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?

[Goat]

Well, my model is not as simple as matter just "exploding". I believe our Earth is much too complex to simply arrive by random chance. So, there would have been an intelligent cause for the formation of the Earth.

But, let's get back to a question I asked earlier. How can the universe be unbounded and Euclidean?

There is the crux of the matter. One thing that has been shown is that complexity can come from simple rules, followed by some sort of filter.

And it can be unbounded and euclidean if the volume of space is big enough so that the 'warping' on a local level is not noticeable.

[otseng]

And it can be unbounded and euclidean if the volume of space is big enough so that the 'warping' on a local level is not noticeable.

QED suggested that here. However, he did not provide any supporting evidence for this. Do you have evidence that the universe is extremely large?

[QED]

Then what would your resolution to Olber's paradox be? The consensus explanation requires a finitely old and metrically expanding universe.

I'm not sure what you're driving at. I'm not arguing that the universe is infinite in size and age. And why would it require a metrically expanding universe?

Well, it's a bit difficult keeping in mind a non-metric expansion given that the amount of observed red-shift has the most distantly observable galaxies moving at around two-thirds the speed of light. Such relativistic velocities would increase the mass of the galaxies in ways we could hardly fail to spot.

But seeing as how you want to stick to an alternative interpretation of General Relativity I don't think a "little thing" like this is going to stop you.

Your model would imply a vast empty region...

Well, my model is not as simple as matter just "exploding". I believe our Earth is much too complex to simply arrive by random chance. So, there would have been an intelligent cause for the formation of the Earth.

Only the Earth? So what about all the other planets orbiting other stars of our galaxy? otseng, I don't think I can carry on this debate if you're going to propose such huge amounts of magic. I'm sure you can see that any alternative cosmological model can be proposed on the basis of sufficient magic. Astronomical observations are interpreted on the basis of GR and the Standard Model. These things make accurate predictions of the order of correctly measuring the distance between New York and London to within the width of a human hair. This isn't meant to be a proud boast or argument from authority -- it's simply the only way I can think of to convey the justification for the degree of confidence that science has in its conclusions.

However, one gets used to the lack of influence this seems to have on the supernaturalist so the only way ahead that I can see is if you can flesh-out your model with something resembling a sensible explanation -- hopefully something which can be distinguished by a unique prediction.

But, let's get back to a question I asked earlier. How can the universe be unbounded and Euclidean?

By being Quasi-Euclidean.

[otseng]

Well, it's a bit difficult keeping in mind a non-metric expansion given that the amount of observed red-shift has the most distantly observable galaxies moving at around two-thirds the speed of light. Such relativistic velocities would increase the mass of the galaxies in ways we could hardly fail to spot.

How would it fit in with Olber's paradox?

Also, I have my suspicions that the red-shift is a result of other factors other than just recession. (Just don't ask me what they are. )

I wonder if a separate thread needs to be created on a metrically expanding universe? It seems to be a debate all of its own.

But seeing as how you want to stick to an alternative interpretation of General Relativity I don't think a "little thing" like this is going to stop you.

I'm unfamiliar with the details of GR. Does it state that the universe is metrically expanding?

otseng, I don't think I can carry on this debate if you're going to propose such huge amounts of magic.

God has to enter the equation at some point.

But, let's get back to a question I asked earlier. How can the universe be unbounded and Euclidean?

By being Quasi-Euclidean.

Could you go into some more detail please?

[Goat]

And it can be unbounded and euclidean if the volume of space is big enough so that the 'warping' on a local level is not noticeable.

QED suggested that here. However, he did not provide any supporting evidence for this. Do you have evidence that the universe is extremely large?

Personally, no,

But scientists claim that the universe is at least 156 billion light years wide

http://www.space.com/scienceastronomy/m ... 40524.html

[McCulloch]

But, let's get back to a question I asked earlier. How can the universe be unbounded and Euclidean?

There are two ways that a space can be unbounded and Euclidean.

1. It could be infinite.
2. It could be a form of a torus.

The Shape of Space Curriculum Materials

[otseng]

But, let's get back to a question I asked earlier. How can the universe be unbounded and Euclidean?

There are two ways that a space can be unbounded and Euclidean.

1. It could be infinite.
2. It could be a form of a torus.

I believe that we can rule out that our universe is infinite.

For a (finite) torus, how would that be Euclidean?

[QED]

Well, it's a bit difficult keeping in mind a non-metric expansion given that the amount of observed red-shift has the most distantly observable galaxies moving at around two-thirds the speed of light. Such relativistic velocities would increase the mass of the galaxies in ways we could hardly fail to spot.

How would it fit in with Olber's paradox?

An expanding metric will subtract light that can't keep up with the expansion. Don't forget - the universe needn't be infinite for a dark sky to be a problem, just sufficiently big.

I'm unfamiliar with the details of GR. Does it state that the universe is metrically expanding?

I expect you'll recall Einstein’s infamous problem with GR – it gave him indications that the universe was not static. He asked astronomers if things looked as though they were moving in relation to each other at great distances. At the time the answer was no which led him introduce a "cosmological constant" into GR to make it static. But the amount of redshift now seen in the most distant objects is too great to be accounted for by a non-expanding metric unless, of course, your theory about red-shift is the correct one. Perhaps I should be pressing you on that one.

But yes, GR is all about describing space-time with variable metrics. The Friedmann-Lemaître-Robertson-Walker (FLRW) metric is a solution of Einstein's equations that seems to give a good approximation to our universe.

otseng, I don't think I can carry on this debate if you're going to propose such huge amounts of magic.

God has to enter the equation at some point.

Maybe, maybe not. But anything God did with the early universe is written into the CMBR and unless we get too silly with the interpretations (i.e. we propose that God was deliberately covering his tracks) then we can rule out some eccentric notions.

From Goat's article about the universe being at least 156 Billion Light years wide...

Indeed, the WMAP data [on cosmic microwave background radiation] contain strong evidence that the very early universe underwent a period of accelerated expansion in which the distance been two points increased so quickly that light could not outrace the expansion so there was a true horizon -- in precise analogy with a black hole horizon. Indeed, the fluctuations we see in the CMB are thought to be generated by a process that is closely analogous to Hawking radiation from black holes.

We have an independent confirmation of the expanding metric predicted by GR and the red-shift of distant objects. Also, Einstein's radius of the Universe is of the order of 10E10 Light years which is the same kind of order as the figure given in Goat's link above.

But, let's get back to a question I asked earlier. How can the universe be unbounded and Euclidean?

By being Quasi-Euclidean.

Could you go into some more detail please?

Now we're going over old ground again -- by being too big a radius to measure.

[Goat]

But, let's get back to a question I asked earlier. How can the universe be unbounded and Euclidean?

There are two ways that a space can be unbounded and Euclidean.

1. It could be infinite.
2. It could be a form of a torus.

I believe that we can rule out that our universe is infinite.

For a (finite) torus, how would that be Euclidean?

Ok.

What is the evidence you have that rules out a finite but very very large universe?

[Beto]

I already said something about the universe being both bounded and unbounded in the quantum field, infinite and non-existent, and all possibilities in between. Has anyone given some thought about this? We can be arguing about something that ourselves choose to become reality, along with all the consciousnesses in the universe. That is, the sum of conscious observation in the universe causes the collapse of the universal wavefunction. In a way, I can consider this indication (however feeble) that we're not alone in the universe and that we're far from being special. If it was just us, we would decide how the universe arises from the quantum field in each "now". Than again, perhaps we do. Perhaps the universe is as large as Humanity can observe.