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If the big bang was the birth of everything, and the big bang was an event in the sense that it had a location and a time (time 0), wouldn't that mean that our universe has a center?

Where was the big bang? What is there now? Are we moving away from the center still? Are these even valid questions?

Qmechanic
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nopcorn
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  • Possible duplicates: https://physics.stackexchange.com/q/16074/2451 , https://physics.stackexchange.com/q/136860/2451 and links therein. – Qmechanic Dec 18 '12 at 11:00
  • Similar question on Astro.SE: http://astronomy.stackexchange.com/q/669/476 – Qmechanic Jan 04 '14 at 17:46
  • arguably, this is not a duplicate; the universe starting at a point would not necessarily lead us to assume that it has a center (perhaps just the opposite). – Eliran Malka Nov 30 '18 at 18:41

4 Answers4

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The big bang was everywhere, because distance didn't exist before it (or as @forest more accurately commented, "measuring distances was meaningless since the distance between any two discrete points was zero",) so from one perspective, everywhere may be the centre (especially as some theorists think, the universe doesn't have an edge)

The real issue is that the question shouldn't matter, as we can only gain information from distances within our visible radius and once we get to that limit, what we see gets closer to the big bang so it all looks closer to the centre.

Tricky eh

Rory Alsop
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    "distance ... was zero" this statement involves an extrapolation of physics into a regime of energy and density far removed from that where the model on which the statement is based (GR; Friedman eqn etc.) is accurate. Better to say that the nature of spacetime in its earliest state is unknown to us but maybe string theory or other versions of quantum gravity could shed light on this. – Andrew Steane Apr 07 '21 at 10:59
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If you think the universe is finite in size, then the analogy to use is an inflating balloon. Draw some points on the balloon, and inflate it. Note how every point sees all the others moving away, and none of them can claim to be the universal center of expansion. If there is a center at all, it is interior to the surface of the balloon. However, in this analogy, the entire universe is the surface - a two-dimensional being on the surface could only talk about the center we perceive in 3D through abstract mathematics, as it is not actually a point in their universe.

Of course, that applied to a finite, "closed" universe. Perhaps the universe is infinite and generally "flat" (as more and more appears to be the case). Then the proper analogy is an infinite flat rubber plane with points marked on it. You could stretch the rubber symmetrically about a particular chosen point A and call this the center. However, this choice is arbitrary. To see this, shift into the frame of one of the "moving" points - call it B. From B's perspective, everything looks like it is moving away from B.

In short, there is no well-defined point everyone can agree is the center of the expansion of the universe.

  • If the universe expanded from a point, and we want to talk about where that point is now, the answer would be everywhere. In this analogy, I feel one should represent the location of the big bang by the entire un-inflated and crumpled up balloon. Then blow it up. It's like asking where the previous state of the balloon went. – j0equ1nn Dec 04 '16 at 23:02
  • In a comment on an answer to that question to which this one is a duplicate, Gerold Broser makes the excellent point that, in the balloon analogy, the radius of the inflating balloon represents the time coordinates. GR doesn't mandate whether spacetime curvature is more in space or more in time, but, observationally, it appears to be much more pronounced in time, which, in fact, would account for predictability. – Edouard Jan 27 '19 at 15:16
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You'll see it clearly in this two images: Image 1

Image 2

As you can see, I've only moved one layer, while the other stays static.

This is a clear example what happens in the universe.

Everywhere is the "center of universe".

Garmen1778
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    What do you mean by "I've only moved one layer"? – nopcorn Mar 26 '12 at 20:30
  • I've done this in photoshop and there there are layers(check out info). The images are like moved. But as I say, some of the "stars" stay static. Not sure if I explained well... :S – Garmen1778 Mar 26 '12 at 20:32
  • @MaxMackie I tried to do it as a .gif but I don't know how to do it. – Garmen1778 Mar 26 '12 at 20:34
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    You could maybe make the layers different colours. – Joe Z. Feb 18 '13 at 01:23
  • Are you aware of anyone who has explored the idea that there is indeed an initial point of origin, and that all galaxies are moving away from one another for the same reason that pellets from a shotgun all move away from each other after leaving the barrel? – mkinson Nov 09 '21 at 18:43
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Depends on the system. During the history the notion of universe had a center. Sometimes the Earth was in the center and later on the Sun was there. The current theory says that the universe is expanding in all direction so the center will be quite difficult to calculate and probably a very empty space.

  • Unless there is after all a radiant point and it is still chugging out matter and energy. We wouldn't be able to see it doing so in any case. – Cyberherbalist Apr 05 '12 at 18:12
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    the center will be quite difficult to calculate and probably a very empty space No, it's not that it's difficult to calculate, it's that there is no such point. –  Oct 05 '14 at 17:14