The period of breaking away from the supernatural or mythical is regarded as the beginning of astronomy, which was done from Thales (624-546 BC). He tried to interpret the heavenly world only with natural philosophical perception, but it was quite different from previous scholars that he unfolded cosmology from a materialistic standpoint.
Anaximandros (610-546 BC) argued that the shape of the Earth was shaped like a cylinder (similar to a cylindrical shape). And he hypothesized that the Earth's location would not be at the exact center of the world, which is of great significance in that it provided future astronomers with an ideological origin to break away from the Earth's centralism.
Anaximenes (585-525, BC) argued that the shape of the Earth is in the form of a flat disk and floats on a huge air cushion. And he developed the logic that there is a soul that operates the natural world, which later develops into a concept of a cosmic soul.
Pythagoras (570-500 BC) was the first astronomer to think that the earth was round. Uniquely, he argued that the universe was created according to moral principles, and that natural phenomena occurring in the heavenly world were also based on those principles.
The idea of Plato (427-347, BC) was not only an axis of ancient natural philosophy, but also evolved into new Platonism and became the ideological origin of the modern astronomical revolution through Renaissance.
Plato argued that geometry is the only means of overcoming human lack of rationality, and convinced that geometry is a lantern that will illuminate "idea" with phenomenal consistency in astronomy.
Plato's cosmology can be confirmed in his book Timaios, which explains that the universe was created by paradeigma.
Plato clearly expresses his thoughts on whether to view the creation of the universe as a real event and the completion of the creation process as a starting point of the universe, or as a permanent "clean order system" of the universe.
In other words, the most beautiful of all that has arisen, and the best of all causes is the universe, so there must be order and beauty, and Plato emphasized that it is never by chance that such order and beauty arise.
Plato explained that Demiurgos pursued the "best" in the process of creating the universe and changed the incongruous and disorderly things into a harmonious and orderly state, and that intellectual things were better than those that were not, and that intelligence could never exist.
Plato thus regarded the universe as "a creature with both soul and intelligence."
At this time, the introduction of the concept of "horn" in the process of defining the motion of the universe is in line with the existence of a soul that moved the natural world claimed by Anacimenez.
This concept of "space spirit" later reappears in Kepler's process of explaining the irregularities of planetary motion (the phenomenon in which the distance between the sun and the planet becomes closer and farther, and the speed of the planet's orbit becomes faster and slower).
Aristotle (384-322, BC) coolly criticized the fundamental idea of Plato's school, which had a strong mental aspect, and never agreed with Plato's claim that "the material world only expresses the real world very well, and the real world is actually an area of abstract thought without reality."
Aristotle's worldview considered all phenomena to be realistic and realistic.
For Plato, real things were abstract objects that existed beyond the material world, but for Aristotle, real things were material things and had to exist immediately.
Aristotle provided the rule to future astronomers that "the celestial sphere with planets embedded in it is stacked in several layers around the Earth to form a perfect spherical orbit and rotate at a constant speed forever."
This is explained in detail in Aristotle's book, "About the Heavenly System," in particular, he argued that all movements in the natural world contained in the universe must be eternal, and that "you produce eternal motion without exercising," or "the driving force of immobility," must exist to sustain them.
Aristotle's ideas, in conjunction with not only astronomy but also Christian doctrines, exert a great influence as a criterion for discussing consistency in the research process of all disciplines until the 17th century.(In the future, I will explain in detail Copernicus about the rotation of the celestial sphere.)
Hipparchus (190-120, BC) is a Greek astronomer who collected and organized astronomical data from Babylonians who made astronomical observations focusing on practical purposes and developed the results into a more sophisticated study.
Hipparcus invented a new concept called "main power source" to explain the retrograde of planets (a phenomenon in which planets seem to reverse the path they have already passed for a certain period of time and then return to the original direction).
With the introduction of the main power source, it is much easier than before to explain not only the retrograde phenomenon of the planets, but also the changes in brightness of the planets according to the relative distance between the Earth and the planets.
However, if you look closely at the common elements of ancient Greek natural philosophers, you can't find a standard that can be applied in the process of each school's conception of a space model except that the Earth was placed at the center of the universe.
Since there was no systematic standard to share except "put the earth at the center of the universe," each person arbitrarily interpreted the heavenly world as if they were pioneering a new realm by attracting metaphysical elements at will.
Moreover, since there was no public pledge to provide solid trust in experiments and observations, the choice of research methods was quite free and diverse.
Eventually, groups of ancient Greek natural philosophers failed to hand over an integrated and systematic geocentric model to future astronomers by interpreting differently the principles of matter and celestial bodies that make up the universe.
Claudios Ptolemaios (90-168, AD) opened a new horizon in astronomy by escaping astronomy from metaphysics and organizing it mathematically.
Almagest, a mathematical argumentation of Ptolemy's data collected through long observations, was originally titled Megale Syntaxis Astoronomias, his astrological encyclopedia Tetrablos.
Ptolemy considered the practical aspect of astronomy more important, unlike the existing Greek natural philosophers who tried to interpret the heavenly system in terms of academics.
For example, the coronation ceremony to succeed to the throne, such as predicting fate through a constellation related to a person's birth date, was to use astronomy to find out when it was good and what movement the planet was doing.
Ptolemy attempted to blend in with Aristotle's space model for a while at the beginning of his research, but eventually could not follow Aristotle. The reason was that Ptolemy's findings in astronomy clearly showed that he could not accompany Aristotle. These facts were confirmed through the contents of Ptolemy's Planetary Hypotheses discovered in 1967.
Ptolemy tried to extract the regularity of the seedlings from the motion of the planets and create a planetary system based on them, attracted by that purpose, he introduced the concept of eccentricity to explain the speed, size, and brightness of the planets.
To briefly explain the eccentricity, the center of the celestial sphere where the planets rotate is slightly off the Earth, where the position of the Earth is eccentric. An eccentricity allows us to explain a phenomenon in which planets appear slightly different in size from their rotation centers (geometric distances are the same) to appear to vary depending on where they are located.
The reason Ptolemy introduced this eccentricity was not to break the principle that planets orbit around the Earth and that planets are moving in circular orbits. However, as a result, the principle of "earth-centered circular motion," which has long protected the astronomical world, was naturally broken.
Ptolemy explained that the reason why the sun and stars (stars) float from the east to the west every day is not because they are not found in the rotation of the Earth, but because celestial bodies with sun and stars are orbiting the Earth every day.
The reason Ptolemy explained the circadian motion of celestial bodies was that if the Earth rotates once a day, its velocity would be so fast that all objects on Earth must fly into space by centrifugal force (then the sun, stars rotate faster) How can you explain the phenomenon of exercising while drawing a circumference of the same size?--the question that Copernicus asked about Ptolemy's claim)
Ptolemy's suggestions seem quite absurd at this point in time, but they were quite popular with professional astronomers and astrologers at the time. This was because although Ptolemy did not fully explain the heavenly phenomena one after another, it was believed that the Almagest was explaining the motion of each planet properly through mathematical arguments. And even if Ptolemy astronomy had some errors overall, it was within the limits recognizable by the academic world.
Thanks to this strong academic trust, Ptolemy astronomy was able to continue its success for a long time without any particular competition until the mid-16th century.
Source: Im Jin-yong, "The Story of Astronomy We Didn't Know."