Oenopides was born in Chios at around 500 BC. He lived in Athens where he became an astronomer and a mathematician.
Oenopides’s main accomplishment was the measurement of the angle between the plane of the celestial equator and the zodiac. He found that this angle was 24 degrees. Two centuries later Eratosthenes measured it better. In addition, Oenopides determined the duration of the Great Year to be about 59 years. This hepled to predict eclispes.
He pointed out the difference between theorems and problems. The theorem serves for the development of a throery, while a problem is a theorem without development.
Furthermore, Oenopides said that for geometric constructions only the ruler (straighthedge) and the compass should be used.
Georgia Kalantzi, Grade 2, 2nd Junior High School of Paralia