December 27 1571 – German Astronomer Johannes Kepler, Descriptor of Planetary Motion, is Born Near Stuttgart

247

*Image Credit: Wikimedia Commons Stricken by a fascination with the sky at a young age, Johannes Kepler would go on to be regarded as one of the foremost scientists in astronomy after being born into a humble home on December 27, 1571. Despite poor vision, his superior mathematical mind would build on the theories of Nicolaus Copernicus to revolutionize European understanding of the Solar System. Born to a soldier-for-hire father and healer mother, Kepler grew up at his maternal grandfather’s inn in the Free Imperial City of Weil der Stadt, near what is now Stuttgart in modern Germany. As early as the age of six, he began to look wistfully at the heavens, amazed by the Great Comet of 1577 as it passed over the tiny town. Three years later, he observed a lunar eclipse. By his late teens, he moved on to the nearby University of Tubingen to learn mathematics and philosophy. Though a smallpox infection left his eyesight impaired and gnarled his hands, Kepler’s aptitude for calculation caught the eye. While he had impressed guests staying at the inn his grandfather owned as a boy, the application of those skills toward the skies gained him a following in his university days — mostly for his accurate horoscopes. By the end of his studies, however, he turned to more serious pursuits: defending the assertions of Copernicus. Using his training as a minister and mathematical knowledge to make a case for the sun being at the center of the Solar System, he argued as both a committed believer in God and brilliant scientific mind. Appointed to the mathematics faculty at the present-day University of Graz in Austria, he noticed a peculiar similarity between the movements of Saturn and Jupiter through the night sky. Working diligently to understand the complexity of Copernican heliocentrism, he figured out the orbits of the six known planets — Mercury, Venus, Earth, Mars, Jupiter and Saturn — could fit inside each other, much like Russian nesting dolls. In 1600, he published his findings in Mysterium Cosmographicum, a nod to Kepler’s belief there was biblical support for Copernicus’s ideas and, thus, God’s architecture for the universe had been discovered. Though his ideas proved somewhat off the mark, particularly as Kepler assumed in Mysterium that each of the planets maintained a perfectly circular orbit instead of their true elliptical paths, his work did much to remove the stain of heresy that stuck to Copernicus’ work. As he moved forward in his career, Kepler continued to refine his ideas, drawing the ire of Galileo Galilei — whose design for a telescope Kepler improved — and French philosopher Rene Descartes. During the early 1600s, he continued observing the sky, now in Prague with fellow astronomer Tycho Brahe. While tracking the movement of Mars using Brahe’s observations, Kepler formulated the backbone of his next work, Astronomia nova. In it, he proposed the first of his laws of planetary motion: “All planets move in ellipses, with the sun at one focus.” Simple — too much so for Kepler’s liking at first — and effective, it remains one of the key tenets in understanding the Solar System to this day. For the rest of his life, Kepler continued to earn the respect of royalty and church hierarchy (despite some believing his work just as heretical as that of Copernicus). In 1617, he published the first of three volumes in Epitome astronomiae Copernicanae, a vigorous defense of the Copernican theory backed by Kepler’s own observations. Enormously successful, it added a third law of planetary motion to the two which appeared in Astronomia. Well after his death in 1630 in the Holy Roman Empire at Regensburg, it remained the best-selling work on astronomy in Europe. Kepler’s place in the pantheon of scientific discovery cannot be understated. Epitome, his masterpiece, served as the inspiration for Sir Isaac Newton’s theory of universal gravitation published in Principia Mathematica in 1687. By the 1830s, the meticulous study of natural phenomena Kepler applied to his work left English historian William Whewell to name him one of the foremost examples of applying the scientific method the world had seen up to that point. To honor this legacy, numerous instruments all over the world have been named in his honor. Also On This Day: 537 – The Hagia Sophia, church to three different religious sects throughout history, opens in Constantinople 1831 – The HMS Beagle leaves Plymouth, England, carrying a young Charles Darwin on the expedition that would lead to his first observations in the theory of evolution 1911 – The Indian national anthem, “Jana Gana Mana,” is sung at the Indian National Congress for the first time 1922 – The Hosho, from Japan, is commissioned as the world’s first purpose-built aircraft carrier 1949 – The Netherlands acknowledges the independence of Indonesia, bringing the Dutch East Indies to an end