Hi, I find the big rip idea a bit short-sighted, it's a self-centred view of the universe. It assumes ours is the only universe and there's an infinite empty space surrounding it that it can indefinitely expand into. I've written my own theory called 'Steady State of The Infinite' in a book of the same title on Amazon.
I hope there's something here to answer your question. By starting off with some simple reasoning, I've built a more complete picture. (1) You can always point ahead and keep going, including beyond our universe – therefore space is infinite. In my book, I call all of space and everything in it 'The Infinite'. (2) Matter/energy can neither be created nor destroyed. That means there has always been something – and that also means before the big bang!
So, if you now see things from the perspective of 'The Infinite' it all looks a bit simpler. For example, our universe can now be treated as an object in 'The Infinite' rather than being all of space. To proceed from here I quote from page 7 in my book;
“Now, if our universe came from a big bang and is expanding, it must have a centre and boundary or edge, if it has an age then it has a finite size. That means it's an object – objects exist in a space, they are not the creation of space as most theories suggest. Consequently, it can't be homogeneous or isotropic and so violates the much cherished 'cosmological principle', which assumes the universe is even and the same in all directions, and from any viewpoint, and has no centre. So, my version of the universe might look different from the centre than from the edge.”
And then from pages 8 and 9;
“If space is infinite it would be too bizarre to think our universe is the only matter in this infinite space.
If it is the only universe and it came out of a big bang, then the big bang would have been the beginning of time. The trouble with this idea is that, as argued in chapter
1, 'there has always been something' and that 'you can't have something from nothing' would imply that the initial contents of the big bang had always been there waiting indefinitely and just 13.8 billion years ago decided to explode into our universe.
What would have caused it to explode after waiting an infinite amount of time? Bizarre. One way around this would be to suggest that the universe collapses and then goes bang again in an endless cycle. Why would there be just one universe doing this with nothing in the rest of 'the infinite'? Again, too bizarre to believe.
Therefore, I think it's reasonable to assume
all of 'the infinite' contains matter and other universes. As there are no boundaries, and if it has always been there, it should by now be
evenly distributed. If not, there would still be a flow of matter across 'the infinite', also bizarre.”
The endless cycle I mentioned is a mainstream theory called the 'cyclic universe'. However in my book, I've suggested why it doesn't make sense to me, so I created my own proposition to explain our universe's origin and fate. When I add in some more simple reasoning about 'information and order', 'cause and effect' and 'entropy', a more complete and mind-blowing picture emerges.
Referring to your question, because 'The Infinite' is full of other matter our expanding universe will meet up with it and stop expanding! There are several possibilities from here; (1) the cyclic universe mentioned above. (2) Our universe merges with the other matter, and, somehow a dense enough patch of matter forms then collapses in on itself and rebounds with another big bang to make a new universe. Bear in mind that on a smaller scale, in a nebula, matter is all the time collapsing in on itself to form new stars. (3) My main theory in my book, which has similarities to (2) but is more detailed and specific, with a surprising twist.
Best wishes, David
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