The Universe Revealed

What is the final fate of the universe?

What is the final fate of the universe?

So far only cosmologists have suggested four final fates for the universe: Big Crunch; Big Freeze; Big Rip; Quantum Phase Transition.

Up until recently, it was thought that the universe would reach a steady state condition in which expansion would be countered by gravity. This would be a universe in a very fine balance. Unfortunately, the expansion never stopped so this won't happen. When astronomers found the existence of dark matter, it was thought that since dark matter is five times more plentiful than normal matter (stuff we can see) it meant that the universe would cease expansion and begin collapsing because of gravity. This would suggest that the universe would eventually compress back to a primordial speck (The Big Crunch) and then expand again into a new Big Bang. In other words the universe is cyclical.

The above idea was crushed when astronomers in the 1990's determined the expansion rate of the universe by measuring Type 1a supernovae in distant galaxies (billions of light years away). What they found changed everything. The universe is not only still expanding, it's accelerating this expansion. This means that with time (trillions of years) the galaxies will move far enough away to become invisible and eventually space will expand enough to cause even atoms to rip apart. This is the dreaded Big Rip concept.

However, current data shows that this is not going to be the case. Careful calculations have shown that the universe will expand to the point in which stars and galaxies will no longer be visible but there will not be a Big Rip effect. Stars will eventually burn out and die. The large blue stars will go first, creating black holes. Stars like our sun will become red giants after burning all of their hydrogen. These stars will blast off their outer shells and end up as a white dwarf that over a trillion years will become a dark dwarf, a carbon hulk, maybe even a large diamond. The only thing left is red dwarf stars. These will burn out in a hundred trillion years. What will be left is a large number of massive black holes left over from the galaxies. These will combine and suck in anything left over. Eventually in hundreds of trillions of years even these black holes will evaporate, and that will be it. Only photons will exist and they will eventually decay. It'll be lights out.

What's causing this rapid expansion? It's dark energy, which is over seventy percent of what's in the universe but is a big unknown. Dark energy became prominent about half the life of the universe ago (about 7 billion years). Some cosmologists believe that this dark energy was the result of something that happened right after the Big Bang. This something is the really scary concept that a quantum phase transition in the vacuum of space will cause the universe to completely change into something else at the speed of light. This transition could happen at anytime. The original universe that existed right after the Big Bang is not the universe that we're in. It had physical laws that were much different than what we have in our universe. A quantum phase transition changed that universe into our universe. So, if it happened once, it could happen again.
Actually, it doesn't matter what happens. We can't do anything about it and in most cases it'll be trillions of years from now.

Thanks for reading.