Nikolai Ivanovich Lobachevsky (Никола́й Ива́нович Лобаче́вский) (December 1, 1792 – February 24, 1856, N.S.; November 20, 1792 – February 12, 1856, O.S.) was a Russian mathematician.
- There is no branch of mathematics, however abstract, which may not some day be applied to phenomena of the real world.
- As quoted in George Edward Martin, The Foundations of Geometry and the Non-Euclidean Plane, Springer (1998 ), p. 225; also in Stanley Gudder, A Mathematical Journey, McGraw-Hill (1976), p. 36.