# Where is the center of the universe?

by thetexan
Tags: universe
 P: 75 So what i'm getting out of this, is that the universe is flat and it connects to its self in a line. But there is no center, even though I can move in 3D? Also the circumference argument is only 2D. The universe is not 2D.
 P: 226 The universe is 3D. The effect we are describing occurs in every possible direction. You will, in a finite, unbound universe, always end up back where you started. Someone stood 6 feet to your left can see 6 feet further left than you can, however, all he sees in that extra 6 feet is the 6 feet extra that you can see to the right, that he cannot (assuming, for the sake of explanation, that the observable universe is equal to the actual universe). If you follow this through for every possible point in spacetime you have a bunch of overlapping spheres that give you the view from each point, but no point has any special property that makes it the center. It isn't too dissimilar from the notion of the earth having a top or bottom. This presupposes it's possible to have a 'right way up', but such a thing is entirely arbitrary.
P: 15,319
 Quote by Flustered So what i'm getting out of this, is that the universe is flat and it connects to its self in a line. But there is no center, even though I can move in 3D? Also the circumference argument is only 2D. The universe is not 2D.
That is because we poor humans cannot actually imagine 3D volumes without boundaries. But we can imagine 2D surfaces without boundaries and extrapolate to 3D.

Back when computer programs were carved on stone tablets with sharpened bone, there used to be all manner of dungeons games comprised of nothing more than 10x10 rooms with stuff in them. There were 10 levels to the dungeon, making for a 1000 room dungeon, 10x10x10. What's cool is that you can walk (or climb) in any direction without limit. Walk 10 rooms West and you find yourself back in the same room. Climb ten floors up and you're back in the same room.

• it is finite in extent - no more than 10 units in any dimension
• it is unbounded - there are no borders, no edges
• there is no centre - no room can claim to be at the centre - in fact, no room can claim to have any special privilege over any other
• from any room, you can see the same distance in every direction i.e. every room exhibits the appearance of being at the centre
• if the entire thing doubled in dimensions (every room underwent mitosis into 2), the entire dungeon would double in size yet it would not grow from any centre
• it is perfectly mathematically trivial
 P: 226 I dunno about you, but I'm out of analogies, so let's hope he gets it this time around...
P: 366
 Quote by Flustered http://www.youtube.com/watch?v=hi6OuLJwvYk http://www.youtube.com/watch?v=VOz4P...eature=related Videos like these and many more show animations of the big bang, they show it as an observer somewhere outside of the universe. They put these on all the science channels as well, why would they put false information like this in the public and give them faulty ideas of the big bang if it is not true. From what you stated this animation cannot be valid because there is no edge or outside of the universe, correct?
The animations are representations only and no they do not accurately reflect the overall topology or intinsic manifold of the Universe. Trying to imagine or visualise the entire Universe from an external vantage point is...well...pointless. Asking for the center is like standing at the north pole and asking which way is north, it has no meaning.

The reason you find general popularizations like this is because they are popular and accessable, but they should be taken at face value and for the popularizations that they are.

To better understand the early universe then I would recommend you read Steven Weinbergs the first 3 minutes.

Additionally you can discard the idea you have on multiverses, if indeed there are multiverses (which I think is speculative at very best) then it is probably unlikely they have any causal connection to our Universe .

Try to remember the BB is not a ballistic explosion in a pre-existing background but was the rapid expansion of the Universe itself - not into a pre-existing empty space as the space itself is part of the expansion. Reality expanded from > plancke time and this is well understood physics, now before plancke time is anyones guess and a different ballgame.

If you have any other questions please ask, I understand it is a difficult concept but honestly is one well worth sticking with

Cosmo
 P: 15,319 Another way of thinking about is this: The universe is all there was and is. At one time in the very far past, distances between points were very very small (smaller than an atom). Then rapidly, distances between points became much larger, and distances between points have been increasing ever since.
 P: 75 This may be a dumb question but how do cosmologist know the BB was smaller than an atom? What if it was the exact size as a proton. Does something in the acceleration say that it was smaller than an atom? If so what about the acceleration proves this? Did the BB just pop into existence, or was the singularity existing there for some time, than decide to blow. Or did it expand the moment it popped into existence?
 PF Gold P: 28 Never mind, very off topic after giving it some thought. RD
P: 36
 Quote by thetexan I am serious and you havent addressed the question. In a mind experiment, if I could stand off some distance from the universe I could point and say...'there it is' and there would be some central area to that thing. Or, using a different approach....since everything in the universe blasted from the singularity it is obvious that the parts of the universe, including space itself is accelerating outward from that initial start. If it isnt then from what are all the elements of the universe accellerating? IF we could play the tape backward we could easily pinpoint the location of the origination point. Just because we cant, or have difficulty figuring out how to locate the point doesnt mean it doesnt exist. And since it DID once exist...that being the point of the big bang...by what logic do you determine that it immediately is lost and cant be found? It seems that everything is accelerating from somewhere common otherwise everything would be accelerating from different origins. Just because everything seems to be accelerating from our vantage point only means we cant tell where the origin is. That does not mean it doesnt exist. Unless you are willing to argue that every body is accelerating from different origins then they must be sharing a common origin. Where? tex
Hey? 'Sup? I was watching discovery channel the other day and they were showing a new mystery in space of a bunch of oddly behaving galaxies. They seemed to be orbiting something that was not there. The center of the universe perhaps? I believe the expansion of our universe is caused by the undetectable dark matter still being spewed into our dimension by the black-hole from which our universe was born into existence?? I'm asking if this is even remotely possible? That is the only uneducated explanation to me!! Peace Brothers and Sisters!!!!!
P: 226
 Quote by Flustered This may be a dumb question but how do cosmologist know the BB was smaller than an atom? What if it was the exact size as a proton. Does something in the acceleration say that it was smaller than an atom? If so what about the acceleration proves this? Did the BB just pop into existence, or was the singularity existing there for some time, than decide to blow. Or did it expand the moment it popped into existence?
The size of the early universe is calculated by taking the current rate of expansion, assuming it has been the same, and working out what happens as you go backward. From this you end up with a very dense universe some 13.7 billion years ago.

