Q: Who was Eratosthenes of Cyrene?
A: Eratosthenes of Cyrene was a 3rd century BC Greek mathematician, geographer and astronomer. He was head of the Library of Alexandria from 240 BC until his death.
Q: What nickname did his contemporaries give him?
A: His contemporaries nicknamed him Beta, (the second letter of the Greek alphabet), because he was the second best in the world in almost any field.
Q: What works did Eratosthenes write?
A: According to Strabo (~63BC–24AD), Eratosthenes wrote On the measurement of the Earth and Geographica.
Q: What discoveries and inventions is he credited with making?
A: Eratosthenes made several remarkable discoveries and inventions. He was the first person to calculate the circumference of the Earth (with remarkable accuracy), and he invented a system of latitude and longitude. He calculated the tilt of the earth's axis (again with remarkable accuracy); he may also have accurately calculated the distance from the earth to the sun and invented leap day. He created a map of the world based on available geographical knowledge at that time.
Q: What else is Eratosthenes known for founding?
A: Eratosthenes is also known as founder scientific chronology; he wanted to fix dates for chief literary and political events from conquest Troy onwards.
Q: Who was Archimedes, who lived in Alexandria at same time as Eratosthens?
A: Archimedes was a great mathematician and inventor who lived worked in Alexandria during same period as Erastothens; they were friends with each other.