Biographies

Aristarchus: magnitudes and distances of the Sun and the Moon

Aristarchus: magnitudes and distances of the Sun and the Moon

Aristarchus was born in Samos - Greece - in the year 310 B.C. and died in 230 B.C. He was a student of Strato de Lampsacos, head of the peripatetic school founded by Aristotle. Years later Aristarchus would succeed Teofrasto as head of this institution between 288 and 287 B.C.

He was a skilled geometer, but little is known about his life. His hypotheses about the universe have been extracted from the references made by other authors after his death. Ptolemy in Almagesto names him as a conscientious observer of solstices and equinoxes. He seems to have interpreted these observations correctly, attributing these phenomena to the movement of the Earth around the Sun. He deduced from this that it was necessary that the Earth's orbit be inclined to explain the seasonal changes.

Archimedes, in the Arenario - The Arena accountant - explains that Aristarchus published a book based on certain hypotheses and in which it seems that the universe is much larger than it is raised. Their hypotheses are that the fixed stars and the Sun remain motionless, that the earth revolves around the Sun following the circumference of a circle with the Sun in the middle of the orbit, and that the sphere of the fixed stars also with the Sun as the center, It is so large that the circle in which it assumes that the earth rotates keeps the same proportion at the distance of the fixed stars as the center of the sphere to its surface.

Plutarch also refers to Aristarchus summarizing his geocentric idea that the sky is motionless and the Earth moves on an inclined orbit rotating at the same time on its own axis. In the same text, Plutarch reports that Cleantes (around 260 BC) denounced Aristarchus for impious, based on the fact that he displaced the Earth from the center of the universe.

Aristarchus considered the Sun as a star and probably the stars were suns. From what is known of his thoughts about the cosmos it can be summarized that he was one of the first to promulgate the Heliocentric theory.

He began measuring distance and comparing relative sizes in cosmology using trigonometry. He explained the movements of earth rotation and translation. He deduced that the earth's orbit is tilted. Wide the size of the known universe - although with a large margin of error since it calculated that the Sun was 19 times larger than the Moon and was 19 times farther away, it is currently known to be 400 times larger and 400 times more far.

Aristarchus could assume that the Sun was one more star than those observed in the sky. Unfortunately, only one of Aristarchus' works has reached us in modern times, "On the magnitudes and distances of the Sun and the Moon", and although most of his ideas are known through third parties, it can be said that it was one of the ones that has presented more advanced to his time.

It is likely that if it were not for the absence of his writings and for the attacks that began to be felt by groups guided by religious beliefs and faith, the history of cosmology would have been different and that Aristarchus "The geometer" had the recognition that it deserves.

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Euclid, the father of geometryEratosthenes and the measurement of the Earth's sphere