Pierre-Simon Laplace

Pierre-Simon Laplace
Nationality	French
Known for	Celestial mechanics, Probability theory, Nebular hypothesis
Contributions	Laplace equation, Laplace transform, Bayesian inference
Occupation	Mathematician, Physicist, Astronomer
Notable works	Mécanique Céleste, Théorie analytique des probabilités
Era	18th–19th century
Field	Celestial mechanics, Probability theory, Gravitation
Wikidata	Q44481

Pierre-Simon Laplace (1749–1827) was a towering French scientist whose work bridged mathematics, astronomy, and physics. A brilliant geometer and analyst, Laplace transformed Newton’s ideas about motion into comprehensive mathematical form and laid the foundations of modern probability theory. His reputation as one of the greatest scientists of his era came from deep investigations into the stability of the solar system, pioneering uses of probability to interpret data, and bold theories about the physical universe. Laplace’s clear, systematic approach and influential writings shaped 19th-century science, even as some of his specific theories were later superseded.

Early Life and Education

Laplace was born on 23 March 1749 in Beaumont-en-Auge, a village in Normandy, France. His family was moderately prosperous; his father sold cider and his mother came from a farming family. Young Laplace attended a local Benedictine school, where his father initially expected him to prepare for the priesthood. In 1766, at age 16, he entered the University of Caen to study theology. However, two local mathematics teachers (Cit. C. Gadbled and P. Le Canu) recognized his talent for mathematics. After only two years of study, Laplace abandoned formal degrees and left Caen for Paris to pursue mathematics full time.

In Paris, Laplace carried a letter of introduction to the great mathematician Jean le Rond d’Alembert. Despite being only 19, he impressed d’Alembert, who became his mentor and helped secure Laplace a position as a mathematics professor at the École Militaire (a military academy) in 1769. There Laplace taught geometry, trigonometry, and elementary analysis to artillery cadets. The salary gave him stability while he began publishing research. In short order, he submitted papers on calculus and difference equations to the French Academy of Sciences. By 1773, at age 24, Laplace’s reputation as a prodigy was established: he had been elected an associate of the academy and had contributed numerous papers on mathematical analysis and its applications to mechanics and astronomy.

In 1788 Laplace married Marie-Charlotte de Courty, and they had two children. Beyond his family life, Laplace moved into high society through his work. In 1785 he became Examiner of the Royal Artillery Corps (passing the young Napoleon Bonaparte among others) and by the 1790s he was a member of scientific committees for the new metric system and implementing the French Revolution’s calendar reform. Despite the political turmoil of the era (the Reign of Terror, the rise of Napoleon, and later the Bourbon restoration), Laplace managed to avoid persecution. He served briefly as Minister of the Interior under Napoleon in 1799, and later as a senator in the Napoleonic government. He was made a Count of the Empire by Napoleon and later a Marquis after the monarchy returned. Throughout these years, Laplace kept up a prodigious output of scientific work, even as political regimes changed around him.

Major Works and Ideas

Laplace’s major contributions fall in two main areas: celestial mechanics (astronomy and gravity) and probability (statistics and error analysis), though he also made significant contributions to other fields.

Celestial mechanics and gravitation. From the 1770s through 1820s, Laplace extended Newton’s law of universal gravitation to explain the complex motions of the planets. His key insight was to use advanced calculus to show that the mutual gravitational "perturbations" between planets cause only small periodic variations in their orbits, so that the overall structure of the solar system remains long-term stable. For example, the orbits of Jupiter and Saturn were known to influence each other in a way that Newton himself thought might require divine intervention to stabilize. In 1773, Laplace showed mathematically that the average (mean) motions of Jupiter and Saturn were actually invariant. He generalized this result to all planets and moons: he proved that the sum of all small influences leads only to bounded oscillations rather than runaway changes. These results removed the last apparent paradoxes in Newtonian astronomy and established that no external “hand” was needed to correct the orbits.

Laplace published his findings in a monumental series of books titled Mécanique Céleste (Celestial Mechanics), issued in five volumes between 1799 and 1825. In these works, Laplace systematically transformed Newton’s geometric arguments into powerful mathematical analysis. He developed new mathematical techniques (including what are now called Laplace coefficients) to solve the equations of motion of planets and their moons, and solved problems of tides and the shape of the Earth. He showed, for instance, that the tilt (inclination) and eccentricity (flattening) of planetary orbits would remain small and undergo only periodic variations. By the early 19th century, scientists widely took his conclusion — that the solar system is essentially stable on long timescales — as a great triumph of celestial mechanics.

