Aristarchus of Samos

Aristarchus, the famous ancient astronomer and mathematician born in Samos: Aristarchus (310 BC-230 BC) was a famous Greek mathematician and astronomer, popular for his theories regarding the heliocentrism of our solar system. He was the first to say that the Sun, and not the Earth, was the center of our universe. This theory brought him ridicule during his lifetime.

However, when his works were unearthed and studied around 1800 years later by Copernicus, the rightness of his theory was proven. Although his works were considered inferior to those of Aristotle and Ptolemy, he has made many significant contributions to science.

Aristarchus was born on Samos island. He probably studied in Alexandria, Egypt, under Strato of Lampsacus. His only surviving work is entitled On the Sizes and Distances of the Sun and Moon.

Aristarchus managed to place the Sun in the middle of the solar system and he also placed the planets in the right order from the Sun. He gave a model of the universe with a stationary Sun and planets rotating in circular orbits around the Sun. The stars, which are actually stationary, seemed to be rotating because the Earth rotates on its own axis.

Aristarchus was one of the first astronomers to calculate the relative sizes of the Sun, the Moon and the Earth. He did this by observing the Moon during a lunar eclipse and by estimating the angle and the size of the Earth. He understood that the Sun, the Moon and the Earth form a near right angle during the last and the first quarter of the Moon.

Based on this, he calculated that the Sun was nineteen times further away from Earth than the Moon. However, he made a mistake in his calculations: he took the angle as 87 degrees while the correct angle is 89° 50'. Thus, the actual distance is 390 times and not nineteen times, as proposed by Aristarchus. Although the geometric theory is current, the calculations were wrong due to lack of precise instruments rather than logic.

His theory that the diameters of the Moon and the Sun should be proportional to their distance from the Earth is also logical but gave wrong results. Today that the intelligence of Aristarchus and his contribution to science has been renowned, scientists have given his name to a crater on the Moon.