If anyone is depressed in the bleak view that some astronomy course textbooks show as the final state of the universe in 10^100 years [that is everything will be ripped apart and peter out like the tail sparks of a firework that has burst], keep in mind that there are other theories that do not require such a slow spluttering dissolution. These alternate theories, at least to me, have been presented with more voracity than those within our textbook.
Frank Tipler (one of my favorite astrophysicist if you haven’t guessed by now) lays out proofs in his book The Physics of Christianity that while the universe appears flat, laws of physics like the Bekenstein bound principle and Unitarity require it to be closed and spatially compact (although so large that to any observer inside of the universe it would appear flat).
Our course book seems to reference this spherical concept on page 699 with the picture of the ant on the balloon, showing that to an ant, a huge balloon would appear to be flat, although the book still continues to assure us that the universe is flat. I believe it’s probably likely (?) that the book is leaving the state of the universe as flat by means of making our ‘introduction to astronomy’ just that: an introduction. The conclusion of a closed spatially compact universe becomes necessary for multiple reasons as Tipler documents in his book, but I won’t go into here.
While it is stated in both our course textbook and Tipler’s book, that the universe will continue to expand at an increasing rate based on current data, this continuous expansion, according to TIpler, won’t occur forever.
Tipler goes into more detail of the expansion of the universe by discussing the Higgs field which is believed to be a negative vacuum that would cause the universe to collapse in on itself excepting that it is not in its true vacuum state (the cosmological constant causing the expansion is only partially cancelled by the Higgs field).
While under normal circumstances, as our course book discusses, the gravitational pull of the universe (and all things therein) will decrease as astronomical objects are pulled further and further away from each other – that is if the universe continues to expand forever; Tipler believes that new forms of energy consumption will be developed (through baryon annihilation) and they will cause the Higgs to reach it’s state of absolute vacuum, and then cause the universe to collapse in on itself.
This ‘big crunch’ is not the end though; Tipler goes on to describe the ‘Omega Point’ and what it necessarily infers – although I’ll leave that information for your own discovery if you choose to read his book.
In the mean time, I’ll state the obvious by saying that I’m not a physicist or an astronomer by any means; so I don’t claim to have represented this information very accurately; but – I wanted to put this information in the forums just to say that if you are interested in this topic; Tipler’s book is a great resource to discuss some alternate views.