Name: 人類還能逃過滅絕的命運多久？ (How Long Can Humans Outrun Extinction?)
Uploaded: 2021-01-14T10:30:30.000Z
Duration: 12 min 44 s
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Modern humans evolved a couple hundred thousand years ago.

And between ice ages, volcanoes, climate change, earthquakes, droughts, floods,

and Reddit being down sometimes, we've seen some stuff.

But on cosmic timescales, two or three hundred thousand years is just a drop in the bucket.

The longer we're around, the more likely we are to witness something truly Earth-shattering,

we'll have to face things like Earth melting as it's engulfed by the Sun.

One way or the other, we're going to have to leave home if we want to survive.

how long could we actually outrun extinction before the universe became uninhabitable to us?

It's such a big question that we've made a special, extra-long episode about it.

Because the answer is a surprisingly long time.

Now, to be clear, we probably won't have to leave home any time soon.

So there's plenty of time to get our spaceships ready.

Like, we might hear a lot about climate change these days,

but no matter how destructive and disruptive it is,

researchers don't think that it will threaten our entire species.

There are plenty of variables to consider, but overall,

the odds are pretty good that  we'll get through it one way or another.

The same goes for one of the Internet's favorite doomsday scenarios: a supervolcano.

Even though that would be rough, it probably couldn't take us all out;

there are just too many people spread throughout the world.

Because even if we dodge a huge asteroid impact or the takeover of artificial intelligence,

our planet will eventually stop being habitable, thanks to the Sun.

And generally, that will make Earth warmer over the next few hundred million years,

For example, rocks tend to erode more easily at higher temperatures, so in the future,

more new, rocky surfaces will be exposed to the atmosphere than today.

Exposed rock can react with carbon dioxide, so the more exposed rock there is,

the less CO2 will be left in the atmosphere.

That might seem like a good thing, given how worried we are today about climate change.

But remember that plants need CO2 like we need oxygen.

And according to some estimates, in about 800 million years,

there actually won't be enough of the gas left in the atmosphere for photosynthesis.

If those estimates are right, that would be the end of all life on Earth bigger than a bacterium,

and they'd go extinct about a billion increasingly warm years later.

Future people might prevent this by building something to block the extra sunlight,

or they could use repeated asteroid flybys to gravitationally inch Earth's orbit away from the Sun.

But they might also decide that Earth just isn't worth it anymore, and could leave.

The most obvious option would be to go to Mars, since it's closest.

We'd still have to give the planet an atmosphere and a liveable temperature,

but with a dash of terraforming, we'd be fine, although Mars still won't be a permanent solution.

Five or six billion years from now, the Sun will finally start running out of hydrogen fuel in its core.

After that, it will fuse helium, and it will start growing.

First, it will engulf Mercury, and then Venus.

And 7.6 billion years from now, its outer layers will probably pass through Earth's orbit, too,

likely destroying almost everything we've ever built.

The people on Mars wouldn't be much better off, either.

Mars will never fall into the Sun, but it will become too hot to be comfortable for life.

solar radiation will rip apart any Martian atmosphere our descendants try to create.

Because while the Sun balloons, the outer solar system may have it pretty good.

Jupiter's moon Europa and Saturn's moon Enceladus are both ice-covered today,

but they'll heat up as the Sun expands and will eventually become water worlds.

In fact, we might be on the move after as little as a hundred thousand years, once more,

Around that time, the Sun will have expanded so much that its outer layers will finally escape into space,

leaving behind a tiny white dwarf star surrounded by a big, cloudy nebula.

Comparatively speaking, white dwarfs don't emanate much energy,

so the newly-minted one at the center of the solar system will leave the remaining planets and moons

And without a good heat source, there's no usable energy.

So any civilization that's still around will have to move on.

By this point, though, we'll probably just fold our Dyson spheres into overhead compartments

and head off to colonize some other planetary system.

Because, hey, if we haven't figured out interstellar travel in seven billion years,

But let's assume we figure it out, and don't spend the next forever binging Netflix.

Today, the closest star is Proxima Centauri, which is about four light-years away.

It's a red dwarf star, which means it will likely outlive the Sun,

and it already has a potentially-habitable planet.

But since red dwarfs also emit some seriously dangerous flares every now and then,

Besides, current estimates suggest that there are billions of planets out there that could support water,

there's really no way of knowing where Proxima Centauri will be that far in the future.

Stellar orbits in the Milky Way naturally get rearranged over billions of years,

so Proxima Centauri might not be our closest neighbor anymore.

Also, and maybe more importantly, the Milky Way won't exactly be a thing in seven billion years.

It will probably collide with the Andromeda Galaxy

even before the Sun expands into the inner solar system.

Or, at the very least, they'll pass close enough to each other to cause some chaos.

Thankfully, there's almost no chance of stars actually smashing into each other,

But the collision will make long-term wayfinding tricky.

Stars will be thrown all over the place while the new galaxy, known as Milkomeda,

Yes, that is the real proposed nickname, and no, I don't support it.

So maybe the next star we'll go to hasn't been discovered yet, or born.

And, even if we do have the technology to leave the solar system,