Is the universe bounded or unbounded?

[otseng]

In the Light, stars, and creationism thread, I proposed a theory to reconcile a young earth with being able to see stars that are billions of light years away. The theory assumes that the Big Bang is true, however, it also assumes that the universe is bounded. In typical cosmology, it is assumed that the universe is unbounded.

Bounded means that the universe has a boundary to it. There exists an "edge" to the universe in which beyond this boundary, our universe does not exist.

In an unbounded universe, there is no "edge". The universe "wraps" around itself. So, if you are to go in any direction in a straight line, you will eventually come back to the starting point.

This is hard to conceptualize, but can be explained like a surface of a sphere. On the surface of a sphere, if you start at any point and then go in a straight line, you will eventually come back to the starting point. Now, instead a 2-D surface on a sphere, the universe is a 3-D topology that curves in on itself.

The ramifications of either of these two assumptions make for drastically different cosmological conclusions.

So, the questions are:
1. Is the universe bounded or unbounded? Why?
2. What are the ramifications of whether it is bounded or unbounded?

[otseng]

If I'm reading it right, it's interesting that the direction of the movement of the galaxy is the same magnitude but nearly the opposite direction of our galaxy's rotation. Not sure what that implies, but it would seem peculiar.

George called it sod's law. It made the crucial data much harder to get at.

I think it would be called Murphy's law here in the States. We Americans always need to have our own terminology for things.

But, even if our galaxy was moving with respect to the CMBR, I'm not sure how that would affect the arguments of either a bounded or unbounded universe.

Oh, that's the topic we're on! Well, it has no direct effect -- but it does mean that we can't be at any "centre" of the universe if it's bounded, and naturally there isn't even "a centre to be at" in an unbounded universe so one of your anthropocentric arguments falls down.

I don't believe that we're in the exact center of the bounded universe. Though the galaxy could be moving, we would still be relatively close to the exact center.

[otseng]

The degree of anisotropy was small - just one tenth of 1 percent (one part in a thousand). However, all was not as expected. "Look at that," I said to Jon. "What do you suppose that means?". Although the anisotropy was close to the magnitude we had expected, its direction was nearly the opposite. That is, the sky was warmest in the direction of Leo and coolest in the direction of Aquarius, which means that Earth was moving toward the former and away from the latter. That is not the direction in which the Galaxy rotates."Unless we have a sign wrong," said Jon, "there's only one explanation." We both knew what the answer had to be: Not only is the entire Galaxy rotating, as it should be, but, unexpectedly, it is also moving through space. And it was moving very fast - six hundred kilometers a second, or more than a million miles an hour.

I'm sure that you will have heard mention of an astronomical phenomenon called "The Great Attractor" It's the object towards which our "Local group" of galaxies is headed. The largest-scale structure of the universe consists of concentrations of superclusters separated by voids and all the galaxies are in constant flux within the Galactic Filaments".

If I'm reading it right, it's interesting that the direction of the movement of the galaxy is the same magnitude but nearly the opposite direction of our galaxy's rotation. Not sure what that implies, but it would seem peculiar.

I've thought about this some more. And I've determined the implication.

Our galaxy is moving through space relative to the CMBR. But, at the same time, we are rotating within our galaxy. These are moving in the same magnitude, but in the exact opposite direction. So, the net effect is that we are not moving.

[QED]

Not only is the entire Galaxy rotating, as it should be, but, unexpectedly, it is also moving through space. And it was moving very fast - six hundred kilometers a second, or more than a million miles an hour.

Our galaxy is moving through space relative to the CMBR. But, at the same time, we are rotating within our galaxy. These are moving in the same magnitude, but in the exact opposite direction. So, the net effect is that we are not moving.

Yet the Sun's orbital speed around the Galaxy is given as something in the order of 200 km/s (from the various Google searches I did). I'm not sure where this discrepancy is coming from.

[otseng]

I'm not sure where this discrepancy is coming from.

It's probably from Mr Sod or Mr Murphy.

[Goat]

The degree of anisotropy was small - just one tenth of 1 percent (one part in a thousand). However, all was not as expected. "Look at that," I said to Jon. "What do you suppose that means?". Although the anisotropy was close to the magnitude we had expected, its direction was nearly the opposite. That is, the sky was warmest in the direction of Leo and coolest in the direction of Aquarius, which means that Earth was moving toward the former and away from the latter. That is not the direction in which the Galaxy rotates."Unless we have a sign wrong," said Jon, "there's only one explanation." We both knew what the answer had to be: Not only is the entire Galaxy rotating, as it should be, but, unexpectedly, it is also moving through space. And it was moving very fast - six hundred kilometers a second, or more than a million miles an hour.

