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HISTORY OF SCIENCE AND TECHNOLOGY

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Aristarchus of Samos (310 BC - 230 BC)

Aristarchus was a Greek philosopher who studied in Alexandria. His tutor was Strato of Lampsacus who was the head of the Alexandrian Lyceum at that time. Aristarchus observed and measured a lunar eclipse and used geometry to calculate sizes and distances. He calculated the radius of the Moon the distance between the Moon and the Earth, and even the distance from the Earth to the Sun. His calculations were not very accurate, although his geometry was correct. Unfortunately, the measuring instruments at that time could not give valid results.

However, Aristarchus did realise some very important facts. He realised that the stars are very far away, he found a more precise value for the solar year. He also knew that the Sun was larger than the Earth and that the earth rotates on its axis, resulting in night and day.

 

Illustration from "On the Dimensions and Distances of the Sun and Moon"

Illustration from "On the Dimensions and Distances of the Sun and Moon"
Public Domain Image

 

It was quite likely that these realisations led to his theory that the Earth moves around the Sun (the heliocentric theory), rather than Aristole's belief that the Sun moves around the Earth (the geocentric theory). Aristarchus's ideas were not accepted at that time. Too many philosophers and astronomers agreed with Aristole and the geocentric theory continued in popularity with Hipparchus (190 - 120 BC) and Ptolemy (85 - 165 AD).

However, Archimedes (287 -  212 BC) quoted Aristarchus in his writings and, many years later, Nicholaus Copernicus (1473 - 1543) revived the heliocentric theory in his book "De revolutionibus Caelestibus". Copernicus had originally credited Aristarchus in his book but he took out the credit before the book was published.

Aristarchus's only surviving work, a treatise called "On the Dimensions and Distances of the Sun and Moon", does not mention his heliocentric theory, perhaps because he feared it would be unpopular. It is fitting that the brightest feature on the Moon, the Aristarchus Crater, has been named after the man who is considered responsible for putting astronomy on course as a scientific discipline.

 

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