# Euclid and Eratosthenes — Greek or African?

Last month the mathematics author John Derbyshire wrote an online article not about mathematics but on his personal views regarding race. Views which eventually got him sacked as a columnist for the publisher. The Guardian newspaper responded through an article by Jonathan Farley. My post today is not about race but rather about some points made in the comments to Farley’s article. In his article Farley said

… Euclid, Eratosthenes and other African mathematicians outshone Europe’s brightest stars for millennia.

In the comments section it was asked

They are known as Greek mathematicians. Why are they quoted in an article about Black mathematicians?

Now, one should avoid getting involved in fights in comments section and fortunately someone had replied in a comment later highlighted by Guardian staff

Well, Euclid is ‘Euclid of Alexandria’ which is in Egypt of course and Eratosthenes was born in Cyrene (modern Libya).

So I don’t think its erroneous to say they were black mathematicians.

Various arguments were made later in the comments about whether North African counted as black. I’m not going to get into this argument either. Instead my post is about the precise origins of Euclid and Eratosthenes.

In my geometry and history of mathematics courses I tell my students that when we talk of Greek mathematicians, we should not think of them as swanning around in Athens dressed in togas. Instead they came from all over the Mediterranean, from what we now call Italy, Egypt, Turkey, Libya and so on. Some even came from Greece. (And they didn’t wear togas. That was the Romans. The Greeks wore a chiton, a type of tunic.) A good example of this is the greatest Greek scientist, Archimedes, who was from Syracuse in Sicily. But what about Euclid and Eratosthenes?

First of all, was Euclid from Greece or was he from North Africa? The simple answer is nobody knows. We know almost nothing about him and some people have suggested that he didn’t even exist at all but, rather like Nicolas Bourbaki, was a collective of mathematicians writing under a pseudonym. (Rather amusingly, the Bourbaki from whom they took their name was of Greek descent!) Euclid could have come from anywhere in the Hellenistic world and being a good mathematician he was attracted to the most important place in mathematics: The Library in Alexandria, Egypt. One could argue that he was from the local area just on the balance of probabilities but given that many of the greats are known to have travelled (eg Pythagoras and Archimedes) that’s not the strongest of arguments. Thus, if we’re looking to Euclid for a poster boy for African mathematics we’re not on the firmest of grounds.

Eratosthenes, on the other hand, is a better bet. He was born in Cyrene which is now Shahhat in Libya. He was certainly in the first rank of his era. Archimedes was a correspondent and though probably Archimedes did not rate him as a true equal, that’s a good sign. Like Euclid, he worked in the Library at Alexandria which for over 300 years was the important place for mathematics. Eratosthenes’ claim to fame is that he measured the size of the Earth to a good degree of accuracy. There is some argument as to whether that accuracy was achieved through good fortune due to the errors in his measurements luckily cancelling each other, but the fact remains that his proposed method was sound.

One problem with the argument that Eratosthenes was lucky is that we don’t have the works of Eratosthenes to look at. For his earth measurement we have a short report by Strabo which probably simplified the argument to make it easier to follow and was likely a precis of a whole book. The argument handed down to us by Strabo involves Alexandria being due north of Syene, which it isn’t, and, so the critics say, this error cancels with others. However, Eratosthenes was an excellent geographer and he probably knew the precise locations of the two towns and his argument was likely sophisticated enough to deal with this problem. Thus, maybe only Strabo’s version is wrong. We’ll probably never know.

To sum up:

Origins of Euclid: Nobody knows.

Origins of Eratosthenes: From what we now call Libya.

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