Science and Invention


What is the Copernican view of the universe?

The Copernican view of the universe, proposed in 1507, argued that Earth was only one of several galactic bodies that orbit the Sun. This theory, put forth by Polish astronomer Nicholas Copernicus (Mikolaj Kopernik; 1473–1543), was controversial in its day because it ran counter to the astronomical beliefs that had held sway for some 1,400 years—those of the Ptolemaic system, which maintained that Earth is the center of the universe and that the sun and the planets all revolve around it.

Copernicus devised his scheme out of necessity, really: He had found that using the Ptolemaic system to predict the positions of the planets over long periods of time yielded haphazard results. Once he made the assumption that the sun, rather than Earth, is the center of the solar system and that all the planets orbit the sun, Copernicus realized that tables of planetary positions could be calculated much more easily—and accurately.

However, Copernicus was not the first to put forth such a radical idea: the Greek astronomer Aristarchus of Samos (c. 310–230 B.C.) was the first to maintain that Earth rotates on an axis and revolves around the Sun. But it was Ptolemy’s ideas that took hold; not Aristarchus’s. Copernicus did, however, take the argument a step further, averring that Earth itself is small and unimportant compared with the rest of the universe.

But the Copernican view had its problems, too: Copernicus assumed that the planetary orbits were perfectly circular. Because of this error, he found it necessary to use some of Ptolemy’s cumbersome epicycles (smaller orbits centered on the larger ones) to reduce the discrepancy between his predicted orbits and those that he observed. It was not until the early 1600s that the elliptical orbit of the planets was put forth, by German astronomer Johannes Kepler (1571–1630).


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