Eratosthenes, Alexandria Egypt, 276 – 194 BCE.Dorian Hoppie

Math 124 Section 1311.20.09

The time that Eratosthenes grew up in was one of chaos. Over half a century

earlier, the man who had single handedly conquered most of Europe, Asia Minor, and

Egypt, and made it look like a piece of cake, had died of heavy drinking and a fever in

Babylon before appointing himself a successor. Alexander’s commanders made the best

of the situation. Ptolemy, and later his long descending family of Ptolemy’s, received

Egypt, and all were under the command of Perdikkas. Eratosthenes was born two years

before the first Syrian war, the first of six wars that wouldn’t end until the middle of the

next century. It is thought that he was born to a humble family, his mother’s name is

unknown, his father has two possible names that are documented, Aglaos or Ambrosios.

Humble, though they may have been, they had to be able to afford an education

for their son, not to mention that according to the Cyrene Constitution, a man had to own

land worth at least twenty minas, and he had to be born to free parents. Scholars blame

Eratosthenes’ childhood for the lack of information, but also the conflict surrounding his

life. Wars and battles burned libraries and official documents, texts that recounted history

in a much more detailed fashion (Nicastro. 61). Young Eratosthenes moved from Cyrene

to Athens for a time, studying under men such as the scholar Lysanias, the philosopher

Ariston, and the poet Callimachus. The great School of Athens, founded by Aristotle had

attracted many scholars and free thinkers from everywhere. Eratosthenes was considered

a Polymath, meaning he was an expert in literary criticism, poetry, geography, and

mathematics. He was criticized for rarely ever accomplishing much, however, and gained

himself the nickname Beta which was the second letter in the Greek Alphabet. After a

time as the writer and mathematician, Eratosthenes moved to Alexandria at the request of

Egypt’s Satrap, Ptolemy II.

While traveling back and forth between Syene and Alexandria, Eratosthenes

noticed on the summer solstice in Syene, that the sun was at the zenith and reach

perpendicularly down into a well, reflecting brilliantly off of the water at the bottom. He

reasoned that the sun is so far away that its rays could be thought of as parallel, and that

they should cast the same angle of light across the Earth’s surface all over. Eratosthenes

traveled back to Alexandria and noted that the shadow cast across the ground at the same

time had a 7º difference. Using that, and the distance between Syene and Alexandria in

stades. He measured the circumference of the Earth, which was only off by 10% from the

modern day circumference. Longitudes and latitudes were also a thing of his time.

His discoveries were welcomed by the age of chaos. Rulers, Generals and

warlords sent their men out to remap territories. The newer more current geography

helped warring cities to gain knew knowledge of bordering lands, giving them

advantages against each other.

Eratosthenes is also accredited with coming up with an algorithm for finding the

prime numbers, which are still being found today. The sieve method was efficient for

smaller primes, although quite tedious The method crossed off primes of smaller obvious

numbers, which made the hunt easier.

He was said to be a conceited individual, arrogant and short sighted in the works

of others and ended his life by starving himself, after having gone blind. Eratosthenes

may have been a joke in his early years, but his studies were the beginnings of many

other great things.