The Planetarium Science Center has been celebrating Eratosthenes Festivity every year since 2003 on 21 June, the day of the summer solstice. School students gather at the Bibliotheca Alexandrina Plaza to measure the circumference of the earth. This is to honor the outstanding scientist and third director of the ancient Library of Alexandria, using the method that he had used 2000 years ago. 450 participants joined this enlightening experiment and benefited from the lectures given by eminent astrologers at the Bibliotheca Conference hall. Also, the experiment was made at the same time in Aswan by a member of the PSC team, and results were compared by video conference in front of the audience.