Somnium (Latin for "The Dream") is a fantasy written between 1620 and 1630 by Johannes Kepler in which a student of Tycho Brahe is transported to the Moon by occult forces. It presents a detailed imaginative description of how the earth might look when viewed from the moon, and is considered the first serious scientific treatise on lunar astronomy. Carl Sagan and Isaac Asimov have referred to it as the first work of science fiction. Somnium began as a student dissertation in which Kepler defended the Copernican doctrine of the motion of the Earth, suggesting that an observer on the Moon would find the planet's movements as clearly visible as the Moon's activity is to the Earth's inhabitants. Nearly 20 years later, Kepler added the dream framework, and after another decade, he drafted a series of explanatory notes reflecting upon his turbulent career and the stages of his intellectual development. The book was edited by his heirs, including Jacob Bartsch, after Kepler's death in 1630, and was published posthumously in 1634.