Questions about the existance of the universe are as yet unanswerable. It might have been a cosmic egg laid by a cosmic chicken for all anyone can prove.
P: 226
 Quote by korben dallas Hey? 'Sup? I was watching discovery channel the other day and they were showing a new mystery in space of a bunch of oddly behaving galaxies. They seemed to be orbiting something that was not there. The center of the universe perhaps? I believe the expansion of our universe is caused by the undetectable dark matter still being spewed into our dimension by the black-hole from which our universe was born into existence?? I'm asking if this is even remotely possible? That is the only uneducated explanation to me!! Peace Brothers and Sisters!!!!!
Galaxies are able to orbit around shared centers of gravity. It isn't necessary for anything to be there. An alternative is a large, old blackhole. Dark matter is actually thought to counteract space expansion, as it exerts a gravitational influence. There is no indication that dark matter comes from black holes, which exist in our dimension. And although I personally treat the starting universe as having been the mother of all black holes, whatever it was, it isn't it anymore.
PF Gold
P: 6,268
 Quote by salvestrom The size of the early universe is calculated by taking the current rate of expansion, assuming it has been the same, and working out what happens as you go backward. From this you end up with a very dense universe some 13.7 billion years ago.
MISLEADING BY FAR. What you are talking about is the observable universe, NOT the universe and this is an extraordinarily important distinction.
 P: 226 If the universe is homogenous, then at which ever point you stand, the result should be the same. Constant expansion, rewound to a denser universe 13.7 billion years ago. This leads to the conclusion that 13.7 billion years ago the entire sha-bang was bound up together. In fact, playing with the expansion rate and altering the age shouldn't make any difference. It all starts at the big bang, not just our observable bit.
PF Gold
P: 6,268
 Quote by salvestrom If the universe is homogenous, then at which ever point you stand, the result should be the same. Constant expansion, rewound to a denser universe 13.7 billion years ago. This leads to the conclusion that 13.7 billion years ago the entire sha-bang was bound up together. In fact, playing with the expansion rate and altering the age shouldn't make any difference. It all starts at the big bang, not just our observable bit.
I agree with what you said above, but NOT that this implies ANYTHING about the size of the early universe other than that it was a lot smaller than it is now. It was very possibly infinite at the start and is infinite now. Of course if it WAS finite at the start, then it's finite now, but we still have no idea how big it was then because we have no idea how big it is now. Your analysis is correct for DENSITY, not size.
P: 226
 Quote by phinds I agree with what you said above, but NOT that this implies ANYTHING about the size of the early universe other than that it was a lot smaller than it is now. It was very possibly infinite at the start and is infinite now. Of course if it WAS finite at the start, then it's finite now, but we still have no idea how big it was then because we have no idea how big it is now. Your analysis is correct for DENSITY, not size.
Given how small an area you could crush the mass-energy of the universe into, the density can only be high if there is less space or the space we have is highly curved. If there were space that was beyond the big bang, it would form a break in the homogenity (we wouldn't necessarily be able to see it from our location).

Anyway, expansionm age and density imply a significantly smaller universe, which we seem to both agree on.
PF Gold
P: 6,268
 Quote by salvestrom Anyway, expansionm age and density imply a significantly smaller universe, which we seem to both agree on.
No, we dont' seem to agree on it. A tiny fraction of infinity is still infinity. I don't know that the U was infinite then and now, but I'm open to that possibility. You do not seem to be.
P: 226
 Quote by phinds No, we dont' seem to agree on it. A tiny fraction of infinity is still infinity. I don't know that the U was infinite then and now, but I'm open to that possibility. You do not seem to be.
Yeah, you're right. I think infinity would be at odds with the observed nature of reality. There doesn't seem to be anything out there that suggets an infinite anything.
Mentor
P: 11,823
 Quote by Flustered This may be a dumb question but how do cosmologist know the BB was smaller than an atom? What if it was the exact size as a proton. Does something in the acceleration say that it was smaller than an atom? If so what about the acceleration proves this? Did the BB just pop into existence, or was the singularity existing there for some time, than decide to blow. Or did it expand the moment it popped into existence?
The Big Bang isn't a "thing", it was an event. Similar to inflation, which was another event soon after the BB. The Universe was once very very dense and expanded from that state into a less dense state. Our current models only take us back to a certain point in time after the Big Bang. Before this point in time our models say the universe was so dense that the model starts making infinities, thus it "breaks down" at that point and predicts nothing. The singularity is nothing more than our model breaking down. (Or so most cosmologists believe I am told)

So your question about the size of the BB and if it popped into existence should be reworded as the size of the Universe and such. And our only answers are: "We don't know"

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