Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asked at 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.

They say life is a journey, but that's no metaphor for nomads, and in the endless

depths of space, we may see entire civilizations that exist not on planets, but traveling

between them.

Yeah. between them. The spaceship Ganymede's hand was commissioned at the Jovian shipyards to serve as part of a colonial fleet in the year 2424, and by the year 3434, a thousand years later, it had undergone many transformations

not just in shape, but in mission and status. That included being a mutinous vessel, delivering

its splinter of the fleet to a rebel colony, and then later as a diplomatic envoy to those

old friends turned enemies.

It's been a freighter, a garbage barge, and even a glorified prison transport during those

centuries, than a pirate ship in the eyes of many, and now on the run from the inner sphere

of humanity's colonization, where they have few friends.

Now they're so far away from the sun that first shone down on Ganymede's hand when it was

built that it could no longer be seen with the naked eye, and passing through a volume

of space almost devoid of humanity.

Those systems nearby are either entirely unsettled, home to a fledgling colony, or perhaps

some automated probe or constructor, preparing basic infrastructure.

That ship has changed greatly since it first launched, retrofitted and expanded in a patchwork

collection of add-ons that no longer resemble the smaller and staker vessel that first set sail from Jupiter.

It's a hodgepodge of connected communities grown like a coral reef out from the main

...