# Does the universe have a centre?

Is there a central point to the universe, and, if so, is this the location of the initial Big Bang?

Nope. Since space itself was created in the Big Bang, and expanded to form the universe, the Big Bang actually occurred everywhere at once.

No, there’s no center of the universe in 3D space. No edge either.

The Big Bang was the creation of all space in the universe (and time, etc.). In effect, the Big Bang happened everywhere in the universe. Astronomers can detect this by the residual cosmic background radiation that is present throughout the universe (the cooling off of that ‘big bang’). It was not like a conventional explosion of stuff outwards.

It’s really tough to visualize since you cannot use an external reference frame (there are no external reference frames that we know of). Consider boundless space. Now imagine it more tightly packed…that’s how it was before now…points of space closer together but still boundless. Now imagine it more spread out…that’s how it will be in the future…points of space further apart and still boundless.

I suppose new points of space are appearing in between the existing points to accomodate this expansion. From where? From Time I suppose. The universe is made of spacetime. We are free to move in 3D space but are on a one-way, forced trip through time.

Anyway, there are many good websites describing Big Bang Theory (and many bad ones too…watch out!) Try this for starters…

But if you plot the movment of things like the galaxies over time, won’t you find that they’re all moving away from one point? Ouch. This concept always hurts.

The center is me.

The center is me.

Nope. Consider hypothetical Galaxies* A, B, C, D. Someone in Galaxy A would see B, C, and D moving away from him/her. Someone in B would see A, C, and D moving away from him/her. Etc. I.E., we see galaxies moving away from us and folks in those other galaxies would see us moving away from them.

• or technically, “galaxy cluster” I should say.

Consider the “balloon analogy”…an expanding balloon with dots on it that represent galaxies. A 2-D person (who cannot see up or down) sitting on dot A would see all other other dots moving away from him/her. That would be true no matter what dot you choose. The whole of space is expanding. Essentially, we’re 3D people sitting on our galactic dots of our universe ballooning into 4D (space + time). Not a perfect analogy (but it helps) because people get stuck on the idea of the inside/outside of the balloon. Maybe consider an infinite chessboard where each node in the grid is a galaxy. There’s no center or edge, right? Now increase the size of each grid block. Each galaxy becomes more distant from every other galaxy no matter which point you choose.

Take that a step further. Pick a grid point. The next grid point over moved away with velocity X. Two grid points away moved at 2X. Etc. The further away you look, the faster the apparent expansion (again, “apparent” because to them, you’re the one that seems to be moving away). This is what Hubble saw…more distant galaxies moving away at a faster rate that corrolated to distance.

anyone else help out here?

Here’s an easy way to imagine it. Everything wraps around. Let’s create a pretend bubble around you, which is your visual radius. You are always in the center of it, regardless of where you go or what you do. People enter and leave your radius, but remain always in the center of their own.

Now make your radius even bigger, to the size of the entire universe. When someone leaves one edge, they are immediately on the opposite edge going the same direction, which is now back towards you, like a globe. Go far enough in any direction, and you end up back where you started. There is no “center” because the “center” is different for everything, that is, everything is its own center.

So yes, YOU are the center of the Universe. But then, I am too. So is everyone else.

Tim

I just wanted to say how much I appreciate the way you fashioned your assertion. You are an exemplary scientist, sir or madam.

This doesn’t make sense to me. If the Big Bang created the universe, what was there before the Big Bang?

I guess it also follows that I still can’t understand the universe expanding. Oh, I get the analogies alright, I just don’t get why it would be expanding. Aren’t the places it’s expanding to already considered the universe?

The biggest problem with the balloon analogy is that it implies that the Universe is spherical, or rather hyperspherical. While that’s one of the standard possibilities for the large-scale geometry of the Universe, it’s not the only one, and in fact, recent measurements seem to indicate that it’s flat. No matter how far you go, or how big your visual radius, you don’t necessarily wrap around.

Also, even if space is curved (and it is, on a small scale at least), you don’t necessarily need to postulate some higher dimension for it to curve in. It’s quite possible to describe and measure the curvature staying within our standard 3 spatial and 1 temporal dimensions.

I suppose I should add that I am NOT a creationist.

