August 18, 2019

Two Ways the Universe Might End

“Dark energy is without a doubt the weirdest thing in the universe. Despite being present in every corner of the cosmos and dominating its evolution, dark energy is so far outside our best existing theories of physics that we’re still trying to figure out if it’s something in the universe or just a basic property of space itself.

And it would be nice to know a bit more about it, because if you look ahead on a long enough timescale, dark energy will almost certainly destroy the universe and everything in it.

Here’s an analogy for how dark energy works. Imagine you throw a baseball up in the air. The baseball and the Earth here are standing in for galaxies moving apart from each other in our expanding universe, and your throw is the expansion set off by the Big Bang.

Now, because both the baseball and the Earth have mass, gravity wants to pull them back together, no matter how hard you throw. Even if you have an inhumanly good arm and throw the ball fast enough to escape the Earth entirely, gravity will still slow the ball down at some level. Maybe the ball will fall back down; maybe it’ll coast through space forever. But what it won’t do is suddenly speed up and shoot off into the sky, defying gravity in the truest sense of the term.”

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