How do we know the Universe is expanding?
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- Опубликовано: 2 окт 2024
- Cosmological redshift was our first clue the universe was expanding. A century ago, Edwin Hubble discovered galaxies outside our own supercluster are all moving away from us. But how do we get from redshift to an expanding universe? That's the tricky part and most people get it wrong.
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Is The Universe Infinite:
• Is The Universe Infinite?
What is the Universe expanding into?
• What is the Universe e...
How Do We Know Things About Stars?
• Basics of Hertzsprung-...
What the HECK is Light?!
• What the HECK is Light?!
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PBS Space Time on Cosmological Redshift:
• How Do You Measure the...
PBS Space Time on the CMB:
• Cosmic Microwave Backg...
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Expanding? - seastormsinger:
• Why is Light the Faste...
Redshift - Yair Eshel Cahansky:
• Is The Universe Infinite?
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List of Topics - aThrasheR:
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Minutephysics also released a video on this topic today (which is obviously a coincidence). As much as I like Henry's work, he glosses over some of the finer points. I really like your approach of tackling things in more depth and feeling out some of the more common misconceptions. Your channel should have way more subscriptions because you're a great explainer.
Cheers
Thanks! Yes, I noticed he posted that today and almost didn't post mine because of it... almost. This comment makes me feel better :-)
The Science Asylum minute fysics also said that the speed of the galaxies can be measured by considering the Doppler effect?
This is one of the best channels on RUclips!! Keep up the good work!!!
You seriously deserve more subscribers!
Oh hell get there.. Trust me. Great videos!
He will manage. And more. In two years he will quit because you know, Coca-Cola buys him out and makes him put mentos in soda. With 100 million dollars in his pocket.
Man, I hope that doesn't happen.
They don`t have big provoking bewbs... sry..
Y do u have that photo of nebula
Agreed!!!!
Never end this videos Nick. Please .... You have a natural and wonderfull gift to offer to who ever need this kind of informations.
Your content is very, very good. Also your entuziasm, and your voice and body posture., not to say about the clones . For me, you are on the same league with Dr. Don Lincoln. And this guy is great !
Your work is appreciated , I just want you to know that ! Thank you!
I don't understand why your channel is not famous! Your videos are too good, sir!
I think because his thumbnails are somewhat not convincing that the content will be valuable. I almost did not chose this video but I am happy I did.
138k Subscribers and 54k views on this video alone. That's some serious RUclips cheddar.
@ابو ليث الخطيب quran is nothing but a science book!
@@MarkTulsa2024 you see, his comment is two years old.. science asylum has only gotten significant exposure more recently.
In holy Quran God said we built the sky by our force and we'll expand it
1 oct 2024 5:21 pm est ( gmt - 5 ) : i think eating ruminant/3-or-4-stomach-owner ( cow , deer/venison , camel , goat , lamb/sheep , moose , elk ) , bring severe bad-luck . i think hindu-religion-way in worshiping/not-killing cow , is more correct . nascar-racer sterling-marlin consume 1 bologna/pig sandwich prior usa->florida-state->daytona-500-race 2 times and
win those 2 daytona-500-race ( 20 feb 1994 , 19 feb 1995 ) . i can not scribe url-source because if i scribe url then youtube automatically delete my comment .
This channel is great for reviews of physics topics, however, I would like to see some kind of videos about questions we don't have answers for yet! I'm sure we would enjoy hearing what you think is missing from our current knowledge basis. Maybe even propose some new theories or experiments. I'm sure this channel brings in an audience that might have access to high-tech labs to test your hypothesis, especially if it has some crazy spiced into it. ;3
Not a bad idea.
I think your subscriber count should be shifted at LEAST one place to the left
F3ynman1um To the right, i guess???? Because it should increase
@@RAJSINGH-of9iytechnically it can work either way
What if the universe instead of expanding is actually spinning?
A rotating universe would have all sorts of weird effects. Maybe a future video?
we already know the universe is not a flat plain, anti-matter proved it.
Wow! finally someone that gives clear, concise answers to "HUGE" questions. Thanks and keep up the good work.
