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 ad-free,

plus hours of bonus content,

check out go.nebola.tv slash Isaac Arthur

and use my code, Isaac Arthur.

My dedication to the sacred duty is total and whole-hearted.

In the responsibility bestowed on me, never will I falter.

And with dignity and perseverance, my standard will remain perfection.

From the Sentinel's Creed at the Tomb of the Unknown Soldier.

Perhaps one of the best-known alien artifacts in science fiction are the mysterious

monoliths from 2001 A Space Odyssey, which we first encounter in the film a million

years ago when some primates find it and get uplifted to understand basic

weapons and tools from which humanity will later emerge. Those monoliths are later seen

on the moon, and their implied role is to uplift intelligence where they find it and also

to monitor it. Arthur C. Clark had earlier written a short story, The Sentinel, in

1948, though not published till 1951, which featured an encounter with an alien monitor on the

moon in 1996 that became the inspiration for his later collaboration with Stanley Kubrick

for their 1968 film 2001.

You do not need to memorize that, there will be no pop quiz after today's episode,

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