George Friedrich Bernhard Riemann (1826-1866)

It suffices to say that Riemann, a German mathematician, was Gauss's brilliant student. He soon became a surprising phenomenon for that great mathematician throughout his long teaching career. One of Riemann's revolutionary ideas was that space and time need not be finite, though they are unbounded, suggesting indirectly the setting for a geometry in which "no two lines are parallel and the sum of the angles of a triangle is greater than two right angles" (Wolfe, 1945, p.61). Riemann set the Riemann Sphere and made it the foundation of the elliptical geometry, a crucial branch of the non-Euclidean geometry.

Reference: Wolf, H.E. (1945). Introduction to non-Euclidean geometry
Figure s087750a, n.d., n.t., google image, retrieved on 4/11/2009
http://eom.springer.de/common_img/s087750a.gif