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

we're asking 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. This episode is sponsored by Audible.

A human floating around outside Earth's gravity is very much a fish out of water,

but our distant ancestors will literally fish out of water, and they adapted to living on land pretty well.

Maybe some of our descendants will adapt just as well to life without

gravity.

Last February, we did a well-received episode on low-gravity planets and the probable effects

on human physiology and evolution. We also talked about how close to the truth science fiction has come in its portrayals,

so taking that concept all the way to zero-g or near-zero-g seemed like an appropriate

follow-up.

Of course, we'll be talking mostly about man-made habitats in this episode because to

hoard an atmosphere in place requires either significant gravity or an

airtight enclosure, but we will talk about some other possibilities, and while this won't

be a very heavy episode, you might still want to get a sealed drink and a non-crumbling

snack and seepelt yourself in for a while.

The terms near zero-g, microg, and microgravity are all interchangeable terms for the same thing.

What astronauts experience in space used to popular be called 0G, but that was a popular

misnomer, because there's a solar system and a universe around us that makes it impossible

to get away from all gravity.

If you're in a circular orbit around the Earth,

...