who was the first person to calculate the circumference of the earth and coined the word geography
The first person credited with calculating the circumference of the Earth is Ancient Greek philosopher and mathematician, Eratosthenes. He lived in the 3rd century BCE and was the chief librarian at the Library of Alexandria.
To calculate the Earth's circumference, Eratosthenes used a method known as the "Eratosthenes' method." He noticed that in the city of Alexandria, located in Egypt, at noon on the summer solstice, the sun was directly overhead, causing objects to cast no shadows. Eratosthenes knew that in the city of Syene, located in modern-day Aswan, Egypt, at the same time, a vertical object cast a small shadow.
By using a simple trigonometric calculation, Eratosthenes measured the angle of the shadow cast by a vertical stick in Syene and compared it with the angle of the shadow cast by the vertical stick in Alexandria. The difference in their angles allowed him to estimate the Earth's circumference.
Eratosthenes' calculated circumference of the Earth was remarkably close to the current value we know today. He also coined the term "geography" to describe the study of the physical features of the Earth and its inhabitants.
So, Eratosthenes is both recognized as the person who calculated the Earth's circumference and the one who coined the term "geography."