Where Is The Center of The Universe?

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Today we’re going to ask a simple-seeming question that will lead to so pretty wacky places. The question is this: If the universe has a center, where is it?
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Hosted by Matt O'Dowd
Written by Matt Caplan & Matt O'Dowd
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Spacetime is produced by Kornhaber Brown for PBS Digital Studios.
This program is produced by Kornhaber Brown, which is solely responsible for its content.
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End Credits Music by J.R.S. Schattenberg: / multidroideka
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[@ardag1439]

Duh, it is at (0,0,0) obviously. I'll have that Nobel prize now.

[@ArghyadeepPal]

Best comment lol, Euclid would be proud.

[@johnretherford592]

(0,0,0,0) actually

[@nathanielacton3768]

@@johnretherford592 Or perhaps use a quaternion with a direction that always points at the big bang :)

[@Unkl_Bob]

We are 0,0,0,0,00|0000,00:00:00 Earth is the center of the universe. The exact center. Or was before the sun and planets formed and it started to wobble around its orbit .

[@GoldenAdrien]

@@Unkl_Bob i can not tell if you are joking, but no, we are not at the center of our universe, and the Earth formed at the same time as the other planets.

[@tycro]

Nobody has ever made me feel more passionate about things I can’t remotely understand than Matt.

[@vhawk1951kl]

When you use the word "universe" what exactly do you mean by it or what do you seek to convey when you use the term "universe"? Why not just own up and admit that you have absolutely no idea whatsoever what you mean by universe or what you seek to convey when you use the term?

[@AllanTingey]

@@vhawk1951kl Quantum weirdness? In my version of the universe, he never used the word “universe”. Your observation seems to have produced a different result!

[@stevelowe2647]

@@AllanTingey exactly what I thought, I read it like 3 times, thinking how am I missing it.. the word isn't even there, & you just got some belter blabbing on about something that he's imagined.. maybe the Klingons kidnapped him & stole his keyboard.. about as random as his comment aye.

[@waynethomas1726]

LOL, yea! I was just commenting above how it wasn't that long ago that it a singularity that went bang. Now might not have been a bang at all. I feel to cheated! LOL

[@lilmike2710]

There's those of us who understands that we can't remotely understand our immesurable universe, and then there are those who pretend that they do. Quite arrogant if you ask me.

[@hsadreamerofrlyeh7516]

After about 2 years of trying to properly understand this topic, this is the video that finally made it click for me. Excellent job!

[@kurtisengle6256]

You actually understand something because of this? What? It's 20 minutes of tripe as far as I can tell. I WOULD BE DELIGHTED TO LEARN SOMETHING FROM YOU. But really doubt that is going to happen.

[@hsadreamerofrlyeh7516]

​​​​@@kurtisengle6256so from my understanding of it, imagine the entire universe as the surface of a balloon not the inside, just the surface of the balloon that you can see and touch. Before air is pumped into the balloon it is the size of a single dot. Everything in existence is at that very centerpoint. Now imagine there is a little blue circle drawn on the surface of the balloon. To keep it simple, that will be the Milky Way where Earth is located. Now let's say there is also a green circle located nearby. Let's say that is some other galaxy. If you pump air into the balloon, the circle will slowly start to expand as the balloon is stretched out. And at the same time the two will grow farther apart as well. That is a VERY basic understanding of the universe expanding. Just replace the idea of the circles being two galaxies with observable universes. I understood that for a while, but it wasn't until this video until it clicked that the air filling up the balloon would be the dimension of time. The more time you put into the balloon the more expands, and if you let the time leak out, run the clock in reverse, eventually everything will shrink back down to that one point. Normally thinking of it as the universe being a balloon you would intuitively want to say well wherever the center of the balloon would be, that must be the center. But you got to view it as the outside layer of the balloon being space and the air inside the balloon as time. That's what made it click for me

[@jeffreymartin8448]

Love this guy. You know new possibilities will be discovered listening to him because he says "But, I'm not sure" fairly regularly. Sometimes I have to watch an episode twice (unavoidable since he goes a bit beyond a documentary for us average brains). I think I've watched all of them since they started !

[@kylouglass]

Can't be sure of anything scientific proofs don't exist

[@dylanglaze990]

I hate when anyone says anything they say or think about the universe is fact. "I think..." Or "I'm not sure but..." Are required. It's simply unintelligent to think you know anything about the universe for certain.

[@SWABManutius]

This open and frank humility is an absolute for anyone honest about trying to understand just about anything. And as Kyle and Dylan point out, the scientific method isn't about reaching certainty or proof so much as rooting out bad theories. It's our certainty-craving minds that want the results of every new study to be definitive or True. This is why science is so important--it is the best system discovered so far for pushing back on our primal need to feel like we understand what we experience, and our inherent bias toward our own subjective interpretation of that experience.

[@technocore1591]

The explanation of how 2d person can point anywhere and be pointing at the center of the universe and it's applicability to a 3d universe was sublime. Thank you. I understood it.

[@scaper8]

@@kendrickmcelfish2805 You know, I didn't even make the connection to the CMBR until you said it, but, yes, that explains it completely!

[@LuisSierra42]

This is probably the first time that i see someone commenting that they clearly understood the topic of the video

[@j.477]

,, jk comments :: feel jealous,, kinda, oim noteven sure what I understood leastetest,, yet love th' ride,, as owlwoyss ...

[@johnarnold893]

No matter where you go your in the center of the universe.

[@johnarnold893]

@Shon Mardani 🤡

[@DrZedDrZedDrZed]

I love this show so much. Thank you Matt ands PBS and everyone who helps make this real. I'm having a kid and I can't wait for the day that I start watching the whole back catalogue of Space Time with him.

[@osmosisjones4912]

How much energy would it take to warp how much space

[@69TheGG]

That’s fcked up

[@MasterBlaster3545]

Ahh you are a universe in its own right ready for your own big bang

[@MasterBlaster3545]

@@69TheGG 🤣

[@puertoricanboy100]

@@osmosisjones4912 The energy subtracted from chromosomes you're missing.

[@px43]

So, along with the 2D surface on a sphere analogy, would that also mean that sending two ships in opposite directions, approaching the speed of light, that they might run into each other again at the "opposite side" of our universe? Or maybe we could look in two different directions and see the same ancient star?

[@AliothAncalagon]

In principle yes. But you could never do that experiment, because the expansion of the Universe is faster than the speed of light. It would be like trying to send two ships into two different directions to have them meet on the other side of the planet, while the planet is expanding much faster than the ships could ever travel.

[@monkatraz]

There is another Spacetime episode involving this, the one about a spaceship colliding with itself by going fast enough to length contract a closed universe to a size smaller than the spaceship. That's the premise anyways - the episode goes into if this would actually happen.

[@sudarshanchatterjee6911]

@@AliothAncalagon if thats the truth then we would not see the stars or any lights from the space

[@AliothAncalagon]

@@sudarshanchatterjee6911 From those spaces there is indeed no light reaching us. Thats why the observable universe has the boundaries that we see. Its the observable horizon of objects that were close enough to us, that the expansion rate which made them move away from us did not surpass the speed of light at the time their light started traveling towards us. In a universe that is overall expanding, two points will move away from each other with a speed that is mostly proportionate to their distance. For close objects thats not much. For further objects this becomes more relevant. And for very far objects this becomes faster than the speed of light. Thats why the latter will eventually become so fast, that their light can no longer reach us. In the very far future this will by the way be the destiny for every other galaxy cluster. Eventually every single other galaxy cluster will be so far away, that we will no longer be able to see it.

