The ultimate fate of our universe is something we have been pondering for a long time. The answer still continues to elude us, but there are several possible outcomes. If the amount of ‘stuff’ (matter, energy, dark matter and any other materials we find) in the universe is too little, the universe will expand forever and as it does the energy inside will become more and more spread out until the ‘big freeze’. Everything stops, like an engine with no fuel. Particles can’t interact and reactions don’t take place as the energy required to do any of this is too thinly spread.
With just the right amount of ‘stuff’, the universe will expand until it reaches a balance point where all the matter is more spread out but expansion stops.
With too much ‘stuff’, the expansion rate is slowed to the point where gravity dominates and the universe collapses. This is sometimes called the ‘Big Crunch’, like a reverse Big Bang. With everything being concentrated back into the point of origin, things would be pretty bleak for us!
Overall these tales of doom can be worrying, but we don’t know which fate will be ours. In fact, it could be the case that we go down a different path all together. Hopefully we’ll figure it out.
Answered by Josh Barker, Education Team Presenter for the National Space Centre