I’m sure this has happened to you.
You have a rubber band and you’ve stretched it, you keep stretching it until you decide it’s about to break and then you let go. It snaps back on itself, colliding before going back to its rest state.
Now imagine the rubber band is the universe, your fingers are the expanding force of the big bang, and the rubber bands want to spring back in on itself is gravity.
That is, in a nutshell, the Big Crunch.
It is one of a few theories on the ultimate end of the universe.
That’s right, not just Earth or our solar system. Not just the Milky Way. The whole universe.
The theory is based on the amount of matter in the universe. If there is a sufficient amount, then the gravitational force of all of it combined should be enough to slow and halt the expansion from the Big Bang, and then draw everything back together.
This would result in a gargantuan black hole of which would eventually dissipate into nothingness as the universe attempts to reach a thermodynamic equilibrium. Or something else could happen, the universe could bounce back, in another Big Bang.
This type of cyclical universe, one that is constantly stretching, collapsing, and then springing back was a popular idea up until the early 1990s when a discovery about the gravitational expansion of the universe changed everything.
See, everyone expected the rate of expansion to be slowing, even if it was increasing in some areas, if we looked far enough out we should see it slowing down.
But the opposite was discovered. The expansion of the universe is increasing, something is pushing everything else away from everything else (except for local clusters where gravity is strong enough to pull objects together, like our local galaxy group, don’t forget that the Milky Way and Andromeda will collide and combine in hundreds of million years).
This was a spanner in the works of physics, what was interacting with the matter of the universe? What could overcome the pull of gravity?
Well, we still don’t really know, but we did name the two most likely culprits; Dark Matter and Dark Energy.
Now as I said, we don’t know exactly what they are. We have guesses and I’ll delve deeper into those in another post, but for the purposes of this post, know that the universe is unlikely to spring back in on itself, it’s far more likely to drift apart.
To keep drifting apart, until our local cluster, our little neighbourhood is completely and utterly alone.
This is The Heat Death, and it’s an incredibly sad theory about the end of the universe.
With Dark Energy pushing everything apart, the Heat Death essentially postulates that everything will drift apart, so far apart that any interactions will be localised until all of the energy in the universe reaches an equilibrium, a state where nothing will change, nothing will move.
Eventually even black holes will dissipate and the universe will be a true abyss.
Nothing moving, no time, no life.
It sounds bleak, but it means that every embarrassing moment, every moment of your life and all lives will eventually be forgotten. Humanity, life everywhere, will cease.
Nothing will matter in the end, you might as well enjoy the time you have with the people you love.