Claudius Ptolemy, a Greco-Egyptian astrologer (born 100 A.D., died 170 A.D.) who published the basic motions of some planets in this solar system around Earth, had a lengthy and strenuous start to that conclusion. It is a difficult task to form an argument, especially an argument composed of how the whole universe operates and moves, even when he had the whole library of Alexandria at his disposal to help support his ideals of motion and geocentric model, it is quite a task to take a hold of and conquer. However, he was able to set his ideas in motion (no pun intended) and studied the skies and Aristotle’s Aristotelian system, finally composing all of his cold hard research into thirteen books called the Almagest, also called The Great System.

In these thirteen books are all of his ingenious ideas and revelations, ranging from solstices, equinoxes, formulas for chord functions, his theory of the moon, fixed stars, and most importantly, his planetary theories. For the entirety of his life, his greatest works, ideals, and contributions are contained in these thirteen books and will be where I will extract his accomplishments, summing up his life’s works. Through this waterfall of realizations, he goes through each book first grasping on a well-known system and commonly accepted ideal at the time, Aristotle’s earth-centered system called a geocentric model, building from this model to add his own details, then predicts the positions of planetary objects with the use of epicycles as well as determining seasons, and lastly, his conclusion of planetary motion with the inclusion of intricate mathematics and eccentric methods.

With every great resolution ever created in history, it must first stem from another great resolution in the past, in Ptolemy’s case, his resolution stemmed off of Aristotle’s Aristotelian system. Aristotle’s original system was the geocentric model, a model where the Earth is essentially the center of the universe. The stars, moon, and planets are all in a celestial sphere encircling the Earth that rotates throughout the day, but never drifts out of said celestial sphere. This model was well accepted during the time of Ptolemy’s life, even if it is not accurate to today’s standard, however, when a system of ideals is widely accepted, others tend to build from that idea, like Ptolemy did. Ptolemy’s contribution to the geocentric model was by being able to predict the positions of the sun, stars, and moon by using a source of planetary measurements called epicycles.

By being able to build on the geocentric model, even if it was an ideal already invented, was a start to being a revolutionary astronomer, so by creating these circular motion measurements called epicycles, Ptolemy was able to continue on to create the Ptolemaic Model, one of his greater contributions. Ptolemy took these epicycles and incorporated them in a diagram in which the Earth stood in the center of its own epicycle (not moving) while other objects, like planets, would orbit in and around Earth’s perimeters. Then, Ptolemy moves the Earth to a slightly different position, known as the eccentric position, to show that the planets move in a gear-like rotation in which the planet is able to speed up and slow down at different points in the model. Another reinforcement of this idea was to place a point called the equant which juxtaposes the eccentric position in which the Earth stays, to show even more clearly that the planet is indeed speeding up and slowing down like a gear. These were sadly just tricks to fool the eye and did not actually represent any actual realistic data, only merely being a magician’s tool. However, the Ptolemaic Model itself, is a model that is still used to this day in the form of current model planetariums to project the heavenly uniform motions of the surrounding planets and uses specific gears to help envision the movement of epicycles.

While providing the details of planetary motion above seems simple, it was hard for Ptolemy to match this system of epicycles with the idea that the heavens were a constant factor of unchanging perfectively, constant in its brilliance. How could the heavens still be constant if the stars go from being brighter, to dimmer? They are able to do this with retrograde motion which happens when a planet reverses its direction because of stars that are ultimately stuck in place, yet then the planets are able to then fix or resume their forward motion after a certain period of time. Ptolemy then concludes that the heavens are then allowed to stay perfect and constant, while the planets are then considered to be varied and flawed, like all physical matter in this world. It is not to be assumed as a heavenly object in essence. Since these planets were worldly objects and not heavenly objects, they then needed to assume a hierarchy, which is where the term deferent comes to play its part. Deferents are the major circles in which epicycles created, since there are many epicycles instead of one. Deferents contained smaller epicycles within them as well; the deferents building on top of the epicycles in essence. With Ptolemy adding in these deferents, the planets are no longer limited to solid circular rotation, but were able to move in different cycles. While these intricate calculations and conclusions were placed by Ptolemy, they were accurate and what constituted his success in drawing his knowledge of planetary motion, however, when the heliocentric model was created, it was just more convenient to stick to all the workings of that model instead of including both ideals from geocentric and heliocentric at the same time, even if parts of the geocentric model was true when it came to Ptolemy’s precision. Ptolemy’s work, even if not appreciated in today’s standards, was not determined to be in vain, but was an important stepping stone to lead down the path to understand the universe and its patterns and interworking pieces.

Reflecting on the work Ptolemy created in his life time, he constituted a great thesis to the operation of motion outside of this world, even if some of his ideals and writing were flawed and deemed to be controversial in the fact that he had many errors in his work and stolen data, he created the Ptolemaic Model. The Ptolemaic Model was then proven to be accurate and useful as well as Ptolemy’s books of Almagest which represented his triumph in understanding motion in the universe. With Ptolemy’s contribution to cosmology, others were then able to form their own conclusions which help us understand the universe to this day. Without Ptolemy’s ideas of motion and epicycles, development would have been pushed back many years or in worse circumstances, not discovered. His ideals, efforts, and life works were not in vain.