Thanks so much for this professor Dave! In all honesty I was avoiding this video because I saw it in my recommendations and I thought it would be complex and hard to understand. You explained it all brilliantly and make me excited to learn more about this! I’ll surely be checking out the rest of this series and be doing some reading on this. Have a great day and keep doing what you’re doing please!
Thanks for your clear explanation Professor Dave. I have a couple of questions as a non scientist. The further away we are looking the further back in time. So how do we know that those galaxies have not slowed up since? If the universe expansion was slowing would you not expect to see older galaxies moving away faster? Also accepting that the universe is expanding, the greater the distance the galaxy the greater the difference in its "direction of travel" from our own. Presumably this is covered for in the maths?
Hubble's Constant can be easily calculated using ONLY the speed of light (C) and Pi 2 X a megaparsec X C, divided by Pi to the power of 21 = 71 K / S / MPS. This equation comes from the "Principle of Astrogemetry"
I just cannot wrap my head around the ideas that: 1. Gravitational attraction between the Milky Way and Andromeda can be greater than the "force" (for lack of a better word) that is supposedly causing all other galaxies to move away from each other. 2. The idea that any object (i.e. a Galaxy) can be accelerating at an exponential rate AWAY from anything else. I am admittedly uneducated in these matters, but as far as I know, there is no phenomena here on earth that is comparable to that, and the only way something can accelerate at an exponential rate is when it's being drawn TOWARD something else. 3. The idea that no matter which galaxy you might be looking out from, every other galaxy would still appear to be moving away from you at an exponential rate. That just doesn't make sense to me. 4. Why isn't this "force" that is causing galaxies to move away from each other so rapidly also causing galaxies themselves to be ripped apart? Can you possibly explain these things in a way I might understand? Thanks!
The reason it's stronger between us and Andromeda is the distance. Gravitational attraction drops off by the square of the distance, so only galaxies very close to each other will be able to attract one another over the force of the expansion. As for an accelerating expansion, there is no fundamental difference between an attraction and a repulsion, here we have a repulsion (dark energy) that is increasing in magnitude over time, due to the expansion of spacetime, and as a force increases, acceleration increases. That's Newton's second law of motion. For all the galaxies moving away, the dots on the balloon analogy is about as effective as it gets, feel free to recreate this one in real life for a better sense of it. As for dark energy not ripping galaxies apart, it will one day. Right now the gravitational attraction amongst the stars in a galaxy is much too strong, but dark energy will grow and grow up galaxies are ripped apart, then systems, and on a long enough timeline even individual atoms will be torn apart. I cover all of this in upcoming tutorials in this series regarding dark matter/energy and the end of the universe, so all will be clearer!
The balloon analogy would be valid if everything was moving away from one central point, the point of the big bang. There is also the idea that everything in motion must be moving in some direction. So if a distant galaxy is moving away from the Milky Way, and an observer somewhere in that galaxy looked back toward the milky way and saw that it was accelerating away from their galaxy at an accelerated rate, that would have to mean they were moving in opposite directions. Bit it cannot be that every galaxy is moving in the opposite direction from every other galaxy. That's the part I cannot understand. Can you explain that?
Imagine the universe as being only the surface of the balloon. The surface has no center. All the dots are moving away from each other in the same way. It's difficult to imagine because it requires envisioning three spatial dimensions curving around a fourth, that's why these lower-dimension analogies are the best we can do.
Ok, this, I guess, is the part I will never understand, trying to imagine three spatial dimensions curving around a fourth. My little brain simply cannot grasp that concept. And because of that circumstance, I cannot imagine that anyone else can, either. This kind of thing is what I think of as being "scientific dogma", where those who claim to be able to imagine this say it, and anyone who wants to be a part of the scientific "in crowd" will say it makes sense to them too, even when it really doesn't. No need to reply again, but I do thank you for your time in trying to explain this to someone like me.
Well no one can visualize four spatial dimensions. But we understand all of this because of the math. It's not some flight of fancy, nor is it dogma in the slightest, the math tells us how things are. Math that is unfortunately way too complicated for me to describe, but maybe one day!
4:23 It should be made clear, that redshift and blueshift can be caused for different reasons. Those are, as far as we know, Doppler effect, gravity and expansion of space.
