Empty Space... forever?

[pallidin]

I suppose this has been asked before, but I am somewhat new to this forum.

Beyond our known physical universe, there is a region of "empty space" Fine.

And if I were on the "edge" of our observable physical universe, and I travelled faster than C away from it, I suppose I would eventually wind up in a region of "empty space" devoid of even photonic emmissions from were I left. Truly "empty"


Does this "empty space" go on forever?

[Jimmy]

Honestly, no one really knows what lies beyond the observable universe. If we did, then it wouldn't be unobservable. Whether it goes on forever or is limited in some way isn't known. I wouldn't say that it is meaningless to speak of such things. They can certainly lead to new theories and perhaps experimental evidence but in the absence of scientific observation it is purely speculation. Educated speculation in some cases but speculation nonetheless.

[MathematicalPhysicist]

Originally posted by Jimmy
Honestly, no one really knows what lies beyond the observable universe.
beyond the observed universe there's the unobserved part of the universe, a simple example is when america was first discovered they thought (in european world) all the world is europe, africa and asia after the discoverers they found that world is consisted with what that was observed.

[Jimmy]

Originally posted by loop quantum gravity
beyond the observed universe there's the unobserved part of the universe.

That's why I said no one knows what lies beyond the observable universe. I'm not sure what you are driving at.

[MathematicalPhysicist]

im saying that there cannot be something outside the universe because the universe is everything and what hasnt been observed yet would be also part of the universe (unless you believe in multiverse).

[Eh]

Originally posted by pallidin
Beyond our known physical universe, there is a region of "empty space" Fine.
No. Who told you that?

[russ_watters]

Originally posted by Eh
No. Who told you that? To expand - there really can't be a big void somewhere if the Big Bang model is anywhere close to correct. The universe has to be pretty homogenious on the very large scale.

Also, some people get the idea of the Big Bang happening and the universe expanding into some big void, but again, thats contrary to the Big Bang theory and contrary to the definition of "universe" which would include any voids (like a balloon expanding inside a bigger balloon).

[UltraPi1]

To expand - there really can't be a big void somewhere if the Big Bang model is anywhere close to correct. That would be a given. I could make a model that expands into a void that would fit observation. Doesn't make it correct, but it does make it possible. I leave this on the table of inquiry for this reason.

Also, some people get the idea of the Big Bang happening and the universe expanding into some big void, but again, thats contrary to the Big Bang theory and contrary to the definition of "universe" which would include any voids (like a balloon expanding inside a bigger balloon).Why would the universe have to include any voids. Why not - The universe excludes all voids?

[russ_watters]

Originally posted by UltraPi1
I could make a model that expands into a void that would fit observation. Doesn't make it correct, but it does make it possible. I leave this on the table of inquiry for this reason. Not really. That doesn't fit the definition of "universe."

And I'm not convinced that a model with a big void into which the matter in the universe is expanding would fit with observation anyway. We should see an edge if that were the case.

[Eh]

Also, that "space" is dynamic and either expanding or contracting is a prediction of general relativity. In order for the visible universe to be expanding into a static void, one must either conclude that GR is not an accurate description of "space".

[UltraPi1]

Originally posted by russ_watters
And I'm not convinced that a model with a big void into which the matter in the universe is expanding would fit with observation anyway.

I am.

[UltraPi1]

Originally posted by Eh
Also, that "space" is dynamic and either expanding or contracting is a prediction of general relativity. In order for the visible universe to be expanding into a static void, one must either conclude that GR is not an accurate description of "space".

Not so much an expansion into the void, but more a conversion of the void into objective reality. Not so much a Big Bang, but a constant progression. At one instant there could be X number of entities that make up the totality of the universe. At the next instant there would be X number plus N. The universe would be a growing boy in this model (in number and volume).

[Eh]

That would be along the lines of saying GR is not an accurate description of "space", by assuming some kind of independent spatial reality exists. We have no reason to think such a "void" exists at all, and so it's much simpler to suggest the expanding universe is the expansion of all the space (ie. metric properties of the field) there is.

[UltraPi1]

Originally posted by Eh
That would be along the lines of saying GR is not an accurate description of "space"Perhaps
We have no reason to think such a "void" exists at all. Well - If it existed there would be no void. You can't observe the void. Observation of existence is the proof that the void does not exist, but isn't that what a void is (Non-Existence)? At least the void we are talking about?

I suppose you are correct when saying there is no void, but for all the wrong reasons.

[Eh]

No, I'm talking about the "void" that is often used to describe completely empty space. A common mistake is assuming the big bang describes a universe expanding into such a void. Not only is that incorrect, but there is no reason to think such a void exists at all. Only the dynamic space of GR is needed to explain the expanding universe, with no embedding empty space.

[russ_watters]

Originally posted by UltraPi1
I am. How would it account for the relative uniformity of the cosmological background radiation?but isn't that what a void is (Non-Existence)? No. Thats not what a void is. A void is a space that exists and is empty. Space itself has measurable properties.No, I'm talking about the "void" that is often used to describe completely empty space. A common mistake is assuming the big bang describes a universe expanding into such a void. Not only is that incorrect, but there is no reason to think such a void exists at all. To expand - since such a void would be unobservable and have no effect on the observable universe, theorizing about its existence adds nothing to any theory - so there isn't any point to assuming it exists.

[John]

It makes more sense that the Big Bang is expanding into nothing. But nothing does not contain the concept of space. As the Big Bang expands, it creates new space.

This leaves open an idea of two expansions. One is an expansion of space itself; the other is the galaxies expanding away from each other within that space. Some of the anomalies, like galaxies that appear to be accelerating, and galaxies that appear to be expanding at close to the speed of light can be answered by considering two types of expansion: the expansion of space itself, and the expansion of galaxies away from each other in that space.

When you consider the idea that space itself is expanding, not into a big void but against something that does not contain the concept of space, you are able to come up with a good physical definition of what strings are, which agrees with the mathematical definition.

[UltraPi1]

It makes more sense that the Big Bang is expanding into nothing. But nothing does not contain the concept of space. As the Big Bang expands, it creates new space.

This leaves open an idea of two expansions. One is an expansion of space itself; the other is the galaxies expanding away from each other within that space. Some of the anomalies, like galaxies that appear to be accelerating, and galaxies that appear to be expanding at close to the speed of light can be answered by considering two types of expansion: the expansion of space itself, and the expansion of galaxies away from each other in that space. Thats somewhat the model I would describe as a possibility. Not that it has to be true, but that it is possible. The model requires that the Earth is darn close to the center of the universe, which is hard for many to swallow. The model would explain why distant supernovae are seen to be farther away than expected, without the need to propose an unfounded dark energy.