We are so pleased to welcome geosciences historian Sally Newcomb back to Ex Libris Universum! Her excitement about the Wenner Collection is gratifying and contagious to us librarians who are processing it. See her first post about the book in the Collection published in 1799 that discusses the new metric system and the possibility of black holes here.
Kelvin, Wenner, and the Ages of the Sun and the Earth
by Sally Newcomb
Again browsing the shelves of the Wenner Collection with Allison, the title of one box stood out immediately: Age of the Earth, featuring articles by William Thomson (1824-1907), aka 1st Baron Kelvin. Kelvin has 24 total papers present in the Wenner Collection, and this box contains three of them that address a great controversy in physics and geology of the 19th century. Naturally, the age of the sun was part of the story. For physicists before the end of the century, the interest lay in the application and fine-tuning of thermodynamics and the necessary mathematics. However, the best calculations for the age of the earth at the end of the century were put into question with the discovery of radioactivity and its impact.
Thomson, W. 1862. On the Age of the Sun’s Heat. MacMillan magazine Vol.V, pp. 388-393, Nov. 1861-Apr. 1862, Cambridge: MacMillan and Co.
Thermodynamics was only one field in which William Thomson - made Lord Kelvin for his accomplishments - excelled. Sadly, as applied to the ages of the sun and earth, it was also the one where his intransigence sullied his reputation in the final decade of his life. Over his long career, Kelvin published many (hundreds of) notable papers in mathematics and physics as well as being admired and awarded for novel instruments and his pioneering work in the fabrication, characteristics, and operation of cables for long distance undersea communication between continents. Kelvin remained interested in the ages of the sun and the earth over the second half of the 19th century, and these three papers (among others he wrote on the same topic) advance his arguments for the origin and maintenance of the sun’s heat and dissipation, and that of the earth.
The first of the papers is “On the Age of the Sun’s Heat”, published in 1862 and found on pages 388-393 of MacMillan magazine. This paper includes Kelvin’s first estimate for the age of the sun. MacMillan magazine was for general readership, so we may find the accompanying articles strange company for Thomson’s paper: as you see in the table of contents, other articles include “Salmon, A Slice of,” “Sonnets,” and “Royal Deaths: The Princess and the Prince” - not an entirely typical place to find a scientific paper.
"On the Age of the Sun’s Heat" table of contents
In “On the Age of the Sun’s Heat,” Kelvin continued joining the second law of thermodynamics to a sun heated by collision of meteorites and the dissipation of that generated heat. He ended with: “That some form of the meteorite theory is certainly the true and complete explanation of solar heat and can scarcely be doubted when the following reasons are considered:” (p. 393) followed by his three reasons. A logical estimate for the age of the earth appeared to be 20 million years, which he found more likely than 100 million and certainly not 500 million. In the paper, Kelvin referenced the “splendid researches of Bunsen and Kirchoff” who identified elements in the sun (p. 389). He strongly questioned the estimates of geologists based on observed rates of change in strata. For reference, the commonly accepted age of the earth now is 4.5 billion years.
The second paper is “The Sun’s Heat”, published in 1887 as an offprint from the Royal Institution of Great Britain, Weekly Evening Meeting, Friday Jan. 21, 1887 pp. 1-21. Kelvin noted that natural history gave no reason for a change in intensity of solar radiation within human history. He agreed with Helmholtz’s meteorite theory as a source of the sun’s heat and again noted that the spectroscope was tracing more and more detail about the sun’s composition. He found a value in horse-power for the mechanical value of the radiation per square meter of the sun’s surface. As he continued, he recognized the inefficacy of more fanciful calculations and improbable mechanisms - at one point he had tried to make a mechanical model for the ether - but continued trying to find a mechanical analog to which he could fit the mathematics. The second part of this paper attempted to determine something about the early history of the sun and whether it is getting hotter or colder. It is an interesting, if somewhat mind-numbing exercise to try to follow his diffuse reasoning.
Thomson, W. 1898. The Age of the Earth as an Abode Fitted for Life. From Smithsonian Report for 1897, pp. 337-357. Washington D.C.: Government Printing Office
The third paper in the box is “The Age of the Earth as an Abode Fitted for Life” published in 1898 from Smithsonian Report for 1897, pp. 337-357. This is Kelvin’s last effort at the age of the earth. Here his quarrel with the geologists and T.H.I. Huxley and C. Darwin reached its full extent. He never accepted the immeasurable lengths of time implied for strata deposition nor the observed changes in organic life. More was being learned about the sun and the melting temperatures of rocks, but Kelvin never agreed that the newly discovered radioactivity of several elements could be a sufficient energy source to give the geologists the time their world required. After a lifetime of innovation and honor, he could not accept the evidence that supplied the “missing link” for the immense reaches of time required by the geologists and biologists.
Among more than a hundred years’ span of biographies enabling a full look at Kelvin and his place in the history of physics are: Lindley, D. 2004. Degrees Kelvin: A Tale of Genius, Invention, and Tragedy. Washington D.C.: Joseph Henry Press, and Smith, C. and M.N.Wise. 1989. Energy and Empire: A Biographical Study of Lord Kelvin. Cambridge: Cambridge University Press. There is a large literature from the geologists’ standpoint, of which one, Lewis, C.L.E. & S.J. Knell (eds). 2001. The Age of the Earth: From 4004 BC to AD 2002. London: The Geological Society of London, can serve as a link to the others.