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.

This episode is sponsored by Audubal.

Our civilization is ancient, with ruins of its early incarnations going back many

thousands of years, but that's just an eye blink against the age of our world.

If we disappeared tomorrow, would the scientists of some successor race millions of years

from now even know we existed?

And if not, can we be sure we truly are the first civilization to arise on Earth?

So today we'll be looking at the Salarian hypothesis and the general surrounding topics of

if our civilization would leave any long-lasting evidence if we somehow disappeared tomorrow,

or if we would even know if some other civilization had existed here on Earth.

That last one is a bit complicated by potentially coming in two forms,

life that previously arose here, like if the dinosaurs

had gotten high-tech and then blown themselves up, or alien life that had colonized Earth at

some point and that colony had failed. Now, today is another sci-fi Sunday episode here on

SFAIA, where we try to look at concepts from science fiction and ask how scientifically

plausible they are. And since this has been a popular topic in sci-fi for over a century now,

unsurprisingly, we're not the force to look at this from a realism perspective.

Indeed, the name Silorian hypothesis was coined by astrophysicist Adam Frank and Gavin Schmidt, director of

the Goddard Institute for Space Studies, back in 2019, when they wrote a paper-up, trying to

...