In 1796, Laplace published a more popular account of his astronomical ideas, Exposition du Système du Monde (The System of the World). Written in clear prose for educated general readers, this book summarized the results of celestial mechanics and introduced Laplace’s famous nebular hypothesis of solar system formation. The nebular hypothesis proposed that the planets condensed out of a large, rotating cloud of interstellar gas (a nebula) that was gradually cooling and contracting. This was one of the first scientific theories of how the Sun and planets could form naturally. Though modern planetary science has refined and replaced some details (for example, angular momentum conservation and gas dynamics), the core idea—that planets form from a primordial disk of gas—is still central in astronomy. Laplace’s nebular model strongly influenced 19th-century cosmogony (the study of world origins).

Another contribution to physics came from Laplace’s work on gravitational potential. In the 1780s, as part of his study of how rotating spheroids (like the Earth) attract other bodies, Laplace formulated the idea of a potential function for gravity. The idea was that the gravitational force at any point can be derived as the gradient (rate of change) of a single scalar function, the potential. This was a powerful unifying concept: the potential satisfies a simple partial differential equation (called Laplace’s equation, ∇²φ = 0, in regions without mass) which appears throughout physics. The Laplace equation (and its variations) now underlie problems in fields like electrostatics, fluid flow, and heat conduction. In studying potentials, Laplace discovered the functions now called "Laplace coefficients," which are related to what mathematicians know as Legendre polynomials and spherical harmonics; these expansions greatly aided calculations of gravitational effects.

Besides astronomy, Laplace’s physics work included experiments with chemist Antoine Lavoisier. In 1780 they invented an ice calorimeter and showed that animal respiration is a form of combustion: humans and animals breathe in oxygen and give off carbon dioxide in essentially the same chemistry as burning. This insight connected biology to chemistry in a new way. Later, Laplace worked on heat and fluid mechanics. He proposed a theory of heat as a subtle fluid called "caloric" that moves from warm to cold bodies. (This caloric model was later replaced by Fourier’s mathematical theory of heat conduction.) Laplace also studied light and sound: he refined Newton’s work on optics and supported a particle (corpuscular) theory of light, a view that was eventually replaced by Thomas Young’s wave optics and later by quantum ideas. Notably, Laplace did compute a correction to Newton’s speed of sound in air by accounting for heat changes during compression, which improved agreement with measurement. He also explored capillary action, double refraction of light, and cooling of the Earth as it relates to heat flow. Much of this later physics work was imaginative and heavily mathematical, though some of it was later modified by the scientific advances that followed.

Probability and statistics. In addition to astronomy, Laplace brought the power of mathematics to bear on probability theory. Prior to his work, probability was often treated as a set of puzzles about games of chance. Laplace recognized probability as a powerful tool with applications across science and society. His major work on this subject was Théorie Analytique des Probabilités (Analytical Theory of Probability), first published in 1812 with a much-expanded second edition in 1820. This two-book treatise laid out the foundations of probability in logical, analytical form. Laplace defined probability as the ratio of favorable outcomes to all possible outcomes (given equal likelihood), and he developed generating functions and series expansions to handle complicated probability calculations, such as in binomial problems. Crucially, he formulated what we recognize today as Bayes’ theorem (giving a way to update probabilities given new evidence) and worked out the first instances of the central limit theorem (showing that, under broad conditions, the distribution of errors or sums tends toward a bell-shaped Gaussian curve). For example, he demonstrated that the sum of many small independent errors in astronomical measurements would follow a normal distribution. This insight explained why normal (Gaussian) errors appear so often in nature and linked probability theory to statistical inference and astronomy.

Laplace also introduced the concepts of mathematical expectation and moral expectation. The mathematical expectation of a random event is the weighted average value one expects (like the long-run average win in a gamble). Moral expectation extends this idea to real-world contexts, weighing outcomes by their desirability or utility to a decision-maker. Laplace applied these ideas to economics, demographics, and legal testimony. For instance, he used life tables and probability to compute life expectancies and mortality, and he analyzed judicial evidence by assigning probabilities to witness reliability. His famous example of the Sun rising (“If the sun has risen every day of your life, what is the probability it will rise tomorrow?”) imposed his law of succession (a crude form of predicting future chance from past events). Though simplistic by modern Bayesian standards, it illustrated his approach that probability could usefully quantify uncertainty about anything, from celestial measurements to everyday predictions.

