Copernicus, Nicolaus, << koh PUR nuh kuhs, `nihk` uh LAY uhs >> (1473-1543), a Polish astronomer, developed the theory that Earth is a moving planet. He claimed that Earth and the other planets revolve around the sun, which he considered to be motionless. Astronomers now know that the sun is just one of many stars orbiting the center of our galaxy. But Copernicus’s ideas about the roles of the sun and planets were essentially correct. He is considered the founder of modern astronomy.
Theories of heavenly motion.
In Copernicus’s time, most astronomers thought that Earth was the center of the universe and stayed motionless. The Greek astronomer Ptolemy had developed this idea in the A.D. 100’s. According to Ptolemy’s theory, the other heavenly bodies moved around Earth. But the theory struggled to explain certain irregular motions of the planets across the sky. Ptolemy explained the irregular motions using complicated arrangements of circular paths. The system of circles accounted for the motions. However, Copernicus saw Ptolemy’s system as a complicated mathematical invention with no basis in physical reality.
Some astronomers before Ptolemy had suggested that Earth did in fact move. In the 200’s B.C., the Greek astronomer Aristarchus had even suggested that Earth and the other planets moved around the sun. By Ptolemy’s time, these theories had been rejected. But Copernicus knew about some of them.
Copernicus sought the simplest and most systematic explanation of heavenly motion. He realized that it required that every planet, including Earth, revolve around the sun. In developing his theory, Copernicus also accounted for Earth’s rotation on its axis and the much slower wobble of that axis. These motions of Earth affect the paths that objects appear to follow in the sky.
Copernicus presented his theory in his masterpiece, On the Revolutions of the Heavenly Spheres (1543). In this book, he showed how Earth’s motion could be used to explain irregularities in the movements of other heavenly bodies. Copernicus could not prove his theory, but his explanation was mathematically strong. It also relied on a simpler set of assumptions than did Ptolemy’s theory. However, Copernicus did use a complex series of circles to account for certain irregular motions. He made this assumption because, like many other astronomers of his time, Copernicus believed that planetary motion was based on perfect circles. In the early 1600’s, the German astronomer Johannes Kepler showed that the planets follow elliptical (oval-shaped) orbits, eliminating the need for complicated series of circles. Also in the early 1600’s, the Italian scientist Galileo made discoveries with the telescope that supported Copernicus’s theory.
Life.
Copernicus was born on Feb. 19, 1473, in Thorn (now Torun, Poland). He entered the University of Kraków in 1491 and studied there for four years. In 1496, he began studying church law at the University of Bologna in Italy. He pursued astronomy on his own time, making his first recorded astronomical observation in Bologna in 1497. Through the influence of his uncle, he was appointed a canon (church official) of the cathedral chapter of Frauenburg (now Frombork, Poland). Copernicus studied medicine in Italy at the University of Padua from 1501 to 1503. He received a degree in church law from the University of Ferrara in 1503. He then returned to Poland to take up his church position.
In 1514, the Roman Catholic Church asked Copernicus and other scholars for help in creating a more accurate calendar. Some historians think that this request inspired Copernicus’s Commentariolus, a brief essay that outlined his ideas about the sun and planets. He wrote the essay and distributed it to a small number of people around 1514. During much of his adult life, Copernicus worked to develop his new theory. He built a small observatory but also used astronomical data gathered by others. Copernicus hesitated to have his findings published. But near the end of Copernicus’s life, the Austrian mathematician Georg Joachim Rheticus persuaded him to do so, resulting in On the Revolutions of the Heavenly Spheres. Copernicus died on May 24, 1543, about two months after his book was printed.