How much is due to Doppler and how much due to expansion of the universe? What if the wavelength of light doesn’t change during travel and it is all due to Doppler (which in turn is due to expansion of space) how would you tell the difference?
@@a9c AFAIK (I'm only a layman!) Doppler effect and space expansion produce the *same effect* but for *different reasons* (causes). But regarding that _all_ (really far!! andromeda galaxy would be still too close!) objects move away from us and also they move away from each other (!) lets us deduce that the cause is different from just a Doppler effect and this is then called _expansion of the universe_ instead. The wavelength shift by both phenomena _interfere_ with each other. (good question btw)
@@ericlind6581 I'm not sure I understand what you mean by that. Of course we only deduce that the space (e.g. in big voids) is (for the very most part) a vacuum. But in reality there may be many issues that all affect the behavior in the end...
@@eigentlichtoll02 that’s exactly my point. We measure waves that have travelled millions light years away but we can only assume the path to us is somewhat “pure”. Also can we really say that light doesn’t change over eons, an experiment we simply cannot conduct?
Professor Dave. Thanks for all your fab videos. I am a high school ( secondary school ) physics teacher in the UK. I think they are great. You always seem to pitch it just right. Accessible yet but with some nice high brow details for the more inquisitive!
This is really good, and I'm going to show it to my students. I have a teeny critique, which is that when you say "emission spectrum" you show an absorption spectrum, no?
Why are galaxies that are further away moving faster relative to us? Given the balloon model, why isn't everything moving away from everything else at a constant velocity ?
He means the spectrum of light that we see in the concept of the static universe model. If all the galaxies are stationary then their spectrum of light which we observe should not change at all. But it’s visible enough to change so they realised that the galaxies were moving apart.
@Michael Terrell II If matter is evenly distributed across the entire universe, the spacetime metric must be expanding. The most important equation describing this is the Friedmann Equation.
It is a consequence of directly linking recessional velocity to red shift in the Hubble law equation and ignoring gravitational red shift. ruclips.net/video/Y969fUR_Vtg/видео.html
Hey hi professor! Can it be that the universe just like other elements has a tendency to become stable. And its expanding in order to make itself stable relative to all the integrated particles present in it? BTW UR VIDEOS ARE ASWM!
How did Hubble realise that the redshifts correlate with not only speed but also distance? I mean didn't we start measuring distance of the galaxies only after assuming such correlation? I can imagine that he used mere brightness as as an indicator... but since then we observed "quasars" which are very bright and also have very high redshifts ... and we ASSUMED that according to Hubble's Law they must just be very HUGE distant galaxies... I mean is there a chance that Hubble was wrong? (Not to mention how Einstain's Relativity theory should technically make light immune to the Doppler effect - yeah I know that we can just try to think that space itself stretches... but really - it's already a "stretch", don't you think? ;P) Im just curious if there are any additional evidence for the Hubble's Law :)
No no, there are many ways to determine such distances, standard candles which is a certain type of supernova, etc. He found that he could plot red shift as a function of distance, which is essentially his law. Also what you are saying about relativity is not accurate, I have tutorials on that in my modern physics playlist, check it out.
His initial plots were of redshirt of a certain type of standard candle called cepheid variable stars. We can work out their actual brightness by their pulsation rate - then we can measure their apparent brightness from how far away they are, use the inverse square law and then we know distance. Plotting distance again red shift gives Hubble’s law.
If Light and sound has a shift effect when it's moving , Does spacetime and gravity also have shift effect? Like how light gets lower and sound becomes lower pitched, does spacetime stretch and gravity get weaker when spacetime is moving away? I feel like the answer to the expansion of the universe lies somewhere in that along with something I have been thinking about. Surface area of atoms or matter. When I think of the early universe, I picture an endless sea full of salt grains. The grains being all atoms. When 2 grains of salt combine together, there are two sides that are now essentially pushing space out of the way, and now the space has nowhere to go, no cracks to fill, so all this extra space goes out and around causing everything to separate further from its neighbors.
Hubble did not believe the Universe is expanding based on counting galaxies. He believes redshift is an " hither to unknown principle of nature". The Universe is stationary, the Gravity Energy is stationary @ v=c. Age=15.84Gy, R=150GPm.
