Siméon Denis Poisson

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Siméon Denis Poisson, 1804 (E. Marcellot).
Siméon Denis Poisson, before 1840 (F.-S. Delpech after N.-E. Morin).

Siméon Denis Poisson (born June 21, 1781 in Pithiviers ( Loiret department ), † April 25, 1840 in Paris ) was a French physicist and mathematician .

Career

He was born in Pithiviers as the son of the soldier and later administrator Siméon Poisson. Before the revolution, the father was discriminated against in the army by the aristocracy and therefore welcomed the revolution, “earned himself” and became president of the Pithiviers district. According to his father's wish, Poisson would become a doctor. For this purpose he was sent to an uncle in Fontainebleau for training , who practiced there as a doctor and surgeon. However, he broke off this training because he was not interested in it and he was clumsy with his hands. In 1796 Poisson was sent to the École centrale in Fontainebleau, a school founded by the Directory , Le Directoire . Due to his good mathematical achievements and his father's relationships, he was recommended and made possible to study at the École polytechnique in Paris. Poisson benefited from the fact that professions were no longer controlled by the nobility and that education should be possible for everyone.

There, at the École Polytechnique, Poisson began to study mathematics in 1798, where he made the acquaintance of Laplace and Lagrange . As early as 1800 he successfully completed his studies with a thesis on Étienne Bézout's theorem and his equation theory. As early as 1802 he became a professor there and in 1806 took over the chair from Jean Baptiste Joseph Fourier after Napoleon had sent him to Grenoble . The article on Bézout's sentence , written in his final year of study, was of such quality that he was able to finish his studies without a final exam and was immediately hired as a tutor at the École Polytechnique. (That was unusual, usually you had to make a detour via a stay in the province.) Before that, the position of 76-year-old Bossut was up for discussion, but he lived for another seven years and the way to the math faculty was blocked. The place of Monge was vacant, but since Monge had done his research on descriptive geometry, Poisson refused because he was averse with his clumsy hands against geometric constructions and drawing diagrams. (This was an insurmountable obstacle for the public service. So he turned to "pure" science.) Poisson was not politically active, but was busy with mathematics, teaching and the Ecole, so that he prevented an action by the students against Napoleon. not because he was for Napoleon, but because he feared for the École. That didn't hurt him, because Napoleon's apparatus saw it as support. In the meantime, he dealt with the relationship between ordinary and partial differential equations . In particular, he investigated the physical problem of the pendulum in the tough (reluctant, rubbing) medium and dealt with acoustics. These studies were purely theoretical because of his awkwardness:

“Poisson… was content to be completely unfamiliar with the vicissitudes of experimental research. It is unlikely that he ever attempted an experimental measurement, nor designed a test arrangement by hand. "

From July 1807 he was mentioned in the Mémoires de Physique et de Chimie de la Société d'Arcueil as a member of the Société d'Arcueil . In 1808 he worked for the Bureau des Longitudes (surveying), in 1809 the newly founded Faculté des Sciences appointed him chairman of the mechanics department.

In 1808 and 1809 Poisson published three important articles for the Académie des Sciences , of which he became a member in 1812, which showed his working methods. First of all, with On the Irregularity of the Mean Movement of the Planets , he examined a problem treated by Laplace and Lagrange of the disturbance of the planetary movements by means of series expansion and approximate solutions. These types of problems interested him:

"... he particularly liked unresolved questions that had already been dealt with by others, or areas in which there was still work to be done ..."

The work on the variation of (arbitrary) constants in questions of mechanics was the result of Lagrange's developments. He reissued Clairaut's The Shape of the Earth , and in extension it confirmed the Newton-Huygensian belief that the earth was flattened at the poles. In 1811 he published his extraordinarily intelligent lectures on mechanics at the École Polytechnique.

Malus fell ill and the institute's physics department became vacant. The mathematicians intended to put Poisson in place when they set the subject of electricity for the Grand Prix in order to increase Poisson's chances.

Poisson was making progress on the subject even before Malu's death in 1812. He submitted the first part to the academy, entitled On the Distribution of Electricity on the Surface of Conductive Bodies. As the mathematicians had intended, this was decisive in choosing Malu's successor.

It also meant a shift away from experimental research to theoretical research, which was believed to be determinative of physics as a result of Laplace.

Poisson took on other duties, as an examiner at the École Militaire and the following year at the final exams of the École Polytechnique.

Poisson's workload is remarkable, besides research and teaching, he organized mathematical affairs in France. In 1817 he married Nancy de Bardi, an orphan of emigrated parents who was born in England. He had four children with her, which added another obligation and yet he was able to take on even more tasks. His research covered wide areas of applied mathematics.

Although he did not set up any new theories, he significantly expanded existing ones, often being the first to work out and recognize what is significant in the theories of others.

Some topics after his election to the academy:

In 1813 he investigated the potential of attracting masses with results that were used in electrostatics. He wrote a great work on electricity and magnetism, then on elastic surfaces. This was followed by articles on the speed of sound in gases, suggestions on thermodynamics and elastic vibrations. In 1815 he published a work that annoyed Fourier:

“Poisson has too much talent to apply to the work of others. Using it just to discover what is known is wasting it .... "

Fourier makes valid objections to Poisson's arguments in his work, which Poissons corrected in later treatises in 1820 and 1821.

In 1823 Poisson published on thermodynamics with results that influenced Carnot . Poisson took many suggestions from Laplace, especially in his work on the relative speeds of sound and forces of attraction. These later works were also influenced by the earlier James Ivory. Poisson's work on attractions was to influence Green's main work of 1828, which Poisson took no notice of.