In 1814, Laplace published Essai philosophique sur les probabilités (Philosophical Essay on Probability), a shorter, more readable exploration of probability theory and its meaning. This work was intended for non-specialists and emphasized the philosophical implications: Laplace argued that probability is a way of dealing with ignorance and that a completely determined (Newtonian) world would have no true randomness. The Essai includes many practical examples (games of chance, birth rates, moral questions), highlighting Laplace’s view that mathematical probability is essential for guiding decisions in the presence of uncertainty.

Laplace’s useful methods from probability endure today. His approximation techniques (like Laplace’s method for approximating integrals) and Bayesian viewpoints influenced later statisticians. Modern Bayesian analysis (combining prior beliefs with evidence) grew from his treatment of conditional probability, though his exact interpretation of probability was more classical (frequentist) than personal. His work on least squares, in particular proving and championing the method for fitting data to minimize squared errors, became a standard statistical tool in surveying and astronomy.

Other contributions. Beyond these fields, Laplace made advances in mathematics itself. He worked on the general theory of differential equations and finite differences. One of his early papers (1770) improved Lagrange’s method for finding maxima and minima of functions. Throughout his career he derived many new infinite series and integrals. He also delved into certain algebraic problems, such as solving equations with symmetric functions and developing what is now called the Laplace expansion for determinants (used in linear algebra). For mathematical physics, he consistently applied the latest calculus developments: for instance, he and Legendre systematically used Legendre polynomials to solve celestial and electrostatic problems with spherical symmetry.

In summary, Laplace’s major ideas were: Celestial Mechanics – formulating a mathematical explanation for planetary motion and solar system stability; Nebular Hypothesis – a theory of planetary formation; Probabilistic Analysis – establishing the calculus of probability and recognizing the normal distribution and inference; Potential Theory and Laplace’s Equation – unifying concept in physics; and numerous technical tools (Laplace transform, Laplace coefficients, and methods in perturbation theory). His published works, including Mécanique Céleste, Théorie Analytique des Probabilités, and Essai philosophique, made these ideas available to the scientific community of his day and beyond.

Method

Laplace’s method of science was to reduce phenomena to mathematics. He was a master of calculus and algebraic manipulation, and he believed that nature’s laws could be discovered and understood through their mathematical consequences. One famous summary of his worldview is the so-called “Laplace’s demon”: an imaginary intelligence that, if it knew the precise position and velocity of every particle in the universe at one instant, could predict the entire future (and retrodict the past). Laplace himself expressed a similar idea: in a strict Newtonian universe, uncertainty about events was due only to ignorance of initial conditions, not to any inherent randomness. Thus in his view chance was “nothing but the expression of our ignorance,” and probability theory was simply the calculus of that ignorance.

In practice, Laplace’s approach was analytical and systematic. For problems like planetary motion, he wrote down the differential equations from Newton’s gravity law and then solved them using series expansions, approximations, and generating functions. He pioneered using power series (infinite sums) to approximate solutions that could not be expressed in simple forms. In probability, he used generating functions (formal power series whose coefficients encode probabilities) to derive distributions of sums of random events, a technique elegant enough that it’s still taught in probability textbooks.

Laplace also believed strongly in the mathematical modeling of physical quantities. He introduced potential functions so that instead of thinking of forces directly, one could describe a scalar field whose gradient gives the force. This idea allowed a unifying viewpoint: he applied it to gravity, heat (caloric fluids), and even the idea of a universal ether for light. He often favored what are called continuum mechanics approaches: for example, thinking of heat as a fluid flow in a continuous medium.

Another feature of Laplace’s method was its broad application. He did not confine probability to games but applied it to meteorology, demography, physics experiments, and even philosophical problems. He would gather all available data (like planetary observations or death records) and use probability to make inferences or to estimate unknown quantities (like masses of planets from orbital data). In doing so he often used early forms of statistical inference. He also emphasized checking predictions against observations when possible—though as critics noted, he was sometimes more fond of theory than of gathering new data.

Laplace’s writing and teaching were geared toward clarity and generality. He insisted on careful definitions of mathematical concepts (for example, his definition of probability in terms of equally possible cases) and logical derivations. His prose, especially in Exposition du Système du Monde, was known for being lucid and persuasive. In lectures and the École Polytechnique, which he influenced heavily, he advocated teaching mathematics in a way that trained students to apply it to any branch of science.