[@sudarshanchatterjee6911]

@@AliothAncalagon that is while u are assuming the size of the universe is infinite. Your assumption would have been correct if there were no gravitational force. May be I'm wrong

[@Vlasko60]

"If you can't explain it simply, you don't understand it well enough". If that quote is true, then no one who has explained it to me understands it well enough.

[@Ryo-sd9rx]

Some days I feel like I understand and some days what Matt says goes right over my head. Watch the video twice or 3 times and see if you get more out of it, idk works for me. Godspeed

[@notme2day]

What if we're in only the most recent big bang? Just as galaxies crash into each other and black holes grow and swallow everything. What if two black holes grow so large and come together, boom,big bang. A cycle that repeats every 100 ish billion years give or take. Just a thought for when you can't sleep ... sorry. ; 》

[@Vlasko60]

@@notme2day Yes, I have those thoughts about the universe being in a cycle of some kind. Probably because it is a more pleasant thought than one and done. I still can't understand the center of the universe arguments. Not simple enough for me. I may have to watch it a few more times as Ryan suggested.

[@_Wai_Wai_]

@@notme2day and then the astrophysicist says the universe is expanding at an increasing rate. Unless our observable universe will merge with another expanding universe, this cycle is not possible

[@angrymokyuu9475]

​@@_Wai_Wai_ Conformal cyclical cosmology makes it possible for an endless expansion to result in a new universe, though the evidence seems to lean into any acceleration of the universe's expansion slowing down(w ~= -0.99) even ignoring the question of whether that acceleration's real at all(a few structures have been found that are far too large for the cosmological principle as currently understood).

[@OleOlson]

I consider myself pretty well versed for an amateur who has only taken a half dozen classes on Astronomy, but the material on PBS SpaceTime is way beyond me. And I love it.

[@keenfire8151]

Would you say you are well uni-'versed' or are you a multi-'versed' type of person? 😎

[@johnfitzgerald8879]

@@keenfire8151 I bow to your greatness.

[@jondunmore4268]

Well, it's "way beyond you" because - as stated - you've *only taken a half dozen classes on Astronomy"!*

[@OleOlson]

@@jondunmore4268 Just the astronomy courses, and they were mostly beyond the intro ones. Also doesn't include the mathematics courses and individual research over the decades. Take the compliment without being condescending

[@jondunmore4268]

@@OleOlson -- Take the joke without being snowflakey

[@peristanom]

If "closed", "open", or "flat" applies to the spatial shape of a universe, would that in any way also apply to its temporal shape? That is, would a spatially finite "closed" universe eventually and necessarily recollapse? Would a spatially infinite "open" universe necessarily expand forever? Would the expansion rate of a spatially infinite "flat" universe necessarily approach zero? Or are these entirely different properties?

[@Kyrator88]

I assume that as time is 1 dimensional it is simply line like, however that is a very good question.

[@onebylandtwoifbysearunifby5475]

Those things shouldn't be dependant. A flat universe would imply infinite, or we would have some boundary problems at the edges. Parabolic should be able to expand indefinitely, as it would never meet itself. A 3-sphere geometry could also expand indefinitely, as it is like asking "what is the maximum size of a circle?" -any size you want. All of these shapes could collapse. That depends on the balance between "dark energy" and matter. All of these geometries could go back the way they came from. Or expand indefinitely. There is also a 4th spatial geometry- a torus. But that has some separate issues. But largely: time is a mystery. Nobody knows what the h*!! it is. It's not just another dimension. That is why it's represented with a Zero in the field equations for G.R.- it's special. ...So... Your answer is probably not. These things should be independent. But we know very little about anything.

[@Dragrath1]

According to the No big Crunch theorem for flat or open topologies in the general domain of the Einstein field equations, yes. The theorem from Inhomogenous and Anistropic cosmology: Matthew Kleban and Leonardo Senatore JCAP10(2016)022 says in explicit technical jargon. There cannot exist a non-singular spacelike hypersurface with maximum volume: given any time slice, there is another with larger spatial volume. Furthermore, in an initially expanding universe there must be at least one expanding region on every timeslice, and if Λ > 0 the expansion rate in that region is bounded from below by that of de Sitter spacetime in the flat slicing. More generally it implies for any arbitrary initial conditions within its valid domain it can be shown by a proof through contradiction that not only must any initially expanding universe expand forever, (while any initially contracting universe must conversely contract forever) but within any possible slice of time the volume of that space will always be larger(or smaller) than the preceding time slice. This theorem effectively shows that within the domain where the proof is defined that for any universe which isn't perfectly homogenous and isotropic at all possible scales within spacetime any inhomogeneities and or anisotropies within an initially expanding universe it will never be possible for the off-diagonal terms of the metric tensor to ever balance out ensuring that these off diagonal nonlinear terms will always amplify any asymmetries outside the domain of the Friedmann-Lemaître-Robertson-Walker metric. Interestingly from this property of asymmetries within an expanding universe ensuring the volume within any time slice always increases it appears that this condition is mathematically equivalent to the second law of thermodynamics that entropy always increases if there is a connection between the geometry of spacetime and entropy which according to black hole thermodynamics there is. Technically even the Friedman solutions obeys this property in the case where the universe is invariant in time (i.e. the trivial solution) suggesting this falsifies the existence of the cosmological principal assumption within the set of all physically valid solutions to the Einstein field equations within any flat or open 3+1 dimensional spacetime because all other solutions must violate the No big Crunch theorem which can be shown to be mathematically identical to the second law of thermodynamics if space has an associated entropy. The same theorem implications though however don't rule out the possibility that some sufficiently small slice of spacetime within an expanding closed general potentially inhomogeneous and anisotropic universe doesn't expand fast enough to prevent collapse however as the nonlinear domain of the metric tensor appears to be naturally predisposed to breaking spatial symmetries and amplifying those symmetry breaks to larger scales. However this is already stretching the limits of the proof so it can't be rigorously defined in a theorem currently. TLDR yes any flat or open universe the rate of expansion can never change sign or be zero. The converse a closed Universe is not necessarily true you can potentially get regions that expand fast enough to overcome the slowing of expansion elsewhere.

[@ObjectsInMotion]

There is no "spatial shape" and "temporal shape", there is only the overal shape of the 4D spacetime. When we ignored time that was for the purposes of visualization, since we need to remove 2 dimensions from 4D spacetime just to be able to visualize it on a screen.

[@spellmender7902]

Yes @PBSSpaceTime please answer this in the comment portion of the next video

[@QuesoCookies]

If every one of infinite points is equidistant from every other point, that would mean that every point in the universe is the center of the universe, so, technically, I am the center of the universe. You may bow.

[@concernedspectator]

Love these segments both questioning and reaffirming assumptions, leading to a deeper understanding

[@osmosisjones4912]

Isn't the rule it's never aliens going against the Kepergigan principal

[@L0kias1]

And I love you brother 🥰

[@ikbendusan]

Love these comments both positively reinforcing the content quality and pointing out its effects, leading to an elevated state of happiness for its readers

[@nishd7161]

@@osmosisjones4912 The rule is "It's never aliens until it is aliens", so no it doesn't go against the Copernican principle. It just means we have a tendency to jump to the conclusion of aliens but historically when the evidence is properly examined it has been something much more mundane. If we get compelling evidence of aliens anyone scientifically minded should believe it is aliens.

