Today is the day that Thales, an ancient Greek philosopher/mathematician/scientist (we don’t really have a good word for those ancient thinkers) correctly predicted a solar eclipse in 585 BCE. Since solar eclipses are physical, objective events that can be projected both backwards and forwards in time, today is the anniversary of an ancient date that humans have a verifiable written record about; a “cardinal date.” It wasn’t originally May 28, obviously, because the calendar has changed, but although it had a different designation, this is the day of the eclipse visible in Greece over 2600 years ago.
Thales was, among Ancient Greek Philosophers, particularly ancient; he was one of the first. He was around before Socrates, and is considered one of the founding figures in what we think of as Ancient Greece. He’s still known for Thales’s Theorem in geometry, and in addition to predicting the 585 BCE eclipse, predicted the timings of the solstices and equinoxes of his era. He was also an engineer, and designed and led a project to divert the Halys River. He probably invented the geometry he used to calculate the height of the pyramids in Egypt, as well as being able to measure the distance out to sea of a ship on the horizon.
As a natural philosopher, Thales was as concerned as his colleagues about what the universe was really made of. His theory was water; everything was ultimately made, he thought, of water. Now we know he wasn’t right, but it wasn’t that bad a guess, given what he had to work with.
I’m calling Thales “Greek,” but nobody knows for sure whether he really was; he might have been Phonician. Most of what we know about him and his life comes from Lives and Opinions of the Eminent Philosophers, written by Diogenes Laërtius. Unfortunately Laërtius didn’t write it until about 800 years after Thales’ time, so the details in it may not be as accurate as you’d hope. We do, however, have an idea about the year he was born. In about 200 BCE Apollodorus of Athens wrote a chronicle that mentioned Thales and the eclipse he predicted. Apollodorus mentioned Thales’ “acme” in relation to when the eclipse occurred. The English word acme is from a Greek word meaning the “flower of life,” or the age when a person is in their prime. If we assume that was age 40, we can use the eclipse as a reliable date to estimate that Thales would have been born about 625 BCE.
In some accounts, Thales had a family, but in other stories he’s quoted as saying he never married and didn’t want to worry about children. Accounts of his travels vary too; he may or may not have visited Egypt and Babylon. There’s no unquestioned evidence either way, but he did (as far as we know) measure the height of the Pyramids, which suggests that he would have seen them. As for Babylon, if you were interested in math in those days, that’s where you would have gone. The Babylonians were very advanced at math and calculated in base 60 (“sexagesimal”).
There is at least one story about Thales suggesting he was wealthy, and got his wealth by figuring out how to forecast the weather. Around Miletus, where he lived, olives were an important crop, and the story goes that one year he predicted a very good harvest, and bought all the olive presses in advance, which ensured his fortune once the bumper crop of olives arrived. A good corollary to that story is that he conducted the whole operation after some wag remarked “Oh yeah? If you’re so smart, why ain’t you rich?”
Thales may have lived to the age of 78 — that’s what Apollodorus said, at least, adding that Thales died of heat stroke while watching the 58th Olympic games around 546 BCE. Nobody really knows. But there’s a crater on the moon named after Thales, there’s a theorem in geometry with his name, he very likely predicted a solar eclipse, and if you visit Union Station, in Washington, D.C., there’s a statue on the main facade called “Thales.” It doesn’t really depict him, of course; nobody knows what he looked like. And it’s part of the sculptural depiction of The Progress of Railroading, for some reason. But even with all the uncertainty around people and events from millennia ago, we do know for sure that there was a solar eclipse visible in Greece in 585 BCE, and a guy named Thales most likely figured out when it was due.
