Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asked at the reason alien civilizations might be rare is because most aliens are huge.

To hear it and every episode early and ad-free, plus hours of bonus content,

check out go.nebola.tv slash Isaac Arthur and use my code, Isaac Arthur.

We often dream of escaping Earth, but maybe space colonization is really about saving it.

If we reach for the stars, we may just find the tools to fix the ground beneath our feet.

What Space isn't?

We often hear people suggest that we need to colonize space, a kind of cosmic

escape plan, that when things get too bad here on Earth, be it war, climate change, overpopulation,

or even rogue gay eyes, who have a backup waiting for us somewhere around the stars.

But as appealing as that idea is, it's also deeply flawed.

The reality is that space is not a lifeboat, it's not a get-out-of-the-apocalypse-free card.

Earth is still the safest place we know of by a wide margin. Most natural disasters,

asteroid impacts, supervolcanoes, even pandemics, are still more survivable here than anywhere

else. And when it comes to intelligent threats, like hostile AIs or rival civilizations,

off-world colonies are actually easier to find and harder to defend. After all, there's no stealth

in space. Likewise, space is not a pre-made paradise. There's no garden planet out there waiting

for us to move in. Every off-earth settlement, whether it's a base on Mars or a spring habitat

in orbit, will require immense amounts of effort, resources, and technology just to survive,

let alone thrive. And here's the kicker, that same effort could do even more good

right here on Earth. You could nuke Earth until it glowed in the dark, and it would still be

easier to fix than to tear for Mars, even before we consider that Earth already has a lot of manpower

...