[@hugostiglitz6823]

@@L0kias1 THE NOTHING

[@zeroformsora]

You should do an episode on Chirality versus Helicity! The whole the imaginary number line is fundamental to how the universe works is just wild to me, I would love to hear your explanation

[@ikilledaman]

Yeah, i know basically nothing about those 2 things and always confused me, so id like to see an episode

[@ElectronFieldPulse]

Isn't the imaginary number line just a way to map out things in 2 dimensions? You could do away with the imaginary numbers and just add a second axis of numbers.

[@rantingrodent416]

It's worth making the distinction that the imaginary number line is fundamental to modelling and understanding the universe, not a real physical thing that is integral to how the universe actually works.

[@ElectronFieldPulse]

@@rantingrodent416 - I just asked this, but I will ask you directly since you might know. Isn't the imaginary number line just like a 2nd axis, giving 2 dimensions to numbers? You could accomplish the same thing with another axis of numbers.

[@Sol_Flare]

@@rantingrodent416 isn't there an imaginary number in the Schrodinger equation tho? Or does that count as modeling

[@andrew13651]

A problem that keeps coming up IMO is that when we talk about all these ideas about ST we use a 'zoom' function in a very similar way as when we take a picture here on earth. What if zooming in and out on any scale (microscopes and/or very macro scales) is similar to how we used to think about size of universe (obviously its contracting because matter is inside and at some point the gravitational pull brings all matter back towards each other - wrong) so what if the way we conceptualize the zoom function regarding edge of universe shape of universe multiverse etc cant be zoomed so simply. What if there is a nonlinear [zoom constraint] of sorts....it would change our interpretations and assumptions from, and could unlock another piece of the puzzle to what is shape/what does it tell us... in a time dimensional blob? 'Zooming' needs to be put under a microscope!

[@bugstomper4670]

OZZY OSBOURNE - Center of Eternity kzbin.info/www/bejne/i4S0eKV7ba-nj5I

[@thejustjoshshow9581]

I have never been helped this much with the geometry of the cosmos. Now one of my all time favorite videos! Thank you so much 🥰

[@73honda350]

Thank, I confirms exactly what I was accused of by my parents when I was 14 - that I thought I was the center of the universe. It's great to be proven correct, especially since all energy and matter is centered around me.

[@anhumblemessengerofthelawo3858]

Read the Ra Material, my friend. It is free.

[@jessepollard7132]

The same thing applies to every person so you are not special.

[@victor-oq7dl]

Pakistan is the centre of the universe according to most people .

[@Diego-tp9ib]

Of course you are the center of the Universe... in your Mind.

[@slyy4096]

@@jessepollard7132 Every person is special, as special as everyone else - except identical twins. Another exception is when you're just plain stupid - rocks, trees etc are more similar to each other than 2 smart people.

[@frasercain]

Finally, now I can point people at this video for the answer.

[@Don2006]

Or you can just quietly point at any direction at all...

[@pbsspacetime]

I'm pretty sure you could answer this yourself, Fraser.

[@NVidea-yz1fg]

13:48 ... "It’s one thing to think that you’re the center of the universe - it’s another thing entirely to have this confirmed by an ancient prophecy." (i.e. Total Perspective Vortex, s. Douglas Adams ;)

[@Nishom0926]

Okay, So, it does mean if I call myself Center of Reality(ಠ ͜ʖ ಠ), it is not wrong as in the past of universe, all Matter and energy was together in singular place. I know it just like simpson, I am the choose one (ಥ‿ಥ)¯\_( ͠° ͟ʖ °͠ )_/¯乁( ⁰͡ Ĺ̯ ⁰͡ ) ㄏ (ಠ_ʖಠ)🤣🤣🤣

[@louislesch3878]

I love it when major KZbin content creators interact with each other.

[@LMarti13]

The reason why this is the best physics channel is that every other channel would simply put out a video explaining that there is no center. The same old stuff. When this channel asks a question, even if it's a "basic" one, I know I'm going to learn a ton.

[@windowsmaster3482]

Whoever asked the question first, was the center Cause it all made sense when that conscious part of the universe made it, so it began from him

[@jeffpkamp]

I remember asking my friend who was doing an astronomy PhD if you could differentiate between expanding space and an expanding cloud of sufficient size. He didn't have an answer for me and I'm glad to see that someone with the math skill looked at the question, and I wasn't off. The question I have is, with the distance to the CMB, what is the lower limit we can set on the possible size of our "cloud" if it were that and not expanding space?

[@shaneacton1627]

I think I heard Alan Guth say that in eternal inflation, the minimum size of our pocket universe is something like 10^23 times bigger than the observable universe. But the theory gives no upper bounds on this, so it could be much larger

[@and_I_am_Life_the_fixer_of_all]

No way to test this by the way, at least not today.. this is theory at best and you'd have to get fancy with physics and math..

[@Malkovith2]

You can take simple questions, explore topics I'm sure I've heard plenty about and yet you always manage to give me new insights. I love it!

[@LuisSierra42]

Because this channel diggs deeper than the other physics channels on YT

[@MrMetalzeb]

You are a really smart teacher (I wonder if that's what I meant in English ..). you speak with the same apparent simplicity of rather disparate scientific topics and I who am not a native English speaker understand them better than disclosures in my own language. Congratulations to always reach a depth of detail that I find satisfactory. Always a good job.

[@ElectroFly100]

Best explanation on this subject so far and I have read quite some material. Still I cannot fully make it up in my mind but I do grasp it a bit better. In the end it's like when we see the Einstein space time sheet represented in 2D plane, they fully neglect the 3D aspects of space.

[@julienston876]

Great subject and amazing episode, as always Any chance that the Euclid mission could help getting closer to an answer?

[@Josecannoli1209]

There is a reference frame to the universe at least. where the CMB has no blue shift or red shift on any side.

[@KittyRenee1212]

I've watched this show for years, but learning advanced algebra with my mom, I understand the mathematics a bit better, and I appreciate what I learn a bit more

[@thomasyunick3726]

@ Kassie Lee- It is very possible the universe has no idea what math is.... or even cares. It was nice of humanity to organize it though.

[@xnonsuchx]

I remember asking a high school science teacher about “white holes” (without having researched) about 35 years ago and if that may have been The Big Bang. He just said it was in interesting question.

[@PlanetXMysteries-pj9nm]

Does anyone feel like me that the reading voice is very soothing and it makes me fall asleep very quickly even though there are many new things I need to hear and learn?

[@StrifeGarza7777]

This episode brought me back to why I loved space time. Rethinking geometry between flat and curved space-time is one of the first episodes I ever watched with Gabe. I don’t know of a stronger way to like this video then just hitting the like button

[@notreally2406]

*took you back Things are brought to you

[@testimonyoftime]

Just curious but who is Gabe?

[@StrifeGarza7777]

@@testimonyoftime he was the previous host of the show 😊 Seemed like a really great guy

[@MirceaKitsune]

Here's a fun one: Next time you go out for a walk, imagine you're still located in the same place, you're just using your feet to scroll the world under you instead. Theoretically this perspective is also correct since everything is relative. So yes, we may be at the center of the universe if that center is the point of our perception.

[@samyaspapa]

Well, I do know that I am the center of my observable universe. ;-)

[@JorgetePanete]

That's mentioned in the game Pneuma 😀

[@rylaczero3740]

Lol sure. Now I feel like a joystick.

[@Ziplock9000]

Nope. The reason we feel like we are in the center of the universe is because it wraps around, not due to observer relativity.

[@Lexivor]

I've seen animation that does that, it's a neat effect.

[@xfirehurican]

Always appreciate your talks. As for myself, I'm just happy to understand, whatever/wherever my 'standpoint'; I'll be an eternal participant in all of this 'starstuff' - in one form/state or another.

