Does the Earth Turn?

Does the Earth Turn?

The Platonists and their Christian successors held the peculiar notion that the Earth was tainted and somehow nasty, while the heavens were perfect and divine. The fundamental idea that the Earth is a planet, that we are citizens of the Universe, was rejected and forgotten. The fundamental idea that the Earth is a planet, that we are citizens of the Universe, was rejected and forgotten. This idea was first argued by Aristarchus, born on Samos three centuries after Pythagoras. Aristarchus was one of the last of the Ionian scientists.

By this time, the center of the intellectual enlightenment has moved to the great Library of Alexandria. Aristarchus was the first person to hold that the Sun rather than the Earth is at the center of the planetary system, that all the planets go around the Sun rather than the Earth is at the center of the planetary system, that all the planets go around the Sun rather than the Earth.

Typically, his writings on this matter are lost. . From the size of the Earth’s shadow on the Moon during a lunar eclipse, he deduced that the Sun had to be much larger than the Earth, as well as vary far away. He may then have reasoned that it is absurd for so large a body as the Sun to revolve around so small a body as the Earth. He put the Sun at the Center, made the Earth rotate on its axis once a day and orbit the Sun once a year.

It is 2,200 years since Aristarcus, and our language still pretends that the Earth does not turn. Image: © Megan Jorgensen (Elena)

It is the same idea we associate with the name of Copernicus, whom Galileo described as “the restorer and confirmer”, not the inventor, of the heliocentric hypothesis. Copernicus may have gotten the idea from reading about Aristarchus. Recently discovered classical texts were a source of great excitement in Italian universities when Copernicus went to medical school there. In the manuscript of his book, Copernicus mentioned Aristarchus’ priority, but he omitted the citation before the book saw print. Copernicus wrote in a letter to Pope Paul III: “According to Cicero, Nicetas has thought the Earth was moved… According to Plutarch (who discusses Aristarchus)… certain others had held the same opinion. When from this, therefore, I had conceived its possibility, I myself also began to mediate upon the mobility of the Earth.

For most of the 1,800 years between Aristarchus and Copernicus nobody knew the correct disposition of the planets, even though it had been laid out perfectly clearly around 280 B.C. The idea outraged some of Aristarchus’ contemporaries. There were cries, like those voiced about Anaxogaras and Bruno and Galileo, that he be condemned for impiety. The resistance to Aristarchus and Copernicus, a kind of geocentrism in everyday life, remains with us : we still talk about the Sun “rising” and the Sun “setting”.