Lord Kelvin

Lord Kelvin

William Thomson, 1824–1907

Kelvin in 1902, with the mariner's compass he patented and sold. The instrument is the point: he is the rare figure in this encyclopedia who was right, was rewarded, and could afford to be wrong later.

Born	26 June 1824, Belfast
Died	17 December 1907, Largs
Buried	Westminster Abbey, near Newton
Glasgow
Chair	Natural Philosophy, 1846–1899
Age on appointment	22
Years held	53
Output
Papers	More than 650
Patents	70
Peerage	1892, the first for a scientist
The two things
Said in 1900	Two clouds remain
Did not say	That nothing remained

William Thomson, first Baron Kelvin (26 June 1824 – 17 December 1907) was a Belfast-born physicist and engineer who fixed the absolute scale of temperature, did as much as anyone to establish thermodynamics, made the Atlantic telegraph work, and was wrong about the age of the Earth for forty-five years.^[1]

He is the most decorated subject in this encyclopedia and the least characteristic of it. Almost everybody else here was ignored, unfunded, or posthumously corrected; Kelvin was knighted, ennobled, paid, and buried in the Abbey. The interest is in what happened anyway.

Glasgow

Thomson was appointed Professor of Natural Philosophy at Glasgow in 1846, at the age of twenty-two, and held the chair for fifty-three years, retiring in 1899.^[1] He then enrolled at his own university as a research student, which is either the most graceful exit in the history of the professoriate or a refusal to leave the building.

In 1848 he proposed an absolute scale of temperature, resting on a thermodynamic argument rather than on the properties of any particular substance, and fixed its zero at about −273.15 °C. The unit is now called the kelvin and is one of the seven base units of the SI. It is still doing the work at the far end of the scale it was built for: the CMB dipole, the largest structure in the microwave sky, is a signal of about three thousandths of one kelvin.

The cable, and the money

The 1858 Atlantic cable worked for three weeks and died, largely because it had been driven at high voltage on the theory that this would push the signal through. Thomson's analysis said the opposite, and his mirror galvanometer and later siphon recorder could read a signal so faint that the cable did not need to be shouted at.^[2] The 1866 cable worked. He was knighted for it in the same year.

Kelvin's tide predictor, in a plate showing it reduced to four constituents. One wire runs from a fixed point over all four pulleys, each turned at its own rate by its own crank; the weight at the end of the wire carries a pencil, and the pencil draws the sum. A tide is a sum of waves, and the machine is the addition.

He took out seventy patents in all: the compass in the photograph above, sounding machines, tide predictors, the telegraph instruments. They made him wealthy, and he was raised to the peerage in 1892 as Baron Kelvin of Largs, after the river that runs past the Glasgow laboratory, becoming the first scientist in the House of Lords.

This is worth pausing on, because it is unusual here. The corpus is mostly men who were right and unheard, or wrong and certain, and Kelvin was neither: he was right about a thing that could be sold, and the selling of it bought him fifty years of unchallengeable authority. What that authority was then used for is the next section.

The age of the Earth

From 1862 Kelvin calculated the age of the Earth from the rate at which a hot body loses heat, and arrived at a few tens of millions of years – far too short for the geology, and far too short for natural selection to have done what Darwin needed it to do.

Every quantity in the calculation was measured and every step was sound. It was wrong because the Earth makes heat, which no one in 1862 had any means of suspecting, and he narrowed the figure over thirty-five years in the direction of greater confidence and smaller numbers. The full account, including the assistant who got it right in 1895 and was ignored, is at the age of the Earth. He made the same error about the Sun at the same time and for the same reason.

He never publicly conceded it. He is said to have paid off a private bet.

The two clouds

On 27 April 1900 Kelvin addressed the Royal Institution on "Nineteenth-Century Clouds over the Dynamical Theory of Heat and Light", and opened:

"The beauty and clearness of the dynamical theory, which asserts heat and light to be modes of motion, is at present obscured by two clouds."
– Lord Kelvin, Royal Institution, 27 April 1900

He then numbered them, and the first is not quite the one usually reported. Cloud I is not the Michelson–Morley result but the question that produced it, which he dates to Fresnel and Thomas Young: "How could the earth move through an elastic solid, such as essentially is the luminiferous ether?"^[6] The aether had to be rigid enough to carry a transverse wave and yielding enough to let the planets through, and that had been the difficulty for eighty years before any interferometer was pointed at it. Cloud II is "the Maxwell-Boltzmann doctrine regarding the partition of energy", which would not give the right answer for radiation or for specific heats.

Kelvin was not standing helpless in front of the first. He proposes, in the same paper, that we "simply deny the scholastic axiom that two portions of matter cannot jointly occupy the same space", and let the aether sit inside ponderable matter rather than be pushed aside by it, each atom condensing the aether within its own volume. It is an ingenious answer and it is wrong, and offering it is the more interesting act: he had named the problem correctly and could not get out of it.