[@littlemulberryleaf1983]

:) good

[@HeliumXenonKrypton]

One of your very best videos, and you've got some good ones. Thank you for this !!!

[@seadlyderious7773]

Question: When we look out at really distant galaxies, we are seeing them when the age of the universe was younger, and the universe itself was smaller. But that much smaller Universe covers the same area of sky as the later (and larger) Universes do. Does that mean that we see the very old universes magnified, as they are stretched over our entire field of view? If we can observe galaxies when the universe was 10x smaller than it is now, are they stretched 10x larger than they would be by simple geometry or looking at something in the distance? How does this scale? In the famous picture from the Hubble telescope of many distant galaxies, they do all seem to be strangely similar in size - does this magnifying effect of the expanding universe act to make things seem clustered together?

[@JanVerny]

Wouldn't exactly say the light is magnified, rather it's blurred and needs to be focused.

[@KibitoAkuya]

Iirc light always travels parallel to space (hard to make sense of parallel to 3d space but idk), which is what causes gravitational lensing(in the local spatial deformation of massive bodies the parallel path is completely messed up), and since space seems to expand at the same accelerating rate everywhere, the perceived size would not be affected by it because space expands but the parallel path never changes it shape (except on gravitational lensing where the local space is very distorted from the average and so is the parallel path because of that)

[@ingoseiler]

Yes, if you take two galaxies of the same diameter that have the right distance from us, the older further away one looks larger than the newer, closer one

[@EebstertheGreat]

I think kind of? Clusters that were x megaparsecs apart 380,000 years after the Big Bang are now about 1100x parsecs apart, as is the light emitted by them. But the radiation has also been stretched 1100 times (from near UV to microwave), so you don't actually get any better resolution. You get the same amount of detail as if the universe were static, I think.

[@jenbanim]

Yes, good intuition! Before getting to your question some context will be helpful: In cosmology there are multiple ways to define the distance to an object - as you might expect it takes some nuance to talk about distance when the universe itself is expanding with time and you deal with things like speed of light delay. The most natural and intuitive measure of distance is called the comoving distance, which you can imagine as the distance you would measure to an object if you were to stop time and extend a really long tape measure to the object. However there are other distance measures that are useful when dealing with certain questions. The concept you've described here - that objects appear to get larger as you look farther away in the universe - is made rigorous by the "angular diameter distance" measure. The wikipedia page describing it is sparse and technical, but take a look at the diagram labeled "Comparison of Distance Measures 0 > z > 10,000" en.wikipedia.org/wiki/Distance_measures_(cosmology) What you should see is that, around a redshift of 1.5, this distance measure reaches a maximum and then turns around. This corresponds to the point at which objects of a particular size start to appear larger in the night sky the farther away they are. In our current best model for the universe (lambda-CDM) this point occurs at very roughly 9 billion years ago and 13 billion light years away (edit: comoving distance)

[@abj136]

Finally an explanation of the topology of the universe and why there might not be a center. The obvious layman assumption is that the big bang meant a 3D-ish colossal black hole going kablooie into a universe. In this scheme, it makes sense to have the present universe be simply a multibillion lightyear sized 3D ball, with an obvious center. Can you explain why such a notion can’t be right? I mean beside the detail everybody already knows that black holes can’t explode.

[@gabor6259]

I have an idea about that but I'm not entirely sure. Imagine a spherical showerhead, it shoots water in all directions. Imagine there's no gravity, so the water keeps going in a straight line. Imagine the holes on the showerhead are very small, very many and very densely packed. If you turned on the shower, you'd see a spherical fog growing outwards that's densest in the middle and gradually gets less dense as it moves outwards. The (observable) universe is not like that, it's homogeneous, you can't point to a direction and say the universe is less dense over there or more dense over there.

[@BradyR95]

The problem with this is that the universe is not expanding from a single point. That would be traceable (to a degree) It is expanding equally in all directions. Everything is expanding away from us in all directions, and at some other random part of the universe everything is expanding away from that point. The geometry of a big ball does not hold up there, unless you are assuming that there is an "edge" that will eventually be reached, or that the ball is infinite (then is it really a ball at all?). I think the theory with the "cloud like shape with a center" in this video is the closest version of the universe to what you are referring to.

[@nic.h]

Theoretically Black Holes do explode at the end of their life. We've been looking for evidence of this, albeit unsuccessfully so far. Although not unsurprising as Black Holes can live for quite some time.

[@KXSocialChannel]

Here’s your answer. Everything is moving away from us. The further it is, the faster it is moving. Do you think we are at the centre of the universe? If so, then there shouldn’t be anything here since everything would have expanded away from this point. Ergo, it’s obvious there’s no centre since you can’t place that centre here nor anywhere. Capiche?

[@skaggreen4212]

Thank you for your great work. Immensely appreciated

[@_The_Worst_]

What were truly a part of might be something so unconceivable that it would melt you if you thought about it...💯✔️

[@levmckinney4726]

You might want to check out Hyperbolica. It's set in a 3d hyperbolic/spherical world; the game is quite helpful for visualization but a bit nauseating.

[@feynstein1004]

It finally got released too. I can't wait to explore other geometries and topologies 😊

[@starfeast]

As a videogame it's a bit rubbish though. Constantly-talking NPCs and busywork that happens in a hyperbolic world but doesn't do anything with the concept. Classic dev didn't understand which part of the game was the good part problem.

[@feynstein1004]

@@starfeast I get that but I think it should get a bit of a pass for being the first of its kind 😅 The next ones will be better, hopefully.

[@Em4gdn1m]

I'm an electrical engineer, and consider myself pretty smart most of the time, but astrophysics hurts my brain.

[@hardopinions]

Astrophysics can be a little dazzling because it's just a little bit out there. But its explanations are mostly ethereal. What really is hard to crack is solid state physics. The pressures can be immense!

[@Em4gdn1m]

@@hardopinions hehe

[@VenturiLife]

I think it hurts everyone's brain.

[@Em4gdn1m]

@@VenturiLife I mean, everyone has their own strengths and weaknesses. Clearly Matt knows what he's talking about and comprehends this stuff without his brain going mush. On the flip side, he may not know how to design an x-ray flat panel detector like I do so... 🤷‍♂️

[@attilakovacs5803]

Actually, I think that this is certainly an interesting exercise for the brain, but in 100 years' time much of this information could be irrelevant. After all, we're talking about a possible model of the universe here, and, as a practical person, I find that there are too many presuppositions and rough estimates in our contemplation when we're trying to prove that this model is indeed practical. I'm not talking about truth here, because that's a philosophical question, I'm talking about a practical, understandable, simple model of our universe, or a part of our universe. Should we make it that complicated, may I ask? The fall of an apple can be explained with Newton's and Einstein's theory alike, but Newton's theory is much simpler and elegant, although less punctual in a greater scale. The theory of relativity was created to explain phenomena taking place at bigger speeds, in the larger scale of the iuniverse. Still, we don't use it to explain the fall of an apple here on our Earth. We think that the theory of relativity is a more general rule in our universe than Newton's laws, but isn't it possible that it has just as limited validity as they have? There might be large areas in spacetime, in the universe (and beyond), in which the laws of relativity lose their relevance. Einstein's model is just a model, too, and who knows if this model is applicable 10 billion light years away, or indeed if it WAS applicable when the light rays that we can see now started from a distant star or galaxy. Or isn't it possible that in other areas of spacetime there ae other local rules that are also special cases of the relativity theory? In any case, I don't believe that we can explain the whole universe with one unified theory (string theory, multiple universes, etc.) It would either be too difficult and unpractical to work with, or it would be impossible to create because it would have boundaries. We should perhaps look for more locally valid, simpler explanations to the observable phenomena. I'm sure, the universe locally can be explained with simple, elegant theories no matter where we are in spacetime. But is it established for sure that the speed of light, for example, is, and has always been the same in each part of the universe? Scientists strive to explain everything with one, final, unified theory. I don't think that one such necessarily exists, and even if it were possible to make up such a unified theory, it will not be able to explain things happening beyond event horizons and in singularities. As these are parts of the reality, too, the unified theory would have a pretty limited validity! So it might be more practical to establish laws of physics of more limited scope for more concrete, more palpable areas of our universe. That way, we might get nearer to the big picture.

