February 3: Jean-Baptiste Biot

Jean-Baptiste Biot

April 21, 1774 – February 3, 1862

Jean-Baptiste Biot was a French physicist, astronomer and mathematician. In 1800 he became professor of physics at the Collège de France, through the influence of Pierre-Simon Laplace, from whom he had sought and obtained the favor of reading the proof sheets of the Mécanique céleste. Three years later, at an unusually early age, he was elected a member of the Academy of Sciences.

In the early 1800s, he studied the polarisation of light passing through chemical solutions, as well as the relationship between electrical current and magnetism. The Biot-Savart law, which describes the magnetic field generated by a steady current, is named after him and Félix Savart. Biot was the first to discover the unique optical properties of mica, and therefore the mica-based mineral biotite was named after him.

In 1804 Biot and Joseph Gay-Lussac made a hot-air balloon ascent to a height of five kilometres in an early investigation of the Earth's atmosphere. It was the first balloon ascent undertaken for scientific purposes.

His researches extended to almost every branch of physical science, but his most important work was of an optical character. He was especially interested in questions relating to the polarization of light, and his observations in this field, which gained him the Rumford medal of the Royal Society in 1840, laid the foundations of the polarimetric analysis of sugar.

Late in Biot's life, Pasteur demonstrated to him the opposite optical rotations (equal angle, but opposite direction) of polarized light passing through aqueous solutions of mirror-image crystals.

Biot was an extremely prolific writer, and besides a great number of scientific memoirs, biographies, etc., his published works include: Analyse de la mécanique céleste de M. Laplace (1801); Recueil d'observations géodésiques, astronomiques et physiques exécutées en Espagne et Écosse, with Arago (1821); Traité élémentaire d'astronomie physique (1805).

The Lunar crater Biot is named in his honor.