In summary, Laplace’s method was highly mathematical and deductive. He took Newton’s more qualitative geometric style and replaced it with analysis: solving problems by calculation rather than geometric construction. He also followed a mechanistic philosophy: explaining phenomena by forces acting through space, leaving no supernatural or unexplained causes in nature. The rigor and generality of his methods set a standard for theoretical physics and applied mathematics that many scientists adopted in the 19th century.

Influence

Laplace’s influence on science and mathematics was immense, both in his own time and for centuries after. He was sometimes called "the Newton of France" because of how thoroughly he took Newtonian ideas and ran with them. His celestial mechanics work effectively closed the book on many problems in planetary astronomy. For decades, no one surpassed Mécanique Céleste in scope; later mathematicians like Gauss, Fourier, and Cauchy picked up threads from Laplace’s techniques to further develop analysis, number of integrals, and differential equations.

Many mathematical tools today bear his name: the bracket-Laplacian operator (∇²) is fundamental in physics, the Laplace transform is a standard method in engineering and control theory, and Laplace coefficients and Legendre functions (seen in celestial and quantum problems) trace directly to his work. The notion of a “Laplace prior” in Bayesian statistics (a uniform distribution) nods to his probability treatments. In probability theory, Laplace was the first to publish the formula for combining independent observations in the normal (Gaussian) distribution, influencing later statisticians like Fourier and Gauss himself. Indeed, the idea of the normal distribution as the law of errors came from Laplace’s work; Gauss independently arrived at a similar formulation soon after.

Laplace also shaped the philosophy of science. His emphasis on mathematical laws legitimized the view that physics ultimately reduces to computation. The success of Laplace’s calculation in astronomy boosted the confidence among scientists that algebra and calculus could handle even the most complex natural phenomena. This style influenced generations of physicists and mathematicians, including those in Britain (like Maxwell and Kelvin) and those studying at the École Polytechnique and Collège de France. His idea that the universe is a grand clockwork, operating by necessity, became part of the 19th-century scientific outlook (until quantum challenges arose). Even today, the question of determinism versus randomness often invokes “Laplace’s demon” as the archetype of a predictable universe.

In astronomy, Laplace’s nebular hypothesis guided thinking about cosmogony well into the late 1800s. Poets and novelists referred to a “nebular hypothesis” of creation, but it was really Laplace (after Kant’s earlier hints) who gave it firm mathematical expression. His view that the solar system could form from a contracting gaseous cloud anticipated modern nebular theory (now including angular momentum disco). His work on stabilizing the solar system also set the stage for later chaos theory: astronomers in the 20th century actually tested how slight deviations (noted by Laplace) accumulate, revealing chaotic behavior in some long-term orbits (like Mercury’s). But it’s telling that Laplace's initial claim of stability lasted over two centuries before refined by computers, showing how groundbreaking his results were.

Laplace’s influence extended to public affairs and institutions. He was integral in early work on the metric system after the French Revolution; in 1795 he helped set up the system of weights and measures, pushing for decimal time and angles. He helped reorganize French science under Napoleon, including the École Polytechnique, where he served as a professor and mentor. The “Society of Arcueil” he co-founded around 1805 with chemist Claude-Louis Berthollet attracted the country’s leading scientists (Biot, Fourier, Poisson, etc.) for collaborative work. Through these organizations, Laplace influenced the next generation of French scientists to favor rigorous mathematics.

Even outside France, foreign academies honored Laplace. He was elected a foreign member of the Royal Society (London), the Berlin Academy, and others. Monuments to him were erected (for instance, a statue at the Paris Observatory), and he was interred in France’s Panthéon, the secular mausoleum for illustrious citizens. Today many scientific terms and institutions bear his name, from the Laplace Institute of Earth Sciences to the computational tool the Laplace transform that engineers use. In summaries of mathematical history, he is always listed among Euler, Lagrange, and Gauss as a foundational figure. For amateurs, he is remembered through quotes and anecdotes: Napoleon’s comment that Laplace “brought the spirit of the infinitely small into politics” (jab at his mathish style) is often remembered and reflects Laplace’s reputation as the ultimate mathematician-statesman of his day.

Critiques

Although Laplace was widely respected, he did have critics and controversies. One criticism was that he was overly theoretical and sometimes neglectful of practical work. For example, as director of the Paris Observatory and the Bureau des Longitudes for many years, Laplace focused almost exclusively on calculation. His colleague and fellow astronomer Delambre later quipped that “one should never put a geometer at the head of an observatory; he will neglect all observations except those needed for his formulas.” Indeed, under Laplace’s leadership the Bureau made little progress on star catalogs, and some at the time lamented that Laplace spent 20 years there without recording a single new star position, concentrating instead on theoretical tables and orbital constants. This anecdote highlights a balance that Laplace perhaps tilted too far toward mathematics and away from empirical observation, even though he used observational data extensively in his calculations.

