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

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This episode is sponsored by Raycon.

We often picture post-apocalyptic civilizations as rather crazy and murderous, and I often

wondered how realistic that was.

Then I asked myself how crazy a lot of folks might be without a few days of internet access.

Suddenly, savage techno-barbarbarians

made a lot more sense. So today we'll be looking at a popular notion in science fiction,

the post-apocalyptic civilization, with a mix of high technology as relics, but otherwise pretty

primitive. As usual, we'll be asking how plausible that really is and how it might come about.

We have plenty of examples in fiction, but probably my favorite, and the one that was on

my mind when I put this topic up as one of the five options on a YouTube episode Topics

poll, which it won handily is Warhammer 40K.

In that universe we have a grand Galactic Empire merge over

many millennia between now and around the year 25,000 AD, or 25K, but it ends up falling apart

for various reasons leading to the Age of Strife, which goes on for about 5,000 more years,

then sees the rise of a new empire that endorsed the present time of the

setting, the year 40,000.

In this era, what high technology from the old empire remains is preserved and jealously guarded

by the techno-priests of the machine, the adeptus Mechanicus of Mars.

...