Somnium

Somnium

Johannes Kepler wrote one of the first works of science fiction intended to explain and popularize science. It was called Somnium, “The Dream”. He imagined a journey to the Moon, the space travelers standing on the lunar surface and observing the lovely planet Earth rotating slowly in the sky above them. By changing our perspective we can figure out how worlds work. In Kepler’s time one of the chief objections to the idea that the Earth turns was the fact that people do not feel the motion. In the Somnium he tried to make the rotation of the Earth plausible, dramatic, comprehensible: “As long as the multitude does not err, … I want to be on the side of the many. Therefore, I take great pains to explain to as many people as possible.” (On another occasion he wrote in a letter, “Do not sentence me completely to the treadmill of mathematical calculations – leave me time for philosophical speculations, my sole delight.”).

With the invention of the telescope, what Kepler called “lunar geography” was becoming possible. In the Somnium, he described the Moon as filled with mountains and valleys and as “porous, as though dug through with hollow and continuous caves”, a reference to the lunar craters Galileo had recently discovered with the first astronomical telescope. He also imagined that the Moon had its inhabitants, well adapted to the inclemencies of the local environment. He describes the slowly rotating Earth viewed from the lunar surface and imagines the continents and oceans of our planet to produce some associative image like the Man in the Moon. He pictures the near contact of southern Spain with North Africa at the Straits of Gibraltar as a young woman in a flowing dress about to kiss her lover – although rubbing noses looks more like it to me.

Do not sentence me completely to the treadmill of mathematical calculations – leave me time for philosophical speculations, my sole delight.” (Johannes Kepler). Image: A Fractal Suite by © Elena

Because of the length of the lunar day and night Kepler described “the great intemperateness of climate and the most violent alternation of extreme heat and cold on the Moon,” which is entirely correct. Of course, hi did not get everything right. He believed, for example, that there was a substantial lunar atmosphere and oceans and inhabitants. Most curious is his view of the origin of the lunar craters, which make the Moon, he says, “not dissimilar to the face of a boy disfigured with smallpox”. He argued correctly that the craters are depressions rather than mounds. From his own observations he noted the ramparts surrounding many craters and the existence of central peaks.

But he thought that their regular circular shape implied such a degree of order that only intelligent life could explain them. He did not realise that great rocks falling out of the sky would produce a local explosion, perfectly symmetric in all directions, that would carve out a circular cavity – the origin of the bulk of the craters on the Moon and the other terrestrial planets. He deduced instead “the existence of some race rationally capable of constructing those hollows on the surface of the Moon. This race must have many individuals, so that one group puts one hollow to use while another group constructs another hollow.”

Against the view that such great construction projects were unlikely, Kepler offered as counterexamples the pyramids of Egypt and the Great Wall of China, which can, in fact, be seen today from Earth orbit. The idea that geometrical order reveals an underlying intelligence was central to Kepler’s life. His argument on the lunar craters is a clear foreshadowing of the Martian canal controversy. It is striking that the observational search for extraterrestrial life began in the same generation of the invention of the telescope, and with the greatest theoretician of the age.

Parts of the Somnium were clearly autobiographical. The hero, for example, visits Tycho Brahe. He has parents who sell drugs (at a pharmacy). His mother consorts with spirits and daemons, one of whom eventually provides the means to travel to the moon. The Somnium makes clar to us, although it did not to all of Kepler’s contemporaries, that “in a dream one must be allowed the liberty of imagining occasionally that which never existed in the world of sense perception”. Science fiction was a new idea at the time of the Thirty Years’ War, and Kepler’s book was used as evidence that his mother was a witch.