* Astronomy

Marius Sophus Lie (17 December 1842 - 18 February 1899) was a Norwegian mathematician. He largely created the theory of continuous symmetry, and applied it to the study of geometry and differential equations.
Lie's principal tool, and one of his greatest achievements, was the discovery that continuous transformation groups (now called, after him, Lie groups) could be better understood by "linearising" them, and studying the corresponding generating vector fields (the so-called infinitesimal generators). The generators are subject to a linearised version of the group law, now called the commutator bracket, and have the structure of what is today called a Lie algebra.
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