Thomas
Young was an English physician and physicist, with a brilliant mind and
eclectic interests. By the age of fourteen it is said that he was
acquainted with Latin, Greek, French, Italian, Hebrew, Arabic and Persian.
So great was his knowledge that he was called called Phenomena Young by
his fellow students at Cambridge. He studied medicine in London,
Edinburgh, and Göttingen and set up medical practice in London. His
initial interest was in sense perception, and he was the first to realize
that the eye focusses by changing the shape of the lens. He discovered the
cause of astigmatism, and was the initiator, with Helmoltz, of the three
colour theory of perception, believing that the eye constructed its sense
of colour using only three receptors, for red, green and blue. In 1801 he
was appointed Professor of Physics at Cambridge university. His famous
double-slit experiment established that light was a wave motion, although
this conclusion was strongly opposed by contemporary scientists who
believed that Newton, who had proposed that light was corpuscular in
nature, could not possibly be wrong. However Young's work was soon
confirmed by the French scientists Fresnel and Arago. He proposed that
light was a transverse wave motion (as opposed to longitudinal)
whose wavelenght determined the colour. Since it was thought that all wave
motions had to be supported in a material medium, light waves were
presumed to travel through a so-called aether, which was supposed
to fill the entire universe. He became very interested in Egyptology, and
his studies of the Rosetta stone, discovered on one of Napoleon's
expeditions in 1814, contributed greatly to the subsequent deciphering of
the ancient Egyptian hieroglyphic writing. He did work in surface tension,
elasticity (Young's modulus, a measure of the rigidity of materials, is
named after him), and gave one of the earliest scientific definitions of
energy.