Hubble gathered the data. The astrophysics community collectively interpreted the data to conclude that the universe is expanding, and observation which has been corroborated in countless years over the past century. Also, I would highly dought that he believed redshift was an unknown principle, it must have been observed on earth with sound waves already.
How do you know how much is shifted due to Doppler and how much due to expansion of space during the trip? If the universe is expanding aren’t some stars moving away faster than light? How does blue shift happen in some stars? (From my phone thanks)
So if the big bang happened at "a specific time" .. If everything -including spacetime- was contracted into a single spot... How much .. time passed before it expanded? All of it? Or none of it? And in general how to measure and understand it? Did time move faster or slower than it currently is as the universe was expanding? Does time continually keep going ever slower or faster as the universe keeps expanding?
One thing I don't understand. In a previous video you talked about galaxies colliding and forming elliptical galaxies, and mentioned that the Milky Way and Andromeda were on a course to collide. But in this video you said that galaxies are moving away from each other. This seems contradictory. Is it more in general terms that galaxies move away, but in a couple instances they'll collide?
following hubble's law what can be inferred about the distance of certain celestial body x if it moves thrice as fast as celestial galaxy y which is 5 mpc away from the earth
Hi. It would be the greatest explanation ever if there was no extra “if”. If the universe were expanding, than those dots on a air balloon were getting not only apart, but bigger also. Therefore all the galaxies on the “edges” of the observable universe also were bigger.
You're taking the analogy a little too far, the dots on the balloon are not equivalent to galaxies, it's just a visual tool to help people understand how all the galaxies can be receding from each other simultaneously. Galaxies are not getting bigger.
Professor Dave Explains May be you are right, but if the universe is expanding then doesn’t it mean the amount of matter near the edges of the observable universe has to be considerably smaller comparing to the central region?
the observable universe doesn't have any physical significance other than to us, it's just how far we can see from here. there are no actual edges to the universe, nor a central region.
Hello Professor. This Lecture was Great and your explanation is too good.... I want to know, How is this Universe Expanding and where it is Expanding? Just like you showed an example of balloon expansion, I can say it expands on the White Space around it. In that view, what is outside Universe?
Murali Kumar theory suggests that matters are constantly popping into our galaxy, where there the matters and anti matter obliterate each other, but there’s speculation of something called black matter, it doesn’t react with anything but it’s there, filling up the galaxy. Anyway these quantum theories isn’t yet solidly confirmed, though has the potential to rewrite a ton of physic laws
It's definitely a good question! The short answer to what's outside the universe is nothing. The universe is space and time, so asking what's outside of space or before time or things like that don't really have any meaning. But I can sympathize with the existential crisis that brings on. Plus we don't know anything about other potential universes and things like that. So feel free to speculate!
Murali Kumar we really don’t know much outside of earth say for example maybe mars is just a projection of what we think is mars, maybe the rovers human sent are hacked before they arrive and touch down, maybe the specimen that they retrieved are placed by aliens, because mars is was like earth before, maybe there are even more intelligent life in mars that we’ll be shot down when we arrive in the future
@@ProfessorDaveExplains That is correct, but if one writes the fraction on one line as you did, then one must write the denominator inside parentheses. Otherwise it means to multiply the fraction with the unit of [length] “Mpc” which does not result in the required dimension for the Hubble constant/parameter of 1/[time]. IOW: 70 km/s Mpc ≠ 70 km/(s Mpc) = (70 km/s)/Mpc = 70 (km/s)/Mpc = 70 km/s/Mpc.
I mean, I guess, but they seem more like lessons.. I'm not being an ass by asking. I know after the hovind massacre, you must be getting a lot of bastards acting bastardly. It just seems an odd descriptive word for them. BTW: the hovind massacre is what got you my subscription. I've just been enjoying your videos on this an other subjects, and really admire your work. Please keep it up! :)
@@amlanadarshdas4470 Science means knowledge in Latin. Knowledge comes from learning what God created. Or do you think everything happened by itself? The more you learn about the world and the atoms and neutrons the more you will get closer to God. Because everything is created just perfectly.
