Monthly Archives: August 2011

Pierre-Simon Laplace 1749-1827

Born in Normandy, France, four decades before the French Revolution, Laplace is sometimes referred to as the ‘French Newton’. His achievements echo loudly in the history of science, and some of his ideas are still in ascendancy today. Laplace personified and defined the late Enlightenment.

In the previous century, Newton had used geometry to formally derive Kepler’s laws of planetary motion from his own laws of motion and universal gravitation (although he did use invented calculus privately). Laplace worked with algebra, and was a true calculus genius. Any student of this branch of mathematics will find Laplace’s name everywhere. The Laplace operator represents the flux density of a changing function. It is useful in describing force fields, chemical dispersion, edge detection in image processing, and many other applications. Laplace’s equation is at the core of many disciplines such as electromagnetism, gravitation, thermodynamics, and fluid dynamics. The Laplace transform changes time functions to frequency functions. Most of its application is in electronic, mechanical, and optical systems that were developed long after Laplace.

By the 18th century, a wealth of astronomical (largely planetary) data had been amassed from Chinese, Greek, Arab, and other civilizations. Laplace’s masterpiece was the five-volume ‘Mécanique céleste’ – a detailed analysis of the workings of the solar system, which combined theory with these observations, and constructed the basic model of the solar system we have today.

One of Laplace’s greatest achievements went largely unused until the middle of the 20th century. He reinvented, formalized, and explored Bayesian probability (named for the enigmatic English theologian Thomas Bayes who first discovered it just before Laplace was born). Bayesian methods feature the explicit use of subjectivity, learning from experience/evidence, and the formalization of causality. They are proving invaluable in analyzing and synthesizing vast and deep complexity, both natural and artificial, in all of science from biology to neurology to computation.

Newton, Darwin, and Einstein may be more famous, but Laplace was equally responsible for shaping the modern (and future) world.