Thales of Miletus: Greek Geometer

Thales of Miletus
Thales of Miletus. Public Domain

Much of our modern science, and astronomy in particular, has roots in the ancient world. In particular, the Greek philosophers studied the cosmos and tried to use the language of mathematics to explain everything. The Greek philosopher Thales was one such man. He was born around 624 BCE, and while some believe his lineage was Phoenician, most consider him to be Milesian (Miletus was in Asia Minor, now modern Turkey) and he came from a distinguished family.

It is difficult to write about Thales, since none of his own writing survives. He was known to be a prolific writer, but as with so many documents from the ancient world, his vanished through the ages. He is mentioned in other people's works and seems to have been quite well-known for his time among fellow philsophers and writers. Thales was an engineer, scientist, mathematician, and a philosopher interested in nature. He may have been the teacher of Anaximander (611 BC - 545 BCE), another philosopher.

Some researchers think Thales wrote a book on navigation, but there is little evidence of such a tome. In fact, if he wrote any works at all, they did not even survive until the time of Aristotle (384 BCE- 322 BCE). Even though the existence of his book is debatable, it turns out that Thales probably did define the constellation Ursa Minor.

Seven Sages

Despite the fact that much of what is known about Thales is mostly hearsay, he was definitely well-respected in ancient Greece.

He was the only philosopher before Socrates to be counted among the Seven Sages. These were philosophers in the 6th century BCE who were statesmen and law-givers, and in Thales's case, a natural philosopher (scientist). 

There are reports that Thales predicted an eclipse of the Sun in 585 BCE. While the 19-year cycle for lunar eclipses was well known by this time, solar eclipses were harder to predict, since they were visible from different locations on Earth and people were not aware of the orbital motions of the Sun, Moon, and Earth that contributed to solar eclipses.

Most likely, if he did make such a prediction, it was a lucky guess based on experience saying that another eclipse was due.

After the eclipse on 28 May, 585 BCE, Herodotus wrote, "Day was all of a sudden changed into night. This event had been foretold by Thales, the Milesian, who forewarned the Ionians of it, fixing for it the very year in which it took place. The Medes and Lydians, when they observed the change, ceased fighting, and were alike anxious to have terms of peace agreed on."

Impressive, but Human

Thales is often credited with some impressive work with geometry. It is said he determined the heights of pyramids by measuring their shadows and could deduce the distances of ships from a vantage point onshore.

How much of our knowledge of Thales is accurate is anyone's guess. Most of what we know is due to Aristotle who wrote in his Metaphysics: "Thales of Miletus taught that 'all things are water'." Apparently Thales believed the Earth floated in water and everything came from water.

Like the absent-minded professor stereotype still popular today, Thales has been described in both glowing and derogatory tales. One story, told by Aristotle, says Thales used his skills to predict that the next season's olive crop would be bountiful.

He then purchased all the olive presses and made a fortune when the prediction came true. Plato, on the other hand, told a story of how one night Thales was gazing at the sky as he walked and fell into a ditch. There was a pretty servant girl nearby who came to his rescue, who then said to him "How do you expect to understand what is going on up in the sky if you do not even see what is at your feet?"

Thales died about 547 BCE in in his home of Miletus.

Edited and updated by Carolyn Collins Petersen.

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Greene, Nick. "Thales of Miletus: Greek Geometer." ThoughtCo, Mar. 2, 2017, thoughtco.com/thales-of-miletus-3072243. Greene, Nick. (2017, March 2). Thales of Miletus: Greek Geometer. Retrieved from https://www.thoughtco.com/thales-of-miletus-3072243 Greene, Nick. "Thales of Miletus: Greek Geometer." ThoughtCo. https://www.thoughtco.com/thales-of-miletus-3072243 (accessed January 17, 2018).