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Thomas Young was an English polymath with interests ranging from physics to Egyptology. He was born in 1773, in Somerset, England into a large Quaker family1 and had nine siblings. He was a child prodigy, learnt to read by age two, and taught himself Latin at age six. Young has been described as “The Last Man Who Knew Everything” [1]. He died in London in 1829 at the age of fifty-five.
At the age of fourteen, Young had learned Greek and Latin and was acquainted with French, Italian, Hebrew, German, Aramaic, Syriac, Samaritan, Arabic, Persian, Turkish, and Amharic languages [2].
Young began to study medicine in London at St Bartholomew’s Hospital in 1792, moved to the University of Edinburgh Medical School in 1794, and a year later went to Göttingen, Lower Saxony, Germany, where he obtained the degree of doctor of medicine in 1796 from the University of Göttingen. In 1793, he offered an explanation of how the eye accommodates itself to vision at different distances based on changes in the curvature of the eyes crystalline lens [3]. In 1797, he entered Emmanuel College, Cambridge. In the same year, he inherited the estate of his granduncle, Richard Broscklesby, which made him financially independent, and in 1799, he established himself as a physician at 48 Welbeck Street, London (now recorded with a blue plaque). Young published many of his first academic articles anonymously to protect his reputation as a physician.
As a gentleman of independent means, Thomas Young had a keen interest in science. Although he had decided on a career in medicine, he did not substantially practice but continued scholarly studies at Emmanuel College, in Cambridge. In 1801, he was appointed a professor of natural philosophy (mainly physics) at the Royal Institution and in the same year proposed that three types of retinal particles might exist, each associated with one of the principal colors “red, yellow, and blue” [4]. In 1802, he became foreign secretary for the Royal Society. In an 1803 paper, he changed his primary colors to red, green, and violet. While it is debated whether Young was the first to propose this idea, his views were one of the earliest statements pertaining to the fundamental property of “trichromacy” that characterizes human spectral discrimination.
Young resigned his professorship in 1803, fearing that its duties would interfere with his medical practice. His lectures were published in 1807 in Course of Lectures on Natural Philosophy and the mechanical arts [5] containing a number of anticipations of later theories.
In 1811, Young became a physician to St George’s Hospital, and in 1814, he served on a committee appointed to consider the dangers involved in the general introduction of gas into London. In 1816, he was secretary of a commission charged with ascertaining the precise length of the second’s or seconds pendulum (the length of a pendulum whose period is exactly 2 s), and in 1818, he became secretary to the Board of Longitude and superintendent of HM Nautical Almanac Office.
In 1827, Young was chosen as one of the eight foreign associates of the French Academy of Sciences. In 1828, he was elected a foreign member of the Royal Swedish Academy of Sciences.
31.1 Trichromatic Color Vision and Wave Theory of Light
Now it is almost impossible to conceive each sensitive point of the retina to contain an infinite number of particles, each capable of vibrating in perfect unison with every possible undulation, it becomes necessary to suppose the number limited, for instance, to the three principal colours, red, yellow, and blue, of which the undulations are related in magnitude nearly as the numbers 8, 7 and 6…. and each sensitive filament of the nerve may consist of three portions, one for each principal colour.
The experiments I am about to relate… may be repeated with great ease, whenever the sun shines, and without any other apparatus than is at hand to everyone.
The lecture was published in the following year’s Philosophical Transactions of the Royal Society of London, [6] and is still reprinted and read today. Thus, with the ripple tank, he demonstrated the idea of interference in the context of water waves and with his interference or double-slit experiment, and he demonstrated interference in the context of light as a wave.
Plate from “Course of Lectures” of 1802, published in 1807 [5]
Young also performed two important diffraction experiments using fibers and long narrow strips. In his Course of Lectures on Natural Philosophy and the Mechanical Arts [5], he gives Grimaldi credit for first observing the fringes in the shadow of an object placed in a beam of light. Within ten years, much of Young’s work was reproduced and then extended by Fresnel.
As Young pointed out “The nature of light is a subject of no material importance to the concerns of life or to the practice of the arts, but it is in many other respects extremely interesting…”