Is there a centre of the universe?

If we think about the theory of the big bang, where the universe started to expand after that moment of gravitational singularity, have we defined a centre of the universe, in the meaning that we can say that our solarsystem is so and so far away from this point of origin?

There was a button I once saw that said “Of course I’m the center of the Universe. Everything seems to be receding from me.”
There is no “center” to the niverse in relation to the “Big Bang”. Mentally I picture it as a center from which everything seems to be radiatying, but this picture is false. Everything is moving away from everything else, and there is no “center”. The analogy I’ve heard ever since I was a kid is that our universe is like the surface of a large balloon. As it inflates everything gets farther away from everything else, but nothing has a preferred position that identifies it as the Center.

Of course, in this analogy the ballloon itself has a center, but that’s irrelevant to the inhabitants of the Space in the analogy, which is confined to the surface[ of the balloon. In a similar way, there may be a hyperspace in which there’s an obvious center of the expansion of our three-dimensional universe, but we in the 3-d universe aren’t privileged to see it.
See Dionys Burger’s novel Sphereland, a sequel to Abbott’s Flatland, in which this analogy is explored further:

http://en.wikipedia.org/wiki/Sphereland

There was a chain of thought that actually included the above in my case too… :stuck_out_tongue:

So I am to think of the universe as a place where everything is trying to disperse away from everything else, but without a centre of origin? The balloon without a centre is kind of difficult to understand, but am I to imagine the ballon and its surface in a way where everything that sprang out from the big bang is constantly moving away from us and everything else without leaving anything behind? The surface of the ballon being all the particles in the universe, with the interior of the balloon being whats left behind (nothing). But if everything is moving away from everything, would’nt there be something in the balloon anyway?

The contents of the balloon in that analogy are irrelevant, as it is the warped two-dimensional surface of the balloon that represents the universe.

Draw a bunch of dots on the balloon and inflate it; imagin yourself standing on one of the dots and all the other dots appear to be receding from you, but there is no point on the surface of the balloon that corresponds to it’s centre.

The big bang happened everywhere, because it was the origin of space as well as time; wherever you are in the universe, you’re in a place that was involved in the big bang, just as much as was any other place.

Damn you, Cal, you beat me to it.

:smiley:

Well, actually, this only demonstrates that you are the least attractive thing in the universe.

Tris

“You must be the change you wish to see in the world.” ~ Mohandas K. Gandhi ~

Here’s the way I think of it: If you were on the surface of the balloon, you’d be existing in a curved 2-dimensional universe with no center. In order to define a center, you’d have to go to the next dimension, the 3rd, in which there’s a clearly defined center of the balloon, with all the points on the surface more-or-less equidistant from it. We, on the other hand, exist in a curved 3-dimensional spacial universe with no center. In order to define a center, we have to go to the next dimension, which is time. So the “center” of the universe is defined by time, not space, which means: if anything can be called the “center” of the universe, it’s the big bang itself, with every point in the universe more-or-less equidistant (in time) from it.

Good explanations pulling out the balloon analogy. I will also mention that something that hurts most people’s heads is that you can’t think of the Big Bang as though the stuff in the universe started out in a little package that started expanding out into space. That little package is space. There is no point of origin–[hippie voice]the point of origin is all around you, man[/hippie voice]. Now the balloon analogy comes into play.

I guess this is the paradox that’s hardest to reconcile, because we’ve all “learned” that at one time (excuse that expression) everything was at one point and there was a big bang and everything escaped from there and became the universe. So we all have this mental image of an explosion from that one point. Now, Mangetout’s explanation presents a contrary vision but one that sort of answers the question. If we can wrap our minds around that version of it - I don’t know exactly how - then we’ve go our answer.

The subject of the Big Bang has always confused me a little. It makes sense well enough that every point in the universe is moving away from every other point. Yet at the time of the Big Bang, the universe consisted of just one point that contained everything. This single point could rightly be called the origin of the universe and seems to me to be as close to the idea of a center that the universe is going to get. I realize that the point I’m talking about is almost certainly unlocatable, but to me there is a difference between saying the universe has no center and saying the universe has a center but it would be really hard to find.

