Physical prowess

William Thomson was a colossal figure in 19th-century science and one of a handful of scientists who shaped the physics handed…

William Thomson was a colossal figure in 19th-century science and one of a handful of scientists who shaped the physics handed on to the 20th century. Apart from his scientific work, he was a successful businessman. When he died, in 1907, he had published more than 600 scientific papers and held 70 patents, writes Dr William Reville

Thomson was born in 1824 in Belfast, where his father, James, taught mathematics. In 1832, the family moved to Glasgow, after James's appointment as a professor at Glasgow University. Educated by his father, Thomson entered the university at the age of 10. He moved on to Cambridge, graduating with high honours in 1845, at the age of 21. He was a champion oarsman and a founder of the music society. Following lobbying by his father, he was appointed professor of natural philosophy - now physics - at Glasgow at the age of 22, a position he held until he retired, 53 years later, in 1899.

In order to make his lectures more interesting, Thomson introduced the demonstration. He would illustrate the law of conservation of momentum, for example, by firing a bullet into a wooden pendulum, using an old muzzle-loader rifle.

Thomson's scientific work was vast and deep. He played a principal role in developing the second law of thermodynamics, one of the fundamental laws of physics. He introduced a new scale of temperature, measured in units called kelvins, each of the same size as a degree Celsius. Zero on the Kelvin scale is equivalent to -273 degrees Celsius - or absolute zero, the temperature at which atoms cease to move.

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Thomson extensively analysed electricity and magnetism mathematically, including the basic ideas for treating light as an electromagnetic phenomenon. He also determined geophysically the age of the earth. When James Clerk Maxwell (1831-1879) later studied electricity and magnetism, he first read all of Thomson's papers on the subject. In the most significant scientific achievement of the 19th century, Maxwell developed the electromagnetic theory of light. Maxwell readily acknowledged Thomson's contribution.

Thomson viewed all physical change as an energy-related phenomenon. He was a great unifier of theories, bringing together disparate areas in physics such as heat, thermodynamics, mechanics, magnetism, electricity and hydrodynamics. This synthesis allowed 20th-century physics to make the next great leap forward.

Thomson was convinced that all forms of energy - thermal, light, electrical, magnetic and mechanical - were interrelated, and he believed the various theories dealing with matter and energy were converging towards a grand unified theory.

James Prescott Joule (1818-1889) established the conversion relationship that applies when mechanical motion is converted into heat. This spurred Thomson to great effort, culminating in On The Dynamical Theory Of Heat, an important mathematics book in which he outlined his version of the second law of thermodynamics.

Thermodynamics is the study of energy flow and transformation. Thomson saw that the conversion of one form of energy into another is never perfectly efficient; some energy is always lost as heat and is therefore unavailable to do useful work. Consequently, every finite system, including the universe, is running down and will eventually stop. This, basically, is the second law of thermodynamics.

Arising from his work on heat, Thomson calculated the age of the earth. He assumed the planet was originally as hot as the sun and has been cooling ever since. He calculated that it would take between 20 million and 400 million years for the earth to cool to its present temperature.

If Thomson was right, several major theories were unworkable. The geologists believed in uniformitarianism; that is, that the weathering forces at work can, by and large, explain the tortured physical features of the earth. But this theory requires these forces to have acted over a period of billions, not millions, of years. Also, the theory of evolution required a much longer period in which to act than Thomson's estimate would allow. Because of this discrepancy, Thomson never accepted evolutionary theory.

In time it became clear that Thomson's estimate of the earth's age was wrong. There is more heat in the earth than Thomson knew about. Much of it is generated by radioactivity, which wasn't discovered until 1895. Modern calculations put the age of the earth at around 4.6 billion years.

The first transatlantic telegraph cable was laid in 1858, but it failed largely because of poor insulation and the large voltages used. Thomson invented a sensitive mirror galvanometer capable of detecting feeble signals, which was an essential element in the first successful cable, laid in 1866. It ran from Valentia Island, off Co Kerry, to Newfoundland, in Canada. Thomson sailed aboard the Great Eastern, the cable-laying ship, risking his life on several occasions. Queen Victoria knighted him in 1866 for his work, and he was raised to the peerage in 1892, as Baron Kelvin of Largs.

Thomson accumulated great wealth through his patents and business interests, enjoying a lifestyle that included a 126-ton yacht and a baronial estate. Spurred by his nautical pastime, he improved compasses for navigation, the British Navy adopting his new design.

Lord Kelvin died in 1907 and is buried in Westminster Abbey, in London. A statue in the Botanic Gardens in Belfast is appropriately inscribed: "He elucidated the laws of nature for the service of man."

William Reville is a senior lecture in biochemistry and director of microscopy at UCC