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

What if the key to colonizing the cosmos wasn't reshaping planets, but enclosing them?

Instead of waiting centuries for a thin, Martian atmosphere to form, what if we could create

an earth-like world overnight by sealing entire landscapes beneath an artificial sky, transforming dead rock

into thriving ecosystems, one dome at a time.

Imagine standing on Mars, breathing fresh air under an endless vaulted sky, not because we

painstakingly terraformed the planet, but because

we built an atmosphere of our own, enclosed in vast planetary domes.

When we think about colonizing other worlds, the first thought is often terraforming, a slow,

uncertain process of reshaping a planet's climate and surface over thousands of years. But what if we didn't

have to wait? What if, instead of sculpting a world to fit us, we built the environment we needed

from scratch? More than that, what if we weren't even limited by the natural gravity of a planet

or moon? This is the concept of a world house, a planetary-scale enclosure designed

to create a stable, controlled biosphere on otherwise uninhabitable world. Why spent a thousand

years coaxing Mars into being habitable when you could give it a space-age greenhouse

overnight? Instead of waiting for nature to cooperate, we engineer a perfect climate

enclosing regions, or entire planets, within vast shells that trap atmosphere, regulate

temperature, and shield the surface from deadly radiation and cosmic debris.

It may sound like science fiction, but the idea has deep roots and real-world engineering,

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