Procyon, not only everything was at that one point, everywhere was too. That “point” was the entire universe, and still is – it’s just bigger now.

If you meant that there was a physical location that once held that point, the problem becomes more metaphysical: a physical location in what? The entirety of the universe was inside that “point”, so no point in the universe today can be said to be that location. In the case of the balloon analogy again, the actual location in 3D space that once held everything is no longer in the universe of the balloon’s surface at all: it would be in it’s 3D center.

Cal, if you ever find out where that button came from, could you drop me a line?

Don’t try to think about the condition of the Universe right exactly at the moment of the Big Bang. All that’ll do is make your head hurt. All we can really think about meaningfully is times after the Bang (possibly only a very short time after, but after). If the Universe is now infinite (which it may or may not be), then it was infinite at all times after the Bang. Was it infinite at the exact moment of the Bang? Undefined. We can certainly say, for instance, that the density of the Universe was greater at earlier times. We can even maybe say that the limit of the density as t -> 0 is infinite. But we can’t say anything about t = 0 itself.

As a practical matter I think that button is correct in its implication that “you” are the center of the Universe.

While there is no center as such as a person who perceives the Universe you will always appear (to yourself) to be at its center. Think of it this way:

Centered on your head draw a circle around it (a really big circle). The biggest that circle can be is a radius whose distance is that of light travelling from the Big Bang moment to you. Anything outside of this circle is essentially non-existant to you as it can have no effect on you. As the Universe ages this circle grows larger (at the speed of light) but a circle centered on your head is not exactly aligned with the one on my head. So in effect you can see a bit further in one direction than I can and a bit less in another. For all intents and purposes you are at the center of the Universe as perceived by you.

Note that I am not saying that there is a “center”, just that from your perspective you are at the center.

OK; try another analogy, perhaps not an entirely accurate one, but hopefully useless nonetheless.

Remember the arcade game Asteroids? Objects disappearing off the rightmost edge of the screen wrap back onto the left and vice versa, also likewise top and bottom edges.
So that rectanglular screen is *all there is of the Asteroids Game Universe * - not only is there nothing outside of it, there is no outside.

If you install a larger CRT monitor in the game, the Asteroids Game Universe has expanded (OK, so have all the objects in it, but let’s disregard that).

So working backwards in time towards the ‘Big Bang’ of the Asteroids Game Universe, a while ago, the CRT monitor was smaller in size, but it was still all there was of the Asteroids Game Universe.

Working backwards in time, the monitor was smaller and smaller - the size of a handheld computer screen, the size of a mobile phone display, the size of a digital watch face, and yet all the time, it was all there was of the Asteroids Game Universe - there was nothing outside of it, and no outside.

Until you get back to the origin of the Asteroids Game Universe - when it was a point - it was still all there was of the Asteroids Game Universe.

The problem we have in visualising this is that anything we use as an analogue, does have things outside of it and does have bounds (although the bounds are often not part of a dimension relevant to the analogy.

But asking where is the centre of the universe is exactly the same as asking which point on the surface of the Earth, is the centre of the surface of the Earth? or which point, on the circumference of a circle, is the centre of the circumference of the circle?

Hi, I heard someone was looking for me.

Chronos asks:

I could have word that I saw it on one of Nancy Leibowitz’ buttons, but when I looked on her site, it wasn’t there. I did, however, find lotsa other neat buttons.
WARNING: If you’ve never been to Nancy’s site, don’t open this if you expect to get anything done this afternoon

http://www.nancybuttons.com/

The Good News is that Nancy says she’ll make you up as custom button if you ask nice and give her money:

http://www.nancybuttons.com/catalog.cgi?action=Custom%20Buttons&

The Bad News is that I’m still waiting for a button I requested from her in 1989. Good Luck.

The balloon analogy is very useful, but note that even experts sometimes use it incorrectly.

The universe is everything.The Big Bang was just as much everything as today’s universe is. Everything has no centre any more than the North Pole is the centre of the Earth’s surface.

I must admit it is a bit hard to think in convoluted ways, but you all have given some pointers at where to start thinking. I bow to you all :slight_smile: