Since when do we know the Earth is a globe?
The premise of a spherical Earth is not new. Ancient Greek philosophy first mentions a spherical earth more than 2600 years ago, around the 6th Century BC.What’s more, more than 1600 years ago, in the 3rd century BC, Hellenistic astronomy established the spherical shape of the Earth and from then on the spherical Earth was the accepted world model.
In ancient times, the philosopher Pythagoras of Samos and his contemporary Parmenides of Elea were both credited with having been the first to teach that the Earth was spherical, and the first to divide the globe into five climactic zones.
Proof of a round Earth was provided by Aristotle, around 330 BC. A century later, around 240 BC Eratosthenes calculated the Earth’s circumference, and in the 2nd Century AD Ptolemy used latitude and longitude for his maps.
Eratosthenes of Cyrene: was the chief librarian at the Library of Alexandria. He invented the discipline of geography and is best known for being the first person to calculate the circumference of the Earth. He was also the first to calculate the tilt of the Earth’s axis. He created the first map of the world, incorporating parallels and meridians based on the available geographic knowledge of his era.