Pierre-Simon, marquis de Laplace (23 March 1749 – 5 March 1827) was an influential French astronomer and mathematician.
Laplace was born in 1749, and became of the foremost mathematicians of France. Collaborating with Antoine Lavoisier, Laplace was able to show that water was a compound of oxygen and hydrogen. After the French Revolution broke out in 1789, Laplace, Lavoisier, Nicolas de Condorcet and Jean-Charles de Borda published a serialized introduction to, and defense of, the newly proposed metric system in the Journal de Paris. Laplace soon became suspected of anti-revolutionary sentiments and was targeted by extremists for his skepticism towards religious matters.
During the period of the revolution, scientists began experimenting with electricity, including its supposed ability to induce flight in humans. Knowing that such an electrical charge was deadly to the test subject, Laplace attempted to stop one such experiment at the College of the Four Nations in Paris. He was put under house arrest, but was freed by the Assassin Arno Dorian, who had been sent by Lavoisier. Laplace then gave Arno a Leyden jar with a non-lethal electric charge, instructing him to swap it for the one used in the experiment. Arno was able to sneak into the college and do so, saving the test subject.
In his five-volume work published in 1799, Celestial Mechanics, Laplace calculated the movements of the planets, and determined their form and influence on the tides. Laplace went on to receive the Legion of Honor, and also worked to restructure France's distinguished École Polytechnique.