite direction). This elasticity has no gradient, it just depends on your acquired acceleration (compared to your state before the acceleration). The gradient is in the acceleration accumulation. Your mass does *not* change because of your acceleration, so your gravity well remains the same as before you started accelerating. Only your clock ticks at a slower rate (compared to your clock rate before undergoing acceleration). You are not stretching or contracting the universe for everyone else, it just appears so from your point of view, because your clock ticks slower and you have a direction of relative motion compared to the rest of the objects in the universe.
4. (@9:30) In your example here, distant clocks (in the direction of your acceleration) would seem to tick at different rates only if you continue accelerating (at the same rate) until you reach them. This is because while you are accelerating your clock would continually slow down compared to those distant clocks. In reality all the clocks in front of you tick at the same rate, and only if you continue to accelerate the clocks would seem to tick faster (because your own clock is slowing down, again compared to your state before undergoing acceleration). If you stopped accelerating, all the clocks would tick at the same rate, because your own clock is no longer slowing down.
5. (@10:05) Just because you are accelerating doesn't mean you are curving space time. The equivalence principle states the effect would be the same for the body undergoing the acceleration, not of the bodes at rest which are observing the acceleration. While you are accelerating, spacetime sure looks curved (sloped) to you.
6. (@10:33) Nobody said curvature (spacetime elasticity, in the case of accelerating bodies) is observer independent. You just had a false premise that an accelerating body would create spacetime curvature that is observer independent. What an accelerating body does is just alter the speed at which it's clock ticks. That again is observer dependent though because for each observer no matter the frame of reference, time flows at the same rate (the speed of light, but in the time direction).
7. (@10:45) All observers can only agree that certain regions of space have more mass/energy than others. They can't agree on how much exactly this energy is or when exactly is it at a certain location. When you accelerate away from a star, it's energy appears to become less than before. Energy is conserved only in it's own frame of reference.
8. (@10:54) A uniform gravitational field does not have a curvature, but it *does* have a slope. That's why it *is* equivalent to an accelerated frame of reference. If you want to imagine it as time flows, then the time between clocks changes in a linear fashion (the rate of change is constant).
9. (@11:43) There is gravity on the surface of the earth because there is spacetime curvature or difference in clock speeds. It doesn't matter if the curvature is linear (as in the case of uniform gravitational field), it's there and it's causing the attraction force.
10. (@11:57) Assuming you are accelerating towards the apple is just equivalent to spacetime being curved and time flowing at different rates and even to spacetime flowing towards earth. None of this contradicts the time flow assumption.
11. (@13:06) -Yes in the frame of reference of the apple it's clocks will tick at the same rate- , but from the apple's frame of reference the Earth's clock would seem to speed up the close it gets to the ground. So again it's the same picture as the couple looking at different clock flows depending on the distance from the ground. Your example is *not* contradicting the point of view of the couple on the ground.
*EDIT:* Actually since the apple has volume and is on a space time slope, the lower part will be more attracted to the ground compared to the upper part. If the atomic bonds are strong enough the acceleration experience by the lower part of the apple will propagate through the EM force through the top part and fall as an apple on the ground. If gravity is strong enough to overcome the the electromagnetic force (as in the vicinity of a black hole), then the apple will break apart. The situation is the same if you apply to much acceleration, the apple will be squished and the top and bottom parts will meet.
12. (@19:06) You are comparing spacetime an uniform gravitational field with a non-uniform one (the slope gets less steep the further from Earth it is). This just means gravitational attraction becomes weaker at higher distances. It would be the same as saying the rate of change of the flow of time is smaller the farther you go from Earth. None of this contradicts the time flow assumption.
13. (@19:37) I can appreciate the effort of trying to trace the origin of some suspicious source of information.
14. (@20:09) If the time flow assumption is just a simple coordinate transformation, you should know it's as true as the original theory itself. You are just doing calculations differently. This finding is a contradiction to the point you are trying to make.
15. (@21:15) Time dilation has a lot to do with curvature. You can't have curved spacetime and not have time dilation. Even more the extent to which time is dilated depends on the extent to which spacetime is curved. Even when you undergo acceleration, from your point of reference, the universe is curving (stretching and contracting around you), again the stretching depends on the amount of acceleration you experience and the tick rate of your clock also depends on the amount of acceleration you experience.
16. (@25:15) Would you acknowledge your own mistake?
about 6:42 he is exactly NOT drawing that analogy. He explicitly said that the problem of that analogy would be that, if true, an accelerating body is wrapping spacetime all across the universe and then when it stops all universe reshapes 'at rest' position. And he called that nosense.
@@enricobelvisi3880 Yes I tagged the wrong timestamp, the author of the video actually draws the analogy at 10:00 onwards. So either he doesn't have a good grasp on general relativity or the equivalence principle or maybe he was just confused at this point (for example if he was making the video late at night after a heavy workday). And why state what he did at 6:42, none of the other videos he's quoting imply that. Seems to me this is how Dialect thinks the other videos were trying to portray things. At 6:42 is just the first time he comes with this false premise, that spacetime elasticity due to acceleration should be reference frame invariant.
@@lamcho00 I think he mean that if you define time dilation as cause of Gravity (NB that he is defining as equivalent to ST curvature), as some of those videos have done, you are impling that your acceleration is causing ST curvature, and viceversa is causing ST flattening when you decelerate, instead of being only 'apparent' observer-dependent phenomenons.
But rereading your comment I would say the point is that Dialect (if I understand his thought correctly) thinks we are accelerating on a flat ST instead of being at 'rest' in a curved ST IN THE NEARBY of the Earth's surface, supporting this view with the parallel geodesics observation- i would like to know by you if this observation is really so unequivocable sign of flat ST, cause I'm not an expert on this point.
And so he derive that other videos are saying: you accelerate in flat ST-->you get Time Dilation-->this change other obj motion in TS. While those video could also be saying: you are in curved ST-->you get Time Dilation-->this change other obj motion in TS.
And in the end, he would state that (if his assumption of being accelerating in a flat ST is correct) if you are accelerating and for example an apple is at rest (free falling) you don't need Time Dilation as a cause to explain the phenomenon, it's almost classical motion. But if his assumption is wrong then his explanation doesn't hold.
I find difficult to accept the Time Dilation story, cause to me this seems only an apparent pheonomenon, but also accept that is not the ST curvature generated by gravity to 'produce' gravitational forces is a bit uncomfortable.
One thing I am thinking is that Dialect idea of flat ST nearby the Earth surface could join with the idea that the geometry of ST could allow globally curved ST shape but locally flat ST shape (as in a minimum of a really big parabola), I don't rememeber where I listened to this idea but is a possible one. So even if we are at rest in a globally curved ST, locally we are in a flat ST (but accelerating? that's the part maybe doesn't fit to mix the two ideas) .
Still confused thoughts....
@@enricobelvisi3880 In a way acceleration is causing spacetime curvature, but only in your immediate vicinity. That's how you get relativistic length contraction. When you accelerate you actually look like you are getting squeezed to the stationary observers. Why call this "apparent" observer dependent phenomenon? It's just how the universe works. Why assume there is a deeper root cause? Where is the evidence? It's not in the video.
You can have flat space time, but still get gravitational attraction. Imagine you have a piece of paper and this piece of paper represents spacetime. If you lay the piece of paper on a table it's flat and if you put a grain of sand on it it'll stay where you put it. In this case space if flat like a dash "--" and there is not space or time dilation between different points on the piece of paper. We can say there is no gravity there.
Now imagine you glue the lower two of the corners to the table and grab the upper corners and lift them at some height wile pulling away from the glued end. Then you again have a flat piece of paper, but now it's on an angle like a slash "/". If you take a point near the top and another near the bottom there would be a difference in potential energy, or in the case with spacetime it would be a difference in time flow rate and space dilation. Again the piece of paper is flat, but if you put a piece of sand on it, it will roll down to the glued end to the table. This is how spacetime is flat near the surface of the Earth. It's wrong to say there is no gravity there, because while being flat it's flat in a different way. The flatness here refers to the rate of change between equally separated points (from the top and bottom part of the paper). The higher the change the closer the angle between the paper and the table is to 90 degrees. If you want to think of it like a parabola, you are not in the maximum or minimum, you are on the steep slope, but you are looking at such a small part of the parabola that it looks like a straight line (flat). Much like how Earth's surface looks flat to us, because we are so small compared to the radius of the Earth.
In both cases you have flat paper (spacetime). And in both cases you can draw geodesics and they'll remain parallel, because the rate of change between points is linear. But in the second case "/" you definitely have gravitational attraction. I think Dialect doesn't differentiate between the two cases and that's one of the reasons why he's wrong.
The idea about flat spacetime is true, but different than how you describe it. I did some reading some years back and it turns out the maximum of Earth's gravitational field is under the surface of the Earth, so there is where you get the global maximum and the flat part (flat like a dash "--" part). It's not even in the center of the Earth, it's a zone between the center and the surface and it makes a surface of an irregular sphere on which you'll feel 0g acceleration due to Earth's gravity. The center of the earth will be a local maximum where you again feel 0g acceleration, but spacetime is not that stretched as in the case of the surface of the sphere mentioned above (time flows at a faster rate).
Just because you'll be at the bottom of spacetime well and feel 0g doesn't mean time will flow at the same rate as in flat space in intergalactic space for example. To reach the bottom of Earth's gravitational well you've acquired acceleration and this means your clock ticks at a slower rate, compared to before reaching that point.
NOTE: I'm not a physicist myself, physics is more of a hobby for me, and not every aspect of general relativity is clear to me either. So take my explanations with a grain of salt. But even with my limited understanding I can see the flaws in Dialect's arguments. I've done some Lorentz transformations and other GR derivations myself so I'm not a complete novice either.
Thank you for the thorough analysis
You lost me at 10 minutes - the accelerating fighter jet analogy - it doesn't work.
In the case of the accelerating jet, there is no curvature in time and the clocks would not be advancing at different rates according to their distance. The difference in the rate of time would only relate to the difference in speed between the jet and the clocks, not the distance of the clocks. The G-force felt is local only, being caused by the acceleration which is the result of a force acting on the jet.
Likewise, the curvature of time around a massive object, such as the Earth, is only apparent to an external observer - it is not apparent or measureable/observable to a body in freefall or in orbit, and the only reason it is curved is because the Earth is spherical. If the Earth's surface were flat and infinite, there would be no curvature, only the gradient.
When no force is acting on a body, it is in an intertial frame of reference. A body in an intertial frame of reference has a constant speed through space and time. Therefore, if there is a gradient in time, a body in an intertial frame of reference must change its course in in order to maintain its speed through time. This means accelerating towards the mass, where the rate of time slows.
On Earth's surface, as in the case of the fighter jet, the G-force experienced is because you are not in an intertial frame of reference. The presence of the ground prevents this and the result is exactly the same as accelerating at 1G.
@@narfwhals7843 What is the equation to calculate the time gradient based on the acceleration? Because such an equation does not exist for a gravitational field.
@@narfwhals7843 Supply the Rindler metric and give back of the envelope calculation. I guarantee it does not use pure acceleration as the input.
@@narfwhals7843 The Rindler effect is the metric seen relative to other accelerating objects, not all of spacetime or objects in non-accelerating references. It can't be used to claim a time gradient in spacetime is observed, as it only applies to objects in the same accelerating reference frames, and spacetime is not an accelerating reference frame.
Also, you can't calculate your absolute time dilation using acceleration. You must have your velocity.
The acceleration outwards of every mass being magically balanced by curvature is causeless physics and circular logic. I love this channel, really one of the best content out there. Please don't fall short of what you stand for. Stay rigorous, consistent, logical and mechanical. If humans have not reached a meaningful understanding of gravity yet, and you have nothing to propose, please state those limitations or explain how are we accelerating upwards, mechanically, and what causes space to shrink and counter that accelerating expansion. How can space have elastic properties? What constitutes that elasticity? What material is it made of? How does mass and energy cause such phenomena? If time dilation and space contraction cancel out for moving observers, can we state these are artifacts of our measurement methods (apparent) and not actual physical effects? If that is so, could we say that special relativity is a theory of how the finite speed of light skews our measurements, not implicating on the nature of reality itself? Please don't stop.
Our wording was a little awkward there, the above commenter is correct. As to space "elasticity", our leading theories of dark matter have space constantly stretching and appearing out of nothing, so you'll have to take that idea up with them until we can get a better grasp on the philosophy of what space actually "is".