@@liamcavanagh5270 then who created god? Science has actually said nothing about god, that's the reason I am an atheist. But if science will say god exists,then I will surely believe
@@amlanadarshdas4470 if you believe in everything what science says then what makes you different from the people who believe everything that God says? You already made yourself a god in form of Science. Make a research about human body. And ask yourself if such a perfect organism can come to existence just like that as a mixture of chaotic chemicals. Denying human soul is like a pc denies its software. But we know that PC is just a hardware that has its engineer, it has a manual that teaches us what is good and what is bad for that device. It warns us about stuff that might destroy or break it down. And finally it has a software. A soul. God is a Maker, User Manual is a Holy Book with guidance, and Software is our soul. And it can be upgraded as well. Every town needs a mayor, every country needs a ruler, every army needs a general, every family needs a head. Do you think this immense universe which is continuously expanding (in book of Muslims God says: We created the heavens and we are expanding it)won't need someone to control it and acts just by itself in chaos? Study astronomy medicine linguistics everything prooves the existence of One behind what we see and don't see.
Thanks so much for this professor Dave! In all honesty I was avoiding this video because I saw it in my recommendations and I thought it would be complex and hard to understand. You explained it all brilliantly and make me excited to learn more about this! I’ll surely be checking out the rest of this series and be doing some reading on this. Have a great day and keep doing what you’re doing please!
Criminally underrated channel, you deserve more than a billion subscribers!
Love it! One correction though: The spectra shown as emission spectra are actually absorbtion spectra.
@@Oussama-sabouh the black bars are wavelengths that get absorbed on their way through the universe
Can't wait for upcoming episodes.. I kinda like space....
Thanks for your clear explanation Professor Dave. I have a couple of questions as a non scientist. The further away we are looking the further back in time. So how do we know that those galaxies have not slowed up since? If the universe expansion was slowing would you not expect to see older galaxies moving away faster? Also accepting that the universe is expanding, the greater the distance the galaxy the greater the difference in its "direction of travel" from our own. Presumably this is covered for in the maths?
Hubble's Constant can be easily calculated using ONLY the speed of light (C) and Pi 2 X a megaparsec X C, divided by Pi to the power of 21 = 71 K / S / MPS. This equation comes from the "Principle of Astrogemetry"
I just cannot wrap my head around the ideas that: 1. Gravitational attraction between the Milky Way and Andromeda can be greater than the "force" (for lack of a better word) that is supposedly causing all other galaxies to move away from each other. 2. The idea that any object (i.e. a Galaxy) can be accelerating at an exponential rate AWAY from anything else. I am admittedly uneducated in these matters, but as far as I know, there is no phenomena here on earth that is comparable to that, and the only way something can accelerate at an exponential rate is when it's being drawn TOWARD something else. 3. The idea that no matter which galaxy you might be looking out from, every other galaxy would still appear to be moving away from you at an exponential rate. That just doesn't make sense to me. 4. Why isn't this "force" that is causing galaxies to move away from each other so rapidly also causing galaxies themselves to be ripped apart? Can you possibly explain these things in a way I might understand? Thanks!
The reason it's stronger between us and Andromeda is the distance. Gravitational attraction drops off by the square of the distance, so only galaxies very close to each other will be able to attract one another over the force of the expansion. As for an accelerating expansion, there is no fundamental difference between an attraction and a repulsion, here we have a repulsion (dark energy) that is increasing in magnitude over time, due to the expansion of spacetime, and as a force increases, acceleration increases. That's Newton's second law of motion. For all the galaxies moving away, the dots on the balloon analogy is about as effective as it gets, feel free to recreate this one in real life for a better sense of it. As for dark energy not ripping galaxies apart, it will one day. Right now the gravitational attraction amongst the stars in a galaxy is much too strong, but dark energy will grow and grow up galaxies are ripped apart, then systems, and on a long enough timeline even individual atoms will be torn apart.
I cover all of this in upcoming tutorials in this series regarding dark matter/energy and the end of the universe, so all will be clearer!
The balloon analogy would be valid if everything was moving away from one central point, the point of the big bang. There is also the idea that everything in motion must be moving in some direction. So if a distant galaxy is moving away from the Milky Way, and an observer somewhere in that galaxy looked back toward the milky way and saw that it was accelerating away from their galaxy at an accelerated rate, that would have to mean they were moving in opposite directions. Bit it cannot be that every galaxy is moving in the opposite direction from every other galaxy. That's the part I cannot understand. Can you explain that?
