Thomas Young
1773-1829
British Physicist, Physician and Egyptologist
Thomas Young's career straddles the turn of the nineteenth century. In some ways he was an old-style natural philosopher, dabbling in many fields—physics, physiology, medicine, linguistics, navigation, insurance—and more concerned with ideas than applications. Yet, ironically, this theoretical trend also put him ahead of his scientific contemporaries; his revival of the wave theory of light was ignored for a generation. He is best remembered for his double-slit experiment demonstrating the interference of light, an absolute measure of the elasticity of solids known as Young's modulus, his optical studies, and his contribution to the deciphering of the Rosetta stone.
Born at Milverton, Somerset, England, of Quaker parents, Young was a child prodigy. Hestudied medicine at London, Edinburgh, Göttingen, and Cambridge universities. Young's interest in science was criticized by medical colleagues as taking time away from his medicine, so he published some papers anonymously.
Thomas Young. (The Library of Congress. Reproduced by permission.)In 1801 he was appointed to the Royal Institution, a British scientific organization, as Professor of Natural History, but quickly found himself at odds with the Institution's practical goals, lecturing on "pure knowledge" rather than the expected topics of the industrial and social applications of science. Furthermore, Young's style of presentation was not entertaining; a colleague remarked that he "was worse calculated than any man I ever knew for the communication of knowledge." Young left the Royal Institution in 1803.
Yet, while Young's lectures had been poorly received, a printed collection (1807) showed the scope of his thought, including his theories and experiments on light. The double-slit experiment, which consisted of passing light through extremely narrow openings and observing the interference patterns produced, led Young to surmise that light must be a wave, and he used the analogy of sound waves to suggest that light consisted of longitudinal waves (a back-and-forth compression) in an imaginary substance dubbed the ether. Later work by Augustin Fresnel (1788-1827) suggested that light consistedof transverse waves (which undulate up and down, perpendicular to the direction of propagation), and Young accepted this correction.
Young's theories on light stepped on important toes. Humphrey Davy (1778-1829) wrote to a friend, "Have you yet seen the theory of my colleague Dr Young, on the undulations of an Ethereal Medium as the cause of Light? It is not likely to be a popular hypothesis after what has been said by [Isaac] Newton concerning it." Indeed, Young's work on light was left in obscurity until revived by Hermann von Helmholtz (1821-1894) and other European scientists a generation later.
Young's published works include papers on the mechanism of the focusing of the eye, capillary action, the regulation and flow of blood, treatment of diseases, and many other topics. He deduced that the eye needed only three color receptors to enable a full range of color perception. He was the first in mechanics to use "energy" in the modern sense (the product of a mass with the square of its velocity), and he introduced an absolute measurement in elasticity, Young's modulus (the ratio of the stress to the strain on a solid). Young also recognized, from experiments with friction, that heat was not an element in itself, but rather a minute vibratory motion of particles.
From 1811 Young was physician at St George's Hospital, London, until he retired from medicine in 1814 and turned his talents to insurance and Egyptology, helping to translate the Rosetta stone. In his personal life Young shed the plainness of his Quaker origins and mixed in popular social circles. He had by all accounts a happy, but childless, marriage. Helmholtz, who is chiefly responsible for reviving Young's work, said that he "was one of the most clear-sighted men who have ever lived, but he had the misfortune to be too greatly superior in sagacity to his contemporaries." Young's ideas had come too soon.
This is the complete article, containing 634 words
(approx. 2 pages at 300 words per page).