@@dialectphilosophy meant dark energy, not dark matter.
@@dialectphilosophy Rather than “dark matter,” I recommend another word for the undetectable, elastic, compressible fluid that is everywhere - aether.
@@dialectphilosophy If we discover what space actually is, we will discover what matter is, beyond or instead of our present ``understanding`` of it being excitations in fields.
Well said... 👋
13:09 while what you said is true so far, I believe this is wrong. Gravitational time dilation is something all observers agree on. Someone far away from earth is inertial and sees the time dilation. It is true space is locally flat, but this doesn't mean clock tick at exactly the same rate. Just minor difference between the ticks.
Whom to believe when everybody is proving previous person wrong?
Time dilation is observer dependent I flat spacetime w no gravity.
Tell us how do you check "gravitationnal Time dilation"? By supposing "gravitationnal Time dilation" between clocks that are "gravitationaly distant" from one another ? Or by an unknown trick of infinite speed exchange of intengled information between those two clocks appart ? Curious to hear about your "Magic method". Or is it more likely just empty words of wind blowing thoughts in the chimeric empire of fairy tails ungrounded beliefs
23:02 I completely disagree, there's not some magic force pushing outwards on every body, that's a reaction force due to gravity, like if I tried to squeeze a ping pong ball in my hand. The force it exerts on my hand isn't the cause of the squeezing, it's vice versa - just the same as the acceleration outwards isn't inherent, it's a reaction force due to gravity. If we could "turn gravity off", a large metal sphere wouldn't just fly apart, it would still remain in one piece, right?
I'm glad you could correct the time dilation mistake made by other RUclipsrs, but this is either a gross misrepresentation or just plain wrong, and in a video where you're trying to "fix mistakes" too.
The videos you attack are correct. As other respondents have indicated and as emphasized by Thorne, Schutz, and other leaders in the field, curved spacetime has a time component which dominates in certain conditions - weak gravitational field and viewed at low velocity. (Like an apple falling from a tree, as opposed to starlight bending around the sun.) It is called the Newtonian limit. The Einstein equation reduces to Newtonian gravity in everyday life situations where only time curvature (otherwise known as the time dilation gradient) applies. The curvature of space in these conditions is de minimis.
Narrowly defined, the Newtonian limit is uncontroversial. It is explicit in the math and in Einstein's explanations of general relativity and universally recognized. The dispute among experts and groupies alike is about physical intuition and is due to systemic pedagogy failure and a philosophical prejudice that both go back to Einstein. When Minkowski introduced spacetime, Einstein famously quipped that since the mathematicians got a hold of it, he no longer understood his own theory. His reputation for abstract thought notwithstanding, Einstein was most at home with imagined concrete events and bridled at the ontological weight Minkowski attributed to the most ethereal of abstractions: spacetime. At this time, Einstein was just starting to work on gravity and it took him several years before he reluctantly conceded the power of a modified version of Minkowski's scheme ( a pseudo-Riemannian manifold) to get him to his destination.
But way before the curved spacetime breakthrough, Einstein did develop a picture of a gravitational time gradient causing the bending of starlight around the sun. Your presentation indicated that you pursued the provenance of the ideas in the target videos and the trail goes cold a few years ago. Please. That's off by about a century. The real source is a 1907 breakthrough memorialized in Einstein's 1911 "On the Influence of Gravitation on the Propagation of Light". According to this paper, the range of differences in time dilation at different points on the radial axis causes gravitational attraction. This is what we now call time curvature.
When he later nailed the new theory of gravity at the end of 1915, this model of time curvature was subsumed into a more complete model of curved spacetime - a phrase he himself assiduously avoided, even though it would have elegantly explained why his earlier deflection prediction was short by half. Here was his unfortunate description of the separate elements involved: "...half of this deflection is produced by the Newtonian field of the sun, and the other half by the geometrical modification ("curvature") of space caused by the sun." This startling quote exposes the gulf between his reliable spacetime math and his resistance to embracing the intuitions implicit therein. It's as if he is propounding a system of mere curved space (not spacetime) and then attempts to coax an exhausted Newton into what should have been an unnecessary assist.
I just reread this for the fifth time and it explains a lot. I remember reading about Einstein's initial gravity estimate being off be 1/2, but I did not understand why. Thanks for at least providing some insight into what happened. Would really like to see this described in a video with space-time diagrams. It does not seem that hard to explain that "gravity" (the attraction of two objects) is caused by multiple things and then explain the differences between the various causes and under what conditions one or the other dominates. This would be extremely interesting. The term "curvature" is not well defined in my opinion, and the idea of space flowing into a massive object is also somewhat unclear. Why does space flowing into an object create any type of force or action if an object traveling through space is not slowed down? Space does not create 'friction' when it passes over an object, right?
Thanks for the note and for the Gravitational Velocity pitch on your site! I vote for Eugene Khutoryansky to make the suggested video and here are a few proposed script elements:
Before you even get into Riemann and curvature, spend a few minutes on Minkowski. After all, this is where Einstein stumbled early, and he was smarter than us. To construct, or as we Platonists would assert, to reveal spacetime, Minkowski uses -c to normalize his dimensions. He converts time into a fake fourth spatial dimension. The result is a matrix with wildly counterintuitive proportionality.
We remove the third spatial dimension so we can visualize a cubic section of spacetime. A cube might measure 300 million meters by 300 million meters by one second! It just doesn’t sound like a cube. I would spend some time trying to visualize this in the video. Then when you add warping, your video might help brook resistance to the dominance of time curvature in low velocity moderate gravity circumstances.
Then the three examples of the relative weight of time and space would be
1.) All about time: Newton’s apple drops on his head. And close to Newton’s solar system except for Mercury to a small extent.
2.) Time effect matched with space: The starlight passing the sun. When Einstein finally got space curvature down, he correctly doubled his estimate of the effect on the apparent star position. An earlier attempt to verify his incorrect prediction was thwarted by WWI. This protected his reputation and paved the way for later stardom.
3.) Space dominates: Life near a black hole - or so I hear.
Wow, great idea for a video.
I had a slightly less thought out idea of comparing the calculations of a plain newtonian orbit vs the calculation of a relativity affected orbit (such as mercury) in a simplified manner.
There must be a way to show at least some of the extra terms used to calculate the orbit of mercury (and why they are not material for the other planets) but so far no physics educator/popularizer has picked this seemingly low hanging fruit!
correct...
Thanks for the note. Einstein's "On the Influence of Gravitation on the Propagation of Light" is worth reading to get some insight into this elusive subject. I am not having any luck finding it for free online, but it is a section in a little indigo-covered paperback called "The Principle of Relativity" which includes pieces by Lorentz and Minkowski that might also help you. Let me give you an overview of the time dilation argument that may help with some of your questions and please tell me if you think it is of any use.
There are several steps to the argument so bear with me. First, we don't live in a world of space and time. It is spacetime. This is not wordplay. Nor is it a simple truism to the effect that you cannot arrange a meeting with a friend for beer without designating both the time and place. It is, according to Herman Minkowski in 1907, (and shortly afterwards according to everyone in physics) the logical consequence of Einstein's relativizing of space and time as separate measurements in his two revolutionary 1905 papers known to us as the theory of special relativity. It is the mathematical means by which objective reality is rescued from the perspectival nature of space and time separately apprehended. How does it work?
Minkwoski converts time to a fake fourth spatial dimension. The conversion factor is minus c where c is the speed of light in a vacuum. If I take my X-15 hypersonic plane out of mothballs to illustrate what a path through spacetime might look like I might fly one mile from point A to B in one second. This is very fast. Yet by six orders of magnitude the displacement is through time as opposed to space. The total spacetime distance is the square root of the sum of the following squares x y z -ct. My plane traveled one mile in space but the equivalent of minus 186,000 miles in time. This exotic four-dimensional system provides us a measurement of the distance between events upon which all non-accelerated observers can agree. Objective reality is restored. But confidence in our experience of space and time as we perceive them separately is forever damaged. We are being asked to take a mathematical model more seriously than our direct experience. As the old joke goes: "Who do you believe? Me or your lying eyes?"
As I indicated in my post above, Einstein understandably hated this at first. but he eventually required a warped and warbled version of this construction to solve gravity. His early tentative step in that direction is in the "Influence..." article. Here Einstein invokes Huyghens who had explained how lenses change light direction by a varying effect on velocity. Einstein thinks this is a good metaphor for the problem at hand. It's just a metaphor and you have to imagine this in a version of Minkowski spacetime where the passage of an object through time is very much like movement through a fourth spatial dimension perpendicular to the other three actual space dimensions. As you "travel" through time your passage is retarded the closer you are to a gravitational source, the way a piece of glass of varying thickness ( a lens) retards the transmission of light to varying degrees along an axis more or less perpendicular to the rays of light - thus altering their trajectory. The light bends towards the direction of retardation (Huygens). And equivalently, the apple falls to the ground as it traverses the very subtle time gradient that is the gravitational field. (Time is passing slightly slower as you approach the gravitational source and the apple is proceeding through time at right angles to the time gradient at the equivalent speed of 186,000 miles every second so even the subtle gradient has a powerful effect.)
There's much more to the story. For purposes of concentrating on your question I am ignoring curved space which comes into play in extreme gravity or velocities approaching that of light. Einstein's original prediction of curvature of starlight near the sun was off by half because he was only taking into account this time effect - not space curvature. Bad weather and WWI thwarted the eclipse observation and thus conspired to keep his reputation intact.
I hope this helps.
@@johnnysilverhand1733
Saying those other videos got it wrong seems to be uncharitable. I'd be willing to concede that the explanations leave something to be desired, but not that they're outright incorrect. That said, this video leaves a lot to be desired as well. Without explaining tensor calculus, no explanation will do the subject justice.
Agreed. Dialect seems to be on their own high horse
No clue what this video was about. It had spent the first 7 mins arrogantly shitting on other You Tubers when I turned off. All I know is we're all travelling in a straight line through spacetime at the speed of light. Mass curves spacetime, so we're drawn together, that's gravity.
point is to clarify mistaking explanation. that is the clue
Dont we move around the sun in an ellipse at 30km/s?
@@lowersaxon I believe we travel in a straight line, but the sun's mass bends space-time so it appears we travel in an ellipse relative to the sun.
22:50 This reasoning makes absolutely no sense to me. There is no acceleration that an apple feels as it falls to the ground?? How can the entire surface of a spherical object at every point experience outwards “acceleration” If at the same time gravity crushes it into an equilibrium? What you are explaining must be the pressure of the body of matter itself battling that of the acceleration of gravity. This video provides me with many more questions than answers.
I have a hard time believing in time dilation being the cause for gravity either. If time dilation directly causes gravity then what about light? Light allegedly does not experience time according to all of these youtube scientists yet we clearly see the bending of light due to extremely powerful cosmic phenomena like black holes don’t we?
This hurts my brain
Yeah, that just came out of nowhere with zero explanation except as a fix for the clock. If he didn't spend sooo much time explaining the "wrong" ways, he might have thought of explaining that
What is the mechanism behind the outward acceleration at every point on the surface of a sphere in space?
For the earth, it's the electromagnetic interaction between the matter particles.
Well, i think that is very good question. Probably frame of reference. If you are stationary in place where spacetime is curved, you need to compensate it's curvature moving you to the center.
Came here because was not agree with above comment, but now completely agree, electromagnetic interaction keeps you stationary
The earths surface is pushing up on you at the same rate that an object falls. Therefore due to the Equivalence Principle this the same as you accelerating outwards st that rate.
couple of questions with the video at 12:42
1.) “…observing the clocks, while on the ground accelerating” is this now real/actual acceleration?
because earlier at 6:08 you said “gravitational attraction is only an apparent phenomenon”
2.) is time dilation merely apparent with respect to the accelerated observer on the ground? then the difference of time dilatation with same spacial displacements of the clocks would be linear (because the acceleration of 9,8m/s^2 remains the same, no matter how far the clocks are away).
But I learned that time dilatation depends on the gravitational potential, which would increase/degrease exponentially with same distances. how does this fit?
3.) free falling apple: although both states are inertial, does it make a difference, if it just started falling or gained already a velocity with respect to the surface (e.g. escape velocity)? or would both see the same time rates on all clocks (i.e. only the fact of free fall matters)?