Imagine the universe as being only the surface of the balloon. The surface has no center. All the dots are moving away from each other in the same way. It's difficult to imagine because it requires envisioning three spatial dimensions curving around a fourth, that's why these lower-dimension analogies are the best we can do.
Ok, this, I guess, is the part I will never understand, trying to imagine three spatial dimensions curving around a fourth. My little brain simply cannot grasp that concept. And because of that circumstance, I cannot imagine that anyone else can, either. This kind of thing is what I think of as being "scientific dogma", where those who claim to be able to imagine this say it, and anyone who wants to be a part of the scientific "in crowd" will say it makes sense to them too, even when it really doesn't. No need to reply again, but I do thank you for your time in trying to explain this to someone like me.
Well no one can visualize four spatial dimensions. But we understand all of this because of the math. It's not some flight of fancy, nor is it dogma in the slightest, the math tells us how things are. Math that is unfortunately way too complicated for me to describe, but maybe one day!
Wow, thanks professor Dave, this really helped me a lot. Thank you so much.
5:50 - Was anybody else waiting for the universe to pop?
incredible discovery, that if space is expanding then it means we started from the same point
4:23 It should be made clear, that redshift and blueshift can be caused for different reasons. Those are, as far as we know, Doppler effect, gravity and expansion of space.
eigentlichtoll02 What I question is that the Doppler effect assumes that space more or less acts like a vacuum. This may not be the case however.
How much is due to Doppler and how much due to expansion of the universe? What if the wavelength of light doesn’t change during travel and it is all due to Doppler (which in turn is due to expansion of space) how would you tell the difference?
@@a9c AFAIK (I'm only a layman!) Doppler effect and space expansion produce the *same effect* but for *different reasons* (causes). But regarding that _all_ (really far!! andromeda galaxy would be still too close!) objects move away from us and also they move away from each other (!) lets us deduce that the cause is different from just a Doppler effect and this is then called _expansion of the universe_ instead.
The wavelength shift by both phenomena _interfere_ with each other.
(good question btw)
@@ericlind6581 I'm not sure I understand what you mean by that. Of course we only deduce that the space (e.g. in big voids) is (for the very most part) a vacuum. But in reality there may be many issues that all affect the behavior in the end...
@@eigentlichtoll02 that’s exactly my point. We measure waves that have travelled millions light years away but we can only assume the path to us is somewhat “pure”. Also can we really say that light doesn’t change over eons, an experiment we simply cannot conduct?
Professor Dave. Thanks for all your fab videos. I am a high school ( secondary school ) physics teacher in the UK. I think they are great. You always seem to pitch it just right. Accessible yet but with some nice high brow details for the more inquisitive!
This is really good, and I'm going to show it to my students. I have a teeny critique, which is that when you say "emission spectrum" you show an absorption spectrum, no?
... i am speachless... Good job Houble
Why are galaxies that are further away moving faster relative to us? Given the balloon model, why isn't everything moving away from everything else at a constant velocity ?
Here's to me passing my midterm tomorrow 😂
short and clear explanation thank you
respected sir
can you please upload the notes they are beneficial for us.
thank you sir
at 4:50 how were the Expected values of each galaxy's spectra obtained?
He means the spectrum of light that we see in the concept of the static universe model. If all the galaxies are stationary then their spectrum of light which we observe should not change at all. But it’s visible enough to change so they realised that the galaxies were moving apart.
It's also worth mentioning that an expanding universe is a consequence of general relativity.
@Michael Terrell II If matter is evenly distributed across the entire universe, the spacetime metric must be expanding. The most important equation describing this is the Friedmann Equation.
It is a consequence of directly linking recessional velocity to red shift in the Hubble law equation and ignoring gravitational red shift. ruclips.net/video/Y969fUR_Vtg/видео.html
@@gravitonrecycler6670 pretty sure that's the observational approach, I was talking about the theoretical/mathematical approach.
Thank you
Hey hi professor! Can it be that the universe just like other elements has a tendency to become stable. And its expanding in order to make itself stable relative to all the integrated particles present in it?
BTW UR VIDEOS ARE ASWM!
Thanks!
Sorry but they are absorption spectra and not emission spectra
Otherwise nice video
How did Hubble realise that the redshifts correlate with not only speed but also distance? I mean didn't we start measuring distance of the galaxies only after assuming such correlation? I can imagine that he used mere brightness as as an indicator... but since then we observed "quasars" which are very bright and also have very high redshifts ... and we ASSUMED that according to Hubble's Law they must just be very HUGE distant galaxies...