On the philosophical side, Laplace’s staunch determinism came under question as science advanced. In his day it seemed reasonable to imagine a fully predictable universe, but 20th-century physics introduced fundamental randomness. Quantum mechanics, with its inherent probability (even in principle) in particle behavior, and discoveries of chaotic dynamics in the 1960s-1970s (sensitive dependence on initial conditions) showed that Laplace’s dream of a clockwork universe was limited. Modern scientists still debate how “predictable” nature is; Laplace himself would have said that any apparent randomness is only due to incomplete information. Today, we might respect the mathematical ideal he proposed but also acknowledge that his worldview was modified by later developments he could not have foreseen.

Some of Laplace’s scientific theories were superseded by later work. For instance, his model of heat as a caloric fluid was replaced by mechanical heat theories (Fourier’s heat equation). His idea that light was composed of particles fell out of favor when the wave theory (and later quantum wave-particle duality) emerged. His nebular hypothesis, while broadly correct, ignored phenomena like angular momentum transfer and turbulence; later astronomers refined planetary formation theories to include these factors. In essence, Laplace sometimes pushed physics toward mechanistic, continuum models that later scientists amended with new experimental insights. However, it’s worth noting that these changes are normal; science often works by building on and correcting earlier models. Laplace’s proposals were stepping stones that future scientists, like Fourier, Fresnel, and Poisson, could compare against and improve.

On a personal level, Laplace was sometimes seen as arrogant or impatient. Contemporary accounts mention that he dominated meetings of the Academy and could be abrupt with peers. He was not known for being humble: he believed strongly in the superiority of his methods. His handling of credit was also criticized; the biography by C.-C. Gillispie suggests Laplace sometimes failed to fully acknowledge the contributions of others (such as Lagrange or Legendre) in his published works. Moreover, his shifting political loyalties earned suspicion: he served under the royal regime, the revolutionaries, Napoleon, and then the restored monarchy, always maintaining his position in science. To some, this opportunism was unjudicious, though it did help him avoid the fates of lesser scientists during the Revolution (Lavoisier was executed in 1794, for example).

In summary, critiques of Laplace revolve around his deterministic philosophy, certain outdated physical theories, and his personality style. Even so, historically these criticisms are generally mild notes in the sweep of his achievements. Most later mathematicians and physicists owe at least part of their work to the problems and methods Laplace introduced.

Legacy

Pierre-Simon Laplace’s legacy is enduring and broad. In mathematics and physics, his name remains attached to many fundamental concepts:

Laplace’s equation (∇²φ = 0) appears in electrostatics, gravity, fluid flow, and more, governing steady-state potentials.
The Laplacian operator (the symbol ∇²) is taught in every physics and engineering curriculum as the divergence of the gradient, a measure of how a quantity diffuses or spreads out.
The Laplace transform, an integral transform named after him, is a staple of modern engineering and physics courses for solving differential equations.
Laplace coefficients and Legendre functions (sometimes called Laplace’s spherical functions) are key in solving boundary-value problems on spheres.
Laplace’s method (asymptotic approximation of integrals) is a standard tool in applied mathematics.
Perhaps most famously to the public, Laplace’s demon is a phrase still used in philosophy of science to discuss determinism.

In the field of probability, Laplace helped usher in what is now called the Bayesian view. Although today we associate Bayes’ theorem with Thomas Bayes, it was Laplace who popularized it and applied it to real-world inference problems, essentially founding Bayesian statistics. His works also bequeathed concepts like the Gaussian distribution and the method of least squares, which Gauss later elaborated.

In astronomy and cosmology, Laplace’s influence continued into the era of astrophysics. The nebular hypothesis he proposed became the basis for 19th-century studies of star and planet formation (later refined by Helmholtz, Chamberlin, Moulton, and others). His calculations of orbital stability gave later scientists (like Henri Poincaré, in the 1890s, and 20th-century dynamicists) a point of departure when exploring chaos. In geophysics, his work on the shape of Earth and interior pressure was foundational to later understandings of geodesy.

