Biot , Jean Baptiste

(1774–1862) French physicist

Biot, a Parisian by birth, grew up during the French Revolution and at the age of 18 he joined the army as a gunner. He left a year later to study mathematics at the Ecole Polytechnique in Paris. On leaving he taught at a school in Beauvais but soon returned to Paris to become a professor of physics at the Collège de France.

In 1804 Biot made an ascent in a balloon with Joseph Gay-Lussac. They reached a height of three miles and made many observations, including the fact that the Earth's magnetism was not measurably weaker at that height.

For the next few years Biot collaborated with François Arago in many fields of research and they traveled to Spain together to measure the length of an arc of meridian, in order to calibrate a standard unit of length. Biot later went on a number of other important expeditions.

His most famous work was on optical activity, for which, in 1840, he was awarded the Rumford medal of the Royal Society. He was the first to show that certain liquids and solutions, as well as solids, can rotate the plane of polarized light passing through them. Biot suggested that this is due to asymmetry in the molecules. From this idea grew the technique of polarimetry as a method of measuring the concentration of solutions.