4.) time dilatation of an orbiting satellite consists of both factors, velocity (SR: time ticks slower for the satellite) and gravitational potential (GR: time ticks faster for the satellite). overall there is a total/net time dilation (TD), where the TD of velocity cancels the gravitational potentials’ TD out and has the higher impact.
But thinking of a free fall, which is the same for a satellite as for the vertical falling apple, according to your video, gravitational potential does not matter hence all clocks tick with the same rate for the satellite (except that all tick faster due to the kinematic TD).
So eventually only special reality (SR) would apply, where both, the observer on the ground and the satellite, cannot agree on who is ageing faster.
Something seems not consistent, either in my head or in your video.
It video contradicts it self. You caught that too.
At that point I thought this was satirical video by a purported flatearther. But by the end he goes on claiming things are constantly accelerating towards other masses in the universe, but spacetime itself around masses is constantly curving inward masses to balance this out...
Anyone who says that something is “100% unequivocally wrong” in this high end level topic that is still being studied is a narcissist who doesn’t understand anything.
Facts aren’t relative bro. They’re either unequivocally right or unequivocally wrong.” Don’t get mad at Dialect just cause you got fooled by a wrong explanation
@@se7964 I’m actually a physics major studying to be a theoretical physicist, and I’m deriving general relativity right now. So no, he is not right. I’ve still yet to see any qualifications for what he’s saying.
@@se7964 When did I admit that I didn’t understand the topic? I literally claimed that I did understand it. And again, I’ve yet to see his credentials that prove he understands it.
@@maxwell8758 you admit that you don’t understand the topic because you’re scrolling through RUclips trying to learn GR from pop-physics videos. My advice is to remember that the components of a four-velocity are not real, and can be interchangeably mixed bwtn time and space depending on the coordinate transformation. These other videos don’t understand the difference bwtn coordinative time and proper time
@@se7964 Your logic is so bad. I don’t know relativity because I’m watching this video? By that logic, you don’t know it either. I always watch videos about science because it’s interesting. I never said I was trying to learn it. I’ve already done this before. And I’m literally also doing it right now! I have a better understanding. This video is needlessly superficial and argues based off of different definitions than truth.
At 12:00 you say the ground is rushing up. Is that all ground, going in a direction, or the earth expanding in all directions at 9.8 whatevers?
When you said "100%, unequivocally, completely wrong", I think you could've done a better job of driving home the point that other channels are wrong. Maybe add a few more adjectives? Like "100%, unequivocally, decidedly, undoubtedly, utterly, completely wrong" would've been better. Plus you could've put flame effects around the "WRONG" in red text to hammer your point into the viewers' heads. In your next video, make sure to leave no stone unturned in putting down other science channels 😊
Lol
XD
😁
Omg I just love this comment so much xD
I'm not sure he was implying they were wrong. Wish he was more clear as well
20:35 Both explanations work, there's no ultimate coordinate system. You can technically switch between some of them and remain accurate like Nick from The Science Asylum did. Also tracing circles and drawing lines isn't wrong, it's literally what a parabola (or any curved line) is: an infinite amount of infinitely tiny straight lines connected together.
Flow=gradient
They are the same thing.
Relatively different coordinate systems. It's like asking two people facing each other, what direction is forward...
Disagree with “infinite straight lines” as a premise for curves.
Infinite straight lines only makes sense if you stop at a level of precision and think “eh, close enough”
It’s infinite points along the curve, almost zero size, but completely precision dependant, which makes those “infinite” lines the closest approximation to curves - which is not the same as “literally what a parabola (or any curved line) is” by definition, as it’s a closest approximation
@@bowkenpachi7759 well, if we're nitpicky af we could try to warp OP's words to make a statement that is correct. A curve can be composed by an infinite amount of lines if we're considering an infinite set of tangent lines lol, so the curve would be described by the infinite amount of points from those tangent lines that contain the curve, but thats obviously not what OP meant, not to mention its not really a good way to describe curves since we still need to obtain its points from the tangents so it doesnt really make sense to describe it like that, but still, a silly little dumb way to try to justify OP's lines comment.
Not really. Time dilation doesn't cause gravity, it IS gravity. Gravity is caused by the warping of space and time. Saying that the warping of time causes the warping of space is incorrect
I think you're overstating your case here. Yes, saying time dilation 'causes' gravity is wrong in the purely scientific sense of gravity being defined as curvature in spacetime. But in the sense of gravity acting like a force in everyday interactions, the idea of 'time dilation gradient = gravity (as an accelerating force)' is a perfectly valid one especially for the lay audience of these youtube videos.
Your point about a guy standing on the surface of a planet not being inertial is a good one, but it ignores the fact that if we shift our perspective to the most comparable inertial reference frame (i.e. an observer at the center of the planet, with no net acceleration required to remain at rest with the overall planet), they STILL see the time dilation gradient for the falling apple, and can use it as an explanation for the apparent acceleration - no non-inertial reference frame required. This means the connection between the time gradient and acceleration cannot merely by a trick of a coordinate transform, and is in fact much more fundamental.
If anything then both your video and theirs are understating the connection between time dilation gradients and apparent accelerations. In the end, both accelerating frames of reference AND intrinsic spacetime curvature can cause time dilation gradients, which always result in apparent accelerations relative to the observer. In a very real sense then those gradients can be said to 'cause' the accelerations we see between objects (the lay meaning of 'gravity'), even as both are in turn merely outcomes of some more fundamental theory in which 'gravity' is equivalent to intrinsic curvature, and time dilation gradients are the result of gravity, and not the cause.
Yes, his argument is pure semantics, and while wording is extremely important in science, none of the people who made those videos misunderstand GR or SR. He's annoyed that instead of saying "time dilation is the cause of apparent gravitational attraction" they said "time dilation causes gravity". Nick, Matt, and others know very well time dilation isn't the source of "gravity".
@@SolidSiren is time dilation the cause of apparent gravitational attraction though? If so, how does a photon, which doesn't experience time at all, experience gravitational attraction?
18:40 of course there would be no change in distance, because spacetime is always LOCALLY FLAT, that means that for small regions arround a point, we can aproximate it by a tangent flat space time, meaning that for small motions there would be no significant deviation from a straight geodesic
I must say, I was very surprised at 23:18. Part of me suspects that you have a very specific interpretation for what is happening with spacetime when it curves in the presence of mass-energy. I've never seen that animation of spacetime "flowing into" a body to counteract an outward acceleration before, though I have heard Leonard Susskind use that analogy before when discussing black holes. To be fair, that is an intuition I almost can't even picture, because a "true" picture of it would be in four dimensions - something we can't visualize - and it would be static. Though, to preface, I happen to believe in the B-theoretic interpretation of time, in which the flow of time is an illusion. But, of course, mathematically speaking, that should ideally be beside the point.
I think the biggest confusion everyone's having here might be, at rock bottom, linguistic. Relativity is, even for most experts, really fucking hard to comprehend. We're forced to resort to constructing analogies and intuitions to guide us through its complexities. I've used the analogy of temporal gradients before because one can mathematically show - in the weak field limit - that the g₀₀(x) component of the metric tensor is overwhelmingly the largest contributor to a weak gravitational field and can be identified - in that limit - with the scalar potential in Newtonian gravity. For whackier gravitational fields and funky frames of reference, this analogy breaks down, but it's a way to illustrate that, without time being included, general relativity couldn't possibly work.
I still need to wrap my head around that intuition you presented at 23:18. I'm still learning - and will hopefully never stop learning -about relativity. But my initial impression is that, while you may have added some nuance, you also could take a step back and recognize that many of the analogies we use hold some truth. There are some truly piss poor analogies out there, in my view (the trampoline analogy comes to mind). Others, though imperfect, may represent aspects of the theory. But I think the degree of "wrongness" you've so confidently attributed towards many RUclipsrs, some of which are very smart physicists, was overstepped. Most of them likely know that mass-energy is the source of curvature and that uniform accelerations can be removed.
We're just trying to drudge through this beautiful and horrifically intricate theory as best as we can. So, take it easy 👍
@pyropulse You have several misconceptions, which I'll try to address here as succinctly as I can:
1) "We can always transform to a frame that eliminates an object's acceleration."
That can only be done locally, that is to say, at a single point. The metric can only be made flat generally at a point; this obstruction indicates curvature.
2) "The error comes from thinking a mathematical association to 'real space' means that real space is actually curving; that literally makes no sense; you cannot curve nothing."
Spacetime is not "nothing." I don't know where you got that from, but to call something with such a rich differential structure "nothing" is at best a vague description, and at worst blatantly false.
3) "I did physics, and I aced every exam with no effort, getting a 4.0 gpa with skipping lectures and just figuring out the exam problems when I showed up; and I would finish my final in 25 minutes when I had 3.5 hours, and got a 98% on it, while next highest was a 72% (UC Berkeley). I only say this because my abilities and understanding are clearly superior, so why should I trust nonsensical nonsense just because inferior people tell me that is how it is?"
The fact that you think spacetime curvature is not only impossible, but not even a sensible concept, disproves the hypothesis that you somehow possess "superior" abilities. Moreover, your need to explain your superiority invalidates you right from the off. If you have you display your virtue in order to get people to notice it, then you never even had the virtue in the first place.
4) "To demonstrate my point, there is a curved spacetime in a purely Newtonian framework, called Newton-Cartan theory."
That theory is a reformulation of general relativity in a language that makes its connections to Newtonian gravity more easily visible. It is a mathematical rewording of the same theory, if you will. It does not demonstrate that spacetime doesn't curve.
@@jmcsquared18 This nickname piss-marked every comment thread by replying to every single comment with similar nonsense. Kudos to your patience and your answer! It made me grin like 😁!
"Relativity is, even for most experts, really fucking hard to comprehend." --- Best comment I've read in years.
@jmcsquared the channel Science Clic also presented the intuition at 23:18. He talks a little bit more about it, but, doesn't give a full on explanation, if I remember correctly.
I've seen a similar representation of with spacetime flowing into the body in a ScienceClic video called "A new way to visualize General Relativity", though he seems to have more videos on GR as well that I haven't yet watched. I'm still trying to wrap my head around all of it too.
I'm an avid follower of all channels mentioned and admittedly learned a lot of physics from them in combination with personal study. They're not "unequivocally wrong", perhaps some technicalities yes, but imo it kind of felt like this video was putting them down to draw attention to this channel.
Your videos are brilliant in their own right. And everyone here has the same passion; to investigate and evaluate a more complete view of the Universe.
No individual person knows everything about everything. Humans are like bees. We all have our slice of expertise that serves the greater species and genius emerges from each of us sharing ideas and why we believe them. It's ok to elaborate on ideas of others and refine them towards a greater truth, but we should learn to be humble and realise we are all searching for the same thing on the same journey.
Having said all that, you do have a good point distinguishing between curvature and constant velocity motion.
@10:49 this is describing a Minkowski Spacetime. Time Dilation is still relevant as the Rocket is an inertial reference frame, only experiencing motion through time, but everything else in the Universe is comparatively percieved as being time dilated.
What all these channels neglect to explain is what a slow moving clock even means to an observer, and where the term Spacetime originates from. Time Dilation is looking at another moment within the history of the Universe. The past and future existing simultaneously. And this is where the term Spacetime comes from; Space and time forms a single overarching entity. A block timed Universe.
The first step to understanding gravity is to understand a geometrically coordinate equivalent block time, then introduce the scewed geometry of the time coordinate components towards mass.
@@narfwhals7843 Ahh true. The vid does say it's an accelerated reference frame. However, acceleration works perfectly well within Special Relativity (meaning not considering curved time). "there is no truth to the rumor that SR is unable to deal with accelerated trajectories, and general relativity must be invoked", Sean Carroll. An Introduction to General Relativity, Spacetime and Geometry (2003). Cambridge University Press (2019). pp. 11.
This makes sense as acceleration should not have any impact on perceived time dilation other than an increasing affect as velocity increases.
You're right. 😊
I was going to leave a response to this video but in in scrolling thru, I found yours and the points you make were similar to mine. So, I will simply say - well done) 🔲
No I think his criticism is valid. The other channels claiming certain effects are "caused by" other things is not reasonable. Namely the claim that gravitational attraction is caused by a time dilation field. A gravitational attraction effect IS necessarily going to go hand in hand with a "time dilation" effect, in order to uphold the laws of thermodynamics. However, it's kind of like claiming that rain is caused by a lack of blueness in the sky. Yes the sky generally isn't going to be blue when it is raining, but it is entirely unreasonable to claim that is the underlying cause of the rain when they are both artifacts of the water in the air condensing into droplets.
