A retrospective: Johannes Kepler

Johannes Kepler was born in 1571, in Weil der Stadt, Württemberg, Germany. He was introduced to mathematics and astronomy at a young age, and at six years old witnessed the ‘Great Comet of 1577’, and three years later he witnessed a lunar eclipse and he was sold on the wonders of the solar system. He attended local schools until it was time to study at a university level where he enrolled at the University of Tübingen, which advocated Lutheran orthodoxy, where he studied arithmetic, geometry, astronomy and music.

Throughout his life, despite his science interest and his desire to seek the truth, he remained a deeply religious man, but at the time people didn’t really know any better and it was the common norm. Kepler believed that God had made the universe according to a mathematical plan, and man being made in the image of God, it was his duty as a Christian to understand. Astronomy, at the time, taught geocentric theories, in which the other planets in the solar system rotated around the Earth. He didn’t share these views, and in 1596 he published his first work considering the elliptical paths of planets, and agreed with Copernicus’ heliocentric opinions and theories. He was the first person to call the ‘Moon’ and the moons that Galileo had discovered around Jupiter ‘satellites’.

In 1609, and 1618 he announced his Three Laws of Planetary Motion.

• The path of the planets about the sun is elliptical in shape, with the center of the sun being located at one focus.

(The Law of Ellipses)

• An imaginary line drawn from the center of the sun to the center of the planet will sweep out equal areas in equal intervals of time.

(The Law of Equal Areas)

• The ratio of the squares of the periods of any two planets is equal to the ratio of the cubes of their average distances from the sun. (The Law of Harmonies)

Despite his astronomical discoveries, his passion remained with religion, until he discovered William Gilbert’s book, De Magnete, Magneticisque Corporibus, et de Magno Magnete Tellure, where he described his theory that the Earth was a giant magnet, and this rang a bell inside Kepler’s head, and started to suspect that this was true for all planets. With his heliocentric belief, he considered that all of the planets had magnetic poles, and they all orbited the Sun, which was the biggest magnet of all. He continued to write books on many subjects, but he became fascinated with light, and how it can travel so far from stars, and how it reacts when it reaches the Earth’s atmosphere.

His later years were filled with death and misery as he lost a vast number of his family to disease and illness, yet still, despite all of his anguish, his faith in God was as strong as ever, until his death in Regensburg in 1630 from fever.

His legacy lived on in the now retired Kepler space telescope that NASA launched to study the planets, and after nine years it was announced that its retirement would come on October 30, 2018.