The daughter of mathematician Theon, Hypatia grew up on the northern tip of Egypt in the great city of Alexandria in the 4th century A. D. Unlike most girls of her time, Hypatia learned to read and write, and as she grew older was tutored in mathematics, astronomy, and philosophy. In time, word spread of her brilliance and scholars from all over the world came to her seeking her advice and opinions in these subjects. Records of her fame as a teacher can be found in the writings of Socrates. One of her most famous students, Synesius, developed the astrolabe under her direction.