I believe one should be quick to jump on people for giving bad reasons for things that are true, they do an enormous amount of harm, perhaps even more than those that say things that are untrue, because it gives more credibility to those saying falsehoods than anything they themselves could say. It's like the Piltdown man. It's like the Piltdown man. That was a fraudulent fossil of a hominid. Ultimately it provided fuel for young Earth creationists to claim as dirt they dug up on the theory of evolution. False claims undermine the credibility of everything else you've ever said.
9:35 no. the equivalence principle is valid in a constant gravitational field. Observers ALL in a constant g.field will observe clocks ticking at the same rate. The reason objects in space tick at different rates is because the curvature is less the further away from earth.
So the Jet flying at 9:39 will see clocks everywhere tick the same if he is indeed accelerating in flat spacetime.
Thank you for this necessary video! But I have a question. If I've understood you correctly, you're saying that the time dilation gradient observed on the ground can't be the source of true gravity (the curvature of space-time) because this gradient depends on the observer. An observer in freefall does not observe a time dilation gradient, but he does observe that he is getting closer to the Earth. This time dilation gradient is due to the fact that the ground is accelerating upwards, and due to this acceleration, we observe a time dilation gradient. But at 2:52 we see in the PBS spacetime diagram a time dilation gradient on a much larger scale: on a scale where the curvature of spacetime is not negligible. So this time there's a time dilation gradient that's not due to acceleration, but to the curvature of spacetime caused by the Earth. But the time dilation gradient caused by curvature doesn't depend on the observer, does it? Because this time it's due to the curvature and not to the acceleration of observers on the ground. So how do we show that this explanation is wrong in this case?
He made a huge mistake in singling out PBS Space Time and The Science Asylum, both are run by actual physicists and only try to explain current theories. they never say that any of the theories are the answer. This really bothered me and too bad, I had been enjoying his videos.
@@bobinmaine1 if the theory is the answer isn’t really the question here. They are all talking about general relativity and trying to explain that theory. But dialect disagrees with their interpretation of the theory.
11:00 How does an stationary sphere object accelerate at all directions at the same time?
I had this same question, and after some probing to get some clarification, I finally arrived at this essential part of the explanation. The issue is, that acceleration in general relativity doesn't mean the same thing as acceleration in kinematics.
In kinematics, it is the rate of change in velocity (a = dv/dt)
In general relativity, it is the net force per unit mass, not counting gravity as a force. (a=Fnet/m)
The equations a=dv/dt and a=Fnet/m are interchangeable ways to define acceleration, as long as you treat gravity as a force, and relativistic effects are negligible. But the problem is, that these are profoundly different when relativity comes in to play.
@@carultch So he is using something also called acceleration but that is not really acceleration to state a fact about the REAL acceleration of Earth. Let's zoom it out for a bit and double check the variables we should have defined ( or take for granted). Earth is spinning around its own axis at (on average) 1,669.8 km/h; around the Sun at (on average) 107,278.87 km/h; The Solar System as a whole is orbiting Sagittarius A (the Black Hole at the Center of the Milky Way) at around (on average) 220 km/s; The Milky Way itself is very likely orbiting a larger object (or 'attractor') , e,g., the mass center of the 'Local Group'... and then it all must orbit something else, but wait... the Universe as we state...I mean, as we know doesn't really have a center. Does it? Now, ask yourself again what 'accelerating in all directions' mean. Tks.
@@thesecondslit1710 Allow me to clarify this. When your environment accelerates due to gravity alone, the two effects nullify each other in terms of your ability to feel either one. You cannot tell the difference between being in free fall nearby a planet, and being in deep space moving at a constant velocity away from all sources of gravity. Because force of gravity is proportional to mass, and because force needed to cause acceleration is proportional to mass, the two factors act uniformly on every kilogram of your body, and no constraint force is required. This is apparent weightlessness, whether it is zero gravity or not. You don't feel gravity; you feel constraint forces.
@@thesecondslit1710 That being said, the gravity due to outside astronomical bodies also nullifies this way. This is why we don't feel the Earth's acceleration due to orbiting the sun, or due to orbiting the center of the galaxy, or due to any galactic motion we have. The only gravity due to outside astronomical bodies that plays any significant role in governing actions on this planet, is the tidal forces, which are only significant due to the sun and moon. The moon, moreso than the sun. The tidal forces are on the scale of nanonewtons for a human body, which is why they are only significant when applied across the ocean that spans a vast distance to different parts of the moon's gravitational field.
That really only leaves the acceleration due to the Earth's own rotation to explain, and this one is easy. Calculate the force needed to accelerate with the Earth's rotation, and it is 0.334 Newtons/kg. Use the speed of 1669.8 km/hr translated to m/s, and the radius of Earth in meters, 6.378e6 meters, and the equation v^2/r, and that's what you'll get. Notice that this is nowhere near Earth's g of 9.8 N/kg. All this ends up doing is making gravity slightly less than what it is at the equator, which is measurable. There are other ways we can measure this as well, such as the Eotvos effect.
@@thesecondslit1710 The "acceleration" that he's using in this video, is not the same thing as the kinematic acceleration due to changes in velocity as you would measure in simple Euclidean spacetime, like you are accustomed to doing at an introductory level. But in the spacetime distortions caused in general relativity, there is an acceleration when you are at rest on this planet. You are accelerating against spacetime collapsing in on itself, nearby the source of a gravitational field. The normal force from your seat stops you from free falling, and the structural forces of this planet stop it from collapsing, following the collapsing spacetime.
The idea in GR is that gravity is "not a force", but is a body's natural nature to follow the path governed by spacetime. Constraint forces stop you from doing this, so that you can be at rest in Euclidean spacetime in the Earth's surface's reference frame.
21:43 Time dilation comes from the line element ds, which is derived from the metric tensor guv, which is found using the Einstein’s field equation. The Einstein’s field equation deals with curvature of space time using the Riemann curvature tensor Ruv, which is just a compactified block of a bunch of metric tensors. The sourcing term in the equation is mass, but time dilation and length contraction are still from the curvature in spacetime. At least in Einstein’s general relativity.
No, the time dilation appears because of accelerating frames of reference, which are constructed via special relativity, then imported to General Relativity via the equivalence principle. And yes, they are associated with the metric, but they are a consequence, not a cause of it.
Thanks for helping correct this stuff, Robin! 👍🏻
@@dialectphilosophy time dilation comes from the curvature of space time and as well acceleration, I made no claim of time dilation causing any of the above.
Edit: acceleration as in deviation from geodesics.
In special relativity, time dilation is a consequence of Lorentz shifts, which is velocity dependent and frame dependent, it doesn’t need to come from acceleration.
@@robinwang6399 Great post!
@@dialectphilosophy This is not true in the case of objects near massive ones. You can orbit a black hole while the theta coordinate changes without altering altitude. This state is called free-fall, where you still experience time dilation from the metric.
Deflection from time dilation is still a thing, at least correct in terms of gravitational lensing and Shapiro delay. The explanation of gravity is due to time dilation isn’t complete, but it’s not wrong. Since any deflection comes from the geodesic equations which depends on the metric which depends curvature tensor which depends on energy momentum tensor, the curvature of space time in some cases looks like a curvature in time. Your explanation of everything accelerating outwards isn’t wrong either, it’s not going to explain anything regarding to tidal forces. Tidal forces comes from geodesic converging at the centre of mass of the massive body (in case of a planet), which comes again from curvature.
Edit: the tidal force part I mean if we take the frame of two objects falling, they should get closer together in a point sourced gravity field, but for a expanding sphere in flat space, this doesn’t happen in the object’s frame. You need to improve the condition that all distances in sphere is constant while the sphere expands, which is equivalent to saying space time curvature.
There is no such thing unfortunately as "curvature in time" which is another popular fallacy of general relativity. There is only curvature of the spacetime manifold, which can be sliced such that, according to a particular observer, the curvature will not appear in the spatial subslice but only the temporal one. However, a different observer can always slice the manifold in a different way, meaning there is never a unified sense of "time curvature". Time dilation as a causal agent of gravity is one-hundred percent factually inaccurate, and a misunderstanding of both the nature of gravity and coordinative time dilation.
@@dialectphilosophy you are talking about space time foliations, the time curvatures in that case is a gauge condition, taking this gauge to 0 causes problems such as geodesics colliding and falling inside the event horizon when doing simulations. The idea of time “curvature” is flawed, as in speaking of space and time separately without constraints is flawed, but it is a interpretation in some gauge.
Edit: I guess it’s really “time dilation can look like the cause of gravity, if you transform your coordinates.” As in case of Shapiro delay, it looks like the wave in the inside gets squished from being “slower”.
@@dialectphilosophy And hilariously enough, the "particular observer" for whom only the temporal curvature will be apparent was the only observer ScienceAsylum was referring to in his video -- and he specifically explained that. He was saying that for that "particular observer" on earth, only the time slice of the spacetime manifold will seem to be affecting gravity -- and therefore, in that frame of reference, the "cause" is predominantly the curvature of the time slice of the spacetime manifold. If you missed that in his video, then perhaps the problem here is your inability to understand the English language -- and your inability to understand basic philosophy (which is shocking for a channel named "dialectphilosophy"). Even though he didn't say all the words that I just did, everything I just said was clearly implied to anybody with a command of basic common ordinary language. So, admit defeat and go home.
So, are you asserting that there IS an ether - spacetime, I guess, and suggesting that Einstein thought so too - or just that everything - absolutely EVERY SINGLE THING - is in an accelerating frame of reference? Or have I got it all wrong? I've laid awake at night for years trying to figure out what it is about two masses that draws them towards one another. If spacetime curves, cool, but why? If mass - the concentrated binding & kinetic energy of (mostly virtual) quarks jiggling about in a nucleon - is what curves spacetime, why? Is it that certain masses end up in one place that creates the curvature, or that the existing curvature - the whole CMBR ripples thing(?) - is what agglomerates the mass?
I found the river/waterfall analogy compelling - and it helps resolve the counterintuitive notion that we're rushing upwards at 9.8m/s2, but then, water is water, spacetime is spacetime, ether is...? What exactly? I was always taught that transverse waves didn't need a medium... If particles are excitations in quantum fields, are quantum fields the ether?
I was intrigued by your comment that literally every piece of matter in the universe is 'rushing towards every other piece of matter.' I kinda thought years ago that what we perceive as attractive gravity could actually be repulsive - in the sense that the universe is rushing away from itself as fast as possible (C) in every direction and that agglomerations of (observable) mass are really just localised, almost foamy, versions of that - bottlenecks of accelerating boats as you show it(!) - and really tiny ones, at that - stars are so, so far apart that even large masses are relatively puny on a cosmic scale. But at the end of the day, and if, say, the universe consisted of two nucleons only, how would they curve spacetime in order to rush away from, or toward, each other & why? (indeed, would there be any spacetime for them to curve?)
Your videos are very interesting & a slightly different take on PBS et al.
Confused as ever, but still curious.
Dominic
Hey there, thanks for watching! As to the question -- why do two masses attract one another? Unfortunately none of our modern theories come close to answering that question -- it's as mysterious as when Newton first postulated it. In this video we were concerned with differentiating cause and effect as the theory of GR views it, in which the apple does not fall to the earth, but the earth accelerates towards the apple. (However, indirectly one can still blame the apple falling on spacetime curvature, as spacetime curvature causes the "river of space" to converge in towards the center of various masses, and thus produces the outward acceleration of the earth.)
GR takes a very substantial, ether-like view towards space itself, which Einstein himself confessed in 1920, and in that manner, is actually quite at odds with the philosophy of special relativity.
I don't think those videos made the mistake of equating gravity with gravitational acceleration. It seemed clear to me that they were using "gravity" as shorthand for "gravitational acceleration", which, after all, is what most people call "gravity".
They did confuse the cause of gravity though. Time dilation is an effect of gravity, not the other way around.
@@jjt1881 at least in the science asylum vid, he don't say that time dilation causes gravity, more like time dilation gives the ilusion of gravity.