I mean is there a chance that Hubble was wrong? (Not to mention how Einstain's Relativity theory should technically make light immune to the Doppler effect - yeah I know that we can just try to think that space itself stretches... but really - it's already a "stretch", don't you think? ;P)
Im just curious if there are any additional evidence for the Hubble's Law :)
No no, there are many ways to determine such distances, standard candles which is a certain type of supernova, etc. He found that he could plot red shift as a function of distance, which is essentially his law. Also what you are saying about relativity is not accurate, I have tutorials on that in my modern physics playlist, check it out.
@@ProfessorDaveExplains Ok, I guess more searching is in order. Thanks for the reply :)
His initial plots were of redshirt of a certain type of standard candle called cepheid variable stars. We can work out their actual brightness by their pulsation rate - then we can measure their apparent brightness from how far away they are, use the inverse square law and then we know distance. Plotting distance again red shift gives Hubble’s law.
Actually Hubble came to the conclusion that the universe wasn't expanding. ladailymirror.com/2011/12/31/hubble-no-evidence-of-big-bang-theory/
Hubble's law ignores gravitational red shift and he did not believe the universe was expanding by the 1940s. ruclips.net/video/Y969fUR_Vtg/видео.html
Stunning explanation ❤️💕❤️
If Light and sound has a shift effect when it's moving , Does spacetime and gravity also have shift effect? Like how light gets lower and sound becomes lower pitched, does spacetime stretch and gravity get weaker when spacetime is moving away? I feel like the answer to the expansion of the universe lies somewhere in that along with something I have been thinking about. Surface area of atoms or matter. When I think of the early universe, I picture an endless sea full of salt grains. The grains being all atoms. When 2 grains of salt combine together, there are two sides that are now essentially pushing space out of the way, and now the space has nowhere to go, no cracks to fill, so all this extra space goes out and around causing everything to separate further from its neighbors.
Spacetime does stretch that's literally the thing that's expanding. Spacetime is not a wave though.
I'm not sure about gravity though
LOVE THIS!!!!
Hubble did not believe the Universe is expanding based on counting galaxies. He believes redshift is an " hither to unknown principle of nature". The Universe is stationary, the Gravity Energy is stationary @ v=c. Age=15.84Gy, R=150GPm.
Hubble gathered the data. The astrophysics community collectively interpreted the data to conclude that the universe is expanding, and observation which has been corroborated in countless years over the past century. Also, I would highly dought that he believed redshift was an unknown principle, it must have been observed on earth with sound waves already.
ruclips.net/video/Y969fUR_Vtg/видео.html
Best teacher!!
How do you know how much is shifted due to Doppler and how much due to expansion of space during the trip? If the universe is expanding aren’t some stars moving away faster than light? How does blue shift happen in some stars? (From my phone thanks)
So if the big bang happened at "a specific time" .. If everything -including spacetime- was contracted into a single spot...
How much .. time passed before it expanded? All of it? Or none of it? And in general how to measure and understand it? Did time move faster or slower than it currently is as the universe was expanding? Does time continually keep going ever slower or faster as the universe keeps expanding?
ruclips.net/video/Y969fUR_Vtg/видео.html
One thing I don't understand. In a previous video you talked about galaxies colliding and forming elliptical galaxies, and mentioned that the Milky Way and Andromeda were on a course to collide. But in this video you said that galaxies are moving away from each other. This seems contradictory. Is it more in general terms that galaxies move away, but in a couple instances they'll collide?
following hubble's law what can be inferred about the distance of certain celestial body x if it moves thrice as fast as celestial galaxy y which is 5 mpc away from the earth
Hi. It would be the greatest explanation ever if there was no extra “if”. If the universe were expanding, than those dots on a air balloon were getting not only apart, but bigger also. Therefore all the galaxies on the “edges” of the observable universe also were bigger.
You're taking the analogy a little too far, the dots on the balloon are not equivalent to galaxies, it's just a visual tool to help people understand how all the galaxies can be receding from each other simultaneously. Galaxies are not getting bigger.
