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 worry that the reason we hear nothing in our search for extraterrestrial intelligence

is that to travel to other stars is just too hard.

But what if a civilization decides it's just too dangerous to allow?

Last year we released our Fermi Paradox Compendium, which was a staggering three-hour-long

episode, and despite that, we found that a lot of the entries in there had to get only

surface detailing discussions, and in there and other episodes, I suggested before that one of

the more disturbing solutions is that a civilization

might not permit space colonization, either from its own world or from any others that might

arise nearby.

I've never heard this given a name before, except as a subtype of stay-at-home civilizations,

and indeed we are not actually thinking this would be a place where they

just decide not to go settle the galaxy.

We could imagine tyrannic empires that fear letting colonies slip away from them in the distant

interstutter space, where they might escape their leash.

However, a point I sometimes raise in our discussion of the phomely paradox, the big question

of why

our vast and ancient universe seems empty of other civilizations, is if you go out and colonize

the galaxy long enough, you are going to find alien civilizations, simply because every colony

...