From Geocentric to Heliocentric: The Evolution of Astronomical Thought

Aristotle

Aristotle once said, “You will never do anything in this world without courage. It is the greatest quality of the mind next to honor.” Aristotle is one of the most well-known, influential scientists and Philosophers of his time. He made significant impact in many areas of knowledge including logic, biology, ethics, and aesthetics. He was born in 384 BCE and passed away in 322. He invented the field of formal logic and was also a teacher who founded his own school in Athens. After his father passed away, Aristotle moved to Athens where he, at the age of 17, joined the academy of Pluto. He studied there for twenty years and was greatly influenced by Pluto in many of his earlier ideas. Aristotle wrote in dialogue form, and many of his early ideas show a strong impact from the teachings of Plato. Some of Plato’s later writings include ideas of discussion he had with one of his very own skilled students, Aristotle.

Much like his teacher Plato, Aristotle believed that the earth was the center of the universe. One debate that he made was that the earth was too big to move, and because of that everything else must move around the earth. Another argument that he made was that if the earth was moving extremely fast there would be fast winds, and there were not. Aristotle also had a theory of the earth being a sphere in which he later proved that his theory was correct by showing the shadow of the earth on the moon during a lunar eclipse. One unlikely theory that Aristotle had was that the further away an object is from earth, the more perfect it and its motion is. He concluded that all the planets were in a fixated position in an invisible sphere at an established distance.

Nicolaus Copernicus

Nicolaus Copernicus said, “To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge”. Copernicus was born in February 19th, 1473 and passed away in May 24th, 1543. He traveled to Italy at the age of eighteen where he studied mathematics and astronomy. While he was at the University of Bologna, he lived with an astronomy professor named Domenico Maria de Novara. Copernicus participated in helping Domenico with making observations of the heavens and with research. He worked as a physician and secretary in a tower where he has an enormous amount of time and opportunity to study the night sky.

In 1514, Copernicus wrote in a notebook about his ideas and theories about the universe. He had an idea that instead of the earth being the center of the universe, the sun is a fixed point between all the planets. The planets movements are detected by their position seen in reference to the sun. He also said that the earth’s rotation was responsible for the sun rising and setting every day. He believed that the sun and the moon orbited around the motionless moon while the other planets were beyond all of that. Copernicus was responsible for changing the view of the universe and gave the later astronomers a great place to start with their research.

Galilei Galileo

Galilei Galileo once said, “All truths are easy to understand once they are discovered; the point is to discover them.” Galileo was born on February 15th, 1564 and passed away on January 8th, 1642. He was an astronomer, a mathematician, and contributed to the scientific method. In 1581 Galileo attended the University of Pisa, where he went to study medicine. Against his fathers wished he decided to study mathematics and philosophy. After several years he left the university without a degree and decided to teach math privately, where he also started studying motion. He applied for the chair of mathematics at Bologna university and was denied. Shortly after he was asked to present several lectures which helped him gain recognition, and he later became the chair of mathematics at the University of Pisa.

Galileo demonstrated during his lectures that the speed an object falls is not determined by its weight. Galileo also made an improved version of the earliest telescope that magnified by a scale of twenty. He later drew the different phases of the moon and explained how the surface of the moon was not smooth. In 1610, with the telescope, he discovered that Jupiter had four moons. He also discovered the phases of Venus, and the stars of the milky way.

Claudius Ptolemy 

Claudius Ptolemy said, “Mortal as I am, I know that I am born for a day. But when I follow at my pleasure the serried multitude of the stars in their circular course, my feet no longer touch the earth.” Ptolemy was born in 100 AD and passed away in 170 AD. He grew up in the royal court of Pella. He later joined Alexander at Mieza where he studied with Aristotle for three years. There is not much information on Ptolemy’s early life other that what can be inferred from his writings. A lot of the theories that Ptolemy had made were later proven incorrect but made a strong foundation for later astronomers to build from. The Almagest was Ptolemy’s first known piece of astronomic work. In this piece of work, there are observations of things that he observed about the universe and astronomy for over twenty-five years. The first few chapters of this book explain that the earth is a sphere and is in a fixated position in the center of the universe. He proposed that the earth was the center of the sun, the moon, and all other planets where they were in a system of rings. His theory predicted that there were fifty-five circular motions in which the planets moved along their appointed paths at their own pace. Ptolemy also wrote a second book called Geographica where he made an enormous number of maps. He explained how to figure out the longitude and latitude, and he also explained how to use a compass, explaining that north pointed up and south pointed down. He made a big contribution to making sure that future astronomers where headed in the right direction with their work and helped them to better understand a little bit about astronomy.

Conclusion

These four astronomers have made a great impact on today's knowledge of how the universe and everything inside of it works. Although a lot of their theories were incorrect, every single one of them made it a little clearer for the next one until it all made since.