I just have a hard time getting my mind around the udea that the universe is expanding and it’s not just all the stuff in the universe that’s flinging outward. If that makes any sense.

Absolutely nothing… no time, no space, no matter, no energy….absolutely nothing. Try to picture that, I’ll bet you can’t - neither can I.

There is absolutely nothing outside the universe (that we can possibly know about or interact with). The universe creates space and time as it expands.

Me too. Cosmology is without a doubt the most confusing and maddening discipline I have ever read about. All Cosmologists should be locked away and absolutely prevented from interacting with normal humans.

The old “cause and effect” trap has jumped up to bite us. The thing is, in the universe that we know and can sense and speculate about, things have a cause. In many, maybe even in most, cases we don’t know what that cause is but we assume there is one.

But experience is strictly limited. And our physics only takes us back to some finite time after the Big Bang. Before that there is no compelling reason to believe that the cause and effect (everything has a predecessor) rules we live, and die, by had any validity.

So the question what came before the Big Bang has no meaning. We just have to learn to live with that uncertainty, at least for the time being.

And, in some cases, there doesn’t have to be a beginning. The simplest example I can think of offhand is the sequence of numbers greater than zero. There is no number that you can point to as the beginning of that sequence. Any number you come up with, no matter how small and say, “That is the beginning,” isn’t the beginning because I can come up with a smaller number between your number and zero…

This is a bitch. You and I, and most of us at first thought, imagine that we could be standing someplace else watching the universe expand. But we are inside, and we can’t see “outside” and “outside” doesn’t exist anyway. The universe isn’t expanding into anything, it is just expanding. Tough as that is, we just have to get used to it.

There was no “before”. The Big Bang was not only the origin of space, but of time as well. You can’t ask what was before time. Hawking describes it as ‘the same as asking what is north of the north pole’.

>> Does the universe have a centre?

Latest reasearch has shown my belly button to be the center of the Universe. It is open to the public weekdays from 9 to 5 and at other times by appointment. No smoking, food or drink please.

If you want to read more about the initial inflation, there is a very interesting book by Alan GUTh (isn’t that a great name for someone working on the Grand Unified Theory of everything), whose name I have forgot on the initial inflation, followed by the expansion. (But ignore his silly and utterly wrong appendix on the mistake he thinks Newton made.) Anyway it is true that the entire universe expands. Although it is probably not spherical, the baloon is not a bad analogy. Imagine flatlanders living on an expanding baloon. Everything is rushing away from everything else, but there is no center (or more precisely, the center of the expansion is not on the sphere), but to flatlanders it doesn’t exist. I am not sure how many flat structures there are in 3 dimensions, but I think that in 2 dimensions there are only three flat geometries: The plane, a cylinder, and a torus. You may think that neither a cylinder nor a torus is flat, but they both have flat geometries nonetheless. I think the Scientific American had an article on possible geometries of the universe in the past year.

Well, in downtown Boston, near the entrance to Filene’s, there’s a large plaque embedded in the ground denoting that exact spot as the Hub of the Universe. This site has a picture of it. Unfortunately, there’s a a fruit stand obscuring it now. I think it’s called the Hub of the Universe Market.

I’d just like to nitpickingly point out that the curvature of a torus is not always zero (i.e., it is not always flat). Your standard donut-shaped torus is in fact curved. Look at the pictures at this site. You can see that the rectangular sections are of varying sizes. If you drew a triangle on the surface, the angles would not add to 180. In fact, if you pick three points on the same circumference (in either direction), the angles of a triangle add up to 540!

The torus with zero (flat) curvature is called, unsurprisingly, the flat torus. It is constructed by joining the two pairs of opposite edges of a rectangular piece of paper. You cannot actually do this with a piece of paper, because you’d have to stretch parts of it out to make the second join, which would deform the curvature. But even if it can’t be constructed, you can visualize the flat torus as a video game screen where characters moving off the top appear at the bottom, and those moving off the left appear at the right. And, despite its inconstructability, it’s a perfectly valid shape for a universe. I don’t know if it has a 3D counterpart, however.

The cylinder, as you correctly pointed out, is indeed flat. You can easily roll a flat piece of paper into one without distorting it – without affecting its curvature. And a triangle you drew on the flat paper will still have 180 degrees on the cylinder.

-b