Tag Archives: Alexandria

Hypatia, the lady philosopher/mathematician/astronomer

Sometimes writing about history is hard. At the beginning of this project, I’d envisioned a fun and slightly wacky tour through Western Civilization presented by a fun and slightly wacky uncle. The story of human beings is often violent and cruel, though. Human beings are flawed creatures. There are parts of civilization’s history that make me heartsick.

I want to tell you about a glorious and brilliant woman who lived in Alexandria, Egypt in the 4th century ad. Her name is Hypatia. She was the daughter of a philosopher and mathematician, and she became a philosopher and mathematician herself. Hypatia was lovely to look at, but her intellect was what made her irresistible. I became interested in her when I read that if she hadn’t outright invented the astrolabe, at the least she played an big part in developing it.

Hypatia helped her dad expand Ptolemy’s work on astronomy. She eventually did her own scholarly work on the stars and the geocentric model of the universe. It might have been she who came up with the idea of ‘flattening’ the spheres to create the star-map that is central to the astrolabe’s design (this is my own conjecture).

Hypatia was also a philosopher. Her philosophy was Neo-Platonism, which adapts Plato’s ideas about what makes the world tick. Hypatia was a gifted teacher. She often gave lectures in the agora (Greek for public square) about philosophy, astronomy, and her many intellectual interests. At that time Alexandria was boiling with religious trouble. Christians and Jews battled with each other and with philosophers who rejected a belief in God. The Roman Empire was in its last days, about to split into East and West. Politics absolutely played a part in the violent clashes between religion and philosophy.

I’m sorry and ashamed to tell you that a mob of Christians ambushed Hypatia, and murdered her. It’s nearly impossible for me to believe that these were followers of Jesus. But it happened. They behaved as a mob—the very opposite of civilization—and murdered a woman for promoting a philosophy that rejects Christianity.

You can read more about Hypatia here and here. There’s a movie about her, too.  Here’s a review—caution: some violence.  (I have a quibble with History Buff’s conclusion that, because of Christianity, scholarship was discouraged in the Dark Ages. Beginning with Charlemagne, the Holy Roman Empire fostered a culture of learning that was encouraged in the monasteries. Monks copied books by hand—the books from the Greek philosophers that had been translated into Arabic, which the monks then translated into Latin. See How The Irish Saved Civilization by Thomas Cahill.)

The well at Syene

So how did Eratosthenes figure out how big around the Earth is? Here’s how:

First, he assumed the Earth is round like a ball.

Well at Syene.

Second, he knew several things about a little town called Syene. It is 5,000 stadia (575 miles or 925 kilometers) directly south of Alexandria. There was a well in the center of town, dug deep and plumb—straight toward the Earth’s center. At noon on June 21st, the Summer solstice, you could see the Sun reflected on the water way down in that well, which means the Sun is directly overhead.

Bird’s-eye view of the Sun’s reflection in the well at Syene.

That’s because Syene is located on the Tropic of Cancer. If you happen to be standing on the Tropic of Cancer and it’s noon where you are on June 21 you can draw a straight line from the center of the Earth, through the Tropic of Cancer, to the Sun.

A stadion is an ancient Greek unit of measurement—it’s 600 feet (an eighth of a mile). Stadion is singular (nominative, singular, second declension); stadia is plural (nominative, plural, second declension). 5,000 stadia = 575 miles or 925 kilometers. I hope I declenched in all the right spots. Many thanks to my Greek-scholar pals Jackie J., Michele J. & Joann W!