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.

We often look out into the galaxy and wonder where all the civilizations are, but could it be that we don't see them because they've all chosen to

exist in fortress star systems surrounded by despoiled deserts of their own making?

When we look up the night sky and see thousands of stars, it naturally raises the question

of if any of those might be home to other peoples, distant kindred of ours, spiritually,

if not genetically.

When we found out the galaxy is so much bigger than even what we see, and itself is but a

pinprick in the universe. It's natural to ask

the question of why we don't see other alien civilizations. This is what we call the Fermi

paradox, the seeming contradiction between our observations of how big and ancient our universe is,

how full of life all planet is, and how absent the rest of the universe seems to be of that life. The universe is, how full of life all planet is, and how absent the rest of the universe seems

to be of that life. The universe is throwing the ultimate silent party, and Earth didn't

get the memo. Either that, our invitation got lost in the cosmic mail. One option that we explored

a couple months back is that life is quite common, and it

just rarely gets very complex. Only for a fraction of time Earth has had life on it, has

had any real plants or animals. So perhaps we are an anomaly, and the universe is full of

worlds that are full of slime, and algae, and not much else. Of course, this suggests in the grand

scheme of things, cosmic evolution might have a pension for the simple life over the drama

of higher intelligence, or even that higher intelligence and consciousness is temporary

...