Where is the center of the universe?

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The discussion centers on the concept of a center of the universe, with participants debating whether such a point exists. One viewpoint argues that everything in the universe originated from a singularity, suggesting a definable center from which all matter is expanding. However, counterarguments emphasize that the universe's expansion does not imply movement away from a specific point, but rather an increase in space between objects. The balloon analogy illustrates that every point in an expanding universe can be considered a center, leading to the conclusion that there may not be a unique center at all. Ultimately, the conversation highlights the complexities of understanding the universe's structure and expansion dynamics.
  • #91
So what I'm getting out of this, is that the universe is flat and it connects to itself 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.
 
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  • #92
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.
 
  • #93
Flustered said:
So what I'm getting out of this, is that the universe is flat and it connects to itself 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.

Some interesting things about this arrangement:
  • 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
 
  • #94
I don't know about you, but I'm out of analogies, so let's hope he gets it this time around...
 
  • #95
Flustered said:


http://www.youtube.com/watch?v=VOz4PkdY7aA&feature=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 :smile:

Cosmo
 
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  • #96
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.
 
  • #97
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?
 
  • #98
Never mind, very off topic after giving it some thought.
RD
 
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  • #99
thetexan said:
I am serious and you haven't 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 isn't 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 doesn't mean it doesn't 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 can't 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 can't tell where the origin is. That does not mean it doesn't 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!
 
  • #100
Flustered said:
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 existence of the universe are as yet unanswerable. It might have been a cosmic egg laid by a cosmic chicken for all anyone can prove.
 
  • #101
korben dallas said:
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 black hole. 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.
 
  • #102
salvestrom said:
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.
 
  • #103
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.
 
  • #104
salvestrom said:
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.
 
  • #105
phinds said:
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.
 
  • #106
salvestrom said:
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.
 
  • #107
phinds said:
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.
 
  • #108
Flustered said:
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"
 
  • #109
On sci channel, Nikodem Poplawski. Google him and check it! This feller also thinks the center of our universe, when found, will be a black hole from which our universe was "puked" and, in my own opinion, still is puking"! Peace Brothers and Sisters!
 
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  • #110
You really can't tell. If everything was energy, then you could just trace the straight line back to the source, but due to matter which has gravity, then light becomes curved and all jumbled up till you really can't find the center or origin
 
  • #111
cyberfish99 said:
You really can't tell.
No, it's not that you can't tell. It's that there isn't/wasn't one.
 
  • #112
DaveC426913 said:
No, it's not that you can't tell. It's that there isn't/wasn't one.

Ah, you beat me to it !
 
  • #113
Fair enough, I stand corrected!
 
  • #114
thetexan said:
There must be a center or someplace close to the center of the universe.

The actual universe can be contained in a physically describable bounding box. This box will have a center. Or, everything emminated from a center, the singularity and the position of that place where the singularity once existed is a fact, even though most will protest that it is unknowable. The point is, there must be some place, maybe known only to God where the center is. If it does exist then there must be some way to extrapolate how and where to find it.

The proof that it does exist or that people were quite happy to conceed that it exists is found in many television shows like Universe where noted scientists always note that, prior to the discovery that the universe is accelerating faster outward, everyone accepted that the universe would collapse back into a singularity. In other words, the big bang was ballistic in nature and will be so in the reverse when gravity brings it all back to a common center point.

So...why doesn't anyone try to figure out where that point is or was?

tex
I know where that point is. It's right in the middle, lol! Peace! P.S. I'm sorry but I just couldn't help myself.
 
  • #115
maybe there is no middle.
could it be at any point anywhere.
we have in our mind that the first action of reaction must mean the middle but in my mind there is no middle in anything
 
  • #116
lostprophets said:
maybe there is no middle.
could it be at any point anywhere.
we have in our mind that the first action of reaction must mean the middle but in my mind there is no middle in anything

I don't really understand what you are saying, but I can say that to our knowledge there is no middle or center of the universe.
 
  • #117
I have read most of the discussion up to date and believe that the question of the whereabouts of the centre of the universe is in danger of joining such topics as religion, politics and global warming by manmade carbon dioxide emissions, in that we are unlikely to get to the bottom of the question. The answer might be found at the end of the scientific process, which requires observation and theory: that is observations are made and a theory formed to explain them. Further observations are made and as long as the observations support the theory, we may have more confidence in the theory, but if observations contradict the theory we should be ready to discard or at least modify the theory.

A relevant observation to the question is the Hubble result, namely, that the further away a galaxy is, the faster it is moving from us. A theory (or analogy), which will also help, is the balloon model of the universe (used also by Stephen Hawking in explaining his Big bang theory). Debris (or galaxies) originating from the Big Bang is contained in the skin of the balloon model. The skin moves away from the point of Big Bang (or centre of the universe) at a speed (estimated with the Hubble constant), which we can denote as V. Now, a galaxy, which is diametrically opposite our observational point in terms of our approximately spherical balloon model will also be moving at V from the point of Big Bang, but in the opposite direction, with resultant parting velocity of 2V. Other galaxies on the skin will be closer and the parting velocities will be less than 2V because they will be made up of the observer's velocity plus a component of the observed galaxy's velocity.

To make this clearer consider the special case of a plane through the centre of the balloon universe, and intersecting the observer's point and the diametrically opposite observed galaxy. The plane will also intersect other galaxies around the skin. On this plane the parting velocities (Pv) between the observer and the observed will be given by:

Pv = V(1+ cosθ) (1)

where θ is the angle between the diameter of the balloon universe, (a diameter which intersects the observer) and the line of inclination (or declination) of the observed galaxy.

From (1) it is seen that the parting velocities of all the galaxies will vary from 0 to 2V as theta varies from pi/2 to - pi/2.

To locate the direction of the universe's centre is now a simple task: just find the direction of the most red-shifted galaxy i.e. the one with the maximal Pv and this line will intersect the centre of the universe. The distance of the centre of the universe along this line, apart from being approximately half way, could be estimated using age of the universe times the estimate for V.

This outline of where the centre of the universe is uses existing robust theories and observations with a little thinking.
 
  • #118
Bill Crean, your post is nonsense. That the universe has no center is observational fact, not theology and you misunderstand the baloon analogy.
 
  • #119
Bill Crean said:
To locate the direction of the universe's centre is now a simple task: just find the direction of the most red-shifted galaxy...

From where?

From Earth? You will find Earth is the centre of the universe.

From Andromeda? You will find Andromeda is the centre of the universe.

From M247? You will find M247 is the centre of the universe.

The observations will be the same no matter where you are. Each point of observations will reveal a spherical observable universe equidistant in all directions, with highest red shift at its farthest points.

How does your explanation work now?
 
  • #120
And this is where you lose most of us astrophysical midgits, right there. It's possible to observe? that there is no center but it is impossible to contemplate the possiblility that there is a center but we just can't find it...YET. Bill has, what seems to me, to be a good analogy. Why is it not possible.

If there was an expansion as it is usually described, it had to expand from somewhere, to somewhere. Either we should at least try to find the center of the expansion as a matter of curriosity or quit using the word 'expansion' to describe whatever it was that happened.

But that might step on a few theories, dog gone it.

tex
 

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