Laplace published The System of the World, in which he put forward a theory of the origins of the solar system. He demonstrated mathematically that Newton’s laws of motion and gravity could result in a simple cloud of dust transforming over time into the Sun and planets.
Pierre-Simon Laplace revolutionized astronomy in 1796, when he published his Exposition du système du monde (The System of the World, 1809), in which he first promulgated his now famous nebular hypothesis on the origin of the solar system. According to Laplace, the solar system derived from a cloud of gas and dust, a gaseous nebula he designated the nébuleuse primitive. In this hot and rotating cloud, the condensation of the material, caused by gravitational attraction, formed the planets. This condensation, according to Laplace, began at the outskirts of the cloud, forming the planets most distant from the Sun first and progressing inward.
Laplace was born on March 23, 1749, in Beaumont-en-Auge, Normandy. The second of the three sons in a family of five children, Laplace enjoyed a comfortable childhood. His father was a wealthy farmer who augmented his income by running a relay station on a busy stagecoach line, where he sold fermented cider to weary travelers. His mother, Marie-Anne Sochon, came from a comfortably wealthy agricultural family as well.
The Laplace family’s economic security provided Pierre-Simon with educational opportunities that allowed him to develop his considerable intellect. He was sent to a Benedictine priory school for his primary education, and at the age of seventeen, he advanced to the University of Caen, where he discovered his passion and aptitude for mathematics. After two years at the university, he spent the next two years teaching mathematics at his former priory school while he saved enough money to finance a trip to Paris. In the city, he met the famous mathematician Jean le Rond d’Alembert. D’Alembert was immediately interested in Laplace and, in 1770, recommended him as a mathematics teacher at the École Royale Militaire in Paris.
Turning his attention and mathematical skills to astronomy, Laplace came to the attention of the scientific community in 1773, when he produced a groundbreaking essay titled “Sur le principe de la gravitation universelle, et sur les inégalites séculaires des planètes qui en dépendent”
Laplace demonstrated that this planetary instability was only apparent; in fact, the variation in the speed of the planets was a periodic phenomenon that could be predicted. Saturn and Jupiter speed up and slow down because of the gravitational effects they have on each other, with a periodicity of 919 years. Laplace thus demonstrated that Newton’s
Illustration of a spiral nebula cyclone.
In 1785, Laplace was an examiner at the Royal Artillery Corps (mathematical skill was essential to effective artillery fire) when sixteen-year-old Napoleon Bonaparte underwent examination to achieve the rank of second lieutenant. Many years later, Bonaparte was instrumental in advancing his examiner’s career, making him a count and naming him a minister in the government.
The transformational zeal of the French Revolution extended beyond politics and into science. Laplace’s scientific reputation placed him in a intellectual, social, and political position in which he was able to help effect profound changes. In 1790, the French National Assembly wished to replace the more than seven hundred different units of measure employed in the country. Laplace was instrumental in developing the metric system,
One year later, in 1796, he published Exposition du système du monde (The System of the World), the work that revolutionized astronomy. It was a huge accomplishment, a series of five books in two volumes devoted to the analysis of the apparent motions of celestial bodies, the movement of the sea, the actual movements of celestial bodies, and the formation of the solar system. Extremely well written and targeted at a semipopular audience, the work not only disseminated Laplace’s theories and analyses but also helped bring Newtonian astrophysics to a wider audience.
Laplace noticed in The System of the World that the planets known at the time (only the seven innermost planets had been discovered) had elliptical trajectories and were almost all in the same plane. Also noting the relatively slow rotation of the Sun itself, Laplace proposed that the solar system had been formed out of a rotating cloud of dust and gas, the nébuleuse primitive.
In 1806, Napoleon named Laplace a comte d’empire and gave him the position of minister of the interior in his government. Much more a scientist than an administrator, Laplace kept his ministerial position for only six weeks before gracefully withdrawing. In an endeavor more to his liking, in 1807, Laplace, along with the well-known chemist Claude Louis Berthollet, organized a group of famous scientists and young researchers called Société d’Arcueil (Society of Arcueil).
Among the significant scientists mentored by the society were physicists Joseph Louis Gay-Lussac and Jean-Baptiste Biot and naturalist and explorer Alexander von Humboldt. Laplace was elected to the French Academy
Pierre-Simon Laplace’s nebular hypothesis is still broadly accepted today as the most probable origin of the solar system. When combined with his demonstration that the solar system is stable and its motion is fully self-perpetuating without divine intervention,
In a eulogy presented at the French Academy on November 13, 1827, Laplace’s successor, Pierre-Paul Royer-Collard, said that
Laplace was born to perfect everything, to deepen everything, to push back the limits, and to solve all of the things people believe unsolvable. He would have completed the study of astronomy if this science could be completed.
Though the hyperbole of his eulogy was probably extravagant, Laplace did demonstrate the power of combining scientific and mathematical skills in the attempt to understand the workings of the physical universe. His scientific creativity, extraordinary mathematical ability, curiosity, and discipline not only unlocked the secrets of the solar system’s origins but also provided a model of synthesis of disciplines for future scientists to follow.
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Bell, E. T. “From Peasant to Snob: Laplace.” In Men of Mathematics: The Lives and Achievements of the Great Mathematicians from Zeno to Poincaré. New York: Simon and Schuster, 1986. Bell provides a brief biography of Laplace from his humble origins in the country side of Normandy to the high status he achieved in the sciences and in politics. -
Crosland, Maurice. Society of Arcueil: A View of French Science at the Time of Napoleon. Boston: Harvard University Press, 1967. Details the work of Laplace and Berthollet, founders of the Society of Arcueil, in encouraging the development of young scientists. -
Gillipsie, Charles Coulston, Robert Fox, and Ivor Grattan-Guinness. Pierre-Simon Laplace, 1749-1827: A Life in Exact Science. Princeton, N.J.: Princeton University Press, 2000. Describes the life and achievements of Laplace. -
Hershel, Sir John Frederic William, and Pierre-Simon, Marquis de Laplace. Essays in Astronomy. Honolulu, Hawaii: University Press of the Pacific, 2002. The editor has collected and translated into English many of Laplace’s original articles in this volume.
Newton Publishes Optics
Astronomy Wars in England
Halley Predicts the Return of a Comet
Quest for Longitude
Flamsteed’s Star Catalog Marks the Transition to Modern Astronomy
Maclaurin’s Gravitational Theory
D’Alembert Develops His Axioms of Motion
Bradley Discovers the Nutation of Earth’s Axis
Euler Develops the Concept of Function
Jean le Rond d’Alembert; Jean-Sylvain Bailly; Leonhard Euler; Joseph-Louis Lagrange.