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.

Welcome to SFIA's Outward Bound Series, or the audio-only version of it anyway.

I imagine most listeners know these are all videos that I upload an audio-only format of for folks who prefer to listen, but if you simply came across these on SoundCloud or iTunes sometime and ever wondered

about the constant references to videos, or thought many of the topics seemed just a

touch confusing, like something was missing, that is because something is missing, all

the episodes are written with video in mind, and I just release an audio-only version of it

each week.

Or rather, too.

The videos are more cinematic and accompanied with music, so we release a version that includes

one and one titled narration only that's just me talking.

I do always encourage folks to check out the videos too, as they contain a lot of handy

visuals, many of which are quite nice these days, thanks

to a lot of folks volunteering to help animate them. Whichever version you're planning to listen

to for Outward Bound, this series began as an offshoot of our earlier Upward Bound series,

as well as an expansion of our Habitable Planet series, to look at how to go about colonizing

our solar system and

what we really mean by colonizing.

Like so many of our series, this one began with only a few episodes in mind and got way bigger.

I originally meant to transition to a new series when we got to Alpha Centauri, looking at

...