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 stars may be quiet, but the silence could be hiding more than absence.

Not every relic is a gift, and some artifacts are better left buried,

because in a universe this old, discovery and doom may be the same thing.

Before the first stars had even burned out, civilizations may have risen, died, and left

behind echoes far more dangerous than their voices.

As we peer deeper into the stars, the question isn't just whether alien civilizations once existed,

or whether they'd left anything behind, and if so, whether we should touch it.

A lone probe still orbiting a star that no longer burns, or even a vault sealed before

Earth even cooled. The cosmos may be full of long-dead empires, but their technology might still endure, scattered

like cosmic driftwood.

This episode isn't about living aliens or distant radio signals, it's about their remnants,

relics, artifacts, and silent machines, left behind by civilizations that may have died

out millions or even billions of years ago.

Some of them might still be running, some might still be dangerous, and some might be waiting to be found.

The terrifying truth is that time does not erase everything.

Sometimes it just buries it deeper, and the silence between stars, it's not always the living

we have to fear, but the long-dead hands that still shaped the cosmos through machines that

...