Astronomy Bio

Peter Florian

Mr. Percival – Period 5

Astronomy

10 October 2014

Astronomy Bio

            Eudoxus (roughly translated to “honored”) and Callipus (a student of Eudoxus) were both great astronomers who contributed greatly to our current understanding. Eudoxus was made famous from his planetary model which attempted to explain the retrograde motion of the planets. However this was not the only thing that Eudoxus was famous for, Eudoxus was also a famous mathematician. Callipus studied under Eudoxus at the academy of plato. He was famous for adding on to Eudoxus’ model of the known universe.

            Eudoxus was born in 408 BC and he studied under the School of Plato. Eudoxus’ father loved to look up at the stars and that is what got him interested in astronomy. Eudoxus then ventured to Tarentum to learn mathematics from Archytas. While in Italy he went to Sicily to study medicine under Philiston. Eudoxus dropped out of the School of Plato due to a disagreement. In order to continue to continue hearing the lessons Eudoxus walked 7 miles each way just to hear Plato’s speeches. During his travels Eudoxus gathered many students of his own including Callipus. Rumor has it that he might have even taught Aristotle. He was famous for developing the astronomical globe and a model that helps to explain the retrograde motion of the planets.

            Eudoxus’ system helped to explain the apparent retrograde motion of the planets by adding orbits inside the orbits of the planets around the earth. At the time of Eudoxus everyone thought that the universe was perfect and if it was perfect than the orbits had to be comprised of circular orbits. Elliptical orbits were not discovered until Johannes Kepler published his laws of planetary motion. Eudoxus explained the orbits by making the planets follow and orbit that follows another orbit around the Earth. People still had a geocentric model because at the time people still believed that the Earth was the center of the universe. The moon was assigned three spheres; one that explained the rising and setting of the moon, a second that explains the monthly motion of the moon and the third that describes the motion of the lunar nodes. The sun was assigned three spheres and the five visible planets were assigned four spheres each. The major flaw in this system was the fact that it could not explain the varying brightness of the planets. Even though this model is really inaccurate it was a great leap forward in the field of astronomy because it was the first attempt to mathematically explain the motion of the planets.

             Callipus was born in the 370 BC at Cyzicus and studied under Eudoxus at the Academy of Plato. Callipus observed the movement of planets and tried to explain them by expanding on Eudoxus’ model of the solar system. Callippus improved on Eudoxus’ model by adding more spheres. In total he added seven: two for the sun, two for the moon and one for each Mercury, Venus, and Mars. This helped to more accurately describe and predict the motion of the planets. He also discovered the solar anomaly which is the variation in the length of seasons.

            Both of these astronomers took giant steps in the field of astronomy to help explain what we observed from the Earth. While both of these models were extremely inaccurate, both were the first attempts to understand retrograde motion. With their limited resources both of these astronomers produced amazing results that greatly affected the way we see the universe today. It is because of people like these two that we learned that we are not actually the center of the universe. All in all we need more people like Eudoxus and Callippus in modern day to try to question what is thought to be known and fully explain it through careful observation.