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.

This episode is sponsored by Raycon.

Only those who risk going too far can possibly find out how far one can go.

T.S. Eliot. In last month's episode, surveying for habitable interstellar star systems, I mentioned

that as soon as I started the topic, I knew it was going to require more than one episode.

So we briefly discussed interstellar probes and man-scaling missions down to a planet in that

episode, but we focused on distant astronomical techniques.

Today we'll be taking a deeper dive into interstellar probes, both fly-by missions and long-term

orbitals.

However, we'll follow up the next two weeks with a look at slowboat colonization of the galaxy

at less than 1% light speed, what we call crotonizing, and the week after that

we'll be asking what life as a planetary explorer will look like.

Today our focus is on those probes though, so don't forget to subscribe and hit the

notification's bell if you want to alert when those and other episodes come out.

In our surveying episode, we point out that the nature

of telescopes and probes at the interstellar scale, meant that you can always get a probe

to park itself around a world a little bit quicker than the time it would take for a colonization

fleet to arrive, but that a fly-by probe, since it can use all its fuel for accelerating

and doesn't need to save any for decelerating,

...