Thomas Young

British physicist

• Born: June 13, 1773; Milverton, England
• Died: May 10, 1829; London, England

British scientist Thomas Young is known for his contributions to the fields of physics, optics, and medicine. He proposed a wave theory of light, challenging the particle theory of earlier scientist Isaac Newton.

Primary field: Physics

Specialties: Theoretical physics; optics; physiology

Early Life

Thomas Young was born in 1773 in Milverton, England, to Thomas and Sarah Young. By the age of two, Young had learned to read. By the age of fourteen, he had mastered multiple languages, including Greek, Latin, French, Italian, Hebrew, Arabic, and Farsi.

Young completed his education quickly and soon began to prepare for a career in medicine. He enrolled at the University of Edinburgh but completed his studies at the prestigious University of Göttingen in the Holy Roman Empire (now Germany). In 1793, he lectured before the Royal Society on the eye and its muscular structure. On the basis of his paper “Observations on Vision,” he was elected to the Royal Society at the age of twenty-one. He later became the society’s secretary.

With the completion of his medical studies in 1796, Young continued his scholarly work at Emmanuel College, Cambridge. That year, he inherited the fortune of his granduncle, physician Richard Brocklesby, which allowed him to be financially independent. Thus, at a very young age, Young had the freedom to pursue inquiries in whatever field interested him. He later moved to London and established a medical practice there.

Life’s Work

While experimenting at Cambridge, Young became increasingly interested in optics and the perception of colors. Drawing on his earlier observations of the eye, Young advanced a theory on colors. He assumed there are three basic colors (red, green, and violet) and that the retina of the eye contains groups of receptors, later determined to be cone cells, that are sensitive to one of these three colors. For example, a red light stimulates a receptor sensitive to red colors, a violet light stimulates a receptor sensitive to violet colors, and so on. Young proposed that other colors are seen when different combinations of receptors are stimulated. For instance, a yellow color is seen when both violet and green receptors are stimulated at the same time.

Young published variations on this theory at several points in his career, eventually including elements of it in his article on chromatics for the Encyclopedia Britannica. Later, German scientist Hermann von Helmholtz developed Young’s theory further, and it became known as the Young-Helmholtz theory. In the 1950s, new technology demonstrated conclusively that the Young-Helmholtz theory is largely correct and that the cone cells in the retina function according to Young’s description.

From his initial forays into optics, Young began to experiment with the nature of light. Having previously investigated the transmission of sound, which he proposed traveled in waves, as well as the movement of waves in water, Young theorized that light travels in a similar manner. In 1802, he invented a simple experiment to prove this theory and demonstrated conclusively that light does indeed travel in waves. As he developed his wave theory of light, Young found that many English physicists were unreceptive to his findings because they contradicted the particle theory of light developed by Isaac Newton more than a century earlier. However, French physicists Augustin Jean Fresnel and François Arago tested Young’s theory, and their experiments helped confirm that Young was correct in his findings.

On the basis of his experiments, in 1801, Young was appointed professor of natural philosophy, the field that later became known as physics, at the Royal Institution. Over the next two years, Young delivered lectures on nearly every subject then studied in physics. Young resigned his professorship in 1803, explaining that it was interfering with his medical duties. The following year, he married Eliza Maxwell.

Although he had resigned his professorship, Young continued to conduct experiments in physics. He made an important contribution to the theory of elasticity known as Young’s modulus, a ratio used to measure the stiffness of elastic materials. In 1818, working with the Board of Longitude and the Royal Navy, he helped supervise the publication of a nautical almanac. In addition, Young made significant contributions to the field of medicine. Young was the first physician to describe astigmatism in the eye accurately. In recognition of his medical work, he was made a fellow at the College of Physicians in Cambridge. He was often invited to lecture on medical matters, and throughout his life, he practiced at St. George’s Hospital in London.

Young applied himself to other areas of study as well. In 1799, French soldiers had discovered a stone buried outside the town of Rosetta, Egypt, on which was carved a proclamation in Greek, hieroglyphics, and a third, unknown language that later became known as demotic. While Egyptian hieroglyphics were present on many monuments, scholars had been unable to decode what they meant. However, the Rosetta Stone placed a known language, Greek, alongside the hieroglyphics, allowing them to be translated. Young began to study the Rosetta Stone and discovered that the third language (demotic) was a mixture of phonetic and hieroglyphic signs. Thus, he was able to trace the demotic writing back to hieroglyphics and decode names and words from the ancient symbols.

Young spent his later years practicing medicine and contributing articles to the Encyclopedia Britannica. He died in London on May 10, 1829.

Impact

Young’s work in the field of physics greatly influenced the development of scientific thought. His work on the wave theory of light not only served to displace the longstanding particle theory of Newton but also led to a variety of advances in the study of light. Early in the twentieth century, scientists determined that light behaves as both a wave and a particle, indicating that Newton and Young were both partially correct. This discovery, in turn, allowed scientists to make important contributions to the developing field of quantum physics. Young’s research regarding how the eye recognizes and interprets different colors also proved to be influential, serving as the foundation for further study in that area.

Although Young is perhaps best known as a scientist, he was also a significant figure in the field of linguistics. He studied and compared the vocabulary and grammar of over four hundred languages, publishing his findings in a series of articles in the Encyclopedia Britannica. Finding similarities along a wide spectrum of languages, Young coined the term “Indo-European” to describe the family of European languages that includes Greek, Latin, Sanskrit, and many other modern languages. Young’s articles and work on the Rosetta Stone were of great help to Egyptologist Jean Francois Champollion, who ultimately translated the Egyptian hieroglyphics on the stone in the 1820s.

Bibliography

Atchison, David A., and W. Neil Charman. “Thomas Young’s Contributions to Geometrical Optics.” Clinical and Experimental Optometry 94.4 (2011): 333–40. Print. Describes Young’s contributions to the fields of optical instrumentation, physical optics, and geometrical optics and discusses Young’s theorems regarding paraxial refraction and astigmatism and image curvature.

Robinson, Andrew. The Last Man Who Knew Everything: Thomas Young, the Anonymous Polymath Who Proved Newton Wrong, Explained How We See, Cured the Sick, and Deciphered the Rosetta Stone, among Other Feats of Genius. New York: Pi, 2005. Print. Provides a thorough biography of Young, drawing on Young’s writings and letters. Discusses Young’s early life, his optics research and theory of color vision, the translation of the Rosetta Stone, his medical practice, his contributions to the Encyclopedia Britannica, and his many other accomplishments.

Wood, Alexander, and Frank Oldham. Thomas Young: Natural Philosopher, 1773–1829. 1954. Cambridge: Cambridge UP, 2011. Print. Chronicles Young’s life and career and includes excerpts from his writings as well as diagrams explaining his experiments and discoveries.