Do we *really* know if the universe has a centre or not?

Question

I'm probably going to regret this, but hey.

I'm familiar with the official arguments as to why the universe supposedly doesn't have a centre, but they've never made sense to me. What they say is that there's no centre of expansion, therefore there's no centre. But centre of expansion != centre. Example: If you place an explosive in the outer edge of a doughnut and then set it off, the centre was not where you placed the explosive. Admittedly, the doughnut has no centre, as it's a torus, but that has nothing to do with where you put the explosive. If it were a jelly doughnut, it would have a centre.

To my understanding, we don't actually understand the nature of the universe's edge. I will gladly admit that I'm not an expert, but from what I've heard, we don't know whether the universe has some kind of boundary, like a domain wall, or whether it just loops back around like an old video game.

Unless I'm missing something, it seems to me that all that's really being effectively argued is that the universe might or might not have a centre; we have no way of knowing, and if it does, it's probably nothing special. If it loops around and/or has a shape like a torus or shell, it has no centre; otherwise, it does.

Again, I'm fully willing to admit that I could be missing something. I just know what I've outlined above. But I'd like to understand this better. Could someone clarify this for me?

Answer 1

The Universe on a large scale closely resembles the Friedmann solution to the Einstein Field Equations.



The Einstein Field Equations have been shown to be correct every time they've been tested.



The similarity between the Universe and the Friedmann solution has many observed points of correspondence (take a course in observational cosmology, I'm not going to go into detail here).



The Friedmann solution has no center within the spacetime manifold itself. That's why we say it has no center.

Answer 2

In essence everywhere is the centre of the Universe. The Hot Big Bang model implies that the entire Universe was once so small that it could easily be contained within a single atom. Soon after the Big Bang there was a period known as the Inflationary Era when the Universe expanded to a proportional degree of its size today.



A commonly used analogy is to think of the Universe as being like a balloon. As we inflate a balloon its surface expands in all directions. We can see this if we paint dots on the balloon and observe what happens to the dots as the balloon inflates. The dots can be thought of as representing the galaxies in the Universe.



We then start to suck the air out of the balloon and observe the surface area decreasing. All the dots will start to move towards each other. Eventually, if we could take all the air out of the balloon the surface area would go to zero and all the dots would occupy the same place at the same time.



So much as it might not feel like it, everywhere in the Universe is actually also the centre!

Answer 3

Well to start with, we now know that the universe does not "loop around", nor is it shaped like a "torus, shell", ball, violin, or sailboat. The recent WMAP mission showed that the universe is totally flat.



Neither does it have any kind of discernable boundary, except for the limit of the redshift, which imposes a limit to how far we can ever detect anything. Just think of it this way: You are a part of the universe. You don't sit upon a perch looking down upon it. Because you are a part of the universe you are made from space, force fields and elementary particles. If you approached a hypothetical boundary beyond which the universe did not exist, then YOU would not exist there, because you are a part of the universe that does not exist beyond the boundary.



As for the centre, currently crumbling dogma is that the "big bang" happened effectively everywhere hence there is no centre. If the redshift is taken literally as evidence of the Hubble expansion, it implies that every unit volume of space is expanding so there is no real centre.



Cheers!

Answer 4

Not only does it not have a center, it can not have a center. Comparing it to a donut is pointless. A donut is a small 3 dimensional object. You are trying to compare that to what is possibly an 11+ dimensional object and may be infinite in size.......



And there is no "edge" in the universe. There's an edge to the observable universe. But that's just what we can see, that's not all there is. We know definitively that the universe extends beyond the observable universe. We can't "see" any further because the CMB is in the way and light travels at a finite speed.

Answer 5

Just because something doesn't make sense to you, personally, doesn't mean it isn't true.



If you take a single point and expand it then everything in the expanded point was once the point itself. In the same way, the universe started out as a single point and expanded so the whole universe is that single point.



Where is the centre of a single point? All of it is the centre. Where is the centre of the universe? All of it is the centre.

Answer 6

There is much of what scientists say that doesn't make any sense. The universe is flat, and it has no centre, or edges, that just doesn't make any sense to me. From documentaries that I've seen, the observable universe looks like a sphere, and continues on in all directions further than we can see. It's probably expanding from a central point, where the big bang happened, that's why it's expanding. I think sometimes scientists just say things that other scientists say, because other scientists agree with it also. We're a long way from understanding the universe, and sometimes I think even the smartest of us are just stupid, or lacking in common sense.

Answer 7

Try to imagine a balloon. The balloon itself is the universe (flat) and the air in the center of the ballon is nothing. As it expend, the surface of the ballon get bigger and bigger and maybe at some point it will end in a Big Crunch. I'm not an expert but that's how I see the shape of the universe according to the theories.

Answer 8

As per contemporary theories the centre exists and it is on Time axis at -13.7 billion years (13.7 billion years from now).

Answer 9

There is no center, but why did you ask this question?

Answer 10

Yes we do and no it doesn't