Just a random saturday wanting to know more about space.
Those two reds(#FF0000 and #FF0001) look completely different, or is it just me?
I think Nerd Clone might deserve his own video. That would be pedantastic!
I didn't get it, what is the proof space is expanding?
There are bunch on ice cubes in a tray, at first all are close to each other, but as time goes by water build around them, ice cube say, look other ice cubes are getting away from me, once we were close to each other and now you can fit so many ice cubes between each one, and those that are further away getting further faster than those that are near me, and wave length is stretching as they travel through the expanding water.
Is the ice cube be qualified to measure distance, can you measure the tray size with ice cubes?
The only thing you can say is, light is redshifted as time goes by.
Space appear to be bigger relative to the mass in it as time goes by.
Mass appear to be smaller relative to the size of space as time goes by.
We need a stronger definition of length and time.
How about: wave length of certain energy at t=0 is 1 length unit and 1 time unit, and from now we are counting waves.
Are the more CMB waves between us and it's origin now than there were when it first went on it's way?
redshift is also caused by passing through objects, as we have observed before and the most obvious example is a sunset. We have also kept track of the redshifts and they are not moving. The universe is not expanding, it is fixed.
This video taught me nothing!
Not because it was bad. Just because I'm too dumb to understand any of the things he stated as obvious. :P
Give me more "Nerd" clone ! The more he says the more I giggle! hahahahaha
The speed of light changes when going trough water or glas etc. It even moves position.
Comment responses have redshifted, stretching their wavelengths into an entire video. 😀👌
Are we factoring in the fact that time itself is relative? Time is moving at different rates depending on the gravity fields through which the light travels.
Nick! I seriously love your videos man! Damn funny! AND informative!
I always watch your videos once they reach my email. One of my top channels on RUclips!
you seriously finished the video saying we know universe is expanding because we know photons changed their collor, but to know how we know they were supposed to be another color we must watch another video???
WTF
disliked for that
What are the factors with which we can say universe is expanding.
Instead of expanding, we can also say that the universe is revolving around a centre point as all other heavenly bodies revolves. As the size of universe is intensely large we may not be able to detect it's revolution, as all heavenly bodies have their own path and some have opposite of each other it may seen as expanding..
Nice, but you are forgetting to include the accumulation of gravitational red shifts as light moves next to, about and through gravity wells. The greater the distance, the more of these gravitational forces add to the red shift. C A Bodor
Gravitational redshift doesn't accumulate. Any redshift that occurs as light leaves a gravity well is only undoing the blueshift that happened as it entered that same gravity well. Over long distances only the cosmological redshift matters.
I hope this question makes sense. If two galaxies appear to be traveling apart from one another and the spacetime is expanding faster then the speed of light, are either of the galaxies going back in time?
It depends on how you define "now" for those galaxies. In both galaxies clocks will tick normally, no crazy backward motion. In "coordinate time" of the mentioned FLRW metric both galaxies will go forward in time at the same rate. It's only when you try to define what events are considered simultaneous to the first galaxy, if you define it as "an event x meters away is simultaneous to me if light from it will come in x/c seconds of my clock" then yes, in some sense the other galaxy will seem to be moving back in time. It's all relative, and notion of "same time" is ill-defined for distant objects in general relativity.
That’s the big question: how can we know that light is redshifted if the already redshifted light is all the telescope can get?
Because we know what the light is _supposed_ to look like: ruclips.net/video/FQJj2kBJ5A8/видео.html
So what is final redshift of light which emitted by distinct galaxy as we are observer on earth with respect to me that galaxy moving away from me and after emission that light travel through space so it experience gravitational+cosmological redshift while traveling and also Doppler as it moves away do final redshift is sum of three redshift???
Yes, the total redshift is the sum of all of them. Though, what you'd call "Doppler" and what you'd call "gravitational" is a matter of perspective. Cosmological redshift is unique: ruclips.net/video/9udKv1NXm7w/видео.html
When the wavelength of light changes, where does the energy go, and by what mechanism? If space can expand, how is it that a speed cannot change?
