World of Scientific Discovery on Jean-Baptiste Biot
During the late eighteenth and early nineteenth centuries, the most avidly debated topic among scientists worldwide was the nature of light: was it a beam of flowing particles, a theory which had become generally accepted, or could there be truth in the wave theories recently popularized by Thomas Young and Augustin-Jean Fresnel? Each side fought bitterly and tenaciously to prove or disprove these theories. From their efforts grew much of our modern understanding of the behavior of light, not the least of which is Jean-Baptiste Biot's study of polarization.
Biot was born in Paris in 1774. His father, who had risen from peasant stock to become a treasury official, enrolled him in private mathematics lessons, with the intention of steering him toward a career in commerce. Biot circumvented his father's plans by serving a brief stint in the army before enrolling at the École des Ponts et Chaussées in 1794. In 1800 he obtained an appointment at the Collège de France, and it was here that he began his work as a scientist.
Biot was involved in a number of interesting experiments early in his career. In 1806 he was sent to investigate reports of material falling from the sky--reports that hitherto had been dismissed as superstition--and his findings mark the beginning of the general acceptance of the reality of meteorites. In 1804, Biot and Joseph Gay-Lussac made a balloon trip in order to measure the intensity of the Earth's magnetic field at high altitudes, a trip whose hazardous descent frightened Biot so badly that he refused to accompany Gay-Lussac on any future experiments. Later, Biot made contributions toward the determination of the velocity of sound.
The turning point in Biot's studies came in 1806 when Thomas Young revived the old wave theory of light. The revival split the physics world into factions and caused a dispute between Biot and his colleague and friend Dominique-François Arago, who had subscribed to the new wave theories. Biot, however, steadfastly refused to believe in light as a wave, and he turned his attention toward developing a brilliant mathematical system to support the old particle theory. Thus began his new interest in optics.
In the fall of 1808, Etienne-Louis Malus (1775-1812) observed that reflected light became polarized, an effect which had previously only been detected in certain types of crystal, such as Iceland spar. Though this phenomenon could only be explained by using the wave theory, Biot refused to accept it as proof, choosing instead to repeat and expand upon Malus's experiments. In 1815 he showed that polarized light, when passing through an organic substance, might be rotated clockwise or counterclockwise, dependent upon the optical axis of the substance.
Biot's considerable research in the field of polarization also formed the basis of much of Louis Pasteur's work and founded the science of polarimetry. In 1840 the Royal Society of London awarded him the Rumford Medal for his work.
Shortly after Hans Christian Oersted discovered that electric currents create magnetic fields, Jean Baptiste Biot and Felix Savart developed the mathematical relationship that can be used to calculate both the magnitude and direction of the magnetic field produced by an electrical current. This relationship, the Biot-Savart law, appears as the defining relationship between magnetic fields and the currents producing them in every modern textbook on physics.
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