BSED Major in Social Studies 2

Eratosthenes of Cyrene

Eratosthenes of Cyrene (c. 276 BCE – c. 194 BCE) was a Greek mathematician, geographer, and astronomer. He is best known for calculating the Earth's circumference with remarkable accuracy using simple geometry. Eratosthenes also invented the "sieve of Eratosthenes," a method for finding prime numbers. Additionally, he was the first person to use the term "geography" and made significant contributions to the understanding of the world map. He served as the head librarian at the Library of Alexandria, one of the most famous libraries in the ancient world.

Eratosthenes was a true polymath, excelling in various fields beyond his notable work in geography and mathematics. Some additional contributions and achievements include:

1. Measurement of the Earth's Circumference: Using observations of shadows in two different cities, Syene (now Aswan) and Alexandria, Eratosthenes calculated the Earth's circumference to be around 40,000 kilometers, remarkably close to the modern value of 40,075 kilometers. He did this by comparing the angle of the shadow cast by the sun at noon in both locations during the summer solstice.

2. The Sieve of Eratosthenes: This was an efficient algorithm for identifying all prime numbers up to a given limit. It worked by progressively marking the multiples of each prime number starting from 2, eliminating non-prime numbers in a systematic way.

3. Chronology and History: Eratosthenes made significant contributions to chronology, attempting to calculate the dates of important historical events. He compiled lists of the winners of the Olympic Games and tried to synchronize events across various cultures and civilizations.

4. Geography: He created a map of the known world, improving the understanding of world geography in the ancient world. His work included the concept of latitudes and longitudes, which later became essential in map-making.

5. Astronomy: In addition to calculating the Earth’s circumference, Eratosthenes also measured the tilt of the Earth's axis, which is crucial in understanding the seasons. His measurement was only off by a fraction from modern calculations.

Eratosthenes was often referred to as "Beta" (the second letter of the Greek alphabet), not because he was second-rate, but because he was seen as second-best in many disciplines—implying that he was highly proficient in a wide range of subjects, even if not the absolute best in one particular field. His work laid foundational knowledge for later scholars in both the Greek and Roman eras.