That energy doesn't go anywhere. It's just _gone:_ ruclips.net/video/cnGYMe6GBeQ/видео.html
If redshift is sum of all three redshift for distinct star then Doppler effect is function of Velocity but star is moving away with Velocity greater than speed of light so Doppler redshift is not finite as it contains 1-v/c term and it become negative.
Cosmological redshift is a _very_ different thing: ruclips.net/video/9udKv1NXm7w/видео.html
please for the love of engineering, GET A NEW CAR. That thing is what we call in the UK a bag of nails :p i understand as a physicist its expected to drive such a car but i believe you have earned the right to drive a cleaner more fuel efficient less catchy firery type car.
1 oct 2024 5:32 pm est ( gmt - 5 ) : that car in 1:50 , is old and not-yet having safety-belt-coercion-alarm . so that car has comfortable driver-chair . i think that car is toyota->camry-year-1991-1996-xv-10 according to wikipedia . if i scribe url then youtube automatically delete my comment .
If light emitted by distinct galaxy is redshifted by gravity of its own + expansion of space + Doppler as it move away from us?
Yes, all the redshifts are present. I discuss this in more detail in a recent video: ruclips.net/video/9udKv1NXm7w/видео.html
if the light is redshifted, then that means that its wave length is getting increased,
and if the wavelength is getting increased, then the frequency of light must get decreased(since speed of light is constant.),
and if the frequency is getting decreased, then the energy of each photon must get decreased (e=hv), right?
if i am not wrong then where is the energy going or getting used up.
please answer.🤓🤓🤓🤓🤓
Sounds like a topic for a video ;-)
It would be funny if that energy loss turned out to be "dark energy" driving the expansion, that would make for a nice positive feedback loop! But iirc someone measured it and it's not enough to explain it.
I opened this video cause I was confused about Doppler effect and relativistic effect, and I didn't see the connection between these two. And I found the answer, they're different things that contribute with different magnitude to the red shift! thanks
Always great explanations! Thanks you for that!
A quick question, as the universe is expanding, wave lengths are “loosing” energy. But with the conservation of energy, would it be possible that this energy is transferred to the space-time itself to make it expand?
You are correct that light waves (especially those from the CMB) are loosing energy over time. You are also correct that spacetime itself is gaining energy (in the form of dark energy making the universe accelerate in its expansion). However, those two amounts are not even the same order of magnitude. We're gaining astronomically more dark energy than we're loosing in light energy. The universe has an energy creation problem, not an energy loss problem.
That being said, it's not really a problem. Conservation of energy requires a certain kind of time symmetry. The universe might not have that symmetry over cosmological time scales, meaning conservation of energy might not hold over cosmological time scales. ruclips.net/video/ahf0zCaqrwM/видео.html
You are the most bestest science teacher on internet :D keep it up untill the end of the universe ;)
The amount of information you put out is amazing. But it is the way you put it out I like the most. Thank you for all the work you put in!
Thanks!
The universe is accelerating, right?
Which force is acting behind that acceleration 🤔
Not all accelerations require forces in general relativity.
Then How do we come to know that the light which we are seeing now was of which wavelength back then? How do we know that a redshift has occurred
iirc.
When a white dwarf in a double star system goes supernova from leaching gas from it's companion, it's always at the same mass. So the explosion is always the same.
This is among the 3 best videos about this topic so far.
Great video! Really helped me picture some of the more complicated ideas involved with redshift thank you so much!
You're very welcome.
I can't wait to hear about how you know what the light you're using to measure expansion was supposed to be in the first place. That has been a question of mine for awhile! Another great video!
If you're interested in a head start on learning that, look up "standard candle". These are events or objects that are fairly easy to recognize and whose spectra are predictable.
I think it has to do with lab tests. When you know what stuff in space is made of (stars have a lot of H and He, for example), you look at their emission lines in a lab. Compare what it looks like stationary to what you observe.
One problem with that is knowing exactly what stars are made of, especially old distant stars that might not have as many heavy elements?
