Ptolemy is a Greek astronomer who lived in Egypt in Alexandria. He takes up all the ancient science in his book Almageste which will allow calculate the positions of the celestial bodies and which will remain the reference until the end of the Middle Ages.
Ptolemy is astronomer and geographer. He makes a map of the inhabited world which uses all the information known at the time. It takes up the sexagesimal system of the Babylonians which will be continuouly used until now.