[@nellkellino-miller7673]

When the most up to date physics starts to look like some of the most ancient philosophies and religions on the planet, you know you're in a good universe. Thank you universe.

[@nellkellino-miller7673]

@[Twitch Streaming Channel] Q A combination of mothballs, dry toothpaste and pretty much anything from under the kitchen sink will get you there. Can't vouch for your lifespan tho.

[@blake7908]

I thought I knew a few things about the universe since I watch so many astronomy videos but I did NOT know that there was no “center” of the universe. I’m shocked and excited to learn this right now. Thought I knew it all. Turns out none of us do!

[@HowitzerBug]

Not a scientist in any way, but a layman with an interest in understanding things better. This video genuinely amazed me within the first 3 minutes. Always learning!

[@warrenarnold]

i am just here to be together with other people slowly going crazy

[@onebylandtwoifbysearunifby5475]

As someone who's studied a bit of cosmology, I found your explanations well done. Good job on this episode folks.

[@notme2day]

You have a great name!

[@onebylandtwoifbysearunifby5475]

@@notme2day Thank you., whoever you are today. Not a bad name yourself.

[@marccawood]

What does it mean to say „the space between galaxies is stretching „ - if space is stretching then all space inside and outside a galaxy (or any object for that matter) and thus even our measurement instruments are stretching meaning we just wouldn’t notice.

[@AN1Guitarman]

This channel is always such a breath of fresh air to return to, there is so much scientific dialogue in the public sphere right now that is so anti-science, scientists, or people who call themselves that, seem to never be open to being wrong and it's such a tragedy to humanity that such people have such power. Thank you PBS space-time for keeping it real!

[@MaryAnnNytowl]

This show always stretches and exercises my brain, even when it hurts it, or when I don't understand it all. Still, the exercise is good for our brains!

[@etzous]

I've watched every episode of this show, and inflation is my favourite theory. The way this episode linked with it, was amazing. How most people not know these things and live their lives.... Physics is truly beautiful...

[@lunechann]

Yay! A new space/science channel that I can binge watch! 😍😍

[@dersonnenguru]

I'd have a "simple" question: Does the Planck length stay stable when space expands, or does it expand with it?

[@WellBeSerious12]

Wouldn't it make sense that since everything is the universe, everything scales accordingly?

[@dgodiex]

​@@WellBeSerious12 No, in that case there wouldn't be any expansion.

[@douche8980]

The Planck length is an imaginary unit of space (not even a single unit itself). Its not anything made of matter and/or energy so I don't see how it would expand since it doesn't actually exist outside of a vague concept much like any other way of measuring things.

[@alvinuli5174]

@@dgodiex In a deep meaning can you see the difference between an expanding and a non-expanding universe?

[@immortalsun]

The Planck length is just a unit of measurement, so I don’t see how it would expand.

[@TheShanewalsh]

The world is a better place thanks to your hard work and clarity. Thank you.

[@joedirte716]

DemocRATS are known for their lack of hard work

[@DavidGuyton]

10,000 extra points for the Calvin reference!

[@slevinchannel7589]

I wanna say something about Science and Atheism on YT, if i may. Ever noticed how Science-KZbinrs and Atheist-KZbinrs are basically 'blood-related'? They even all cover Kent Hovind and such people; which aint a Coincidence. The Fanbases don't overlap enough though. Professor Dave pointed out in his video about the Discovery Institute: Some right-now literally fight for a Reverse of the Seperation-of-Church-and-State, which would be devastating. Telltale says to that: We need more Science-Enthusiasts and Atheists in-Office (he even provides infos how to run for Office).

[@manmarvels]

Snap out of it. This is all fake without a hair of truth. PLANK SATELLITE. FINDOUT THE REAL TRUTH. EARTH HAS ALWAYS BEEN THE CENTER.

[@ja-si]

Good move. Using Kelvin, he'd only get 273 points!

[@slevinchannel7589]

@@ja-si Even more good news: YT has many Science-KZbinrs.

[@macronencer]

6:59 This bit is the coolest thing I've seen this month.

[@macronencer]

...except that I've just realised something. If you're on the Moon and someone on Earth points to you, thinking they're pointing into the past, they're actually in YOUR PAST, so they are, in a sense, pointing at the future, which means that the line spirals outwards from that sphere and never hits the centre. My head hurts.

[@matgeezer2094]

Really good video - the question asked towards the end 'in an infinite flat universe that starts from a singularity, did the universe go from point like to infinite in one step', is a thought I've had, and it's made me query the possibility of an infinite universe'

[@TheMalT75]

In a very practical sense, everybody is the center of his own "observable" universe. As mentioned very nicely here and in previous videos, at a certain distance the relative velocity of receeding objects approaches the speed of light, so anything lost beyond that event horizon of this Hubble sphere is forever unreachable according to our current understanding of physics. Keep that in mind, when you imagine yourself on the "2D sphere", because the observable universe there is still a fairly small and flatish patch and you will never return to your point of origin if you travel in a straight line: your point of origin will be lost, while you still have a symmetrical Hubble sphere around you. Incidentally, as does your twin on earth that you left behind to resolve some kind of paradox, right?

[@chickenmonger123]

@Solitaire All Int. No Wis or Cha.

[@courtneys.7113]

i was about to comment, lol i have decided we are all at the center of the universe because if you look at any one point, it looks like the center

[@chickenmonger123]

@Solitaire Ah, but you do. Unfortunately.

[@fluentpiffle]

Everything is at the 'centre' of Universal being..This is what the word 'infinite' means to a finite-thinking entity, but within the infinitude there is only a 'centre' when a particular point is indicated. The same for any kind of 'measurement', and 'direction'.. These things do not have any relevance in infinitude, only to the finite entity that indicates them.. "But maybe that is our mistake: maybe there are no particle positions and velocities, but only waves. It is just that we try to fit the waves to our preconceived ideas of positions and velocities. The resulting mismatch is the cause of the apparent unpredictability." (Stephen Hawking, 1988) "Commendation from NASA for research work at Massachusetts Institute of Technology on the Earth's atmosphere and the Moon's surface for navigation of the Apollo spacecraft to the Moon.. Dr. Milo Wolff has found the structure of the electron consisting of two spherical quantum waves, one moving radially outward and another moving radially inward. The center of the waves is the nominal location of the electron 'particle'. These waves extend infinitely, like charge force. All 'particle' waves mix and contribute to each other, thus all matter of the universe is interrelated by this intimate connection between the fundamental 'particles' and the universe. The natural laws are a direct consequence of this Wave Structure of Matter (WSM), thus WSM underlies all of science". spaceandmotion

[@sativares]

@@courtneys.7113 Yes. A relative center in an absolute center. Fits well with duality.

