I'll have another go at this. I forgot to mention a few other details. Before the universe ends, our solar system will (unless we discover some way to keep the sun in check) end in 4-5 billion years. The universe could be infinite as I said earlier or it could end tomorrow, but by all means it's looking like it might show us what is going to happen in trillions or even quadrillions of years.
As for the theories which started this thread:
Philosophically and with an amateur interest physics and astronomy I would examine each idea.
- The Big Freeze/ Heat Death theory - which means that everything either goes to absolute zero or continues to heat up until matter no longer exists in the state that we know it, but have we established an upper limit on heat AND have we shown that other types of particles could not exist at a higher temperature than say at the heart of the sun?
- The Big Rip - Sounds bogus. Sounds like the theory of what happens when we die. I believe (opinion) that time and the other dimensions, height, width, length and the others known as Calabi-Yau spaces are all part of the universe and so to have the universe with just time is not to have the universe but something that is not named or simply time.
- The Big Crunch - which to me sounds a lot like my infinite universe theory. One would think that if the universe crunched back up that perhaps it would re-explode and start all over again, a sort of Hindu Reincarnation idea.
- The Multiverse theory - which is very much along the lines of Erich Von Daniken's (sp) idea for Chariots of the Gods, in which he postulates that God didn't create man, but rather intelligent aliens. This argument has the same problem of God having created man in that if something created something else then what created the creator? So the universe is a conglomerate of smaller universes, but this is not "The Universe" then by definition but again something else which has no name or simply multiverse.
- The False Vacuum - again infinite universe just changing itself to something new.
- And finally the Multiple Level theory, again infinite universe theory just by a different mechanism.