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French physicist and mathematician who put the final capstone on mathematical astronomy by summarizing and extending the
work of his predecessors in his five volume Mécanique Céleste (Celestial Mechanics) (1799-1825). This work
was important because it translated the geometrical study of mechanics used by Newton to one based on
calculus, known as physical mechanics. In Mécanique Céleste, Laplace proved the dynamical
stability of the solar system (with tidal friction ignored) on short time scales. On long time scales, however, this
assertion was proven false in the early 1990s. Laplace solved the libration of the Moon. In this
work, he frequently omitted derivations, leaving only results with the remark "il est aisé à voia" (it is easy to
see). It is said that he himself could not always fill in the derivations later without days of work. For a revealing
quote, see the remark made by Laplace's translator Bowditch. After reading Mécanique céleste, Napoleon
is said to have questioned Laplace on his neglect to mention God. In stark contrast to Newton's view
on the subject, Laplace replied that he had no need for that hypothesis (Boyer 1968, p. 538).
Laplace also systematized and elaborated probability theory in "Essai Philosophique sur les Probabilités"
(Philosophical Essay on Probability, 1814). He was the first to publish the value of the Gaussian
integral, . He studied the Laplace transform, although Heaviside developed the
techniques fully. He proposed that the solar system had formed from a rotating solar nebula with rings breaking off and
forming the planets. He discussed this theory in Exposition de système du monde (1796). He pointed out that
sound travels adiabatically, accounting for Newton's too small value.
Laplace formulated the mathematical theory of interparticulate forces which could be applied to mechanical, thermal, and
optical phenomena. This theory was replaced in the 1820s, but its emphasis on a unified physical view was important.
With Lavoisier, whose caloric theory he subscribed to, he determined specific heats for many
substances using a calorimeter of his own design. Laplace borrowed the potential concept from Lagrange, but
brought it to new heights. He invented gravitational potential and showed it obeyed Laplace's
equation in empty space.
After being appointed Minister of the Interior by Napoleon, Laplace was dismissed with the comment that "he carried the
spirit of the infinitely small into the management of affairs" (Boyer 1968, p. 536).
Laplace believed the universe to be completely deterministic.
Additional biographies: MacTutor (St. Andrews), Dublin Trinity College, Bonn
Bell, E. T. "From Peasant to Snob: Laplace." Ch. 11 in
Men of Mathematics: The Lives and Achievements of the Great Mathematicians from Zeno to Poincaré.
New York: Simon and Schuster, pp. 172-182, 1986.
Boyer, C. B. A History of Mathematics, 2nd ed. New York: Wiley, 1968.
Gillispie, C. C. Pierre-Simon Laplace, 1749-1827: A Life in Exact Science.
Princeton, NJ: Princeton University Press, 1997.
© 1996-2007 Eric W. Weisstein
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