Will the Big Rip basically be the Big Bang for the next universe?

[swampwiz]

I was reading that the Big Rip will cause the whole universe to go singular, which sounds to me like another Big Bang. I was reading up on the Big Rip at Wikipedia, where it says that the observable universe is getting smaller, which makes no sense since the universe is expanding.

 

[phinds]

I was reading that the Big Rip will cause the whole universe to go singular, which sounds to me like another Big Bang. I was reading up on the Big Rip at Wikipedia, where it says that the observable universe is getting smaller, which makes no sense since the universe is expanding.

The Big Rip is seen as an unlikely scenario under current conditions and there is no reason to believe conditions will change.

The observable universe is getting slightly larger with time.

 

[PeterDonis]

I was reading that the Big Rip will cause the whole universe to go singular, which sounds to me like another Big Bang.

The Big Rip's "end" of this universe does not correspond to the Big Bang of another universe; that's not what the Big Rip model says.

I was reading up on the Big Rip at Wikipedia, where it says that the observable universe is getting smaller, which makes no sense since the universe is expanding.

Yes, it does make sense (in the sense of the Big Rip model being consistent--which is not the same as it actually describing our universe; as @phinds notes, our best evidence is that it doesn't). The size of the observable universe is determined by how far away an object can be and still send light signals towards us that will eventually reach us. This is determined by two effects that work against each other: the light signals move towards us, but the expansion of the universe carries the light signals away from us. If the universe's expansion is accelerating and the rate of acceleration is itself increasing (which is what the Big Rip model says--as opposed to standard dark energy, where the rate of acceleration is, at most, constant--it never increases), then the second effect outweighs the first and the distance to the edge of the observable universe decreases with time.

 

[Bandersnatch]

The size of the observable universe is determined by how far away an object can be and still send light signals towards us that will eventually reach us.

I don't think that's right. The observable universe should be the particle horizon. At least that's what it commonly signifies in the LCDM context. What you're describing is the event horizon (same as the article).

 

[PeterDonis]

The observable universe should be the particle horizon. At least that's what is commonly referred to in the LCDM context. What you're describing is the event horizon

Looking at the Wikipedia article [1], it seems like they're using the following definition of "observable universe":

"...this implies that the size of the observable universe is continually shrinking; the distance to the edge of the observable universe which is moving away at the speed of light from any point moves ever closer"

This seems to be describing the event horizon, so that's what I assumed the OP was referring to. For clarity, the article should probably have used the term "event horizon" instead.

[1] https://en.wikipedia.org/wiki/Big_Rip

 

[Bandersnatch]

Come to think of it, proper distance to the particle horizon in the Big Rip scenario should grow to infinity, right?
What does it do in terms of comoving distance, though?

 

[kimbyd]

The Big Rip is seen as an unlikely scenario under current conditions and there is no reason to believe conditions will change.

The observable universe is getting slightly larger with time.

More precisely, there are very strong theoretical reasons to believe that a "big rip" scenario is fundamentally impossible. There's no way to rule it out experimentally, but the possibility of a "big rip" would make it really hard for physics to make sense at all.