Pierre-Simon, marquis de Laplace (23 March 1749 – 5 March 1827) was a French mathematician and astronomer whose work was pivotal to the development of mathematical astronomy and statistics.

In the history of science, "Laplace's demon" is a thought experiment described by Pierre-Simon Laplace in a paper published in 1814 involving a hypothetical entity envisioned such that if it knew the precise location and momentum of every atom in the universe then it could use deterministic principles to reveal the entire course of cosmic events, past and future.

Leavitt's discovery of the period-luminosity relation of Cepheid variables radically changed the theory of modern astronomy, an accomplishment for which she received almost no recognition during her lifetime.

http://en.wikipedia.org/wiki/Henrietta_Swan_Leavitt