Nicolaus Copernicus 1473-1543 Polish Astronomer

In Copernicus' time, most scholars accepted the position of Aristotle and Ptolemy that the earth was the unmoving center of the cosmos. Although others, for example, Nicolas of Cusa had previously proposed the idea that the earth moves, Copernicus was the first to provide a detailed heliocentric, or sun-centered, theory of the planetary system that fit (reasonably well) with astronomical observations. In particular, Copernicus held that the earth rotates daily on its own axis and that the earth and the other planet rotate around the sun.

Because of its elegance, Copernicus' theory appealed to many scientists and philosophers including Giordano Bruno and Galileo. The theory had two important scientific implications. First, it implied that the universe must be much larger than had previously been thought. If the earth moves around the sun, and the stars appear fixed from the earth, that implies that the distance of the stars must be very large with respect to the orbit of the earth. Second, Aristotle had proposed that objects fall to earth because they are returning to their "natural" place, the center of the universe. However, if the earth is not the center of the universe, then a new explanation is needed. The search for a new explanation eventually led to Newton's theory of universal gravitation.

In fact, Copernicus' theory fit astronomical observations only slightly better than did Ptolemy's theory. This was because Copernicus assumed that the planets traveled with uniform speed in perfectly circular orbits. His assumption was consistent with traditional view that circular motion was most appropriate motion for celestial bodies. A century passed before Johann Kepler showed that the planet's orbits were better described as elliptical.

In 1533, Copernicus described his theory to Pope Clement VII who approved of it. However, the position of the church changed. In 1633, Galileo was arrested by the Holy Inquisition for his support of the Copernican theory. The Catholic church was not alone it its opposition. Martin Luther also condemed the Copernican theory.

The Copernican theory had an enormous impact on thinking about the place of humans in the universe. The assumption that humans have a special place at the very center of the universe could no longer be justified.