I'm sure that you will have heard mention of an astronomical phenomenon called "The Great Attractor" It's the object towards which our "Local group" of galaxies is headed. The largest-scale structure of the universe consists of concentrations of superclusters separated by voids and all the galaxies are in constant flux within the Galactic Filaments".

If I'm reading it right, it's interesting that the direction of the movement of the galaxy is the same magnitude but nearly the opposite direction of our galaxy's rotation. Not sure what that implies, but it would seem peculiar.

I've thought about this some more. And I've determined the implication.

Our galaxy is moving through space relative to the CMBR. But, at the same time, we are rotating within our galaxy. These are moving in the same magnitude, but in the exact opposite direction. So, the net effect is that we are not moving.

For now.. once we get to the other 'side' of our orbit, we will be going away faster.
At one point in our 'orbit' in the galaxy, we will be going twice the speed that the galaxy is going in relative to the CMBR. 1/4 of the time are we going towards it.. 1/4 of the time we are going directly opposite of it, and half the time , we are going side to side relative to it.

[McCulloch]

Let us suppose that the universe is bounded. That would mean that there is an edge to the universe somewhere. Now, if a photon were moving towards the edge, what would happen? Would the photon leave the universe? I don't think so. Would the photon bounce back? Can we suppose that the edge of the universe is a giant mirror?

I think that the only solution to this is that if the universe is bounded, it must be expanding at the speed of light, therefore the photon near the edge of the universe would never reach the edge. Is there any evidence that the total volume of the universe = ( the age of the universe the speed of light ) ?

[Furrowed Brow]

Let us suppose that the universe is bounded. That would mean that there is an edge to the universe somewhere. Now, if a photon were moving towards the edge, what would happen? Would the photon leave the universe? I don't think so. Would the photon bounce back? Can we suppose that the edge of the universe is a giant mirror?

I think that the only solution to this is that if the universe is bounded, it must be expanding at the speed of light, therefore the photon near the edge of the universe would never reach the edge. Is there any evidence that the total volume of the universe = ( the age of the universe the speed of light ) ?

I don't think there is.

Your formula got me thinking. To know the volume of a bounded universe we need to know its geometry. In a very simple model we might think of a sphere with volume 4pi/3*r^3. But that is only a very elementary guess. Modern physics talks about branes and many more dimensions than that. But really we don't yet know the geometry.

Perchance we might happen to exist in only three dimensions of some higher dimension geometry. For example the volume of a 4 dimensional hyper sphere is (pi^2)*(r^4), and the surface of such a sphere is 2*pi^2*r^3. If the 3D universe we observe is the 3D surface of a 4D sphere then questions of volume become the wrong kind of question. Would it be right to try and quantify the volume of a surface?

Not to say we inhabit such a surface, but the point is that some of our questions and ways of conceiving of the problem may turn out to be poorly formed. To make a better assessment we need to know the geometry.

Bringing this back to the question of whether the universe is bounded. To be able to answer the OP we need something approaching a theory of everything, and probably some very highfalutin math. I suggest this might be one question beyond the abilities of us amateurs.

[otseng]

I think that the only solution to this is that if the universe is bounded, it must be expanding at the speed of light, therefore the photon near the edge of the universe would never reach the edge.

Actually, cosmologists believe the universe is expanding faster than light. Which to me doesn't make much sense.

After skimming through this, it gives a good alternative explanation to red shifts.

Is there any evidence that the total volume of the universe = ( the age of the universe the speed of light ) ?

It would seem to me that the maximum volume for the universe would be equal to (4pi/3)*(the age of the universe*the speed of light)^3. (I'm still not convinced that the space fabric is stretching.)

[QED]

I think that the only solution to this is that if the universe is bounded, it must be expanding at the speed of light, therefore the photon near the edge of the universe would never reach the edge.

Actually, cosmologists believe the universe is expanding faster than light. Which to me doesn't make much sense.

After skimming through this, it gives a good alternative explanation to red shifts.

Edward Wright disagrees. Theories about Tired light have been around for a long time but have so far failed to hit all the buttons that Big-Bang Cosmology has.

It would seem to me that the maximum volume for the universe would be equal to (4pi/3)*(the age of the universe*the speed of light)^3. (I'm still not convinced that the space fabric is stretching.)

So do you think that all the galaxies are rushing away from us (apart from a few local ones)?

[otseng]

So do you think that all the galaxies are rushing away from us (apart from a few local ones)?

I do think that the galaxies are receding from each other. And I'm not saying that I believe that tired light is totally correct, but it might have some merit.

We had lost several posts due to the hack, so I'd like to bring back up the discussion - are there Euclidean geometries that would not be bounded?