The Copernican Revolution

The Earth has been in existence for over four billion years, and the universe for much longer, but modern humans have only existed for approximately two-hundred thousand years. Since the beginning of human thought, people have looked to the sky and wondered what lay beyond what we can see. With the advancement of the human mind along with technology, the perception of the cosmos has drastically changed over time. One of the most important changes in our thinking was the Copernican Revolution, when Copernicus aimed to replace Ptolemy’s earth-centred model of the solar system with a sun-centred one. The advancement of science facilitated the changes in our perception, and it can be argued that our knowledge about the universe is getting closer

These seven celestial bodies were believed to be surrounded by a stellar sphere that moved westward, creating what was known as a two-sphere universe (Kuhn, 1957, p. 53). This conception of the solar system gives no description of the dimensions of the planetary orbits and does not explain the irregularities of planetary motion, however it still held an important role in the later development of astronomy. This earth-centred theory contained structural information that became common knowledge among astronomers and non-astronomers alike (Kuhn, 1957, p. 54). In the fourth century B.C this structure provided a qualitative explanation of the lunar phases and eclipses, and it aided in creating accurate conclusions about the Earth’s circumference, as well as the distances of the sun and moon (Kuhn, 1957, p. 54). These brilliant findings by ancient astronomers were not affected during the Copernican Revolution, which made it harder to move away from the Ptolemaic system. Although ingenious, these successes do not answer the questions posed by the continuous irregularity of planetary

73). To do this, he first used an epicycle-deferent system developed by two greek philosophers, and although this system solved some of the basic problems of the planets like retrograde motion, it created further irregularities. Ptolemy used more combinations of circles called eccentrics and equants which accounted for the irregularities caused by the epicycle-deferent system, but this subsequently created even more problems (Kuhn, 1957, p. 72). The discrepancies created were minor, but astronomers still searched for a solution. Ptolemy’s successors often adjusted the theory of compounded circles by adding more circles, increasing the complexity of the theory itself (Kuhn, 1962, p. 69). The addition of new epicycles, deferents, eccentrics and equants only further intensified the theory and the mathematics that went along with it, and any discrepancies it fixed seemed to cause new problems somewhere else. For almost 1800 years, the system of compounded circles in an earth-centred universe dominated the astronomical field, and every attempt to solve problems within the field were attacked using this system (Kuhn, 1957, p. 74). It was not until the sixteenth century that the need for a paradigm shift became apparent. A paradigm shift occurs when