Philosophers and Eclipses

BYU philosophy professor Dan Graham discusses the astronomy of pre-Socratic philosophers and why they deserve more credit.

PROVO, Utah (Sept. 14, 2017)—Philosophy professor Dan Graham is soft-spoken, with a slight build and thin-framed glasses. But during his presentation “Philosophers and Eclipses” for the weekly philosophy lecture series, he boldly claimed some scientific ground on behalf of his forebears. He said, “Everybody recognizes that the early Greek philosophers, so-called pre-Socratics, had a scientific way of doing cosmology; they had some really cool ideas. But they . . . never got anything right. . . . This was a mistake. Ultimately they got some things right and made some scientific breakthroughs that they never get credit for.”

To truly understand the beginnings of astronomy, Graham invited the audience to imagine Babylonia in 1640 BCE. Believing that anything in the sky could be a sign from the heavens, pre-Socratics took record-keeping very seriously. Thanks to their records, they discovered cycles of eclipses that allowed them to predict future eclipses. Graham admitted, “they did not know why this happened—it was purely empirical—but it worked.”

The first recorded philosopher to offer a “quasi-scientific” theory for natural phenomena was a man from the Aegean area named Thales. He proposed that the earth was floating on a large expanse of sea like a raft, and when the sea got choppy, it would cause earthquakes. After Thales, Greek philosophers came up with many other theories, including some to explain eclipses: an eclipse as a bowl of flame with a fiery side and a dark side, the sun’s loss of fuel, and the covering of the sun by a cloud were all theories put forth. But not until Parmenides and later Empedocles realized that the moon did not, itself, shine, did the ancients begin to approach the truth. Parmenides beautifully described the reflected light from the sun onto the moon, now called heliophotism, as “a lamp by night, wandering around the earth with borrowed light.” Empedocles described it similarly, “[The moon] spins around the earth, a circular, borrowed light. [She] looks upon the bright circle of her lord’s face opposite her.”

This idea was embraced by a philosopher named Anaxagoras. “He’s the hero of the story as far as I can see,” Graham said. Born around 500 BCE on what is now the Turkish coast, he moved to Athens in time to witness two eclipses during his lifetime. He took Parmenides’ theory further, deriving some logical conclusions. He asserted that the moon must be opaque, solid like the earth, and spherical to allow for crescent-shaped cycles.. He also stated that heavenly bodies exist continuously. This is important because, up to that point, there were some who believed that a new sun rose every day. However, in order to have a full moon, the moon must be reflecting light from the sun all night long. Hence, the sun must exist all night as well. Furthermore, Anaxagoras deduced that the sun must be farther from the earth than the moon and their orbits circular.

All of this sounds very logical and straightforward, but Graham was quick to remind the audience, “The one striking thing about this is before Anaxagoras, [there were] all these different theories of solar eclipses. And after Anaxagoras, there were no new theories. Even the mathematical astronomers start picking this up. Nobody had a better theory than this.” Anaxagoras’ theory was so impressive, in fact, that Aristotle used it as a “paradigm of good science.” So, the next time you have the good fortune to observe the path of totality, Graham hopes you will do one thing. “When you think about eclipses, thank a philosopher.”


Olivia Madsen (B.A. French language, ’18)

Olivia covers events for the Philosophy department of the College of Humanities. She is a senior pursuing a degree in French language with a minor in international development.


Photos courtesy of National Geographic and Encyclopedia Britannica.