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.

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When we say our future in the solar system is to become an interplanetary species,

folks tend to think of a handful of planets, but as

we see today, our destiny awaits us on a million smaller worlds too.

So today we are continuing our look at becoming an interplanetary species.

This is part five of our series loosely following

the National Space Society's Roadmap to Space Settlement as our guide, and I've linked

the complete document in the episode description. Last time we looked at establishing our

first colony on another planet, Mars, and today we'll cover the roadmast milestones 26, 27, and 28, settling asteroids

and moons, as well as orbital habitats of our own creation.

Now back in Part 2, we looked at colonizing the orbital volume around Earth, and we talked

about the importance of the Moon as a source of raw materials.

An important point we made there was that because the Moon's lower gravity, only a sixth of Earth's, and the fuel costs of lithium materials out of Earth materials. An important point we made there was that because the moon's lower

gravity, only a sixth of Earth's, and the fuel cost of lifting materials out of a gravity

well, it's actually much cheaper to move raw materials from the Moon's surface to the

construction yards in low Earth orbit than it would be to lift them up from Earth's surface

...