What if theres another 4th source for redshift, and it's not about expanding space? What if were seeing that version and the expansion explanation is just an illusion? Is that possible or impossible?
i know you cover it in a later video, but want to point out (for people to look forward to). The further down the "red" end of the spectrum you go, the less energy the photon has. So if a photon red shifts due to expansion the energy decreases without (as far as we can tell last I checked) going anywhere. "Conservation of energy is... sometimes... violated?"
I have a question. If E=hf and when the universe is expanding light is redshifted, this means that the energy of the photon has decreased since its emission. Where does that energy go? Is it like a resistance to the expansion of space?
Sounds like a topic for a video ;-)
Your Camry-based Doppler shift doesn't work very well. It would work better if the engine revs were constant. The frequency increases as it revs up, and decreases when it changes gears.
I'd see if you can find a railroad and show the phenomenon with a fast-moving train.
I know it's 4 years but I'm still gonna comment
you are doing a really great job .. your channel stands out of the rest
I wish you all the success in the world
Thanks!
In principle all suns and galaxies in the universe are in motion in all possible directions and velocity. That is to say red versus blue shift counts are statistically even. If our telescope has a filter to hide blue shifts signals what is left to count are red shifts.
On the other hand the cosmic space is not a void. Instead it contains nanometer size particles, size ranging from less than 400nm (violet) to larger than red 700nm (red). However, if the space between us and a quasar is filled with a relative higher concentrations of 450nm (blue) particles, it becomes a blue filter, masking off blue signals leaving behind red shift for Edwin Hubble to count.
1:51.... Should have used the horn.... or can't you afford a, "disturbing the peace", fine?? Come on, you must be rich now with all that sweet, sweet RUclips revenue... LOL *: )*
How do we know that that measurement isn’t affected by what we do on earth like remote controls or radio waves?
If the size of the universe is determined by a philosophical beginning (the Big Bang), and you are limited by your instruments to determine the distances you are able to detect, how can you affirm in which direction the objects of the Universe are moving? In relation to which starting point? Since you don't know in which direction they are moving, how can you say that the Universe is expanding? It may only be the small part of the observable Universe (in fact maybe much larger than we believe it to be) that is expanding! How do you know there may not be other factors that create the redshift, as, for example, a large quantity of invisible Hydrogen in the Universe?! It would be more honest to admit that, scientifically speaking, mankind doesn't know and most likely will never be able to know - 1. The starting point of the beginning; 2. The time elapsed since the beginning; 3. The direction the Universe is moving; 3. Whether it is expanding or contracting, etc, etc. Maybe we should admit that our ephemeral philosophical guesses about our beginnings determine our very faint interpretation of the observable field, possible through our very limited capabilities. We don’t know! We can’t know! We probably will never be able to know!
The speed of light never changes? How do we know? How do we know it was the same 1 billion year ago? Space-time has changed, Space expand, how do we know the speed of time never change? From inside the universe I guess it is impossible to know the quantum time. But if it changes, it might changes speed of light too. What is the smallest unit of time? the plank time? does time can be divided to infinity? I think I'm going crazy!
Because humankinds Consciousness is expanding.
As we expand our Consciousness
Into 4 and 5 D of course the Universe will expand..
Just my hypothesis.
Nerd Clone is the best...
As Michelson Morley experiment shows, the speed of light is constant. But we cannot asure that light speed has been the same value through all the story of universe. According to wave equation in Maxwell theory, the speed of an electromagnetic wave depends on 2 factors, magnetic permeability and electric pemittivity of free space, and both properties of free space could not be necessarily constant through the time. WE could not probe this possibility because we don´t have nothing to compare the speed of light now and the speed of light at old times. We don´t know the exact nature of the space, and may be this 2 values were much higher at the beginning of universe when it was more "dense", and so c may be was be much lower. If so, this could be also consequent with a red-shift from far stars.
How do we know the universe is expanding for the entire 13.8 billion years? Are we only sure it's been expanding for the last 95 years, ever since the discovery in 1929? If we've only been watching for less than 100 years, then should we refrain from imagining that it could be a pulsating type of universe? Expand for 100 years, contract for 100 years, expand for 100, contracts for 100, and so on....
