I noticed on an almanac site that December 27 was the birthday of German astronomer Johannes Kepler, born 1571. Kepler intended to become a theologian, but when he read Copernicus’s Six Books Concerning the Revolutions of the Heavenly Orbs, he changed paths.

Copernicus’ writing put forth the evidence that the planets revolve around the Sun, not the Earth. That was not only a radical theory in its time, but it was one that questioned the religious views at the time.

New Astronomy 1609

Science and religion continues to clash on many issue today, with topics like evolution being the best known examples. That’s what I like about Kepler’s story. He  saw Copernicus’s theory as evidence of a divine blueprint for the universe. He decided to prove the theories through scientific observation.

Like Darwin, they were religious believers who hesitated to publish theories that would overturn beliefs. But the evidence was overwhelming.

Kepler’s defense of Copernicus, The Cosmographic Mystery (1596) was his start, He would eventually posit three laws of planetary motion. The first two were published in 1609 in New Astronomy. Johannes Kepler’s book, outlining his theories of planetary motion, made the radical claim that the planets move in ellipses, not perfect circles. Kepler’s second theory is that an imaginary line joining the planet and the Sun would sweep out equal areas during equal periods of time — in other words, the planet moves faster during the portion of its orbit that is closest to the Sun. His final law, published in Harmonies of the World (1619), describes the mathematical relationship between the distance of a planet from the Sun and the length of the planet’s orbital period.

Kepler’s theories were based on data collected by astronomer Tycho Brahe. He had to make thousands of calculations to work out the peculiarities of Mars’s orbit, describing the experience as “my war with Mars.”

I also owe Kepler for his role as “the father of modern optics.” We share poor vision (his from a childhood case of smallpox). He explained the mechanics of vision in the eye, and also explained how both eyes work together to produce depth perception. He then developed lenses to correct nearsightedness and farsightedness.

Thanks Mr. Kepler, for helping us see more clearly, literally and figuratively.