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.

You might stick around and watch this whole episode, or you might decide not to, but be aware

that whatever you decide will impact the rest of your life and the entire future of the universe.

The butterfly effect is one of those concepts that's made it into popular usage, but

mostly without a proper discussion of what it really is and what its more impactful aspects

are.

Just as an example, which we'll get to later, it's what prevents us from being ultimately

predictable by computers or resurrecting the long dead, no matter how good

are computing gets.

It arguably ties in a lot to free will and alternate futures in a very fundamental way, though

again that is arguable and we'll get to that.

First though, what is it?

You'll have heard the expression that the beating of a butterfly's wings can cause a hurricane

on the other side of the planet, and that's where the name derives from, but it's not an ideal

one for illustrating the notion in my experience, as people tend to assume tiny little

perturbations ought to dampen out over time.

This comes up with a lot of discussion of time travel and the effects

of changing just one little thing. To the contrary, small perturbations tend to amplify,

and that butterfly example is from a time travel story, A Sound of Thunder, written by sci-fi

Titan, Ray Bradbury. If you've seen any science fiction about jumping back in time to see or hunt dinosaurs,

...