XIX 



PIERRE SIMON LAPLACE 



1749-1827 



Pierre Simon Laplace, horn at Beaumonf-en-Auge, Normandy, 

 March 28, 1749, became a teacher of mathematics at Beaufort before 

 he was eighteen years old. He gained d'Alembert's attention by a 

 letter which he wrote to him on the principles of mathematics. After 

 lyyo he engaged zvith Lagrange in determining the permanency of the 

 solar system by studying its perturbations and interactions, and finally 

 suggested how these changes were periodic. His monumental work, 

 in five volumes, ''Mechanics of the Heavens" (i/pp-i82j), gave a 

 comprehensive description of the movements of the solar systemi, and 

 his ''System of the World" proposed the nebular theory of the origin 

 of the universe. His researches were important in the development 

 of modern astronomy because he substituted a dynajnic for the de- 

 scriptive point of view. He died at Arcueil, March 5, 182/. 



THE NEBULAR HYPOTHESIS * 



Buffon is the only individual that I know of, who, since the discov- 

 ery of the true system of the world, endeavoured to investigate the 

 origin of the planets and satellites. He supposed that a comet, by 

 impinging on the Sun, carried away a torrent of matter, which was 

 reunited far off, into globes of different magnitudes and at different 

 distances from this star. These globes, when they cool and become 

 hardened, are the planets and their satellites. This hypothesis sat- 



* Translated from Exposition du Systeme du Monde, (Paris, 1796). 



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