Electromagnetism Jean-Baptiste Biot made many contributions to the scientific community in his lifetime – most notably in optics, magnetism, and astronomy. In 1804, he used lines of equal magnetic field intensity in an article authored together with the Prussian naturalist
Alexander von Humboldt. The
Biot–Savart law in magnetism is named after Biot and his colleague
Félix Savart for their work in 1820. In their experiment they showed a connection between electricity and magnetism by "starting with a long vertical wire and a magnetic needle some horizontal distance apart [and showing] that running a current through the wire caused the needle to move" (Parsley).
Meteorites In 1803 Biot was sent by the
Académie française to report back on 3000
meteorites that fell on
L'Aigle, in
Normandy, France (see
L'Aigle (meteorite)). He found that the meteorites, called "stones" at the time, were from outer space. With his report, Biot helped support the German physicist
Ernst Chladni's argument, published in 1794, that meteorites were debris from space. Prior to Biot's thorough investigation of the meteorites that fell near l'Aigle, France in 1803, very few truly believed that rocks found on Earth could have extraterrestrial origins. There were anecdotal tales of unusual rocks found on the ground after fireballs had been seen in the sky, but such stories were often dismissed as fantasy. Serious debate concerning the unusual rocks began in 1794 when Ernst Chladni published a book claiming that such rocks had an extraterrestrial origin (Westrum). Only after Biot was able to analyse the rocks at l'Aigle was it commonly accepted that the fireballs seen in the sky were meteors falling through the atmosphere. Since Biot's time, analysis of meteorites has resulted in accurate measurements of the chemical composition of the
Solar System. The composition and position of meteors in the Solar System have also given astronomers clues as to how the Solar System formed.
Polarized light In 1812, Biot turned his attention to the study of
optics, particularly the
polarization of light. Prior to the 19th century, light was believed to consist of discrete packets called
corpuscles. During the early 19th century, many scientists began to disregard the
corpuscular theory in favor of the
wave theory of light. Biot began his work on polarization to show that the results he was obtaining could appear only if light were made of corpuscles. In 1815 he demonstrated that "polarized light, when passing through an organic substance, could be rotated clockwise or counterclockwise, dependent upon the optical axis of the material." His work in chromatic polarization and
rotary polarization greatly advanced the field of optics, although it was later shown that his findings could also be obtained using the wave theory of light. The transverse-wave explanation by
Augustin-Jean Fresnel is much simpler and is consistent with the equations of
James Clerk Maxwell. Biot's work on the polarization of light has led to many breakthroughs in the field of optics.
Liquid crystal displays (LCDs), such as television and computer screens, use light that is polarized by a filter as it enters the liquid crystal, to allow the liquid crystal to modulate the intensity of the transmitted light. This happens as the liquid crystal's polarisation varies in response to an electric control signal applied across it.
Polarizing filters are used extensively in photography to cut out unwanted reflections or to enhance reflection.
Cream of Tartar Potassium bitartrate was first discovered inside a wine container in Iran. The modern application of the substance began in 1768, and in 1832, Jean Baptiste Biot discovered the physical properties of
cream of tartar. The item gained most of its popularity when the French began using it frequently in their cooking.
Arc measurement In August 1806, he was commissioned by the
Bureau des Longitudes, together with
François Arago, to continue the
measurement of a meridian arc in France and Spain begun by
Delambre and
Méchain (the
meridian arc of Delambre and Méchain). == Selected writings ==