Apollonius, of Perga (c. 245-c. 190 BC)

Greek mathematician, called 'the Great Geometer'. In his work Conica/The Conics he showed that a plane intersecting a cone will generate an ellipse, a parabola, or a hyperbola, depending on the angle of intersection. In astronomy, he used a system of circles called epicycles and deferents to explain the motion of the planets; this system, as refined by Ptolemy, was used until the Renaissance. It is thought that Apollonius may have studied at the school established by Euclid at Alexandria, especially since much of his work was built on Euclidean foundations. Of his eight-volume treatise Conica, seven volumes are extant. The first four books consisted of an introduction and a statement of the state of mathematics provided by his predecessors. In the last four volumes Apollonius put forth his own important work on conic sections, the foundation of much of the geometry still used today in astronomy, ballistic science, and rocketry.