Professor Dave Explains May be you are right, but if the universe is expanding then doesn’t it mean the amount of matter near the edges of the observable universe has to be considerably smaller comparing to the central region?
the observable universe doesn't have any physical significance other than to us, it's just how far we can see from here. there are no actual edges to the universe, nor a central region.
ruclips.net/video/Y969fUR_Vtg/видео.html
Hello Professor. This Lecture was Great and your explanation is too good.... I want to know, How is this Universe Expanding and where it is Expanding? Just like you showed an example of balloon expansion, I can say it expands on the White Space around it. In that view, what is outside Universe?
Murali Kumar theory suggests that matters are constantly popping into our galaxy, where there the matters and anti matter obliterate each other, but there’s speculation of something called black matter, it doesn’t react with anything but it’s there, filling up the galaxy. Anyway these quantum theories isn’t yet solidly confirmed, though has the potential to rewrite a ton of physic laws
It's definitely a good question! The short answer to what's outside the universe is nothing. The universe is space and time, so asking what's outside of space or before time or things like that don't really have any meaning. But I can sympathize with the existential crisis that brings on. Plus we don't know anything about other potential universes and things like that. So feel free to speculate!
Thanks for the quick response Professor.....
Burn My Uncle Right! Also Speculation brought us all the way from none to this much advancement in Science..
Murali Kumar we really don’t know much outside of earth say for example maybe mars is just a projection of what we think is mars, maybe the rovers human sent are hacked before they arrive and touch down, maybe the specimen that they retrieved are placed by aliens, because mars is was like earth before, maybe there are even more intelligent life in mars that we’ll be shot down when we arrive in the future
H₀ ≈ 70 km/s/Mpc, not H₀ ≈ 70 km/s Mpc.
when you divide a fraction by something, it can go in the denominator of the fraction. those are algebraically equivalent.
@@ProfessorDaveExplains That is correct, but if one writes the fraction on one line as you did, then one must write the denominator inside parentheses. Otherwise it means to multiply the fraction with the unit of [length] “Mpc” which does not result in the required dimension for the Hubble constant/parameter of 1/[time]. IOW: 70 km/s Mpc ≠ 70 km/(s Mpc) = (70 km/s)/Mpc = 70 (km/s)/Mpc = 70 km/s/Mpc.
eh fair point i suppose, or rather i could have put a dot between s and Mpc to signify multiplication
eccezionale 😍👌👌👌👌👌🙏🙏🙏🎹🎹🎹🎹🎹🎶💥📒📚🌍🌎🎇
I don't understand
❤
Why are these called tutorials?
That's what they are.
I mean, I guess, but they seem more like lessons.. I'm not being an ass by asking. I know after the hovind massacre, you must be getting a lot of bastards acting bastardly. It just seems an odd descriptive word for them.
BTW: the hovind massacre is what got you my subscription. I've just been enjoying your videos on this an other subjects, and really admire your work. Please keep it up! :)
"And We have built the heaven with might and We continue to expand it indeed" (Quran 51\47) Science+Religion=Real Knowledge.
Science is real knowledge, religion is superstition
@@amlanadarshdas4470 Science means knowledge in Latin. Knowledge comes from learning what God created. Or do you think everything happened by itself? The more you learn about the world and the atoms and neutrons the more you will get closer to God. Because everything is created just perfectly.
@@liamcavanagh5270 then who created god? Science has actually said nothing about god, that's the reason I am an atheist. But if science will say god exists,then I will surely believe
@@amlanadarshdas4470 if you believe in everything what science says then what makes you different from the people who believe everything that God says? You already made yourself a god in form of Science. Make a research about human body. And ask yourself if such a perfect organism can come to existence just like that as a mixture of chaotic chemicals. Denying human soul is like a pc denies its software. But we know that PC is just a hardware that has its engineer, it has a manual that teaches us what is good and what is bad for that device. It warns us about stuff that might destroy or break it down. And finally it has a software. A soul. God is a Maker, User Manual is a Holy Book with guidance, and Software is our soul. And it can be upgraded as well. Every town needs a mayor, every country needs a ruler, every army needs a general, every family needs a head. Do you think this immense universe which is continuously expanding (in book of Muslims God says: We created the heavens and we are expanding it)won't need someone to control it and acts just by itself in chaos? Study astronomy medicine linguistics everything prooves the existence of One behind what we see and don't see.
@@liamcavanagh5270 hmm