Culturally, Laplace is remembered as one of the “last great encyclopedic scientists,” bridging the 18th and 19th centuries and laying the groundwork for the Age of Industrial Science. He is often mentioned in the same breath as Euler, Newton, Lagrange, and Gauss. His Astronomy and Probability combined, demonstrate that the world can be understood as a logical mathematical machine, and that belief dominated science well into the modern era. The famous anecdote of Napoleon’s remark – that Laplace “brought into the ministry the spirit of the infinitesimal” – highlights how his persona symbolized mathematical rigor even in politics.

Monuments to Laplace exist in academia and the wider world. Statues of him stand in Paris (for example, at the Panthéon and Paris Observatory) and in other countries. His name is given to craters on the Moon and Mars, asteroids, and streets; it also appears in textbooks everywhere. Even Einstein praised Laplace as having reduced celestial physics to its ultimate analytical form. When Laplace died on 5 March 1827, the French Academy of Sciences cancelled a meeting in mourning – a rare honor, showing the high esteem of his peers.

In science history curricula and encyclopedias, Laplace’s contributions are taught as cornerstones. He helped make calculation an indispensable part of science, and his achievements paved the way for later advances in mechanics, electromagnetism, thermodynamics, and statistics. Elements of his writing, such as the sharp logical development in Mécanique Céleste, were models for scientific exposition. In that sense, his legacy is not only in the results he obtained but in the method and style of mathematical science he championed.

Selected Works

1796: Exposition du système du monde (“The System of the World”) – A popular, semi-technical book explaining the mechanics of the solar system, including the nebular hypothesis of planetary formation.
1799–1825: Mécanique Céleste (“Celestial Mechanics”) – A five-volume treatise that translated Newton’s laws into advanced mathematical analysis, addressing planetary motion, lunar theory, tides, and more. The full work appeared gradually, culminating in 1825.
1812: Théorie Analytique des Probabilités (“Analytical Theory of Probability”) – A two-volume formal introduction to probability, establishing key techniques (generating functions, series expansions) and results (Bayes’ theorem, the normal distribution, method of least squares).
1814: Essai philosophique sur les probabilités (“Philosophical Essay on Probability”) – A shorter, accessible work on probability and its applications to philosophy, science, and daily life. It offered a non-technical overview of probabilistic reasoning for general readers.
1771: Traité du calcul intégral sur les différences infiniment petites – Laplace’s first published paper (1771, in Latin) on integral calculus and methods he used in mechanics. Though much shorter than his later books, it introduced some of his early mathematical methods. (He also published many shorter Mémoires to the French Academy in the 1770s and 1780s on topics in equations and astronomy.)

Timeline

1749: Born 23 March in Beaumont-en-Auge, Normandy, France.
1766: Enters University of Caen, initially studying theology.
1769: Moves to Paris (age 19) with letter to d’Alembert; becomes professor of mathematics at the École Militaire.
1769–1771: Publishes first papers on calculus and equations; gains notice in the Académie des Sciences.
1773: Elected associate member of the French Académie des Sciences; solves the Jupiter-Saturn orbital problem (showing mean motions invariant).
1780: With Lavoisier, invents ice calorimeter; shows respiration is combustion.
1784: Appointed examiner at French Artillery School; examines young Napoleon Bonaparte.
1786: Proves with mathematics that planetary eccentricities and inclinations remain bounded (long-term orbital stability).
1788: Marries Marie-Charlotte de Courty; they will have two children.
1793–1794: Leaves Paris during the Revolution’s Terror (avoiding its dangers); returns after Robespierre’s fall.
1795: Institut de France reopens; Laplace becomes member and helps found Bureau des Longitudes.
1796: Publishes Exposition du système du monde (nebular hypothesis).
1799: First volume of Mécanique Céleste published.
1804–1814: Serves as French Senator under Napoleon; awarded Count of the Empire (1806), later Marquis (1817) under Restoration.
1812: First edition of Théorie Analytique des Probabilités.
1814: Publishes Essai philosophique sur les probabilités; also popular Exposition widely read.
1825: Final volumes of Mécanique Céleste in print (Laplace is 76).
1827: Dies 5 March in Paris; buried in the Panthéon as one of France’s great scientists. After his death, the Académie des Sciences commemorates him as “one of the greatest scientists of all time.”

Laplace’s career spanned the Enlightenment, the French Revolution, and the Napoleonic era. Throughout, his mathematical mind left an indelible mark on science. His analytical vision of the cosmos and probability laid groundwork that still underlies fields from cosmology to data science today.