We know that wavelength decreases when it enters from air to water or glass.
We say that frequency doesn't change.its okay but
Is there any practical po
Proof that color of light doesn't change it should change there should be blue shift as wave length decrease
The Science Asylum : My question has nothing to do with this video, but you do such a great job replying, figured I might as well ask here; Why is gravity still considered a force if we have come to realize that it is just the bending of space-time that we are feeling as gravity. If gravity is still considered a fundamental force, how come other forces like acceleration, which can act like gravity, are not considered fundamental forces?
It's all about context. On a fundamental level, no physicist considers it a force. Most physics just isn't done on a fundamental level because the fundamental level is complicated and the math is hard. We only do physics on that level when it's absolutely necessary. When you're trying to figure out what happens to falling apples, orbiting satellites, or even how our solar system works; pretending that gravity is a force works just fine and it's WAY easier.
The Science Asylum What about scientist that attempt to unify all 4 forces. do they accept that gravity is not a force but still try to bind it in there somehow or what?? wouldn't attraction by electromagnetic forces be a simpler and more logical way to talk about "gravity."
Well, none of the fundamental forces are "forces" in the way we talk about them in classical physics. Quantum field theory is weird like that.
your videos are to youtube...
as Carl Sagan’s Cosmos was to TV!
I love Nerd clone.
Imagine spraying a water hose from the roof a skyscraper. Imagine the water droplets represent galaxies in our own universe. When the Milky Way water-droplet-galaxy is somewhere around half way down the skyscraper, it will appear like the universe is expanding in just the same way we see it now. All the droplets near us would be expanding slowly away, while all the droplets near the ground and near the roof will appear as if they are rushing away.
Since the Universe is expanding, Yiu can think this as a orbee and fill it with water. It grows, Like the universe.
Very good, as always! Good job.
If the passage of time and gravity also cause red shift, doesn't that mean that the universe might not be expanding? Maybe the reason it looks like it's expanding faster is because redshift grows exponentially overtime. I don't know, I'm sure I'm wrong but the expanding thing doesn't make sense to me so I'm trying to wrap my head around it.
But...why would the universe grow. That doesn't make sense. What if what we are seeing is just what we are capable of seeong given our current technology.
Why does the universe need a start? Beginnings and endings are human constructs we creates based on the idea our consciousness ends. What if it just is, always has been, and always will be?
Great video, I love the cosmos
Very nice presentation
I learn physics from some guy on youtube who argues with himself...
He's a clone.
so the universe is expanding at an increasing rate, but it's currently counteracted by forces like gravity. So when the expansion hits some absurdly high speed, would the laws of physics sorta change? For example, 2 things with any non-zero amount of space between them held together by gravity and/or the other 3 fundamental forces would eventually be unable to do so because the space between them expands faster to separate them than the other forces can pull them together. What about when it hits the point where atoms can no longer hold together as space expands so quickly that protons, neutrons, and electrons are pulled apart? How would the laws of physics look like in that kind of universe?
I like wondering about random hypotheticals, it's fun.
I think dark energy is nothing but energy released by black-holes at the center of each galaxy. Black hole is the main engine for each galaxy for transportation i believe. By seeing some of these galaxies outward movement, its creating a illusion like universe is expanding. Remember newton's laws. Also think why some galaxies are colliding. Because of its own movement due to the energy from its engine. Plz share your comments.
Since this video was posted, there is some discussion as to whether the expansion rate is actually accelerating (the entire motivation for postulating dark energy). See the following video: ruclips.net/video/B1mwYxkhMe8/видео.html. My understanding of Sarkar's logic: (1) test the fundamental assumption of isotropy at longer distances, using unaltered data, and the results called this assumption into question; (2) if the estimate and uncertainty surrounding the apparent anisotropy in large-scale movement are taken into account, and you ask whether the supernova data require a positive cosmological constant to explain the pattern, it was found that there is very little evidence that a positive lambda is needed in the model (1.4 sigma); (3) point out that other lines of evidence for dark energy (e.g., BOA or cosmic microwave background) are all really tests of whether the data fit the standard model, not whether the standard model with a positive lambda is the BEST model; and (4) there is an apparent bias favoring publications that support the standard model (which I realize is not uncommon in science). Altogether, I think it is a compelling case that much more raw data about distances & velocities are necessary, since this is one of the few direct tests of a positive cosmological constant.
