Somnium

Following the Copernican Revolution, Kepler was probably the most important astronomer in the story of our understanding of the Solar System. He worked with Tycho Brahe and became court astronomer to Emperor Rudolph II in Prague, and it was his work that demonstrated the elliptical orbit of the planets. It was while he was in Prague that he wrote the story called Somnium (The Dream), which was circulated among friends in 1611 but was not published until after his death. The dream is, really, a scientific thought experiment in which Kepler considers how various astronomical features, such as an eclipse, would appear from the moon as a way of promoting the heliocentric view of the Solar System. Kepler's dream concerns an Icelandic boy whose mother consorts with demons who are able to transport him to the island of Levania, which is their name for the moon. There he meets beings who are tall, because of the gravity, and pale because of the light, and who introduce him to different ways of observing the heavens. Why it's on the list: Somnium had an unfortunate effect, in that a garbled account of the story seems to have been responsible for Kepler's mother being tried for witchcraft. After she was acquitted, Kepler added a huge number of notes to his manuscript to explain away the allegory and make it seem more like a scientific treatise. Nevertheless, writers from Isaac Asimov to Adam Roberts have declared that this is the first science fiction novel.