[@jenn011754]

Here is one of the things that keeps me awake at night. I have a question. How do you do mapping in space when the distances are so far that you have to use time as well? The earth rotates and orbits the sun which orbits within the milky way arm which revolves around a central black hole in the local group, which orbits within the Virgo Supercluster which is near the Shapely Supercluster. If a person in the Shapely Supercluster wanted to go to Earth what kind of mapping program would they use? I find this really interesting and would like to know. Thank you.

[@shaneacton1627]

If you constructed a 4D map by projecting the movement of all observable objects into the future, that 4D map would be static, and you could navigate it more easily. The big difference would be that in a purely spacial map, you can travel in any direction, and arrive at any point. But in a 4D space+time map, the speed of light limits the directions you can travel, so not every point in the map is reachable.

[@Temuldjin]

The scales would be massive, but a 3D map would suffice. In the same way when a sniper takes a extremely long distance shot he have to factor in the rotation of the earth, one would have to factor in all those variables (the ones you mentioned) + time (we can travel " x " distance in " y " amount of time) so that have to be factored in aswell.

[@jamespage6013]

That's actually a very complex question, and the way scientists deal with that is by defining various types of distances, such as "luminosity distance" or "apparent size distance" (with their associated maths definitions), that try to take into account different aspects of an evolving universe. These distances often don't even agree, there is no "true" distance at such scales, since you'd need to be able to observe the whole length of space between them simultaneously. But definitions like these help get some sort of handle. Nevertheless, this is why scientists often simply use redshift as a stand-in for distance, since it roughly mimics distance (larger reshift the further away), is something you can directly measure without any interpretation involved, and is a simple unitless number. Hope this helps!

[@TheAlondane]

Intergalactic logistics departments must have their work cut out for them

[@ShawnHCorey]

There are various ways of measuring distance to stars and galaxies. But these are only good to about 20 million light-years. Beyond that, the red shift of the light from the galaxies is to calculate their distances. This assumes that the Hubble constant is constant and the expansion of the universe is linear. In other words, we measure the distance to nearby galaxies using some technique and calculate the Hubble constant from that and their red shift. But beyond a certain point, we can no longer measure their distance so we use the Hubble constant and their red shift to calculate their distances. For example, the hot plasma of the early universe is thought to be about 4000K at the time of the recombination epoch, which created the Cosmic Microwave Background (CMB). Since the CMB is about 3K today, it has a red shift of about 1090. Applying the Hubble constant to it gives the distance of about 13.8 giga-light-years. To answer your question, they would use the red shift of the far-away galaxies and the Hubble constant to calculate the distances to the galaxies.

[@charlesjmouse]

Short answer: It depends on how you define 'center'. Thanks for yet another excellent video.

[@cvedeler]

Technically, Copernicus didn't think the Sun was in the outskirts of the galaxy. He thought the Sun was at the center and all the stars were in a fixed sphere some distance past Saturn. But your point is still valid.

[@TreyRuiz]

If there was a period before the Higgs mechanism and all particles were massless, wouldn't that mean that time would have proceeded by instantly?

[@kylekoschalk7011]

Good question. Roger Penrose's Cyclic Conformal Cosmology says that once all mass is gone, there are no longer any clocks to "tell time" anymore, and distance is irrelevant without time, so everything kinda recombines into a single point again then BOOM - another big bang. At least that's how I understand it. I think PBS should speak to this as you are correct that there was a period after the big bang where only massless particles should have existed and so it would be fun to think about what "time" means during that period of the universe's evolution.

[@bane4743]

@@kylekoschalk7011 time is only relevant if gravity exists. The only information left after black holes evaporate would be massless right? So time wouldn't be needed for the universe to experience. I believe they actually talked about this topic before so i agree with you.(edit yeah time is perceived the same way as if the universe is stretched out or at small point. So it would be instantly. )

[@edibleapeman2]

For decades, I’ve been a casual/lay connoisseur of physics, quantum theory, and all the other nerdy adjacencies which have no doubt contributed to my difficulties with getting a girlfriend, but I have never before felt so close to “understanding” why/how physics breaks down at the singularity. This video opened my eyes just a single micron more and I thank you for this insight.

[@RJDGAMER]

I love your videos honestly. i was was watching this and it looked like AI video. but i love it and i love you guys at PBS spacetime!

[@john9982]

All I got to say is, "see you later, in my dust, that's in the past" love you show.

[@Nobody_Special310]

Maybe the center of the universe is the friends we made along the way.

[@Divinemakyr]

This question dates back to a few videos ago: if cosmic strings have existed since the early universe, ie., billions of years, then wouldn't more of them have been devoured by black holes? More importantly, and what I guess you could say I'm curious about, is how do black holes interact with cosmic strings? I've done a small bit of research on this and didn't find any satisfying answers through Google, but I most likely didn't look hard enough. I would enjoy an answer from you, though, as I love this channel so much.

[@BleachWizz]

12:30 - I thought of that and thought that would happen. I never knew enought math to calculate it by myself, but it's nice to know somebody found out it's true.

[@HelloThere.....]

I think the reason we cannot find the center is because we're in a black hole and the center is the singularity. Black holes create a 360° geodesic in the dimension of time, which means as you travel forward through time and towards the singularity, you are also moving across a loop in time, all futures point toward the singularity which is looped around in time, meaning all futures point toward the past. The center is in the future and past at the same time. This would also explain redshifting, horizons, the expansion and its acceleration, and it's omnidirectional nature. In the black hole, spacetime starts to curve more acutely as time passes, and a galaxy farther than us may appear closer than it is and vice versa. It's like being able to look at the back of your head when inside of a black hole, light and spacetime is bent and curved dramatically. You could explain the acceleration of the universe this way instead, that it's not expanding per se, it's just that because of tidal forces, a galaxy 1bil lightyears away, that was visible for all of time might pass a horizon and be invisible tomorrow, because the distances between objects result in greater effect due to tidal forces curving spacetime more dramatically as objects approach a singularity. You might say, then wouldn't we detect the gravity and know? NO!! Because we'd be in free fall. It might even explain the cosmological constant, and dark matter. It might explain why the universe isn’t ripped apart and where all that phantom gravity is coming from.

[@MR-hx5vz]

Okay, here's how I understand it: -- The universe is constantly expanding outward in all directions from a single point; -- The location of that single point is infinite across spacetime, so that the outward expansion is from any and every single point, so any random point is the center of the universe; -- The expansion is in 4 dimensions outward in all directions from any random point - up and down, forward and backward, left and right, and all vectors derived therefrom - and "outward" is forward in time, therefore; -- "Inward" from all directions toward any random point is backwards in time, all the way "in" to t=0. So now I find myself wondering, is Dark Energy necessarily a force unto itself, or could it just be the force of the Big Bang expanding constantly into spacetime with everything else, outward in all directions from all points inward, the origin point itself of the Big Bang just continuing to expand infinitely? Ow... I think I sprained my brain.

[@codetoil]

Dark Energy is a "Force unto itself". It applies constantly, similar to how there is always a downwards pull from gravity on earth.

[@bluesquare23]

I like how this channel explains really abstract and cosmic concepts in a simple way. I will never get to a point where I understand the nitty gritty details of this sorta stuff. Nor do I really want to. But it is cool to think about the big what ifs of the universe. Maybe they'll know someday :)

[@1112viggo]

gee thanks, until i read that, i felt kind of stupid for not getting it...

[@manmarvels]

You need to get your head out of that smelly place.

