(This post is part of my Patreon-supported New Worlds series.)

Much like childbearing, sleeping is a fundamentally biological process with a lot of culture built around it.

Even the biological part can be treated as fair game for worldbuilding, of course. In the Forgotten Realms shared setting, elves don’t actually sleep; instead they go into a meditative state called “reverie.” From the perspective of a Dungeons & Dragons game taking place in that setting, it’s functionally the same thing — it serves the same purposes in terms of preventing the fatigued state and helping spellcasters regain their abilities — but it’s a different state, and elves need only half as much time spent in reverie as humans and other races do in sleep.

Relatively little of the interplanetary science fiction I’ve read pays much attention to this topic, but it ought to be a common one. Not just as a matter of alien biology: although our sleep cycles are definitely influenced by light, that doesn’t mean you can just rely on a different day-night cycle to shift people onto, say, a 30-hour rhythm and have that work out. Non-24-hour sleep-wake disorder is a condition (much more common among the totally blind, but also sometimes found in the sighted population) wherein a person’s circadian rhythms don’t conform to our planet’s rotation; treating that requires medication and/or light therapy, and even then, it isn’t always successful. Much like populations living at high latitudes, where the variation in daylight between summer and winter is extreme, humans on other planets would likely need to take active steps to function within a different cycle.

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