Pythagoras was born in Greece in 569 BC and traveled extensively, studying with philosophers in Egypt where he joined the priesthood. He learned arithmetic and music from the Babylonians before founding the Brotherhood of Pythagoreans in Italy. The Brotherhood believed that reality has a mathematical basis and discovered the Pythagorean theorem that the sum of the angles in a triangle equals 180 degrees. While Pythagoras may not have invented the theorem, the Pythagoreans were likely the first to prove it.