There is every reason to welcome English translations of any of Kepler’s works, and in particular of his Somnium seu Opus posthumum de Astronomia Lunari (1634), which is not even available in the critical edition of Kepler’s works by Max Caspar and others, but only in the nineteenth-century edition of Frisch. Except for a recent edition of his Snowflake (Clarendon Press, 1966) and a translation (1965) by Edward Rosen of his Conversation With Galileo’s Sidereal Messenger (Dissertatio cum Nuncio Sidereo), neither of them major works, none of Kepler’s works has been completely translated into English; and his Latin is by no means easy. The Somnium was in the press when Kepler died in 1630. He had written the text of the dream itself in 1609, and it had circulated in manuscript. In about 1621 he began to annotate it copiously—the notes are four times as long as the text. It was published together with a letter to Paul Guldin, S.J., on lunar geography, and Kepler’s Latin translation of Plutarch’s On the Face in the Moon, also annotated, which unfortunately is not included in the translation under review.
Of all Kepler’s strange works this is one of the most bizarre. The interpretation of the main part of it presents few difficulties, and he stated clearly his chief motive for writing it. It gives a detailed picture of the universe as it would appear to a moon-dweller, together with conjectures about lunar climatic conditions, geography, and inhabitants; and, as Kepler states, “the object of my dream is to work out, through the example of the moon, an argument for the motion of the earth, or rather, to overcome objections taken from the general opposition of mankind,” that is, to break down the common-sense resistance to Copernicanism by making people realize that moon-dwellers would be equally convinced that their home was the stationary center of the universe. What is strange and mysterious is Kepler’s way of introducing his lunar astronomy. His dream, which he calls a fable, consisted of reading a book, which recounted the history of an Icelandic youth, Duracotus, whose mother, Fiolxhilde, was a witch. She sold him to the captain of a ship, which, fortunately, carried letters from an Icelandic bishop to the great Danish astronomer, Tycho Brahe, then living on the island of Hven. Duracotus studied astronomy there for five years, and then returned to Iceland, where his mother, by magic rites, summoned a spirit (daemon) of the moon. The daemon tells how, during lunar eclipses, he and his fellow spirits travel from the earth to the moon, sometimes taking with them some human, beings, but only thin and desiccated ones, old witches being especially suitable. After a short description of the journey, during which the human travelers are anesthetized, the daemon gives a long discourse on lunar astronomy and geography, that is, the straightforward scientific part of the work. Kepler’s notes on this introductory part are often as bewildering as the text—sometimes autobiographical, sometimes allegorical, sometimes irrelevantly factual.…
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