Ooops... you forgot a couple of other reasons light could be Red Shifted (conviently ignored by 'science' today): Any change in the dielectric constant along the path of light or charge differential. Even a small change would cause a Red Shift which would be indistinguishable from an expanding, accellerating Universe. Go Blue!
Always thanks to your videos I really pulled out good scores in my test because you were great. I have suggested you to all my friends
What if space is seemingly ever expanding and now accelerating, because it's essentially a system boot. Think about it. There are theories of our universe being a simulation. What if we are instead the boot up of a system, and our goal is to advance and find answers, solve all sorts of problems and equations, sort of like a processor searching through all the system components and drives to make sure they are in proper working order.. and the expanding universe is NOT infinite, but working towards the end of the boot up system check. The expansion is how much we've "checked".
That's freaky in the book which muslims follow (Quran) there's this fact that the universe is expanding in one of the chapters, though the book was found about 1400 years ago!so the only way for the book to know this fact which we discovered now is because it's truly from the creator of the universe himself 'God'!by the way thanks for the video it is sick awesome and really explained how humans discovered this fact clearly thanks lovee this channel!peacee be upon u💖
The expansion of the universe isn't getting faster, it's getting slower. We might well observe distant galaxies moving away from us faster than nearby galaxies, but that's because they're older. The greater the distance we observe, the further back in time we are looking. If distant galaxies are moving away from us faster than nearby galaxies, that implies the universe was expanding at a faster rate in the early universe than the more recent universe.
Heat death is cancelled.
You keep showing new links to videos... Too many videos to watch than my PC can handle!!! My PC threatened me for a strike, or it will practice harakiri!!! :P
409 or it could be just looking at something that far away through space itself, is similar to looking at the sun or moon through thicker atmosphere as the horizon, making it apear more red. Seems to me, if everything moving away is red, and its all moving away, then it should all be red.
Hmmmm :/ ,,,,Are you sure that univers is expanding ? The farther away galaxy is the greater it's redshift, so the faster
moving away. But the farther away you looking the more back in time you
are seeing ... and the closer to the presence time you looking the
lower redshift. Then the results showes expansion of the universe is decreasing
as the time passes toward the presence and in the future! Just a simple logic !!
"The further back in time we look, the bigger the red-shift."
How is that not evidence that the expansion of space is slowing down?
Things only _appear_ to be moving away faster because they're farther away in space. We can also measure the _rate_ of expansion in various places though, which shows that it's actually speeding up in more recent time periods.
So what I believe you're saying is that the difference in red-shift between two galaxies one million light years apart with the closest galaxy only one million light years away is greater than the difference in red-shift between two galaxies one million light years apart with the closest galaxy only one billion light years away, is this correct?
Your visible spectrum has problems. The magenta on the right isn’t part of the visible spectrum
The trick here is:
Galaxies are not moving away from each other 'in space' but 'with space'.
If we observe red shift due to relative movement of galaxies 'in space' then it is Doppler effect and if we observe red shift due to relative movement of galaxies 'with space' then it is Space expansion.
Wouldn't gravitational red-shift essentially be the same thing as expansion red-shift since gravity is simply the warping/stretching of spacetime?
P.S. Thanks for the shout out!
Kind of... space is actually bigger /closer/ to a source of gravity though, so in some ways it's backwards.
I was thinking about that too, but, it seems to me that you would need bunch of black holes around the edge of observable universe, to explain it with gravity - the red-shift is uniform and gravity produces red-shift when you are escaping it => edge of observable universe would have to have a lot of mass.
...and having a bunch of black holes at the edge of the observable universe isn't consistent with our cosmic distribution data.
