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.

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plus hours of bonus content,

check out go.nebola.tv slash Isaac Arthur

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Science fiction is popularized asteroid mining and cities in the sky, but could the future of mining

be in cloud cities hanging far above distant worlds?

As we get ready to finally start returning to the moon and contemplating mining it to

get to the resources we need to settle the rest of the solar system, it is a good reminder that

very little of the actual resources in our solar system, and probably most others, is

inconveniently minable low-gravity airless moons and minor planets. Off of Earth, in our

own inner solar system, Venus makes up more mass

than everything else they are combined, Mercury, Mars, all moon, Mars-zone two little tiny moons,

and the millions of asteroids in the belt, yet its surface is covered with a terribly thick

atmosphere, whose contents are more like something coming out of a rocket jet than what

people inside that rocket could live and breathe. Beyond the belt, we have the gas giant Jupiter,

which outmasses every other planet in the solar system combined, and most of that remaining

mass is in its smaller sibling Saturn, which itself has the largest moon in the solar system,

Titan, with a thicker atmosphere than Earth's. Most of the remaining largest moon in the solar system, Titan, with a thicker atmosphere

...