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.nebler.tv slash Isaac Arthur and use my code, Isaac Arthur.

Whether Jammin 4 or Endor from Star Wars or Pandora from Avatar, science fiction

has shown us many planets with life that were actually moons.

But as science begins showing us our first real exo moons, we may discover that some already

have life on them or may make good candidates for future

settlement.

Earth has one of the largest moons in the solar system and the only moon of significance

around a rocky planet. Indeed, our moon is five or six times more massive than Pluto,

while Jupiter and Saturn's largest moons each have nearly half the mass of Mercury.

Now the reality is that our solar system is probably not a very representative example of

what there is out in the universe. Indeed,

Earth's moon has long been suspected of being particularly anomalous and possibly a critical

factor in why Earth has life. But with the exception of our moon around our planet,

which may or may not be bizarre in galactic terms, we have every reason to think that a planet

as big as Jupiter could

have moons which are fully as big as Earth. We have even found thousands of planets bigger

than Jupiter, most of them warmer and closer to their star than Jupiter. Now that's probably

not the norm either, any more than 7 feet or 2 meter tall humans would be, but they sure are easy

...