The Poisson distribution appears for the first time in the studies on the probability of judgments in criminal and civil cases, an important work on the calculation of probability, published in 1837 . The Poisson distribution describes the probability that a random event takes place in a time or space interval under the condition that the occurrence is very unlikely, but the number of attempts is large so that the event actually occurs a few times. He also introduced the expression "law of large numbers". Although the work is considered very important today, it received little attention in its time, except in Russia, where Chebyshev developed the ideas further.

Poisson did not share the chauvinistic attitude of many scholars of his time. Lagrange and Laplace wanted to know about Fermat as the inventor of differential and integral calculus, he was after all French in contrast to Leibniz and Newton. But Poisson wrote in 1831:

“This [differential and integral] calculus consists in a number of rules ... and not in the use of infinitely small quantities ... and in this respect of its foundation it is no older than Leibniz, the author of the algorithm and the notation, which generally prevailed. "

He published between three and four hundred mathematical papers. Despite this large output, he only ever worked on one topic at a time.

“Poisson never wanted to do two things at the same time; if in the course of his work he came across a research project that had no direct connection with what he was doing at the time, he was content with writing a few words in his little notebook. The people with whom he usually communicated about his scientific ideas knew that as soon as a paper was finished he would move on to another subject without a break, and that he usually chose from his notebook the questions to study. This way of foreseeing which problems have a certain chance of success and being able to wait for them before tackling them shows a forceful and methodical spirit. "

Poisson's name is associated with a variety of ideas: Poisson's integral, Poisson's equation in potential theory, Poisson brackets in differential equations, Poisson transformation , Poisson's ratio in elasticity, Poisson's constant in electricity.

He was hardly respected by other French mathematicians, either during his lifetime or after his death. His reputation was fueled by the respect he enjoyed from foreign mathematicians, who were more likely to recognize the importance of his ideas.

Poisson was only devoted to mathematics. François Arago (1786–1853) attributes the quote to Poisson:

"La vie n'est bonne qu'à deux choses: à faire des mathématiques et à les professer."

"Life is only good for two things: to do math and to teach it."

From 1812 he was a corresponding and from 1830 a foreign member of the Prussian Academy of Sciences . In 1818 he became a Fellow of the Royal Society and in 1820 the Royal Society of Edinburgh . In 1822 he was elected to the American Academy of Arts and Sciences . In December 1826 he became an honorary member of the Russian Academy of Sciences in Saint Petersburg .

His name is immortalized on the Eiffel Tower, see: The 72 names on the Eiffel Tower .

The lunar crater Poisson and the asteroid (12874) Poisson are named after him.

Scientific work

Mémoire sur le calcul numerique des integrales définies, 1826

Poisson was a student of Pierre Simon Laplace and dealt with the physical fundamentals of waves , worked on acoustics , elasticity and heat as well as the electrical properties of solid bodies . In 1812 he published an extension of the Laplace equation to include the surface charge. In 1813 Poisson investigated the potential inside attractive masses (only inner layers provide a force contribution, the potential of the outer layers is zero), and the results were used in electrostatics; he made a contribution to potential theory . In 1818 he predicted the Poisson spot if light should have the character of waves. He doubted this, however. He had heated discussions with Augustin Jean Fresnel as an advocate of the wave theory of light . The dispute was ended by the experimental proof of the stain by François Arago . In 1838 he published his theory of probability. This included the derivation of the Poisson distribution .

The relationship between pressure and volume in the event of an adiabatic change of state entered physics as Poisson's law :

In thermodynamics, also known as calorics or heat theory, one speaks more of Poisson's equations:

It is the so-called adiabatic (often called).

The Poisson number is named after Poisson . It indicates the relationship between the elastic longitudinal expansion and the elastic transverse contraction that occurs at the same time when a rod is subjected to tensile stress. The Poisson's number, also called Poisson's ratio, is between 0 and 0.5 for ordinary materials.

As a mathematician, Poisson worked in many fields, including differential geometry , calculus, and probability . Several mathematical terms are associated with his name, e.g. B. Poisson's integral formula, Poisson kernel, Poisson distribution , Poisson equation , Poisson number and Poisson bracket . In total, he published over 300 works.

The first published example of an evaluation of an integral by means of an integration path in the complex came from Poisson (1820), who was, however, familiar with the then unpublished work of Cauchy from 1814.

After the laws of deviation were found by Matthew Flinders , Poisson presented them in mathematical form.

literature

Web links

Individual evidence

  1. ^ Biography of Siméon-Denis Poisson. ( Memento from February 9, 2012 in the Internet Archive ). PDF.
  2. ↑ JR Hofman: Poisson's 1812 Electricity Memoir. In: André-Marie Ampère (Cambridge 1995), 113-118.
  3. ^ A b P. Costabel: Biography in Dictionary of Scientific Biography. New York 1970–1990.
  4. ↑ a b Siméon Denis Poisson.
  5. ↑ J.-A. Barral (Ed.): Oeuvres complétes de François Arago ... Volume II, Gide et J. Baudry, Paris 1854, p. 662.
  6. ^ Fellows Directory. Biographical Index: Former RSE Fellows 1783–2002. (PDF file) Royal Society of Edinburgh, accessed March 30, 2020 .
  7. ↑ Augustin Jean Fresnel et al: Œuvres complètes d'Augustin Fresnel. P. 369 (French).
  8. ↑ Nahin: An imaginary tale. 1998, p. 196.
personal data
SURNAME Poisson, Siméon Denis
BRIEF DESCRIPTION French physicist and mathematician
DATE OF BIRTH June 21, 1781
PLACE OF BIRTH Pithiviers ( Loiret department )
DATE OF DEATH April 25, 1840
Place of death Paris