The first cloud became special relativity within five years. The second became quantum mechanics, and descended first on Max Planck. Between them they consumed the physics Kelvin had spent his life on, and he had named them both, in order, in a single sentence, at the age of seventy-five.

The printed version carries one further thing worth recording. It is much longer than the lecture, having been extended over thirteen months of further work, and it opens with an acknowledgement to William Anderson, his secretary, for the drawings and the arithmetic – a labour, Kelvin notes, "involving the determination of results due to more than five thousand individual impacts", the whole of which Anderson performed.^[6] He is thanked inside a square bracket and does not appear again.

The sentence he did not say

He is nonetheless quoted, constantly, as having announced at about that date that physics was finished and only the decimals remained.

There is no source. The attribution appears from about the 1980s and never earlier, and the words are a paraphrase of Albert Michelson, who said in 1894 that the future truths of physical science were "to be looked for in the sixth place of decimals".^[3] Michelson was not claiming the thought as his own either; he offered it as a remark of an eminent physicist he did not name. So the most famous statement of nineteenth-century complacency is a misquotation of a paraphrase of an attribution to nobody, and it has been fastened onto the one man who is on record saying the opposite in the same decade. It is Stigler's law applied to an error rather than a discovery, and it works just as reliably.

Wrong, and right, about the future

He did make predictions, and one of them is genuinely bad. Asked in December 1896 to join the Aeronautical Society, he replied that he had "not the smallest molecule of faith in aerial navigation other than ballooning", and declined.^[4] Seven years later the Wright brothers flew.

Against that should be set the episode nobody quotes. When N-rays were announced in 1903 and half the physicists of France were detecting them, Kelvin was among those who looked for them carefully and reported seeing nothing at all, which was correct, and which is the harder thing to publish.

Death

He died at Largs on 17 December 1907. The Royal Society asked the Dean of Westminster whether he might be buried in the Abbey; the Dean agreed, and he lies in the nave immediately south of Isaac Newton, with John Herschel and Charles Darwin close by.^[5]

The company is exact and a little cruel. Newton's chair he never held; Herschel was at Babbage's elbow the evening the engines were thought of; and Darwin needed an old Earth, was told by Kelvin that he could not have one, and had been dead twenty-five years before the objection was answered. In the year Kelvin died, Bertram Boltwood published the first mineral ages from radioactive decay, and they ran past a thousand million years.

See also

• The age of the Earth – the calculation, the narrowing, and the assistant who was right in 1895
• Luminiferous aether – his first cloud, and what the century did with it
• Max Planck – on whom the second cloud descended, and who did not enjoy it
• Radian – first printed by his elder brother James, in a Belfast examination paper
• N-rays – where his failure to see anything was the correct result
• Stigler's law of eponymy – which the quotation he never said obeys precisely

References

1. ^ Standard biography: born Belfast 1824, Glasgow chair 1846–1899, died Largs 1907. He published more than 650 papers. The research-student enrolment after retirement is not a joke of this encyclopedia's making.
2. ^ The 1858 failure is usually laid to Wildman Whitehouse's high-voltage practice; Thomson's instruments made the 1866 cable readable at low voltage. Knighted 10 November 1866.
3. ^ A. A. Michelson, 1894. The "sixth place of decimals" is his; the sentiment he explicitly attributed to an unnamed eminent physicist, so the chain of custody is broken at the far end as well as the near one. The Kelvin attribution has been traced no earlier than the 1980s.
4. ^ Kelvin to Major B. F. S. Baden-Powell, 8 December 1896, declining membership of the Aeronautical Society. The remark is genuine, is dated, and is the strongest evidence that the famous quotation was not needed in order to make him look foolish about the future.
5. ^ Westminster Abbey's own record: the Royal Society applied to the Dean, the funeral was on 23 December 1907, and a memorial window by J. Ninian Comper was put up near the grave in 1913, the gift of engineers in Britain and America. It carries figures of Henry V and Abbot Colchester, and Kelvin's name underneath them.
6. ^ Kelvin, "Nineteenth Century Clouds over the Dynamical Theory of Heat and Light", the Friday evening lecture of 27 April 1900, printed with large additions as Appendix B to the Baltimore Lectures and in the Philosophical Magazine for July 1901. The quotations are from §§1–3 and from the bracketed prefatory note of 2 February 1901. Kelvin's own statement of Cloud I is broader than the version usually attributed to him, and he credits it to Fresnel and Young rather than to any experiment of his own century.

External links

• Nineteenth-Century Clouds over the Dynamical Theory of Heat and Light (1901) – the lecture, as printed in the Philosophical Magazine
• William Thomson, Lord Kelvin – Westminster Abbey – the Abbey's own account of the grave and the window above it
• Kelvin with his compass, 1902 – the photograph reproduced above