Can a "Dead Universe" be Revived?

[geordief]

does this theory depend on the creation of matter being some kind of singular event?
I mean , supposing all the matter in the universe was to escape the attraction of gravity and that entopy increased neverendingly and without return, how is that to say that this region would not interract with another are that was not affected by this state (it would have come into being separately ) and so would breathe new life into said "dead universe"
I am not saying this should be the case but how can it be ruled out and so what firm basis could there possibly be for a total big whimper?

 

[Chalnoth]

does this theory depend on the creation of matter being some kind of singular event?
I mean , supposing all the matter in the universe was to escape the attraction of gravity and that entopy increased neverendingly and without return, how is that to say that this region would not interract with another are that was not affected by this state (it would have come into being separately ) and so would breathe new life into said "dead universe"
I am not saying this should be the case but how can it be ruled out and so what firm basis could there possibly be for a total big whimper?

Are you talking about the heat death of the universe? Because there's really no way around that. New universes likely will be born, and likely are being born all the time, but ours will eventually die. And it is extraordinarily unlikely that we will be able to access any of these new universes.

 

[geordief]

Are you talking about the heat death of the universe? Because there's really no way around that. New universes likely will be born, and likely are being born all the time, but ours will eventually die. And it is extraordinarily unlikely that we will be able to access any of these new universes.

thanks for your answer.
I realize now, just by the titles of the various other posts in this forum , that mine is a rudimentary question.
To answer your question, I was talking about (what I thought was the import of this very well known theory) the heat death of absolutely everything.
From the way you put it ,this was never on the table and it was only ever a matter of localised heat deaths .
Perhaps I was overrecting by imagining that the talk was of a really final end to space/time in every conceivable sense of the term.

And it is extraordinarily unlikely that we will be able to access any of these new universes.

I wasn't imagining any possible attempt to contact external sources of heat at the stage where our own universe might be slipping into a heat death.
I was just saying that in fixed terms this heat death couldn't occur because there would always (probably) be an exterrnal heat source that would show up in the vicinity (or even internally) and start the ball rolling again.

 

[Chalnoth]

I was just saying that in fixed terms this heat death couldn't occur because there would always (probably) be an exterrnal heat source that would show up in the vicinity (or even internally) and start the ball rolling again.

Well, no, it doesn't work that way. Other regions of space-time will never have access to our region, and will never be able to heat it up. The only reasonable mechanisms we have today for producing new, low-entropy regions involve a teeny tiny fluctuation that just happens to have the right properties that it undergoes a tremendous rate of expansion, becoming a large universe. Such fluctuations look, to the outside, like microscopic black holes that appear out of the vacuum and then rapidly decay. The large universe they generate can never interact with the parent that spawned it.

 

[Ich]

Such fluctuations look, to the outside, like microscopic black holes that appear out of the vacuum and then rapidly decay.

Can you point me to any papers, websites, or whatever describing this? It sounds interesting, but implausible.

 

[Chalnoth]

Can you point me to any papers, websites, or whatever describing this? It sounds interesting, but implausible.

Well, I'm not familiar with any papers related to the subject, but it's a relatively easy result you can derive yourself. Just ask the question, "What is the Schwarzschild radius for the mass comprising one Hubble volume?" You end up with a radius that is larger than the Hubble radius (about four times larger, actually). So as long as the curvature isn't too strongly negative, any new universe that is finite in extent and starts within an existing space-time will look to the outside like a black hole.

We expect it to be a microscopic black hole because we expect the amplitude for the generation of anything but microscopic new universes to be vanishingly small. And we expect it to decay rapidly in the parent universe because the laws of physics must work in all reference frames, so the growth of the new universe cannot be observed in the old one.

 

[Ich]

Hmm...

sorry, no, I won't follow your line of thought right now.
I don't have a counter-proof, but I can't follow your derivation. This may be entirely my fault, but I don't think I understand the underlying physics to a degree that enables me to say yes or no.
As an example: If the universe were finite and open, but inside its Schwarzschild radius, we'd expect that its components reach arbitrarily high r coordinate in finite time. At the same time, we'd expect static outside observers to have a finite r coordinate. Which means that the inside universe will reach every point of the outside universe in finite time, contrary to a BH solution.

As I said, this is something that bugs me, and I still don't understand it. Maybe I'll come back to it later.

 

[geordief]

Well, no, it doesn't work that way. Other regions of space-time will never have access to our region, and will never be able to heat it up. QUOTE]
could I ask you where I might find this particular topic discussed? (Does Hawkins do it?)

Could it be considered a contradiction in terms for us to have any theory at all about a region in space or space/time with which any interraction at all is forbidden? Or is that just jesuistry (on my part of course-not quite sure what that word actually means but I mean showing something with logic when it really isn't true)

 

[Chalnoth]

Hmm...

sorry, no, I won't follow your line of thought right now.
I don't have a counter-proof, but I can't follow your derivation. This may be entirely my fault, but I don't think I understand the underlying physics to a degree that enables me to say yes or no.
As an example: If the universe were finite and open, but inside its Schwarzschild radius, we'd expect that its components reach arbitrarily high r coordinate in finite time. At the same time, we'd expect static outside observers to have a finite r coordinate. Which means that the inside universe will reach every point of the outside universe in finite time, contrary to a BH solution.

As I said, this is something that bugs me, and I still don't understand it. Maybe I'll come back to it later.

My understanding of this isn't that great, but from what I gather, the realistic models for this sort of process force the spatial curvature of the new universe to be closed anyway. This makes sense from an energy standpoint as well, as closed universes have zero total energy.