[@nin1ten1do]

you nee dthat stuff to understand propertly.. but well we can fall deeper as on veritasium or other crap..

[@HaroldVonAnusIII]

There is an observable point while watching any these amazing videos, at precisely 4:12 in, where my capacity for understanding spontaneously breaks down and contracts to an undefinable, shapeless massless state. Then I go have some ice cream

[@vinnieg6161]

Simple? I'm struggling to understand what's going on lol

[@ynntari2775]

_"well, the size of the universe at T=0 is 0×infinity. Which is neither 0 nor infinity, it's the point where the maths breaks"_

[@LucidBmx]

How if the observable universe is 46 billion light years in each direction are we not the centre of the universe?

[@TheDerwisch77]

"Well, if there's a bright center to the universe, you're on the planet that it's farthest from."

[@generalchaos1285]

Perfect time to post this! Excited to watch!

[@chancellor9000]

Oscar/Emmy-worthy graphics, Ajay Manuel!!!

[@Brandon-rc9vp]

I'm gonna continue to watch this to see what you say, but what I hope comes up and what would be interesting in terms of actually representing your title is a description of how much tension is allowed in the 'everything is moving away from us theory'. I suspect there is some variability, and that it may be possible to analyze that variability to some degree using trusted techniques. One important question I hope you will answer in this or later is exactly how uniform expansion appears based on best current knowledge.

[@WeeklyDosisofScience]

You're onto something intriguing! In the context of the "everything is moving away from us" theory, it's important to understand that the expansion of the universe is not a result of objects physically moving away from a central point. Instead, it's the space itself that is expanding between galaxies, causing the observed redshift in their light. As for the question of variability and uniformity in this expansion, current observational data suggests that on large scales, the universe appears to be expanding uniformly. This is known as the cosmological principle. However, on smaller scales, there can be variations due to the presence of local structures like galaxy clusters, which can have their own gravitational effects. Analyzing the variability of the expansion and understanding its nature is an active area of research. Astronomers use techniques like measuring the redshifts of distant galaxies, studying the cosmic microwave background radiation, and conducting large-scale surveys to gather data and refine our understanding of the universe's expansion. So, while the concept of uniform expansion holds at large scales, scientists continue to explore and analyze the intricate details and variations within the fabric of our expanding universe. It's a captivating field of study that keeps pushing the boundaries of our knowledge.

[@slyy4096]

It's amazing how Matt can focus one eye at camera and the other focuses at the script.

[@ime06]

Could you do an episode about the recent paper claiming to resolve the black hole information paradox? I love your channel, thanks for the great work!

[@piratedgenes]

Hey, can you please share a link to that particular paper? I couldn't find it.

[@alexanderjenkins7929]

Would you do a video on how and why the math breaks down at the singularity for an infinite universe, and talk about the various solutions that have been put forward to explain this? Thanks 🤘🔥

[@robinspanier7017]

listening to you makes me feel more challanged then just dimensionally

[@Majorohminus]

If the universe is sufficiently big, we would never be able to measure or even know the true nature of the universe. Could be there is a global angular momentum but we can't observe it.

[@stevelowe2647]

I've always wondered how they can estimate the age of the universe at 13.7 billion or whatever, because a) they can't see it all, I believe they think they see 4%, but also, I might be wrong with the number, but it's substantially more than 13.7, I seen somewhere the observable universe is about 46 billion lightyears, but if the universe is 13.7 billion, how can they see light that's travelled 46 or whatever billion lightyears. I might not understand how it works properly, but it doesn't add up, not to me at least. Surely you'd have to generalise its position forward in time, but how do they do that?

[@marvinpatel777]

QUESTION FOR MATT: We know that the fundamental forces were once United when the universe was hot enough, then is it possible that after many years the now known fundamental forces will split up, like electromagnetism would split into electric and magnetic force for example?

[@mahikannakiham2477]

Electric and magnetic force are already "split" and it took Maxwell's equations to reunite them.

[@trueethics6190]

how do we know that? do you have proof of this knowing that is not just a theory?

[@davidhand9721]

In the event of vacuum decay, something like this should happen. Not EM splitting into E and M; they're relativistic transforms of one another and propagate via a single boson, so there's no axis to split along. But theoretically, vacuum decay would break symmetry in the same way that the Higgs field did, so some family of currently massless indistinguishable bosons could divide itself up by turning some of those bosons massive. The forces mediated by the massive bosons would appear to be a totally separate force at low temperature, just like the weak force. There is almost no chance that atoms and nuclei will be stable after that, so no one will survive to test that theory. It's all speculation.

[@marvinpatel777]

@Solitaire yes

[@marvinpatel777]

@@davidhand9721 this speculation of yours seem interesting, maybe even correct.

[@lqr824]

0:30 the illustration shows everything going around the earth in circles. No-one ever thought this, before or after Copernicus. Copernicus, in turn, thought the sun was the center of the universe, and had no idea the sun was a star, nor had any comprehension of what a galaxy was.

[@OlGregge]

I just figured out that using a syringe with bubbles suspended in it visualizes this in a weird way. if you block the nozzle and squeeze, the bubbles shrink. the total volume of the entire syringe(universe) is still effectively the same, but the bubbles become further apart, though not when measuring from the very center . This now makes me wonder if the expansion of the universe is technically weird dark matter shrinking action.

[@kyleespinoza7201]

I personally interpreted the Big Bang as something similar to a Black Hole's singularity: it's not a physical place, but an inevitable time. That being said, I'm ready to have my world rocked by the future videos exploring eternal inflation.

[@rochestephan]

I am confused, I thought the CMB doppler shift differential told us that the earth is moving relative to the cosmic microwave background at ~630km/s, wouldn't the center of the universe be in the direction of the most red-shifted CMB spot ?

[@Williamfuchs420]

That would be in the past. Everything is moving away from that past point. The “center” of the universe the way I understand it doesn’t exist in what we see as the present but instead it is the beginning of the universe itself. The big bang is the center.

[@sailingmohican2767]

Think about it...if the universe starts from a single point bang then 14 billion years later no matter what planet you go to and set up a telescope it will aperear that your at the center of the universe because every thing is moving away from your position..and if it don't then the big bang didn't happen 😉 I just wish people would quit worshipping Einstein and simply think for themselves ..lol

[@stevelowe2647]

@@sailingmohican2767 I appreciate what you're saying, but people take Einsteins word because they don't understand fully, so it's not really a matter of think for yourself, when they're trying to educate themselves & they take the common understanding as their understanding. I don't mean this in a rude way, but Einstein most likely understood these things much better than you do. Not a dig like I said, because he understood it better than I do, & you quite possibly understand it better than I do. And I'm not sure if this is what you meant at the end, but I read it as you saying that you don't need to take Einsteins word on the origins of the big bang, but he wasn't the one who originally theorised the big bang.

[@tomlakosh1833]

Just the opposite, see my comment above. High z galaxies have a long axis that points toward the center, i thimk.

[@rychan0]

I have this same question. There is one region in our expanding universe that has no relative velocity to the CMB. Whereas we are moving 368 km / s with respect to it. What is special about that region? How far away is it?

[@skeltek7487]

The redshift to distance distribution and CMB do not necessarily mean space is expanding. Both would be a natural consequence, if nuclei and atoms were shrinking over time and thus generating different wavelengths of emitted photons at different points in time, while also perceiving incoming light as redshifted, since the average size of atoms decreased over the aeons. And the Blackbody distribution of the CMB would be a natural consequence of different kinds of frequencies accumulating in space at different times and distances. It is a mathematical isomorphism, but most physicists get confused by the complex isomorphism function.

