Hello, SFIA audio listeners. In this month's Nebula exclusive, big alien theory,

we're asked at 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.

All universe is a strange place, with underlying rules we'll only just begin to understand.

But could the strangest thing of all about our universe be that we are able to live here to

observe it in the first place?

Knowledge is power, and the kind that earns interest on your investment.

The more you know about any situation, the easier it is to learn more about it, because

you know the right questions to ask, and every new answer or test result yields more information.

Much like a jigsaw puzzle, each piece gets easier as you go, since there are less pieces

to try to fit to any remaining empty spots, and you've grown more familiar with that image

and the subtle differences in texture or color that help you see which pieces fit with part of

the wider image.

The universe as a whole is quite the jigsaw puzzle, and we can only see it

by what's visible here on Earth, a tiny grain of sand against the wider galaxy, which

itself is a tiny grain next to the wider cosmos. It would be akin to studying all the Earth

from inside just one room of a house, with just one window that's all fogged

up and scratched.

This means we've often had to work from a standpoint of very little information about the

universe and very little way to gather more.

One of our core assumptions in all of modern astronomy and cosmology is that universe

...