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.

We often discuss on this show the vital roles black holes may play in humanity's future,

how we may even come to live around them one day,

but what if we already live inside one, and the whole universe is a black hole?

Black holes are pretty weird, and given that, lots of weird questions come up around black holes.

One question that sometimes comes up is if we live inside a black hole and how we would know if we did.

We're going to discuss today why people think this could be true, as well as problems with the notion,

since we often discuss civilizations

powered by black holes or living near or around them, we might also wonder whether

it's possible for them to live inside one rather than just nearby. Now there's some good

and bad reasons suggesting we might live in a black hole, and also many good and bad reasons

for why we cannot. One is that since we have black in a black hole, and also many good and bad reasons for why we cannot.

One is that since we have black holes in this universe, then the universe itself cannot be one.

I assume this is based on the notion that reality can only get warped into a singularity once in

the TV show Babylon 5, how opening a hyperspace jump gate inside another jump gate

makes it explode, and how putting a bag of holding from D&D inside another will rip a hole in reality.

We don't really know that black holes don't operate that way, but we have no particular

reason to think they do, either. As for reality warping, we need to keep in mind that

while dead stars going supernova and ending up with a point-like hyperdense center, called a singularity,

...