[@ciggac]

I once had the vague thought that given what we know about time dilation and spaghettification, that the big bang could have been the outpouring of a blackhole from "somewhere" else. I'm not educated enough on the subjects involved to really explain the idea past that, but being that things like the speed of time, or the scale of size, are limited to what we understand to be baselines, we could be in a sort sequence of "black hole funnels" where everything is just compressing to slower and finer resolutions.

[@notme2day]

What if we're in only the most recent big bang? Just as galaxies crash into each other and black holes grow and swallow everything. What if two black holes grow so large and come together, boom,big bang. A cycle that repeats every 100 ish billion years give or take. Just a thought for when you can't sleep ... sorry. ; 》

[@queensavethegod]

Thank you so much for the time and effort you put in the show. Thank you for making easy something impossibly complex. When I hear you talk about extra dimensions, I can't stop thinking that Schroedinger's equation states "i" as a term. Does it mean the electron might happen to find himself existing in a dimesion made of complex numbers? If so, where are those extra complex dimensions? Is it possible for us to perceive them? Thank you.

[@earlie1234321]

Yes, For example the Aharonov-Bohm effect is usually taken to be a demonstration that the complex (as in complex number) nature of the wavefunction of the electron is something physical that can be measured and not just a trick to make the mathematics nicer.

[@TheTruthKiwi]

God I love knowledge and intelligence. Thanks Matt and PBS, great stuff. :)

[@epiclivestreams6733]

I thought infinity times zero was just zero because it could either be zero infinities, which is just saying there is not an infinity in the same way an empty shoebox has zero shoes, or it could be infinite zeros, which is still zero because zero does not change when added to itself.

[@tommywhite3545]

I liked the image at 13:40 or so. Is there any way I could find that anywhere? Also loved to hear about the Lemaître-Tolman metric. When _I_ say there are models of the universe that do have a centre and an edge, but are mostly "pushed aside" because of conceptual and mathematical issues. Like what happens at such an edge.

[@leftysheppey]

I've not searched really hard, but if you Google "logarithmic map of the universe" you might find it. If you don't, there's plenty of similar images :) I think I've seen that image on KZbin before, so it might be on a stock image site.

[@MrMeldro]

It is weird that I was able to follow this episode and understood everything that was said without pausing or loss of focus due to the heavy subject. I really felt like I was the centre of the Universe :)

[@TrimutiusToo]

Finally a video that properly explains that singularity is where our math breaks!

[@LuisSierra42]

They do have a video dedicated to that specifically

[@TrimutiusToo]

@@LuisSierra42 kinda...

[@Mentos6]

I can hardly believe I'm saying this but I actually understand what you are saying and made sense of it in my head.

[@TiagoCavalcanti-ji6hu]

Dude, I was doing something else by the end of your video and kinda overheard, wow... you scared the bejeesus outta me, pal!

[@junkmail1336]

Anyone ever think the universe is just like the “flat land” analogy. Where a 3D sphere passing through a 2D plane appears as an expanding and contracting circle, and a 4D sphere passing through a 3D plane appears as an expanding and contracting sphere? Would the university rotating in higher dimensional space explain the expansion of the universe and the “great attractor” contracting space in other places? The universe may not even be a uniform/semicircle shape but an amorphous blob/bubble in higher dimensional space rotating on multiple accesses?

[@warrenarnold]

the world is not flat

[@notreally2406]

3D is not a plane

[@vhawk1951kl]

When you use the word "universe" what exactly do you mean by it or what do you seek to convey when you use the term "universe"? Why not just own up and admit that you have absolutely no idea whatsoever what you mean by universe or what you seek to convey when you use the term?

[@Cornexium]

@@notreally2406 It is a plane if you think of it as the surface of a 4D object

[@douche8980]

@@vhawk1951kl I don't know the exact text book definition off hand but to me a universe is any collection of atoms (smallest known unit of matter) where all these atoms are within a finite distance from each other no matter if said distance is larger than number or even scale humans can conjure up or imagine. If even a single atom is an infinite distance from the others than such atom/s would be an entirely different universe on its own.

[@johnretherford592]

Question. In the expanding hypersphere model described, would the answer to the often posed question "what is the unverse expanding into" be that the universe is expanding into the future?

[@klin1klinom]

Time dimension is expanding into the future, but what the remaining 3 dimensions are expanding into? Does it even make sense trying to describe that which doesn't exist?

[@johnretherford592]

@@klin1klinom interesting thought, thinking about it makes my head spin lol.

[@AliothAncalagon]

I always try to imagine it with the analogy of a video game world. If you program it to be bigger, it doesn't expand "into" anything. You won't make the world of Skyrim bigger and then you suddenly hit the edge of the Fallout 4 map. Any game world you would make bigger, could forever expand without ever reaching anything that is not part of said game. The game world expands into itself. Its expansion creates new space that wasn't there before.

[@johnretherford592]

@@AliothAncalagon yeah, that's a good analogy. And that seems to be the point of view I usually see it discussed from, or at least that is just growing, it doesn't need anything to grow into. But this growing hypersphere idea seems like it allows for other possibilities to me, although I really have no idea.

[@AliothAncalagon]

@@johnretherford592 Absolutely, other possibilities aren't entirely off the table.

[@kvin9286]

Just love these vids and keep up the good work. Also Im definitely completely wrong here but I would like to believe what we call dark matter or dark energy is just a basic property of space itself. It is the medium that allows transmission of electromagnetic waves. Also space seems to be able to expand infinitely. But not sure if we can even draw an analogy to any material like rubber. It probably doesnt behave anything like a physical material.

[@terrafirma9328]

I think this also. The property is that we can't see it because we are inside a black hole looking out, but not just that, it is more like we are on the edge of a black hole and looking in or out is the same and what we see is the stuff close enough to us that the light has not gone beyond the event horizon of the spacial edge of the black hole aka dark energy/matter🤯

[@Ketpain]

What would happen if we preformed a sound experiment at 432hz in sand, in space. Or even started at a higher frequency representing the amount of energy in the universe. As we lower the Hz, it would start to form patterns. The very beginnings of formation. What pattern would it form? Would it even form a pattern? Could we match it to the Universe in the 3d world, instead of gravity pushing it down into 2d? Could scientists devise a way to observe that on a more massive scale? Would this be a new universal map?

[@eppodagawd6521]

The singularity at the beginning of time isn't really a discontinuity on the math side. It is a natural strong deformation retract of the manifold representing the universe, i.e. space-time, assuming the radius of the space-part of the universe scales nicely with time (as cosmologists seem to believe based on the Hubble observations). Maybe I'm missing something? I really enjoyed this video (as usual)! Thanks so much :)

[@creator4413]

@@RockBrentwood right on man. You definitely kicked that guys ass

[@albertowachsman7878]

I've been trying to understand this for a long time, and this video is the clearest ever on the topic. Usually I find this series too hard to follow, but this time he nailed it in making it understandable. Thumbs up!

[@TriMarkC]

Agreed. “The 2D person on a 3D planet can’t point down” finally made it click for me.

[@danielkamers5440]

I wonder how hard would be (to JWST, for instance), if possible at all, to find a gravitational mirror for us (so as for seeing our own sun past reflected)

[@user-hp1mt9du6t]

Great video! Thank you so much. Simple intuitive uneducated guess: what if our Universe has dispersed (or diluted) center? Similar to the Bacground Radiation photo, but more dynamic and sort of frozen in time. Along the line of current status of Big Bang or something? Take a good care.