Biot, J-B
Name: Jean-Baptiste Biot
Achievements: Research into optical physics
Born: April 21, 1774; Paris, France
Died: 3 February 3, 1862; Paris, France (Aged 88)
Field & Discipline: Science; Physics; Physicist
Language: French
Father: Joseph Biot
Mother: Unknown
Siblings: Unknown
Spouse: Mlle. Brisson
Children: Unknown
Education: College Louis-le-Grand, Paris; Ecole Polytechnique, Paris
Major Work:
“Traite elementaire d’astronomie physique” (1805, “Elementary Treatise on Physical Astronomy”)
Life & Times:
Biot’s father was an official at the Treasury and Biot received a good classical education and took private lessons in mathematics. He volunteered to serve in the army when the revolutionary wars broke and enlisted in the artillery in 1792. He was not inclined towards commerce as his father wished, and in 1794 he became one of the first pupils at the newly established Ecole Polytechnique.
He graduated in 1797 and was appointed professor of mathematics at the Beauvais Ecole Centrale, one of the secondary schools which had been set up by the government to supply modern teaching with an emphasis on science. Three years later, Biot became professor of mathematical physics at the College de France in Paris.
Throughout his career, he continued to undertake official scientific investigations as well as pursuing his own research. In 1801, together with [collaborated with] Cuvier*, he investigated the voltaic pile and edited the official report of a committee set up to report on [reported on] Volta*’s discovery.
In 1803 Biot was dispatched by a skeptical government to investigate stories about a meteorite which was said to have fallen in the department of Orne. He brought back samples of different meteorites and wrote a paper on his findings which marked the acceptance of the reality of meteorites in France.
In 1804 he went up in a balloon with [flew with] Gay-Lussac* with the aim of finding out if the magnetic intensity at the earth’s surface decreased with altitude. They used a mathematical formula worked out by [work related to] Laplace* to calculate their altitude from a barometer reading, and announced that the magnetic field remained virtually constant up to a height of four thousand meters.
In the same year, Biot carried out experiments on the conductivity of heat along metal bars. He found that the steady-state temperature decreased exponentially along the length of the bar and [work related to] Fourier* later provided a mathematical formulae for this.
In 1806 Biot collaborated with [collaborated with] Arago*, on an expedition to calculate the arc of the meridian in Spain and the Balearic Island. During his time on the islands of Ibiza and Formentera, Biot also studied the composition of air in the swim bladders of fish. He also carried out experiments on the compression of gases, lowering carefully-measured mixtures of gases beneath the surface of the sea to see if they would combine to form their compounds.
He discovered that the chemical affinity between molecules was affected by pressure. Measuring the arc of the meridian was being undertaken by others such as [work related to] Gauss* in Germany and in 1817-18, Biot traveled to Britain in order to extend the measurement of the arc of the meridian to the north.
After Arago relayed the news to Paris about [work related to] Oersted’s* discovery of the connection between magnetism and electricity, Biot worked with the physicist Felix Savart on investigations in this field and in 1820 they presented their findings which showed that the intensity of the magnetic field set up by a current flowing through a wire is inversely proportional to the distance from the wire. This became known as the Biot-Savart law and provided a valuable aid to further research into electromagnetic theory. Biot’s most important work concerned the polarization of light.
Biot accepted and developed Isaac Newton’s corpuscular theory of light and he wrote a biography of Newton for the “Biographie Universelle”. Biot later quarreled with [quarreled with] Brewster* (who was also working on polarized light) about the latter’s interpretation of Newton, but he was influenced conceptually by the molecular model of polarization produced by the French mathematician, [influenced by] Coulomb*. After [work related to] Nicol*, the Scottish scientist, invented his prism, scientists had access to a convenient way of producing polarized light and physical optics was a much debated subject.
Biot’s most valuable contribution was to discover that some crystalline solids, when in solution, could rotate a plane of polarized light. Up until this time, it had been accepted that only when they were in a solid state could substances rotate a plane of polarized light. He later found that sugar was among those crystalline substances which, when in solution, had an effect on polarized light. He invented a saccharimeter for measuring the density of sugar solutions which was later improved by the instrument maker [work related to] Soleil*.
Biot’s discovery that the concentration of a solution determined the angle of rotation of a plane of polarized light provided a useful tool for chemical analysis. In 1840, he was awarded the Rumford Medal of the Royal Society of London in recognition of his work on polarized light.
Biot was a prominent member of the French scientific community and was also friendly with a number of foreign scientists such as [a pal of] Sir John Herschel*, with whom he discussed physical optics, [a pal of] Somerville*, and [a pal of] Dalton* who undertook pioneering work into the combination of gases. He wrote over three hundred scientific papers and published several books.
Extra Connections: His work was translated by [translated by] Fechner*
He was a fan of [a fan of] Smithson*
He knew [knew] Venturi*
He collaborated with [collaborated with] Thenard*
He met [met]George Peacock*
He fell out with [fell out with]Colby*
Assessment: Biot’s work on the rotation of polarized light by liquids provided a valuable scientific tool for chemical analysis.
Oneliner: J-B Biot, French physicist and polarized-light expert
Bibliography:
- Crosland, Maurice, The Society of Arcueil, Heinemann, London, 1967.