The first person to calculate the circumference of the Earth and coined the word "geography" was the ancient Greek philosopher and mathematician, Eratosthenes.
The first person credited with calculating the circumference of the Earth and coining the word "geography" was the ancient Greek philosopher and mathematician, Eratosthenes of Cyrene. Eratosthenes lived from 276 BC to 194 BC and served as the Chief Librarian at the Library of Alexandria. In 240 BC, he calculated the Earth's circumference by observing the angle of the Sun's rays at two different locations: Alexandria and Syene (modern-day Aswan). By measuring the difference in the angles, Eratosthenes was able to estimate the Earth's circumference to be approximately 39,375 kilometers (24,662 miles). He also wrote the book "Geographika" (Geography), which laid the foundation for the field of geography.
