The Earth revolves around the 'center of fire'
The universe is composed of Uranos, Cosmos and Olympus.
At the time when Pythagoras lived, the Greeks believed that the earth was round and flat. It looked like a discus. And they believed that their country was in the center, and that the center was the Delphi Holy Land, which was famous for its god's residence, Mount Olympus or Trust.
They thought that the world like this disk is divided into two parts, being crossed from west to east by the sea. The sea was called the Mediterranean Sea. The eastern sea following it was called the Euksenos Sea. These are the only two seas that the Greeks know. Around the world, an ocean called Okeanos flows from south to north on the west side of the Earth and vice versa. The flow is consistent, so no storm can cause waves. The sea and all the rivers on Earth take water from there.
They thought the sun and moon rose in the east of Okeanus at dawn, giving light to God and humans and running in the air. Of course, the Earth was thought to be still and not moving. Except for the North Star and other nearby stars, all stars rise from the Okeanos and build into it. There, the sun god rides a ship with wings. Then He go around the north side of the Earth and go back to the east, back to the rising place. As depicted in Greek mythology, the Earth is at rest in the center of the universe in a flat disk shape, and the sun and other celestial bodies move around the Earth.
The Pythagorean universe: Uranos, Cosmos and Olympus. celestial bodies are spherical and circular, because celestial bodies are complete.
The Pythagorean school used mathematical notions to come up with a scientific model that is much more advanced than mythology. In particular, it is surprising that a model of Ji Dong-seol was already raised at this time. According to the Pythagorean school, the universe was divided into three parts. First, Uranos, the sub-moon world, including Earth, followed by Cosmos, the celestial world from the moon to the star's celestial sphere, and Olympus, the residence of various gods.
They thought the Earth, the celestial body, and the entire universe were spherical. Because the spherical shape is the most geometrically complete of the three dimensions. The various objects in the universe move in the same circular shape. The circle is a complete geometric shape, and the circular motion is a complete and immortal movement, so I thought it was appropriate for a noble and complete celestial body to do the circular motion. Such movements move more slowly as the celestial position is noble. The axiom that celestial motion is consistent and must be circular was inherited by Plato and Aristotle, and it was powerful as the governing principle of astronomy until recently.
Earth is one of the planets, the birth of primitive Ji Dong Seol(Heliocentric system ).
Pythagorean Philolaos proposed a universe model in which the Earth travels once a day from west to east around a central fire at the center of the universe. The same side of the Earth is always facing the central fire, which is as if one side of the moon is always facing the Earth. They imagined that there was another celestial body called the counter-earth between the Earth and the central fire. The central fire is not visible from the Earth because the counter-earth always blocks the central fire in line with the Earth. Philolaos is known to have been a prominent Pythagorean school leader enough for Plato to visit for learning. At that time, Philolaos believed that the Earth was one of several planets and revolved in a circular orbit.
This concept of central fire is different from what the solar system reveals today, but replacing it with the sun makes it a model that is quite close to the solar system today. The hypothesis that the Earth rotates around a central fire is in context of the theory that the Earth revolves around the sun(Ji Dong Seol). However, they never imagined that the Earth would rotate.
A Pythagorean model where the Earth rotates daily around the central fire indicates that all moving objects in the universe rotate around the central fire from west to east in unison. They imagined that this cycle would increase with the noble celestial body. The fact that Earth, the lowest celestial body of the universe, rotates around the central fire once a day, the moon rotates once a month, and the sun rotates once a year. They thought that the planet outside the Earth orbits around the central fire, but the star is stationary without rotating around the central fire.
The Pythagorean school claimed that each star exists at a certain proportion of distance from the Earth, just like the ratio of notes in the scale. However, the parallax between the stars, i.e., the relative appearance of the stars in Earth's orbit, was not observed at the time, so the Pythagorean school's first universe model had to be modified. The fact that the parallax between the stars does not appear was thought to be due to the very small orbit of the Earth around the central fire. The Pythagoreans didn't know that it was because the distance to the stars was so far.
Later, Pythagorean scholars Hiketas and Ekphantos assumed that the Earth was at the center of the universe and revolved around its axis once a day. This hypothesis solved the question of why the parallax between stars did not appear, and did not harm the stem of the Pythagorean universe model. This model, which abandoned Earth's revolution and took a rotation, later became the primitive Chen dong seol(Ptolemaic system).
Pythagoras and his school greatly influenced later philosophers, especially Plato. Plato inherited many of the Pythagorean theories. These include the importance of the soul, the concept of Idea, and the importance of mathematics (geometry) related to Idea.