Eratosthenes, a Greek mathematician, was the first to calculate the Earth’s circumference with remarkable accuracy over 2,000 years ago using a simple yet brilliant method. He observed that at noon in Syene (modern-day Aswan, Egypt), the Sun was directly overhead and cast no shadow, while at the same time in Alexandria, a shadow formed at an angle of about 7.2 degrees. Realizing that this angle represented 1/50th of a full circle and assuming the Sun’s rays were parallel and the Earth was spheri

Eratosthenes of Cyrene (c. 276-195 BC) was an ancient Greek polymath who became chief librarian at Alexandria's legendary library. Born in Cyrene (modern Libya), he studied in Athens before being summoned to Alexandria by Ptolemy III. Though critics nicknamed him "Beta" for always placing second in every field, his colleagues called him "Pentathlos" for his well-rounded expertise in mathematics, geography, astronomy, poetry, and music theory. His final years brought blindness, and rather than li