Where is the center of the universe?

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.

phinds

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.

salvestrom

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.

phinds

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.

salvestrom

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.

Drakkith

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"

korben dallas

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!!!!!

cyberfish99

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

*DaveC426913*

Quote by cyberfish99

You really can't tell.

No, it's not that you can't tell. It's that there isn't/wasn't one.

phinds

Quote by DaveC426913

No, it's not that you can't tell. It's that there isn't/wasn't one.

Ah, you beat me to it !

cyberfish99

Fair enough, I stand corrected!

korben dallas

Quote by thetexan

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 doesnt 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.

*lostprophets*

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

Drakkith

Quote by lostprophets

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.

Bill Crean

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.

phinds

Bill Crean, your post is nonsense. That the universe has no center is observational fact, not theology and you misunderstand the baloon analogy.

*DaveC426913*

Quote by Bill Crean

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?

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korben dallas	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!!!!!

cyberfish99	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

lostprophets	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

phinds Recognitions: Gold Member	Bill Crean, your post is nonsense. That the universe has no center is observational fact, not theology and you misunderstand the baloon analogy.