Adam Brown

The ultimate fate is a really long time in the future, so you probably shouldn't be that confident about the answer to that question.

In fact, our idea of the answer to what the ultimate fate is has changed a lot in the last 100 years.

About 100 years ago, we thought that the universe was just...

static, wasn't growing or shrinking, was just sitting there statically.

And then in the late 20s, Hubble and friends looked up at massive telescopes in the sky and noticed that distant galaxies were moving away from us and the universe is expanding.

So that's like big discovery number one.

There was then a learned debate for many years about

You know, the universe is expanding, but is it expanding sufficiently slowly that it'll then re-collapse in a big crunch, like a time reverse of the Big Bang, and that'll be super bad for us?

Or is it going to keep expanding forever, but just sort of ever more slowly as, you know, gravity pulls it back?

but it's fast enough that it keeps expanding.

And there was a big debate around this question, and it turns out the answer to that question is neither.

Neither of them is correct.

In possibly the worst day in human history, sometime in the 1990s, we discovered that, in fact, not only is the universe expanding, it's expanding faster and faster and faster.

It's what we call dark energy, or the cosmological constant is this...

just a word for uncertainty, is making the universe expand at an ever faster rate, accelerated expansion as the universe grows.

So that's a radical change in our...

Understanding of the fate of the universe.

And if true, it's super duper bad news.

It's really bad news because the accelerated expansion of the universe is dragging away from us lots of distant galaxies.

And we really want to use those galaxies.