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.

The vast gulfs between stars may take decades or even centuries to travel,

requiring enormous generationships, carrying families and whole ecosystems with them.

What will life be like on board such arcs.

When Jessica was three years old, her family bordered the Francis Bailey, a massive colony ship bound for La Cile 8760, an M-0, orange-red dwarf, 13 light-years from Earth.

She barely remembers waving goodbye to Earth in 2263 AD, and knows Earth

mostly through videos and VR of the world, not her family's small apartment in Tennessee,

or their dog who couldn't come along for the journey, and who remained with her grandmother,

Emily. Jessica never really thought of herself as part of the original crew for the ship.

She never got any training for space before the flight, unless you count the zero-gravity

bounce house at the daycare she went to for the last few weeks before they departed when they

were living at the space dock. By the time she was 20, the number of people born on the trip was nearly as numerous

of those who signed up, and those who were kids when the voyage began were the smallest

of three groups, and occupied a strange spot in the ship's emerging culture.

As a ship carrying settlers for a new planet, even though most of the colonists were making

the journey in cryostasis,

many were making the journey awake, and many of the crew were also believers in big families.

Jessica herself was married at 19, a mother at 20, and a widow at 22. Her husband, Frank,

was killed when working on the outer hole when a damaged section erupted

...