  In the 1820's, Nikolai I. Lobachevsky (b. 1793, d. 1856) and Janos Bolyai (b. 1802, d. 1860) independently tackled this question in a radically new way. Lobachevsky built on the negation of Euclid's Postulate an alternative system of geometry, which he dubbed “imaginary” and tried inconclusively to test for validity at the astronomical scale by calculating the sum of the internal angles of triangles formed by stars on the sky. Bolyai excised the postulate from Euclid's system; the remaining rump is the “absolute geometry”, which can be further specified by adding to it either Euclid's Postulate or its negation. From the 1790's Carl Friedrich Gauss (b. 1777, d. 1855) had been working on the subject in the same direction, but he refrained from publishing for fear of scandal. Since Lobachevsky was the first to publish, the system of geometry based on the said “absolute geometry” plus the negation of Euclid's Postulate is properly called Lobachevskian geometry.