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.

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 orbitors. However, we'll be taking a deeper dive into interstellar probes, both flyby missions and long-term

orbiters. 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, 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 to the nature of telescopes and probes at the

interstellar scale, may 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, can get there in half the time. And of course, a telescope can actually

get there backward in time, seeing the world

...