This really should have been handled like how ElectroBoom and Steve Mould and Veritassium had and settled their disputes. Shoutouts to their respective channels by the way.
Their exchanges about the mould effect and about the nature of how electricity flows through wires were civil, respectful, fun, and just as informstive as entertaining and didn't have this air of putting either of them down even when one of them was wrong about something or learned something new.
That should be like the gold standard of disputing another creator and holding a debate or exchange, especially since it seems like the issue could have been resolved with a conversation with them, and in the comments, it even seems like there's very interesting details to clarify and dig into that would be more informstive.
However, I can definitely understand a disdain for oversimplified explanations they lead to faulty understandings of concepts that are born from "dumbing it down" too much in the attempt to make the knowledge more digestible to a key person. At a certain point it is very challenging and even crushing to have to do what feel like butchering a concept in an attempt to communicate it to someone who doesn't have the background to understand it or relate to it. It's very easy to then get a sense of harsh superiority with the "right" way of doing or understanding the concept. I get it, I've been there. I've been they person who would just insist that if someone wants to truly understand they unavoidably have to apply themselves and engage with the material. The thing is, expecting everyone to do that isn't sustainable and it limits how far knowledge can go.
It is unfortunate that in your case these oversimplified models hindered your progress, but you must take the time to appreciate how far that communication got you in the first place and others like you, and how it gives people who have only a casual interest in science something they can handle.
It's so easy to take for granted that they make graduate level topics easy to understand and relatable to engage with. The value in this cannot be denied.
But regardless, this is a good thing as it promotes everyone to be vigilant of where they get information from and to not blindly accept things as doctrine but to always cross reference and seek to know for oneself to the best of one's ability. That is a good takeaway, along with the intellectual content if this video.
This! I would love to see a RUclips science "battle" :D
Rinkamime, sometimes it's just as simple as 'wrong is wrong', and there is NOT value having a whole bunch of profiteers pretending to be at a level to teach something they really don't understand. It's dishonest of you to portray those wrong videos as merely "oversimplified", so you can make your point they still have value. They don't. You said it's unreasonable to expect everyone "to apply themselves and engage with the material", but he's not expecting everyone, just those who want cross over and claim they can TEACH a subject, then yes it is definitely reasonable to expect those who teach (and/or profit from pretending to teach) to understand what they are teaching.
@@Grrrnthumb Did you read the comments of the channels called out posted to this video, ie PBS Spacetime and Scieny Asylum? I'm of the impression that this very much is a misunderstanding, and in.many instances they even outright say in their videos that they are simplifying the subjects.
And there definitely is value in what they've done. Like are yours eripusly going to say that people who don't have a background in calculus but have an interest in science being introduced to the scientific concepts on a level they can engage with at their level (ie, they aren't just gatekept out of it all together) is not a net plus? The guy said in his own video that it was videos like there's that held his curiosity about science and fueled his enthusiasm. Sure *he* encountered issues where the way he learned things were a road block for him, but like, he's speaking for himself here. I personally can attest to how videos from the channels he mentioned actually got me *ahead* in a lot of my science classes and I went into those classes primed on certain topics. Sure I didn't know everything, but there were lots of rewarding profound times when I'd witness so ething "click" where the stuff I'm learning reminds me of a video I watched and then it all makes sense and is infinitely more meaningful. It also felt good to be the one answering questions preemptively with wyd I knew, and having my background knowledge, being able to apply what all I learned from those channels in new ways as I problem solve
In other words, speaking for myself, I most definitely benefitted. I was watching videos like this since middle school so by the time I was on college so many things were a breeze and just rehashes of things I generally knew, just with the mathematical rigor added into it once I was prepared for it.
But as I said, I've been on the giving end of this attitude to, where I'd just get impatient with people and be like " okay no I can't simplify this anymore, google it or get a text book or something."
It takes character to amdit that that is a failure, but I'm not a teacher xD
Cosndier the words of Feynman where I think he said that if you *can't* communicate a concept in terms that let people can grasp it, you yourself don't understand it well. This is a real art qbd it has very real value.
Now like, if you want to go intellectual edge lord and be like "well ACKSHUALLY it's really like this" for everything they say in every one of their videos then by all means, but at least do so knowing that, it is definitely a good thing to be able to communicate these topics in ways let people can grasp well, and that they do well in my experience and humble opinion.
And again, read their comments and you'll see really clearly they all of this is really just either a misunderstanding, or at worst, is a video made out of spite and frustration.
@@occultninja4 Yes I've seen all those & read most of the comments. You're being dishonest on at least 3 things: 1) That the author of this video left any possible room for a "misunderstanding". Did you even pay attention to this one? Either he's plain wrong or they are, no middle ground possible here. 2) You're dishonest in your implication that you understand the underlying facts enough to claim there could be a gray area/misunderstanding on this issue. 3) It's dishonest to use fake debating techniques like restating the author's view in crazy, false, exaggerated ways like implying he (or I) want to 'ackshually be an intellectual lord and correct every point on every one of their videos'... clear sign you care more about winning a debate than finding truth.
@@Grrrnthumb I don't get where you're coming from with the dishonesty thing. But whatever, let's just agree to disagree. We have different views on this. I'm fine leaving it at that xD Evidently we aren't seeing eye to eye on this and if youve actually read the threads of the other content creators and still don't understand where they are coming from, it's a lost cause. It should be pretty clear cut to understand I'd imagine, or at least, to be able to relate to without assuming foul play or malicious intent. But maybe you're just not convinced and if so, that's you I'm not pressing you. My limited free time isn't going to be sucked up in an internet argument xD I've stayed my stance and opinion, and Lile, bare minimum, I adamanelty hold to my original commebt that the way this video was aimed could have been done more constructively.
But I'll unconditionally respect your opinion though!
What about ScienceClic?
Totally solid GR.
23:36 so is spacetime kind of constantly flowing into the center of a mass? Now a black hole also makes more sense, as things seemingly flow into it, because they are "stationary" on that path? Where the mass is accelerating.
Question: why would an outside acceleration be the cause of an apparent attraction between masses if it is balanced by spacetime curvature?
Answer: it isn't. The explanation of those RUclipsrs is actually closer to the truth than you realize, but you need to look at the falling apple (or squirrel) from the point of view of a hypothetical observer at the center of the Earth.
At the center of the Earth, you're surrounded by an equal amount of mass in all directions, so you're not attracted towards any particular direction, so you're just floating inertially. If you were to carry an accelerometer, it would show 0 in all directions. If you look at an apple near the surface of the Earth falling towards you, you can draw the trajectory of that apple through time and distance and find it curved. In this scenario, you're actually looking at space time curvature, as your time axis is a geodesic - and so is the time axis of the apple [if it were to carry an accelerometer, it would show 0 in all directions as well]. And indeed, the curvature of the apple's time axis is the only possible explanation why it would fall towards you, because neither you nor the apple experience any acceleration.
Observers at the surface of the Earth make a similar observation as our observer of the center of the Earth, because they're not moving inertially [which would mean that we just fall through the surface towards the center]. Our being accelerated upward is the explanation *for us* why *we* see things falling down: the acceleration just keeps us stationary with respect to an inertial frame that is the key to understand the cause why the apple falls.
You're correct in pointing out that clocks ticking at different rates isn't the cause of the phenomenon called gravity. But surface acceleration isn't the causal answer, either [it only explains why we're stationary with respect to the center of the Earth]. Curvature is the true cause, when understood appropriately.
And to play your game now:
Now the question is if you can acknowledge your mistake. You've been fooled by the word "acceleration" into thinking that this somehow translates to an attraction between massive objects. I'm relying on the readers of this comment to bring this to Dialect's attention and make them publicly apologize.
😁👍🏽
Your explanation seems reasonable. The true cause of Gravity in General Relativity is curvature caused by energy and mass.
@@marope I'm not sure why the creator felt the need to attack other videos, under the guise of properly applying Einstein's Equivalence Principle and explaining the cause of apparent gravitational attraction, but anyone serious about learning relativity and gravity, wouldn't solely rely on a single RUclips video.
I don't think any of the videos intentionally mislead anyone into believing that something other than the energy/momentum density of matter is the cause and source of gravity.
The confusion comes from the different terminologies used in _Newtonian_ Gravity, _General_ Relativity, and _classical_ mechanics. The definition and descriptions of tidal forces/acceleration, gravitational attraction, gravitational field, and spacetime curvature have all changed since Einstein's paper on _General_ Relativity was published.
I don't think you can use the center of the earth as a reference frame to locate objects that are falling towards the earth. In general relativity, reference frames are only valid locally, due to the curvature of space-time. As the objects falling towards the earth are actually very far from the center of the earth, more than 6,000 km away, you can't use the reference frame at the center of the earth to locate falling objects, or to measure their acceleration. The ground accelerating upwards is indeed the reason we observe objects falling to the earth's surface, because if the ground didn't accelerate and followed its geodesic in space-time, then it would move closer to the center of the earth due to curvature, and the earth would collapse on itself into a black hole. And so the distance between the ground and an object above it would increase over time, instead of decreasing as we observe it. To counteract this collapse, the ground is forced to accelerate outwards so that the earth remains constant in size.
@@arthurdurand4098 So if we had a lab at the center of the Earth, we couldn't explain stuff falling towards us or what?
I confused by questions like “does gravity cause warped time” or “does warped time cause gravity.” It’s like asking do “trees cause forests” or “forests cause trees.”
Trees cause forests because you first need trees to have a forest but you don't need a forest to have a tree. It's a bad analogy but it's good because it shows how most analogies in natural sciences are wrong and do nothing to make things easier to understand.
Actually, both are wrong. It's like saying fevers cause coughs, or coughs cause fevers. Both are effects/symptoms of the real issue: an infection. Matter or energy warping space-time is the cause. Gravity and time dilation are the effects, or the children. You can't say child A caused child B. The cause/creator is the mom.
I'm wondering where is that point where the distance between geodesics begin to grow? Were they really exactly the same before that point, or the difference being so tiny we couldn't measure it before? Thank you! (in reference to the video at ~19:00)
While I respect this channel’s contribution to the subject, I don’t think slamming other channels attempts to contribute WRONG in such an arrogant manner. Particularly due to the simple fact that even this channel’s “ABSOLUTE” is predicated on General Relativity. The entire question stems from the original (GR) breaking down. The person responsible for figuring out how to merge physics into microphysics, where the math complements the subatomic structure of the “microverse” will be responsible for defining the next phase of humanity. This will require people presenting radical ideas and thinking outside the box. The box in this case being general relativity. Dialect needs to remember that everything is wrong until proven correct.
What causes the space to bend into the condensed energy?
It's easy to explain gravity by making such an assumption, but to understand the true cause, it would be more interesting to understand the cause of spacetime curvature.
And if the the ground has been constantly accelerating up for billions of years relative to space moving down through it, does that mean space is now moving down through the earth at billions of times the speed of light?
You can say that space is falling. But from my understanding of GR, a "falling space" is not accurate. It's just the solid surface on earth keep accelerating upward in its own (local) frame of reference, and when you look at that frame "from afar", it doesn't move.
It is important to state that a global frame of reference does not make sense in GR.
Tis the greatest question…..not what is the purpose of life, but why do masses curve spacetime.
@@longhoacaophuc8293 saying the volume between geodesics shrinks to keep the entire planet in the equilibrium stage while every section of the planet is accelerating outward are more accurate.
@@longhoacaophuc8293 My issue with the provided explanation is that it starts by saying the ground is accelerating up, and then it says spacetime curvature opposes it, keeping it from expanding outwards. But what causes the upward acceleration to begin with? I find it makes more sense to start by saying spacetime curvature brings the material of the earth closer together. When the atoms that make up the earth collide, the repelling forces between them start to oppose the spacetime curvature. These repelling forces are what drives the grounds upward acceleration, doesn't this make more sense? (No physics background here, I could be missing lots of stuff x) ) I think starting the explanation with "the ground accelerates up" is a bit counter intuitive.
@@japar107 yes, the pressure caused by the internal interaction from the material that make up the earth is the cause of the net acceleration on the surface since gravity is no longer a force.
