Over two thousand years ago in Ancient Greece, mathematician and astronomer Eratosthenes of Cyrene (276 BC – 195 BC) became the father of modern geography and coined many terms that are still in use today.

He is best known for calculating the circumference of the Earth by measuring the length of shadows during the summer solstice, and was the first to calculate the ecliptic plane of the Earth which enabled him to devise the first 365-day calendar with a leap year included every four years.

However, Eratosthenes continued to innovate when he became chief librarian at the Library of Alexandria. He used its archive to map the entire known world and described it in terms of five climate zones: two freezing zones around the poles, two temperate zones, and a zone comprising the equator and tropics.

Then, Eratosthenes placed a grid over the Earth, using parallel and meridian lines to link the world together, and thus made it possible to estimate distances between remote locations.