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

This video is sponsored by CuriosityStream.

Get access to my streaming video service, Nebula, when you sign up for CuriosityStream

using the link in the description.

Many things could cause people to flee to the stars, be it a flight from ruin or a pursuit

of new worlds and opportunities, but such an exodus might

be a protracted or even perpetual state, around which a civilization might arise.

So last week we were looking at future types of government, and this week we'll be

continuing that discussion as we contemplate the popular science fiction trope of wandering

fleets with no

homeworld to call their own, often operating under some oligarchy of ship captains,

something called a navarchy, and we'll explore what might cause such a civilization to exist

and how they might operate. We see this nomadic fleet civilizations in many a story, but two

of the best known are the remnant

survivors in Battlestar Galatica, whose homewards were taken away by the Cylons,

a race of artificial intelligences they had made, and the Corns of Mass Effect, whose

homeward was taken away by the Geth, a race of artificial intelligences they had made.

There are also the Eldar Craft Worlds in

Warhammer 40,000, giant ships that fled their old civilizations descent into chaotic debauchery.

...