SOURCE: "Johannes Kepler and the New Astronomy," in The Eye of Heaven: Ptolemy, Copernicus, Kepler, American Institute of Physics, 1993, pp. 305-22.

In the essay below, originally published in 1973 and reprinted in 1993, Gingerich provides a concise, lucid sketch of several of Kepler's complex astrological and mathematical principles, calling him the "first astrophysicist."

Johannes Kepler was conceived on 16 May 1571 at 4:37 A.M. and born on 27 December at 2:30 P.M. We therefore see that 1971 was the four-hundredth anniversary not only of Kepler's birth but also of his conception. The existence of such accurate dates reminds us that Kepler lived in an age when astronomer still meant astrologer and when the word "scientist" had not yet been invented. Kepler wrote down these dates when he was 25 years old and much fascinated by astrology. Like many of the world's greatest scientists, he had a profound feeling for the harmony of the heavens; Kepler...