William Thomson (Lord Kelvin)
William Thomson, 1st Baron Kelvin
Royaume-Uni de Grande-Bretagne et d'Irlande
9 min read
British physicist and mathematician of the 19th century, he made fundamental contributions to thermodynamics and electromagnetism. He is the originator of the absolute temperature scale that bears his name. He also oversaw the laying of the first transatlantic telegraph cable.
Frequently asked questions
Famous Quotes
« If you can't measure it, you can't improve it. »
« Science is the measurement of truth. »
Key Facts
- Born in 1824 in Belfast, died in 1907 in Largs (Scotland)
- Proposed in 1848 the absolute temperature scale (kelvin, SI unit)
- Stated the second law of thermodynamics alongside Clausius in the 1850s
- Oversaw the laying of the first successful transatlantic telegraph cable in 1866
- Ennobled in 1892 with the title of Lord Kelvin, the first scientist to enter the House of Lords
Works & Achievements
Thomson defined a temperature scale based on pure thermodynamics, independent of any material substance. Absolute zero (0 K = −273.15 °C) corresponds to the complete absence of thermal motion; this scale is today the SI unit of temperature.
Thomson stated that heat cannot spontaneously flow from a cold body to a hot one — a fundamental principle that explains the irreversibility of natural phenomena and the concept of ever-increasing entropy in the universe.
Following the failed attempt of 1858, Thomson oversaw the successful laying of the first permanent cable linking Ireland to Newfoundland. His inventions — the mirror galvanometer and reception system — were decisive in ensuring reliable transmission.
A treatise on mechanics and mathematical physics that unified Newtonian dynamics with the new concepts of energy. It became the standard reference for an entire generation of British physicists.
An analogue machine that automatically computed tides by harmonic decomposition of lunar and solar forces. Used by the hydrographic services of several countries, it foreshadowed the analogue computers of the twentieth century.
A series of twenty lectures delivered in Baltimore synthesising classical physics — mechanics, heat, electricity, and light. Published in 1904, they capture Thomson at the very limits of classical physics, sensing the revolutions that were to come.
Anecdotes
William Thomson entered the University of Glasgow at just 10 years old, accompanying his father who taught mathematics there. At 15, he won the prize for excellence in astronomy. This exceptional precocity would lead him to become a full professor at the same university at age 22, a post he held for 53 consecutive years.
During the laying of the first transatlantic telegraph cable in 1858, Thomson was on board the ship. The cable worked for a few weeks before failing. During the second attempt in 1866, it was his invention — the mirror galvanometer, capable of detecting minute electrical signals — that finally made a stable link between Europe and America possible. Queen Victoria knighted him in recognition.
In 1848, Thomson proposed a temperature scale based not on the properties of a particular liquid, but on the universal laws of thermodynamics. He defined absolute zero (−273.15 °C) as the theoretical temperature at which all thermal motion ceases. This scale, named 'kelvin' after his death, is today the international unit of temperature in science.
Thomson spent years calculating the age of the Earth from our planet's rate of cooling, concluding it was approximately 20 to 100 million years old. This estimate, well-argued for its time, proved to be radically underestimated: radioactivity, discovered shortly before his death, heats Earth's interior and was unknown to him. This error illustrates how rigorous science can be overturned by an unexpected discovery.
Lord Kelvin was passionate about sailing and owned his own yacht, the Lalla Rookh, aboard which he conducted numerous experiments. He invented an improved maritime compass and an automatic depth sounder — instruments that saved many lives at sea. He readily filed patents and thus became one of the wealthiest scientists of his era.
Primary Sources
The determination of temperature has long been recognized as a problem of the greatest importance in physical science. [...] The numerical value of an absolute temperature does not depend on the physical properties of a specific substance.
When equal quantities of mechanical effect are produced by any means whatever from purely thermal sources, equal quantities of heat are put out of existence; or, heat and mechanical effect are mutually convertible.
The mirror galvanometer is the only instrument sensitive enough to detect the feeble electrical impulses which can be transmitted through 2000 miles of submarine cable.
The more I study the science of physics, the more I am struck by two great difficulties, two great clouds that hang over our understanding of the universe.
The foundations of dynamics may be said to consist in the following propositions: a material point is a portion of matter so small that, for the purposes of the investigation, it may be treated as a mathematical point.
Key Places
Birthplace of William Thomson on 26 June 1824. His family later moved to Glasgow when his father obtained a university chair there.
Thomson studied here from age 10, then served as professor for 53 years (1846–1899). His physics laboratory was among the first of its kind in the United Kingdom. The River Kelvin, which flows alongside the campus, gave him his baronial title and lent its name to the unit of temperature.
Thomson studied mathematics here from 1841 to 1845, finishing second in the prestigious Mathematical Tripos. It was here that he discovered the formal analogies between electrostatics and the theory of heat.
The coastal town where Thomson owned his main residence, Netherhall, and moored his yacht. He died there on 17 December 1907 at the age of 83.
The burial place of Lord Kelvin, interred in January 1908 near the tomb of Isaac Newton — a testament to the exceptional status accorded to his scientific contributions.
The European starting point of the transatlantic telegraph cable. It was from this Irish shore that the first messages were sent to Newfoundland in 1858 and again in 1866, under Thomson's technical supervision.
