Georg Friedrich Bernhard Riemann developed the way we think about spatial geometry in such a way as to revolutionize concepts of modern theoretical phsyics. Riemann developed the famous Riemann Integral.
Born September 17,1826 in Breselenz, Germany. A student of Dirichlet's, Riemann studied in Berlin until 1849. In 1849, Riemann returned to Gottingen to join his colleagues Gauss and Dirichlet. In Gottingen, Riemann completed his legendary PhD thesis in 1851. Through Gauss's recommendations, Riemann was appointed to a post at Gottingen University and in 1854, Riemann published a classic paper entitled Uber die Hypothesen welche der Geometrie zu Grunde liegen. Dealing with theoretical spaces and the geometry of space, Riemann's works were incorporated into Einstein's Relativistic theories.
Riemann greatly developed non-Euclidean geometry. Riemann gave an inaugural lecture on June 10, 1854 in which he reformulated the whole concept of geometry which he saw as a space with enough extra structure to be able to measure things like length. This lecture was not published until 1868, two years after Riemann's death but was to have a profound influence on the development of a wealth of different geometries. Riemann briefly discussed a 'spherical' geometry in which every line through a point P not on a line AB meets the line AB. In this geometry no parallels are possible (the latter paragraph is courtesy of http://www-groups.dcs.st-andrews.ac.uk/~history/HistTopics/Non-Euclidean_geometry.html#67)
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