The issue I take with Relativity is its inability to explain how gravity is an energy source. I say that because the heat energy released during precipitation isn't like some battery that has stored evaporation heat energy, which is traceable to a conversion of mass into energy like fusion or oxidation. If gravity causes things to accelerate in a way that adds heat, then that additional energy requires the acceleration is kinetic energy being converted into thermal energy. What is implied by that gets into other issues, but I have my own thoughts on what it is on my channel if anyone is curious.
ruclips.net/video/R3LjJeeae68/видео.htmlsi=C5z_mOtRBawXB-M7
Gravity doesn’t cause things to accelerate. Things accelerate due to their own mass, and gravity responds to that by curving spacetime to compensate. Gravity is just the curvature of spacetime. It can’t cause anything to accelerate. Acceleration is caused by a force.
The appearance of gravity causing things to accelerate is a misunderstanding about our own acceleration, when we think we are at rest. We see something in free fall, moving inertially, but we perceive it as accelerating, because we are seeing the differential with our own acceleration, and an optical illusion caused by the misconception that we are at rest.
@@douglasmurdoch7247 I'm fully aware of Relativity's definition of gravity. I have a hard time accepting it.
First off, the violation of the conservation of energy that's required for the CMB to remain unaffected by the uneven expansion of spacetime, while all other sources of radiation are redshifted.
Second, it can't explain the rotation curve of galaxies without and the lensing of galaxy clusters without leaning onto Dark Matter as a crutch.
That, and the intricate structures within galaxies themselves as they aren't basic spirals no more than a smiley face would resemble any one man.
Then there's the infamous oil and water relationship that Relativity has with Quantum Mechanics.
Furthermore, the superluminal movement of galaxies has to be assumed to be expanding spacetime without any ability to confirm that independently, which would falsify Special Relativity, and open up a can of worms in physics that makes such an assumption desirable.
Then there is the acceleration of water molecules moving against the atmosphere during evaporation and precipitation phases due to the effect of gravity that is dissipated as heat. Such heat is not traceable to fusion from the Sun or oxidation from a campfire.
@@Hydroverse I fully agree that dark matter is a crutch. I have a deep seated instinct that dark matter isn’t real, and that it’s a stop-gap to glue together our flawed math.
It's amazing to me people accept "gravity is fake!" as an answer. That's bullshit, it's a real force. It's way more likely gravity is an electromagnetic effect somehow than that Einstein is right about "spacetime curvature."
These RUclipsrs you reference definitely helped my understanding of gravity and the physics of spacetime. And you have also helped shaped my understanding. At this point, my layperson's view of gravity is that it is like a "current" flowing towards the centers of massive bodies. A falling apple is just caught in the "current" towards the Earth's center of mass. Standing on the surface of the Earth is like standing under a waterfall of spacetime and any loose object above you will move towards the center of mass at the rate of the "current" which on Earth is 9.8 m/s2. This helps simply explain how we can be "accelerating" while standing still on the surface of the Earth.
That was my thought before I watched Science Asylum's video and I was happy because that "flowing" spacetime makes no sense to me - where does it go in the center of the mass? That time explanation got rid of all of that, which was great!
My explanation for now is the difference in spacetime distortion between two objects. For example, the distortion of earth's spacetime is just "closing" the distortion of an apple, which "accelerates" the apple. Like if you have a ball in a hose and push it forward by compressing the hose behind it. Since it is spacetime itself that is changing, no actual acceleration of the apple takes place. Once the apple hits the ground, the constant pressure against the ground makes it effectively accelerating upwards.
@@Korbin0815 Re. your last sentence. At 9.81 m/s^2 ? Is that where it's coming from? I watched his (Science Asylum) video, back when it came out. I am lost at "the ground goes towards the falling object" explanation but his assumption that there is a time gradient really sounded, for me as a person with biology background, plausible and at least understandable.
@@Korbin0815 could it not just be that the centripetal force of the earth as it rotates through space produces the force we feel as gravity? We’re so small relative to a planet, we’re essentially a spec on the surface. Earth is a rocket ship. It’s accelerating though space in different frames of motion while spinning. Essentially imagine a car with a tennis ball, but then that car driving is inside another huge car that is also driving. It makes sense to me that we’re just being pushed inwards due to how the forces of motion operate, but at a planet, solar system, galactic scale.
You are simply wrong. Being wrong is not a virtue especially when you are spreading misinformation
@@gonzalochocanoart no that is false
12:00 If the ground if rushing upwards to meet the apple, if we drop an apple from two opposite poles of the Earth, then earth will explode since the grounds on the opposite poles is rushing in opposite direction? Or atleast since the Apple does not have much mass, the earth will get stretched\ expanded due to the trying to rush towards the two apples?
amazing video! this is the best video. as you could see, coordinate-free mathematics will be highly required for true research of Gravity. it is really absurd to see how many wrong interpretations have been spread out by pseudo-physics youtubers
But you forget that the owner of the channel is also a pseudo-physicist whose messages are not based on science, but which he simply makes up himself.
@@Astro-Peterreading further now I see you’re a troll. Makes sense. This is a brilliant video and someone’s jealous :-)
@@se7964 : Here we are on a channel that at least claims to have a scientific interest. If that were the case, then personal insults would generally be forbidden. In fact, I regularly experience personal hostility when I express criticism. It seems to be more of a religious community than people who are genuinely interested in science. The author of this channel is waging a campaign against the understanding of special relativity. His ideas about it are simply not accurate. Apparently he doesn't even understand what an inertial system actually is. In this respect, I actually can't take his well-crafted videos seriously and you should also be a little more critical.
the issue of GR is just how hard to visualize it without simplifying it to the point where you end up not understanding what you are trying to do anymore.
Yet we can easily visualize many God entities and their intentions, their thoughts and desires toward us and the world... ( the hubris in those religious preachers heh, 'believing in something you don't understand isn't the problem, the problem is to be Sure to understand about something you don't know ;)
The real issue is simply failing to understand the easy basics and as long as we won't understand them, we will be like those kids who wonder about something so far away in their mind and mystically incomprehensible while you are just explaining them simple addition.
We are mystified by General Relativity like those kids are mystified by additions.
@@sobreaver i get what you mean, but the delivery was trash.
It's not "hard to visualize" it is incompatible with reality and logic.
Despite this, many people can IMAGINE it.
After all that build up I was waiting for what the correct explanation is and all I got is “you are accelerating towards the apple”.
That explains less than any of the other videos. Its about equally useful to saying “gravity makes objects accelerate downwards”
Why am I accelerating towards the apple? What causes that? Curvature? Well why would curvature cause that? (Unless there is a force involved?) and what causes such a force?
I started questioning myself if I stumbled on flat earther youtube.
Also ends with “granted, this is a very abbreviated explanation”. Which is what you just accused the others of doing.
Lol. Exactly.
Devil's advocate: the reason you would be accelerating towards the apple is the same reason that the pieces of an object accelerate away from the center of the object: the normal force, caused by the fact that matter can't be less than a given distance away from itself (which in turn is cause by the other 3 fundamental forces).
This, however, leaves the central question unanswered: why does spacetime curve towards mass?
What is the “shortest path between coordinate grids”? 15:01 the world line on the Spacetine diagram will be curved if the object wants to take the shortest path between coordinate grids.
Brilliant. Not sure I get even 50% of it but my intuition maybe gets another 40% or so... the last 10% I reserve for healthy skepticism in case some part of this excellent video isn't quite right. I too very much appreciate the work that it took to sort out the complicated RUclips science pedagogy mess and present it in such clear, graphic terms. Does anyone know if the Veritasium video "Why Gravity is Not a Force" gets it right, or at least more correctly, like this one here? In any case, this is fantastic investigative science journalism. Many thanks!
I was also curious, and yes, Veritasium gets it right. I liked their explanation better in some ways even
Well done, except no one is right. This kind of videos are all metaphors for the real thing, you can't really explain to someone a coordinate transformation and so on in a single video, I believe the less you actually dive in theory and maths of the models, less accurate is your analogy. Folks from Scienceclic did the same analogy, but with a whole series on GR an even that is incomplete. Lay people won't leave any of these videos with a degree, they have their purpose on motivating a spread of science to uninvolved people. The only way to really grasp what is gravity is from a "full" course (with real math), like Eigenchris' series on tensors (algebra+calculus) and general relativity, or a book, like Gravitation from Misner, Wheeler and Thorne, or maybe the hardest way, going to an university
Then you get lost in the math / MODELS and don't even pay attention to physical reality. Our universe does not have 4 dimensions. It doesn't have curved space. Those are observed facts.
@@paulthomas963 the problem is that "reality" is just a layer of existence, our models compile a set of phenomenology in a way that is understandable and workable to us. Math is a language taylored to try to code nature's observable (or possible) behavior, many times proven right, some times proven wrong, what really matters is if a mathematical code happens to be numerically right (at least to 95% confidence) and mostly conceptually coherent within itself and other areas of Physics. To that point, light might behave like waves in a puddle or little pebbles throw at each other, it can also change frequency or bend in vacuum as if there is refractive media there, so choose your favorite mathematical narrative and defend it with actual research using it. I think that somewhere along the path perceptions change and models adapt.
PBS Spacetime is known for stating a positive for the title. Part of their style to assume the affirmative, while always adding the nuance.
I consider this video to be a bit of a cheap shot.
Especially knowing there's a Nobel Prize waiting for you if you're able to connect the dots on the actual nature of gravity, I think it's good to stay highly sceptical of people posing an absolute truth claim, without the nuance other channels might add.
12:00
So if the Moon moves in space around the speed of the Earth, it should have the same gravity?
And the apple on the side of the Earth, that looks the opposite direction from the Earth's movement should not fall down, but up?
Interesting to say the earth is moving up to meet the apple, however that can't be right because what if we had 2 apples falling, from opposite ends of the Earth eg North and South. This implies the Earth stretches.
In reality different objects accelerate in various directions at the same time. The general relativity explanations work when look at one object but seems to fail for multiple objects at the same time in different locations.
Also one of the principles of relativity is invariance so it should not matter which frame of reference you are observing from. So equally the apple is considered as falling to Earth.
General relativity still fails to explain the true cause of gravity. It is just a series of paths that are followed - but why exactly, what makes it that way? It's like space is a set of rail tracks and masses must follow that track, why?
Interestingly he hasn't answered this question...
@@Nygaard2 The problem is when you try to be very clever and you produce a very confusing argument (like this video). General relativity is based in tensors and differential calculus, that are quite difficult to explain in layman words. In reality the explanation given by those other channels, explaining the time dilation, etc, is just a simplification, an analogy so people can understand the basics. And I don't think it's a bad analogy.
The equations Einstein wrote relates the presence on matter (actually something more general described in the energy-stress tensor) with the local geometry of Space-Time, there is no a single parameter called gravity in the whole system of equations. The only thing you can argue is that the curvature of space-time is the cause of the phenomenon that Newton described as the force of Gravity, but that's it.
Only "one part" of this distortion of the space-time is felt a dilation of the time measured by a clock following a "free movement" trajectory, that is the base for the explanation used in those videos the author doesn't like.
And to answer the question, one analogy that is sometimes useful is thinking of space-time like a body of water, and instead of a mass, you have a sink in this body of water.
Around the sink the liquid moves toward the sink, pulling everything suspended with it.
Stuff suspended in the liquid, lets say little wooden beads, that don't move with respect the liquid are equivalent to inertial systems, and don't feel any "gravity force". Beads that move with respect of their surrounding water are like objects accelerating in real space, and "feel" forces. Indeed, the water around will try to stop them.
If you put some strainer around the sink that stops the beads, the beads will feel a force pushing them against the strainer, the strainer would be the analogy of a planet surface, and the force the beads feel is an analogy of the gravity force.
In this analogy the beads at the strainer surface are accelerating, because they do not move at the speed of the surrounding water, so the strainer surface, although stationary, is also accelerating!, but going nowhere because is the water what is moving.
When they say the surface of the earth is accelerating is in a similar sense of the strainer, but the thing that is "moving" is not water, but space-time.
Well, this is just an analogy, useful for visualizing the concepts, but that is it, for the rest, you need the equations.
I hope my clumsy explanation has helped.
@@ernestuz Thanks, it did :)
@@ernestuz I thought that was a really good explanation. :)
I liked your video.
1) why: because you spoke slowly allowing me to sort and comprehend each point. I still prefer reading as I can take as long as I need to comprehend each point.
An appeal to Authority fallacy is always possible.
That’s why complicated ideas are built up one by one. Sometimes, initial ideas are not entirely correct, but more like observations with more and more details added.
