Enormous flying creatures, cave-dwelling serpent-monsters, and fortified cities of people on the Moon… these were the imaginative speculations of Johannes Kepler in the early seventeenth century, when he penned the scientific and literary contents of the Somnium, his “dream” of a trip from the Earth to the Moon.

Arguably, the Somnium can be called the first work of science fiction, because it daringly mixed astronomical theories of the day with speculative fantasies of spaceflight and another populated world (the Moon).  Even today, it is difficult to tell what is fiction and what is science in the pages of the Somnium.

Indeed, Kepler was toying with the implications of a Copernican universe, in which the planets revolved around the Sun.  So the argument goes, when scientists, such as Kepler, accepted the implications of a Sun-centered universe, then the Earth became a planet, while other planets could be imagined as Earth-like.  This moment of realization marks both the birth of science fiction and the destruction of Aristotelian distinctions between the immutable heavens and the mutable center of the universe: the Earth.  With Copernicanism, the Earth ceased to be a special center, while parts of the heavens traveled with the Earth around the Sun.  These ideas raised many questions:  If the Earth was a planet, revolving around the Sun as other planets do, then what if those other planets are Earths too?  What if we are not alone?  What would the inhabitants of the Moon or Mars be like?  Would they be Christians?

In his science fiction tale, Kepler explored the daring implications of these ideas.

The story, in part, narrates the adventures of an Icelander named Duracotus, who ventures to the lunar surface via witchcraft and a lunar eclipse.  There, Duracotus discovers much about the Moon’s inhabitants, who are half primitive and half enlightened.  The primitive “Privolvans” live on the “dark side of the Moon,” which is a harsh environment of extremes.  Due to the climate and the scarcity of water, the “Privolvans” are nomadic and predatory.  The more advanced “Subvolvans” live on the side that looks to the Earth as their “moon,” using the phases of the Earth to tell time and season.  Because the enlightened “Subvolvans” have the Earth as a beacon of learning, they have also constructed fortified cities, surrounded by circular city walls (which Earthlings see as “craters”).

The story contains much science.  Despite Kepler’s reliance on supernatural means to get from here to there, he has much to say about the intense stress of extreme velocity on the human body, the lessening of gravity, and possible devices used to help humans survive in the airless vacuum of space.  His geographic discussions of the Moon are also based on years of observing the lunar body through telescopes.  At the time, many of Kepler’s maps of the Moon were unrivaled in accuracy and detail.  Additionally, his science fiction tale is accompanied by over 100 scientific footnotes containing detailed equations and “proofs.”

The story also contains much fiction.  Kepler let his imagination roam freely, which is predictable for a man of science who was also a man of alchemy, astrology, and other forms of knowledge that are now considered “occultist.”  Kepler was highly imaginative, and he was willing to take many risks if observations and scientific theories lent themselves to “bizarre” conclusions about the plurality of other worlds, possibly similar to ours.

In some ways, he started a speculative conversation that we continue today.

As you populate your worlds with npcs, buildings, and “new life,” take a moment to ponder the longevity of this intellectual exercise.  Learned and brilliant individuals, such as Johannes Kepler, have been doing it for centuries.  Parchment was the seventeenth-century Foundry.