It is well-known today that the sun is the center of the solar system and many people consider this knowledge obvious. However, if we would look from a history perspective the sun-centered (heliocentric) concept was slow to evolve. “In the 2nd century ad, Claudius Ptolemy proposed a model of the universe with the earth at the center (geocentric). His model depicts the earth as stationary with the planets, moon, and sun moving around it in small, circular orbits called epicycles.” (Toomer, p. 187) Ptolemy’s system was accepted by astronomers and religious thinkers alike for several hundred years. Ptolemy's earliest and most famous work, originally written in Greek, was translated into Arabic as al-Majisti (Great Work). In Europe, medieval Latin translations reproduced the title as Almagesti, and it has since become known simply as the Almagest. (Toome

Polish astronomer Nicolas Copernicus believed that the Earth revolved around the Sun, upsetting the long-accepted Ptolemaic view that Earth was the center of the universe. Fearing his theory would be judged heretical by the Roman Catholic Church, Copernicus delayed its publication until shortly before his death in 1543. Later scientists were punished for similar beliefs, including the Italian astronomer Galileo Galilee, who was forced to renounce his theories in 1633. By the late 1700s, however, many great thinkers of Europe had adopted the Copernican view, among them English physicist Sir Isaac Newton. The following is a translation of Copernicus’s theory of how the universe operates. (North, Fontana of History and Astronomy)

But, beside religious backing Copernicus had to have a scientific evidence. In an attempt to support his heliocentric model, Copernicus dedicated years to the mathematical proofs for heliocentric orbits. The math turned out to be somewhat less complex than that of Ptolemy, with only 48 circles to contend with instead of 80. However, Copernicus still relied on multi-circular orbit models to describe the motion of the planetary bodies accurately. (Copernicus, On revolutions) How was his theory any truer than that of Ptolemy?

Ptolemy used the term epicycle to describe the small circle around which he claimed objects in space move. To make his theory of epicycles appear sound, he had to introduce variations from traditional mathematics. This departure from traditional assumptions was one reason the Polish astronomer Nicolas Copernicus rejected Ptolemy's system in the 16th century and developed his own heliocentric theory, which correctly stated that the sun was located at the center of the solar system. Even so, Copernicus retained an elaborate system of epicycles.

Another important feature of Copernican theory is that it allowed a new ordering of the planets according to the

Some topics in this essay:
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