For example, Newtonian physics isn’t wrong. It works perfectly well in many cases. What Einstein did was to refine it through a more detailed, and different point of view.
The maths ARE the physics. Our words and diagrams are only representations of the Maths.
For example, music.
The notes on the paper are equivalent to the math. They ARE the music. What we hear is an interpretation of of the notes, which are not perfect.
There is always difficulties with trying to explain complex ideas with words, written or spoken.
Our brains evolved to survive nature. Not to accurately perceive it.
Anyone reading this should be familiar with the concept. That is why we can visualize 3D objects but not 4D, 5D......etc. our brains have not evolved to do so. But the maths enable us to accurately describe any
n- dimentional object.
As we have seen through this video, even with educated people trying to explain phenomena, there are differences.
Knowing this, we should see how less educated people fall for ideas such as the Earth is flat.
They don’t have the requisite knowledge, and critical thinking skills to even comprehend their mistakes.
I like the vast majority are always victims of Dunning-Kruger. Perhaps even Ed Whitten is....
LMAO. i watched this at 2x playback speed.
Dunning-Kruger, the wacky "result" which allows midwits to call other midwits dumb while sounding scientific
I would argue that if you think that notes on the paper are the music then you have done very little music. Notes are a handy tool to describe music but they are NOT the music. If they were then every performance by every performer would be the same and that just isn't true. If the problem is that people get caught up in simplifications and mistaking them for the real thing then you are not to that effect either.
You assume you understand the consequences of the dunning-kruger effect, but it tells us that you don't XD
I don’t think music is a suitable analogy
Those videos you mention had been very puzzling to me for a long time. I'm a nuclear engineer, not a physicist, but I have studied enough of General relativity (granted, a long time ago!) to doubt these explanations. What had me questioning this is that the internal forces that would leave the squirrel unchanged should be on the same order of magnitude as the gravity, i.e. not small and actually measurable, which is not the case.
Indeed, the phenomenon they are describing is spaghettification, the effect of which is not overall movement but dismantling of the body. It appears in intense gravitational force gradients, such as the one encountered at the horizon of a black hole, not on Earth.
I think the confusion comes from an oversimplification of the equivalence principle. What it states is that for an observer with a constant acceleration in outer space (curved trajectory in a flat spacetime) everything outside behaves as for a free falling observer in a gravitational field (straight trajectory in a curved spacetime).
What this really means is that the effect of gravity is homogeneous to acceleration, i.e. it can be expressed as a second order derivative of the metrics, i.e. gravity is curvature.
But those two situations are really different, as spacetime curvature due to gravity is observer independent and free fall referential is inertial, whereas an accelerating referential is by definition not inertial. What happens to both experimenters is of very different nature.
You need to read An Engineering Model of Quantum Gravity. Then you might understand that gravity, time dilation, length contraction, and space-time curvature are all observables resulting from the damping of the quantum harmonic oscillations that make up matter, not space-time, due to the local mass/energy density "in the way". Time is what is measured with a clock. Space is what is measured with a ruler. These tools are variables in the quantum vacuum.
Cool, I will check it out.
So, if one were plopped outside of space-time (and no other phenomena occurred), one would expand (explode) because there is no space-time to counter (annihilate) the mass' outward acceleration?
All those other videos are analogies, just as GR is a mathematical analogy - nothing wrong with that as far as the average Joe is concerned. But your analogy is actually misleading and flat out wrong while pretending to be above the rest.
Bottom line, I have not seen one person who understands gravity on a fundamental level; and maths is not understanding if you cannot explain it to a barmaid.
Everybody knows that GR is incomplete, hence one should not think of it as the final word but a challenge to build on it.
I'm all for hearing another equivalent explanation, but you mostly provided an exercise in semantics. I was never confused by what you call "gravity" vs "apparent gravitational attraction." On the other hand, you did get me to watch your entire video, so maybe you win.
If the entire Earth is accelerating to meet falling objects, then why doesn't the Earth develop a measurable change in its size? His point doesn't make any sense.
@@carultch If I remember correctly, he was fuzzy there. Something about the curve being exactly shaped to hold Earth together. However, gravity is equivalent to acceleration (roughly speaking). Earth is accelerating, often imperceptibly, towards objects, but also towards its own center. It is definitely accelerating towards the Sun, but keeps missing. :-) Many forces, or accelerations, cancel out.
@@carultch Publisher of this video is kind of just semantically gaslighting everyone, I agree. Ultimately, he is speaking about observational orientation in the fourth dimension. Like, if we could step out of our dimensionality to observe what is happening in the fourth, this is what we would see... So in terms of a simpler explanation, it's absolutely not. Seeing as he spends half his time trying to use the failed analogies he argues fall flat, to explain his reorientation for it to not stick in anyone's mind. In terms of it being more correct... that has no merit in a system created to be "relative" to the specific observer being invoked. His arguments about not being gentle to children with information they have no conceptual framework for handling, is whatever you want to interpret it as. I know how I do...
@@Robert_McGarry_Poems I feel like the publisher of the video could do a better job with explaining what he means by "acceleration". Most of us learn this term as a kinematics concept, which is clearly different than what he has in mind.
What he seems to have in mind as his meaning of the word "acceleration" is the net non-gravitational force per unit mass. So in the simple case of an apple in a tree, that's the tension in its stem divided by its mass. How this is a kind of acceleration, is something he could do a better job of explaining.
@@carultch I very much agree. Language is even more complex than GR, or we couldn't use it to explain GR. Having that said, he switches between conventions as a matter of fact, as opposed to... As my teachers used to say, showing his work. That is, unfortunately, not great. Conventions allow us to use the insights of those whose shoulders we stand on. If we go mixing and matching parts of random conventions together, I want to see the translation... Otherwise, how do we know what rigor might actual exist in any alleged insights?
Outstanding!!! I have seen all the RUclipsrs shown in this video. They trace the misconception back to Edward Current! I remember when he first uploaded that video and was blown away at how I could finally understand (misunderstand) what gravity really was.
how do you know that's where they got it from? are you saying that this guy was the first to describe it this way?
11:56 if gravity is accelerating trough space then why is apple nod falling in the sky in the back side of the Earth? Sorry for my inglishu
I think your explanation too are incomplete !
It's easy to see those youtubers are not that wrong: free falling objects follow geodesics, then you just look at the geodesic equation and see which factors influence it the most near a slow massive object, you find it's the time gradient in the metric tensor. The rest is pure geometry.
It's not the math that is wrong, it's their conclusions that are wrong.
My understanding from the other videos is that we are constantly moving at the speed of light through space time, the majority of that movement is through time as the speed we move through space is very slow. Mass bends space time & its these geodesics that cause gravity. I'm definitely more confused after this video.
ruclips.net/video/XRr1kaXKBsU/видео.html this video may help you
@pyropulse you are using the word "speed colloquially". Speed through time is not dx/dt. It's a ratio between time and proper time.
"Do you feel like you are moving the speed of light" is the type of argument a flat earther would use.
Noooooooooooooooooo.
Moving at the speed of light?
Dude, are you on a new stuff in market(don't take it as offensive). 😂
We are definitely not moving at the speed of light. Anything with mass needs infinite amount of energy to be accelerated at the speed of light.
@@TheKingBeyondEverything bro, it's C through time, not space over time. Your Worldline is a 4-vector that has a conserved speed through spacetime. The colloquial speed of light is a 3-vector that is a quotient of space over time.
@@andrewferris8169 ok
@23:30 Where does space go? Space is visually represented as moving inward toward the center of a gravitational mass, so what happens to space when it gets to that center? @dialectphilosophy
GR is hardcore stuff.
I've been wrong so many times i've lost count. And i continue to be - just a little less each time.
But the more you live, the more you learn you have even more opportunities to be wrong then you previously thought ;)
Einstein : As our circle of knowledge expands, so does the circumference of darkness surrounding it
@@sobreaver thank god the area far exceeds the circumference
I am still not sure if I truly understand gravity! The more I think of it the more closer I am drawn towards the event horizon
15:41 thank you for posting this video. The subject matter to a certain portion of us out here :-) never gets tiring… I do have to agree with some of the comments as I have read them; it would help tremendously in your presentation to be mindful of conjecture. Everything is theory until proven . As an example, regardless of what your degree path is, we all have to take the arts, so I had to take an English literature class, which was being conducted by a gentleman who had gotten his doctorate interpreting Shakespeare . On the very first day of class, he would pull lines from the plays, and tell us precisely what Shakespeare meant; point being if you did not agree with him, you were not going to pass his class, and that was rather obvious and I quit that first day. the information you have presented is fascinating, and very informative, but to postulate that you are right and everyone else is wrong betrays true science. From a Laymans perspective, for example, one has to immediately conclude from your argument that gravity is a constant. the way gravity behaves does indeed suggest your interpretations but if we know that gravity varies, depending upon mass that would have to appear that objects would therefore overtake each other depending on mass. Again, from a Laymans perspective in order for your theorem to be functional one can only conclude that space, and time are expanding at the same rate.
Everything is a hypothesis until proven.
No offense, but saying something like "Everything is theory until proven" is truly cringy and only reveals you don't have a rudimentary understanding of how Science really works (don't worry, neither do many "scientists").
There is NO SUCH THING as "scientific proof"! Proofs only exist within the domains of Mathematics and Logic, in closed systems in which all variables are known (which is NEVER the case in Science). You can only ever DISprove a theory, never prove one. A theory is nothing more than a more or less plausible (and incomplete) EXPLANATION of observed phenomena that can only ever be replaced by a more strongly supported theory.
It is exceedingly ignorant to employ the false reference to "scientific proof", and it is this very misuse of language (the mind shaper) that contributes to people being so confused about such matters.
@@OzReel
Also wrong!
Please read my other reply.
12:00 If we are accelerating and we reach the falling object in space, and acceleration has to have a direction as well. So 180 degrees apart, when two objects fall in the opposite sides of Earth, how are we accelerating simultaneously to both of them? I know you can answer this but point is each video I see in youtube about gravity confuses me more than earlier, though I get some additional information each time.
Beautiful explanation!!! It precisely matches the model I recently published as "Ground State Quantum Vortex Proton Model" in Foundations of Physics.
interesting :) Thanks for sharing
I have my doubts about all these scientists the more i watch these videos
Relativity is based on acceleration. These so-called scientists are either parrots mimicking what they are told or outright charlatans peddling the physics of a fake universe.
And they have the nerve to degrade flat Earthers. You relativists need to take a look at your own physics before you criticize someone else's.
Then you’re learning the most important lesson in science!
Why can't gravity be a force similar to buoyancy? In water, a balloon released under water is repelled upwards with a force that is dependant on how much water it displaces. (the bigger the balloon, the more water is displaced.)This happens because air is less dense than water. Why couldn't the same (or opposite) principle be applied to space? Mass displaces empty space, which somehow disrupts the equilibrium. This somehow causes mass to attract other mass with less density.
_"This happens because air is less dense than water."_
Why do people become politicians??? Because they are more dense than everyone else.
_"This happens because air is less dense than water. Why couldn't the same (or opposite) principle be applied to space?"_
Because there is more of a gravity source for water to be pushed to the center of the earth than the air that weighs a lot less to be pushed to the center of the earth.
_"Why couldn't the same (or opposite) principle be applied to space? "_
Because there is no earth out in space.
Interesting stuff. I've been thinking about the topic for a long time and had questions about the time curving to velocity claims. So space is flowing into mass?
Flow=gradient
If something goes from not flowing, to flowing, then the concentration of that something must change. I.e. it's instantaneous density. Whether or not that resembles mass density is another topic all together. But, you can't make an argument about flow without the consequences of that flow. An equivalent statement to pressure can be made about how gradient density causes what can be perceived as motion along that flow. Or, relatively speaking, from the point of view of inanimate objects like particles, the cause of inertial acceleration.
I'm confused on how this is considered two different things...
@@Robert_McGarry_Poems I've kind of worked through the fact that flow is not really feasible based on the fact that what we see is not a flow into a gravity well but rather an acceleration. But evidently the Schrodinger equation says that there is a contraction of space and time as one approaches a BH.
It appears that space expands where there a low quantity of mass/energy and contracts in inverse circumstances.
I find spacetime to be a fascinating topic and suspect there's a lot there that we're not seeing.
