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 add free, plus hours of bonus content,

check out go.nebola.t.v.t.v. And use my code, Isaac Arthur.

Corin theory says that dinosaurs came to an end when a giant asteroid from space crashed

into Earth.

Wouldn't it be ironic then if we sent asteroids out from Earth into deep space to colonize

other worlds?

A few weeks back, we were discussing interstellar colonization strategies, and next week we'll

be discussing planetary terraforming strategies for when a colony ship arrives at a new world,

but one of the strategies we didn't cover last week was the possibility of using asteroids as

spaceships to travel to new systems.

Now, normally I don't think of this as a good option, for many reasons we're discussed

today, but the big one has usually been there simply a fuel hog compared to far less

massive ships made from hollowing out the asteroid and refining its oars to make a ship.

When I was writing interstellar colonization strategies though, I talked about how big or

was better when it came to colony ships, as they

have more cargo, redundancy, and endurance. Those are fuel hogs too, but you wouldn't

really care because the fuel in question, hydrogen or perhaps deuterium or helium-3, is so

incredibly abundant. So the idea of launching some asteroid massing a trillion tons into space, using trillions

of tons of fusion fuel, seems absurd at first, but the economics say otherwise.

As it turns out, the fuel part is the easy part.

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