The German astronomer Johannes Kepler described what later became known as the three laws of planetary motion in the early 17th century. His first and most famous discovery was that the planets move around the Sun in orbits shaped like ellipses.
Astronomical observations made by the Danish astronomer Tycho Brahe (died in 1601) helped Kepler formulate his laws, and likewise Isaac Newton was helped by Kepler's discoveries when he published his description of gravity, the law of universal gravitation, in 1687.
Image: A portrait of Johannes Kepler (credit: Mary Evans Picture Library)
Kepler describes how the planets move around the Sun.
The discoverer of pulsars explains that science isn't always orderly.
Professor Dame Jocelyn Bell Burnell, the discoverer of pulsars, explains that science isn't always orderly.
Johannes Kepler (German: [ˈkʰɛplɐ]; December 27, 1571 – November 15, 1630) was a German mathematician, astronomer, and astrologer. A key figure in the 17th century scientific revolution, he is best known for his laws of planetary motion, based on his works Astronomia nova, Harmonices Mundi, and Epitome of Copernican Astronomy. These works also provided one of the foundations for Isaac Newton's theory of universal gravitation.
During his career, Kepler was a mathematics teacher at a seminary school in Graz, Austria, where he became an associate of Prince Hans Ulrich von Eggenberg. Later he became an assistant to astronomer Tycho Brahe, and eventually the imperial mathematician to Emperor Rudolf II and his two successors Matthias and Ferdinand II. He was also a mathematics teacher in Linz, Austria, and an adviser to General Wallenstein. Additionally, he did fundamental work in the field of optics, invented an improved version of the refracting telescope (the Keplerian Telescope), and mentioned the telescopic discoveries of his contemporary Galileo Galilei.
Kepler lived in an era when there was no clear distinction between astronomy and astrology, but there was a strong division between astronomy (a branch of mathematics within the liberal arts) and physics (a branch of natural philosophy). Kepler also incorporated religious arguments and reasoning into his work, motivated by the religious conviction and belief that God had created the world according to an intelligible plan that is accessible through the natural light of reason. Kepler described his new astronomy as "celestial physics", as "an excursion into Aristotle's Metaphysics", and as "a supplement to Aristotle's On the Heavens", transforming the ancient tradition of physical cosmology by treating astronomy as part of a universal mathematical physics.