In some cosmological theories the edge of the observable universe DOES have a lot of energy depending on your viewpoint, that is. But still, in those theories it has physical consequences. Like expansion of space. Compare it with the firewall of a black hole. In some viewpoints it is predicted to be there (infalling objects).
If the universe is expanding, is time-space stretching? If so, why aren't the planet's getting farther from the Sun? It's said dark energy might be the anti-gravity force. Again, if it can move entire galaxies, why doesn't it work within our solar system?
Tell me how you know where the original light came from and how you know, at these distances, that the light sources are the same. Also tell me how you know the one way speed of light and if you know all the properties of light and exactly how light interacts with all of the different densities of space.
I coud tell the two red boxes were different. the right one was a lil lighter or brighter or oranger, or had more yellow in it... whatever you wanna say. but then i have a form of colorblindness that turns green lights white and causes me to mix up light reds and dark pinks, blues and purpes, and greens and reds. though i have always had a higher sensitivity to the shades and tints of each color moreso than avg. sooooo pros and cons i suppose.
I'm sorry I just can't understand why?
I hypothesize the universe might not be expanding and increasing in speed due to it could be possible that light is slowing down and not a constant and time therfore is the constant. Which would also mean light has mass (a very very very very small amount)
Some please explain or tell me I'm wrong but this would make more sense to me
The immense scale in which the universe expands and the absurdly tiny scale that the light frequency resides, how can one affect the other.
It's like the scale of my physical body and the scale of thre quantum world. things that happened in 1 don't necessarily affect the other.
Obviously all this is in question form not in statement form.
The car example wasn't very good, because the car was accelerating, so the engine wasn't at a constant RPM, and the car wasn't moving very fast, particularly since it started from a standstill, so there wasn't all that much doppler effect going on in the first place. You'll notice a much stronger effect when you stand next to a car race track, for instance. ruclips.net/video/FyU6-cg5EW0/видео.html
Ok, Space is expanding, it's accelerating, but is it thrusting? if so, is it thrusting up or down?
and if it is, is the thrusting varying? if it is is the variation of the thrust varying? and if it is is...?
While this video does a really good job at describing cosmological redshift, it doesn't really explain how we know that it is cosmological redshift causing light to redshift over long distances, and not a whole bunch of other possible solutions that would fit the observations of light redshifting over long distances. Besides the redshifting, what are other signs that point to cosmological redshift being the solution, and are there any testable predictions we do with cosmological redshift?
Ok, Thought experiment, lets say that expansion is not the cause. So then gravitational red shift, light travels from the center of a galaxy and is red shifted by the time it exits its galaxy, now it travels though the universe until it reaches our galaxy, but we live on the outer part of our galaxy so the light is not blue shifted much which would make that light still appear red shifted to us. So why is this not the case and expansion is?
How do you think is universe expanding? Has it got any boundary? I'm meaning to say that how can you expand when there is nothing out there. Fill up a ballon in a carton ,it will stop after sometime.
So if we are saying the universe is expanding just by observing the light itself and not seeing it moving further away perhaps we don't understand light the way we think we do. perhaps light just changes the further it travels.
so if were going to try to look farther back in time shouldnt we be focusing on radio light?
How long will it be before we don't see any more lights from the space (except the sun maybe?), because all the light has shifted outside the visible spectrum?
So, the big bang created space time and matter once things cooled down a bit. Space time expanded in a dramatic fashion initially, then slowed down but did not stop expanding. Outside of this expanding space time is nothing. Where am I wrong, how would we test it?
But at a concert the bass travels further than the high notes so how do you know it isn't just like that?
Still doesn't explain why it's not 'universe is infinite and galaxies just moving away from us' instead of ' universe is a certained place and itself is expanding'?
I believe this is the incorrect way to show the Doppler effect. the approaching part was correct but when the car leaves you it suddenly has a lower pitch and becomes 'normal' again.
Very confusing!
Farther away galaxies are moving at a faster speed, at the same time the farther away galaxies are as they were in past. That means galaxies in the past moved faster. How does that mean that distant galaxies are moving away faster from us now and the universe is expanding?