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

If we ever meet aliens, the first thing we'll realize is that our expectations were deeply human,

and that aliens will be, in every meaningful sense, alien.

We often imagine aliens with strange faces, odd voices, or bizarre customs, but what truly

sets them apart won't be their appearance.

It will be how they think, what they value, and how they act.

And when it comes to behavior, there is good reason to believe that our guesses, shaped

by human experience and storytelling storytelling might fall drastically short.

But that doesn't mean we're completely in the dark.

While alien minds may be forged environments while they differ from our own,

some traits are so foundational to intelligence and survival

that we can expect to find them almost anywhere, life's head to claw its way up from the bottom.

A good place to start is with three sobering assumptions, drawn for the 1995 science fiction

novel The Killing Star, by Charles Pellegrino and George Zabrowski. While relatively obscure,

the book is noteworthy for its stark, realistic approach to interstellar contact, not just imagining what aliens

might look like, but how they would behave when encountering a new and potentially dangerous

civilization like our own. Rather than focusing on diplomacy or cultural exchange, the

Killing Star explores how an alien species might act if it applied pure strategic logic,

shaped by evolutionary pressure

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