Astronomy

Aristarchus lived from about the year 310 B.C. to about 230 B.C. Aristarchus was the first Greek philosopher and mathematician to make sense of the solar system. Others before him thought that the Earth is a sphere and that it moves, but he was the first to understand the heliocentric theory, which states that the sun is in the middle. In 288 or 287 B.C. he followed Theophrastus as the head of the Peripatetic School established by Aristotle.

Aristarchus has only one existing book that is "On the Sizes and Distances of the Sun and Moon." In it he calculated the diameter of the Sun, which is about seven times the diameter of the Earth, and estimating the Sun's volume is about 300 times the volume of the Earth (the actual diameter of the Sun is about 300 times the diameter of the Earth.) In this book there is nothing indicating his heliocentric theory. Aristarchus' book on the planetary system with the Sun in the center did not survive. He also added that the universe is many times larger than generally assumed by astronomers, and the fixed stars are at an enormous distance from the Sun and its planets. Aristarchus regarded the Sun as one of the fixed stars, the closest to the Earth.

Aristarchus had no followers in his generation, or even in the next generation. About a century after Aristarchus, Seleucus, a Chaldean of Seleucia on the Tigris, who lived and wrote about the year 150 before the present era, adopted the teaching of Aristarchus.

Hipparchus is thought to be the greatest astronomer of ancient times, but he rejected the heliocentric system of Aristarchus, he did not reject it on a religious opinion, but on a scientific one. A system with the Sun in the center of circular orbits could not account for the abnormal motions of the planets, but the theory of epicycles could, and this theory has the Earth motionless in the center of the universe. Therefore the religious belief and the mathematical study, both, condemned Aristarchus and his teaching that the Earth circles around the Sun.

...