@@Eric-Marsh it's all relative to the question you are asking, what reference frame, and therefore framework answers the question best for your given instantaneous moment in spacetime. But you still need to build a sharable convention for translating that to other people. 😊 Cheers.
Yes it flows and "accelerates" due to the inverse square law in a gradient. Earth's surface it flows in at 9.8mps²^ that for 6.000km from the centre of earth, 12.000km from the earth's centre gravity is quarter'd due to the inverse square law so it's 2.7mps²^.
And everything in-between and beyond is in a gradient. It doesn't move twitchy like an old Pac-Man arcade game, it's goes in smoothly hence we use the word flow.
Ok now I am REALLY confused about this whole idea of space time, gravity, relativity. Specially after reading some of the comments below to try to get a better grip on this.
I'm an Electrical Engineer by training and always thought I was fairly intelligent. I also try to be a lifetime learner. But this just blows everything I thought I new into deep space and I am now a blithering idiot.
Thanks for all to trying to explain it from your point of view in the video and responses, but at times it appears to be a pissing contest to be blunt.
It makes no sense to me that the earth is accelerating up to an apple "falling". So if two apples are "falling" from opposite hemispheres then the earth should split in half and move towards the apple in my mind. Do this simultaneously all over the sphere of the earth with "falling" apples and the earth explodes.
YES I do NOT get the explanation here. Not say its wrong cause I'm NOT a physicist and only studied under grad physics.
Network Engineer checking in; Im in a similar boat to you Tim. Unfortunately, I don't think this video or the comments are going to give us the answers we desire because, as you aptly said, there is a pissing contest going on.
It seems that no matter where you look, no one can agree 100% (let alone 50%) on this topic which tells me that there's more to this than any of us know.
I like to think about it like space time is "falling" into the center of the mass and in doing so it drags down whatever is not subjected to any other force.
@@107thFruit Yep
I had thought that both objects were attracted to each others mass, with each "moving" proportionally award the other. Ie for all piratical purposes the earth doesn't move.
So sounds like a bunch of Post Hole Diggers arguing.
@@haroldbn6816 possibly- see my real below to Harold.
To clear your mind from all this Einstein mess, you will have two Come back to Poincaré wisdom that stated since 1885, alike Kant, that nor "Space" nor "Time" are physical observable. What could be thoughts as observable is thé "distance" for instance between two objects. But not even, since the way to measure such thing IS by using a spectromètre that gives you SPECTRAL RAYS DATA. That is the only certainty WE have : SPECTRA.
The rest is theoric CONVENTIONAL reconstruction of what could explain such SPECTRA. And IS what we call MODELS. There is several. Curved metric as in GR is not the only one, nor even the best. Not even correct...
Thus a clear step forward out of this Einstein mess of entengled confusions, is to upgrade to SPECTRAL GEOMETRY developed by Alain Connes and GEOMETRIC ALGEBRA developped by Hamilton, Grassman, Clifford, Hestenes. These are général frame works in which the hall picture of facts, not arbitrary asumptions and ungrounded dogmas, can be more clearly unified in order to clear this century mess
4 minutes in and you’ve said nothing constructive.
I think you are missing the fact that they are performing a perfectly legitimate Lorentz transformation to show that the curvature of spacetime (not perceivable to the standard observer) is what causes the effect we attribute to gravity, and if you combine that with Quantum Field Theory you have the reconciliation of Relativity and Quantum Physics. I also was wondering, when you are talking about the ground accelerating upward and engaging the SR equivalence principle, the there wasn't going to be a flat earth reference in there. It's perfectly acceptable to have your inertial frame of reference where the universe distorts because of your velocity. That's what special RELATIVITY is.
The description of relative gravity was very well laid out, but the abridged version of the actual cause of real gravity left something to be desired.
We have two follow-up videos, "The Sky is Falling Up" and "The River Model" -- check them out!
so everyone else is wrong and your right ?
Just -- everyone is wrong. I know this for a fact because these explanations contradict physical reality. Spoiler: math is not physically real.
I think we shouldn't point fingers at other people being wrong, provocatively. We all need to contribute by referencing thoroughly and remember to link to full publications. In the 45 years since I've been around, there have been a lot of conflicting viewpoints, but until there is some kind of overwhelming agreement, everyone's contributions should be appreciated and argued professionally.
I do like the arguments posed here. The 2-way speed of light assumption argument about moving references and the speed of 1-way light being different that than the reverse speed at the same reference speed, really opened my ideas.
Thanks for the discussion.
9:30 How are the clocks ticking differently if the field is uniform?
Someone complains about the trashing other videos in this one about true nature of gravity. If Dialect didn't do so, I wouldn't be able to make a comparison by myself. It would be just another brilliant explanation among many. But who is right then? Sometimes it's necessary to point out where others are wrong. It's a huge help. I had watched all the videos mentioned in here, and I felt very confused at the time. This one helped me to understand. Who cares about not being "p.c." if it's for a good cause.
This is a very good video. I would add that a bit more explanation that gives an intuitive understanding of what "upward acceleration at the surface of the Earth really is" would be good. The "curved space" description at the end is adequate for someone who has already studied GR a bit, but is probably impossible to understand if you have had no physics beyond SR. To be fair, I'm still trying to figure out what this explanation would entail so this is not a criticism...it's more a request.
You're completely right and your feedback is definitely appreciated. We really struggled with what to include in this video; we knew the main bulk of it needed to debunk the bad physics in the other videos, but unfortunately that didn't leave much time for the more accurate explanations. We will be addressing these ideas more in our upcoming videos though, so stay tuned!
@@dialectphilosophy SO in your upcoming videos you would fully explain the real cause of gravity?
This needs to be edited down to 10 minutes.
I believe I can do it in 10 seconds. But don't forget, never talk about the fifth Dimension or the Men in Black will come and rip off your head.
What I also find a bit strange is that among my hundreds of posts a month here or on Facebook, I sometimes only get one thumbs up. Have you all become puppets because you are all not allowed to comment on the fifth dimension???
Because you released a follow-up, YT started promoting this one again. Nice.
Now, at 12:55, I have thought about that for quite some time. However, if the apple falling shouldn't see the time gradient, how come GPS satellites experience a quantifiable time dilation? They are also in free fall, right? Also, Kip Thorne himself calculated the time ratio between the ship and the planet in Interstellar, when around the BH. Aren't all these orbits equivalent? Thanks
Gravity: Imagine a sheet called space moving through a 4th dimension where the 4th dimension was called time. The fabric’s direction of travel is from a place we call the past to a place we call the future. The surface of the sheet is what we will call the present. This 4th dimension is not the same as our ordinary experience of time but is related to it. If you put a lead ball on the moving fabric the ball would resist the movement so as to cause the fabric to deform. The ball and the fabric pushing the ball would lag behind the rest of the fabric. According to our definitions, the ball could be said to be in the past. If another ball were put on the fabric it would deform the fabric too. If the two balls were close together they would approach. The balls would seem to be attracted to one another but in reality, the same place is moving toward the both of them. When you fall the Earth is moving toward you.
You know what this was probably the most informative thing of this whole video, and comment section on gravitational curvature.You just opened my mind to visualise the bending of a space time curvature.
"When you fall the Earth is moving toward you"
Then answer me this. Every country(plus 2 jumpers on the poles) on Earth places one of their citizens to do a skyjump. They all get to their planes and when they are at, let's say 10 000 ft. They check their watches, and then, exactly at the same time all the skydivers around the world jump off their planes. Towards which jumper the Earth moves?
@@nudestoteles The Earth is moving toward all of them at the same rate but it is only moving toward them in the fourth dimension. Think of a water glass moving through space. There are stationary marbles around the rim of the glass. Because the glass is moving past the marbles the bottom of the glass is moving toward all of them at once. From a two-dimensional standpoint, the marbles are opposite one another but from a three-dimensional standpoint, they are all in a line. In the same way, the jumpers are opposite one another from a three-dimensional standpoint but from a four-dimensional standpoint, they are all in a line. The center of gravity of the Earth is the bottom of the glass. The center of gravity is the furthest back in time and is moving toward all the jumpers at the same rate. The closer the jumpers are to the center of gravity the further back in time they are.
@@nudestoteles this is already impossible, the earth is flat! 😎
Instantaneous moments sliced up into infinitesimal branes which flow together creating our perception of a 3+1 spacetime. But what, other than our convention to label it that way out of convenience, causes the smoothe interaction of these branes from one instant to the next? What, if not our failed observationally built model of entropy driven thermodynamics, is that fourth dimension people are so quick to invoke but never define? Kind of like a gradient or a flow of density. Almost as if language is recursive and we need to agree on the relative starting point of the labeling to be in convention with one another. Almost as if starting your explanation with a holographic simplification, and then switching convention mid step to 4D talk is bad language form. Logarithmically speaking, base and order are pretty important concepts.
maybe, are you trying to stir up controversy(for clicks) where it's a bit fuzzy?
I don't know that your explanation was more edifying than the others, since you're both using abstract visualizations to represent these ideas.
It seemed more like a dig at the other channels rather than just trying to communicate science effectively.its okay to have a desire for your pedagogy to be integrated with the mainstream but you honestly seem hositile.
You explained it differently but we still don't really know that's the "best explanation." I'd rather see an experiment to demonstrate the concept than a visualization to become convinced.
I'm not sure you're doing any more good than the other videos, except at stirring up contempt.
If you really want me to agree with you you should try and contact those other channels and get them to address your concerns, maybe they will agree with you if you make a persuasive argument?
Interestingly enough, we wrote to each channel featured in this video weeks before we put it out. Very politely and in a non-crackpotty way we put forward our case, and asked if those channels would give us a comment/response/rebuttal or further clarification for our video.
None of them did. Only Eugene responded to us, and only after the video came out, but he declined to clarify his explanation any further. (You can see his answer in the comments).
This video was intended for an advanced audience; we didn't expect it to go as viral as it did. The layperson's explanation is given in our follow-up "The Sky is Falling Up" which we'd recommend you watching if you have confusions still.
Well said 👏👏👏👏
@@dialectphilosophy "This video was intended for an advanced audience." 😂😂😂😂😂😂😂
@@dialectphilosophy I think you did a well enough job showing that it is mistaken to simplify apparent gravitational attraction as being caused by time dilation.
However the video spent an inordinate amount of time dunking on the other creators ; whereas the alternative explanation of apparent gravitational attraction given at the end of the video felt rushed and incomplete.
Your perspective on general relativity and the explanations of the metric tensor have been excellent, and even the explanation of time dilation not being the cause of apparent gravitational attraction was very clear.
This video was a bit of a low point in the overall momentum of the channels explanations on this topic. Im watching all your videos in order, so i am excited to see the direction you take in future videos from this one.
I agree that the tone was off-putting and somewhat hostile , and i agree that the alternative explanation given at the end was lackluster. That being said its pretty clear that the general point of these videos he mentioned-that time dilation CAUSES apparent gravitational attraction-is based upon a misinterpretation of the geodesics.
Whats telling is that technically none of these videos are well backed by recent scientific papers and are basically reinventing the wheel by recapitulating stuff from the days of Newton , Mach , and Einstein.
String theory is pretty silly oftentimes, but all five of these videos had extremely non-useful explanations of gravity. Thankfully most people don’t actually have to “use” gravity or gravitational effects in their day to day life, making it fairly harmless popular science.
Additionally, very few people talk about it, but observational phenomenon that are agreed upon by physicists can nevertheless have competing philosophical interpretations as to the meaning of these observations without technically violating any of these observations. I see Dialect as a channel that is more focused on providing alternative interpretations to the accepted math of general relativity. So long as an interpretation doesn’t violate the observations of the phenomena, it is technically speaking philosophically valid and potentially “more accurate” than other interpretations.
As you mentioned it would be interesting to see some sort of experiment designed to elucidate any physical differences between these explanations-for example, an experiment that confirms observationally that time dilation is a second order effect rather than a first order cause.
The fact every part of my brain is constantly accelerating outwards from the center is literally blowing my mind 🤯
I think it's all accelerating in the same direction in Earths gravity well, atleast I hope so!
Not a fact. Sorry.
Yep, more non-sense and misinformation
23:41 "because every single mass in the universe is literally accelerating towards every single mass" even distance galaxies? so can we just assume the Hubble Constant(the rate of the expansion of the universe) is just the true gravity(the curvature of space) over powering the acceleration of local frames or reference?