World of Scientific Discovery on William (Lord Kelvin) Thomson
William Thomson was among the most prodigious minds in British history. He was responsible for landmark accomplishments in the fields of thermodynamics, geology, and electrophysics, as well as for the invention of numerous scientific devices. In 1892 he was awarded the title Lord Kelvin of Largs; it is by this name that his most influential discovery, the Kelvin scale of absolute temperature, is best known.
Thomson's father lectured at the University of Glasgow; the younger Thomson began attending his father's classes at age eight, entering the University as a student at age eleven. There he studied mathematics, ultimately finishing second in his class. His thirst for knowledge unabated, Thomson enrolled in postgraduate studies first at Cambridge and later at the University of Paris. At the age of twenty-two he was appointed to the newly created chair of Natural Philosophy (an early catch-all label for science) at the University of Glasgow--the same school at which he had watched his father lecture.
The British scientific community eagerly awaited Thomson's first scientific publication as a professor (his first paper was written when he was in his early teens and was read to the Royal Society of Edinburgh by a senior professor). They did not need to wait long: the same year he was appointed he announced his derivation of the true age of the Earth--a number drastically lower than that previously accepted by geologists. Thomson explained that his calculations were based upon the amount of time needed for our planet to cool down after formation. Assuming the Earth's temperature was originally the same as the Sun's, the amount of time to cool was somewhere between 20 million and 400 million years, most likely about l00 million years.
Previously, geologists had decided that the Earth was several billion years old, with the temperature remaining very near normal temperatures for most of that time; these findings were eventually found to be much closer to the truth. However, Thomson's theories seemed so convincing that many scientists of the time scrambled to fit their own theories within the Earth's new short life-span. Probably the most important idea to come of this was the concept of evolutionary mutation. Biologists had believed that evolution followed a slow, steady path; now, they were forced to consider that it contained "jumps" through which the process was accelerated. Though Thomson's theories were eventually disproved, the concept of evolutionary mutation remains.
While studying the age of a cooling Earth, Thomson became very curious about the nature of temperature. In particular he was interested in Charles' law, authored by the French physicist Jacques-Alexandre-César Charles. His law states that when a gas is cooled from zero degrees celsius, its volume decreases by 1/273 for every degree drop. While this law had been proved and proved again, it presented a disturbing implication: if the temperature were reduced to -273° C, the volume of the gas would be reduced to zero (losing 273/273). No scientist could explain how matter could take up no volume--that is, until Thomson.
Thomson proposed in 1848 that it was the gas' energy of motion, not its volume, that was decreased by the falling temperature. At-273° C the energy level would reach zero; the molecules would stop moving, and it would effectively take up no space. Because no further reduction in temperature could occur, Thomson labeled -273° C as absolute zero.
The concept of an absolute zero was very useful in the creation and verification of many thermodynamic theories. Thomson quickly introduced a new temperature scale, called the absolute scale, with this ultimate low point as its zero. It was essentially a re-working of the celsius scale with all of the temperatures reduced by 273 degrees; on this scale, now known as the Kelvin scale, the freezing point of water stood at 273 K, the boiling point at 373 K. Thomson's scale would eventually become an instrumental tool in James Clerk Maxwell's developing of the kinetic theory of gases.
In 1851 Thomson continued to bolster his reputation as Britain's predominant thermophysicist by introducing the idea that all energy runs down, dissipating itself into the environment as heat. This concept of degradation was later explored by Rudolf Clausius and was re-introduced in a much clearer and more explicit form as the Second Law of Thermodynamics, better known as entropy.
Thomson was knighted in 1866 for his work in salvaging the first telegraph cable to span the Atlantic. During the 1880s he lectured on the virtues of Victorian science, a school of thought that believed all of the important discoveries in physics had been completed. So committed was he to this idea that he completely rejected the theories of radioactivity, ignoring the onset of the next great scientific age. He died in 1907 and was buried next to Isaac Newton in Westminster Abbey.
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