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.

This episode is brought to you by Brilliant.

Our universe is enormous and ancient, so we suspected of being home to many alien races,

and yet it may be but the tip of the iceberg.

We may live in a multiverse so vast as to dwarf our universe home to our encounterable species.

The Fermi paradox is the big question of why in a universe so vast and ancient, we don't

see any other bigger and older civilizations, and it rose from our realization in the early

20th century

of just how big and old the universe really is.

At about the same time, we began to contemplate how we might have parallel realities in

alternate universes, leaving even more potential to search for alien life.

Our approach to the search for extraterrestrial life, or SETI, never really discusses multiverse

options for the simple reason that almost everyone assumes we can find our first example

of intelligent aliens in our own galaxy, and need not consider the whole wide universe,

let alone other universes to find example number one.

And yet there are several reasons this assumption might be wrong, and that our first

encounter with aliens may involve alternate realities.

Even if it doesn't, the topic of interacting with and meeting aliens through the multiverse

is interesting in its own right.

...