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.

The search for extraterrestrial intelligence, SETI, is all about finding alien civilizations,

and the bigger they are, the easier they should be to spot,

and there's few things a mega-civilization might build bigger than an iceen sphere.

No. than a Dyson sphere. One of the biggest topics this channel covers is the idea of massive space habitats

and whole clouds of trillions of them being built around stars.

Conglomerations refer to as Dyson's sphere or Dyson Swarms.

And another is the phy paradox.

The big question of where all the aliens are, in a universe so old and vast that it seems

impossible that other civilizations would not have arisen yet, today we'll be discussing

the connection between these concepts

and if such Dyson Swarms exist, how they would be visible to us if they do, and why they

might not be visible, get hidden, or even not be built in favor of other approaches by alien civilizations.

All the way back in this show's first official season 1 episode, the Fermi Paradox

of the Dyson Dilemma, we discussed how Dyson swarms should be an inevitable project

of any space-faring civilization, and in many ways that discussion is the reason this show exists.

We spend a lot of time talking about what big, high-tech civilizations might do, and why the apparent

absence of these sorts of structures, such bright and loud displays of their existence,

would seem to indicate there are no loud alien civilizations, or perhaps even any alien

...