KELVIN
Who was the greatest physicist of the twentieth century? Albert Einstein, right? Most people would say that, especially now, it being the 100th anniversary of the publication of his three papers (among them, the special relativity one) during his "miracle year" of 1905. Those with more than the average knowledge of physics might have a more nuanced view of who else should be considered the genuine greatest. They might suggest others, like Richard Feynman, Lev Landau, Dirac, Bohm, Bohr, Schwinger, Sommerfeld, maybe Hawking, maybe Fermi. Worthy gentlemen, all of them. I had no difficulty coming up with their names right off the top of my head, and I left out quite a few.
Who was the greatest physicist of the nineteenth century? Ummm . . . hmmm. Maxwell, maybe? Some equations are named after him. Joule? They named a unit of energy after him. Helmholtz? (But what did he do?) Faraday? Great experimentalist, but he couldn’t do math. How about Sir William Thompson? You know–Lord Kelvin, remembered chiefly these days, if at all, for saying heavier-than-air flight wouldn’t work. He also has a unit of temperature named for him.
Kelvin?
But what did he do? you ask. Pretty much everything, I reply.
I can forgive anyone for being ignorant of the work of Lord Kelvin. My copy of the Encyclopedia of Physics (Addison-Wesley, 1981) makes scant mention of him, and then only in a couple of articles. One article mentions his work in electromagnetism, the other his work in thermodynamics. He made prodigious contributions to both areas of physics, yet he didn’t even get his own half-page biography in the book. To add insult to injury, in Sir Horace Lamb’s classic tome Hydrodynamics, Kelvin is referenced either by himself or with his co-author P. G. Tait more often than any other scientist save one, Lord Rayleigh. So that’s a third branch of physics in which Kelvin was a towering figure in the nineteenth century.
I also was ignorant of Kelvin. I had assumed he’d had something to do with thermodynamics because of the temperature scale, and for figuring out that there even was an absolute zero, but that was about it. I even grew up within a mile of a huge Kelvinator manufacturing plant (they made refrigerators), but until I read a biography of Kelvin (see below) a few weeks ago, I never connected the name of the company with the scientist. Then I became interested (within the last few years) in vortex knot models of subatomic particles. Since Kelvin spent many of his later years working out the properties of the "vortex atom," it became impossible to avoid him.
So when one of my book clubs listed a new biography of Lord Kelvin called Degrees Kelvin (1) by David Lindley as a featured alternate, I jumped on it. This column is not a review of that book, but I will say a couple of things about it. The first is that it struck me as being a very good biography about a now fairly obscure but nevertheless very important scientist. Lindley came to write the book not because he was long fond of Lord Kelvin, but because while he was writing a book about Ludwig Boltzmann, he encountered the young Kelvin, William Thompson, a brilliant scientist, highly regarded by his contemporaries. Realizing that he’d missed out in not knowing the real Kelvin, he wrote the book to remedy that situation for others. My second comment is that "Degrees Kelvin" is an unfortunate choice for a title. You see, one measures temperature in Kelvins, not in degrees Kelvin. I expect the title will perpetuate that common mistake. That having been said, the book is a good read, well worth your time and money.
When he was just sixteen, before he had even started his studies at Cambridge University, William Thompson began publishing papers in the mathematical journals. His father was an able, though not remarkable, mathematician, so he helped William get that first paper published, even though his son supplied all the genius behind it. The paper involved the work of Fourier (of Fourier series fame) on heat flow. Young Thompson was enamored of Fourier’s work, and so when another paper came out by a mathematician named Kelland, which claimed that Fourier’s work was inconsistent and full of contradictions, sufficiently so to render his claims invalid, Thompson took up the challenge to refute Kelland.
And refute him he did! Fourier’s original paper was a bit sloppy, the author having assumed a bit too much about the likely perspicacity of his readers, omitting some explanations and making a number of goofs. The paper was also unfortunately riddled with printing errors. But young Thompson saw through these problems. As Lindley puts it: (Kelland) ". . . simply saw the problems and stopped dead. Where Kelland displayed a pedantic sense of logic, Thompson demonstrated real insight. He showed himself more acute than Kelland and more rigorous than Fourier." (Lindley, p. 19)
This makes Thompson a prodigy of the highest order.
Thompson continued to do exceptionally well at Cambridge, publishing a dozen papers in the Cambridge Mathematical Journal while an undergraduate. His third paper in that journal was particularly remarkable, for it was his first work of real physics. In it, Thompson was able to apply Fourier’s heat flow mathematics to Michael Faraday’s electric "lines of force." Lindley says: "Fourier’s treatment of temperature distributions became in William’s adaptation an equally general way of dealing with distributions of electric charge. The method (subsequently developed by Thompson and others) is still taught today." (Lindley, p. 35)
Not bad for a kid who would, were he around today, be too young to vote.
Kelvin’s early promise would not be squandered–he had an exceptional academic career, was highly respected by both his peers and the public, and became as famous in his day, at least in England, as Einstein became in ours. However, unlike Einstein, Kelvin was known for more than just scientific work. He had a practical, inventive side that few theoretical physicists ever share, and that few can adequately appreciate. Some of his contemporaries thought Kelvin wasted too much of his time on practical matters, like undersea telegraph cables, and a reliable maritime compass. But his talent for tinkering is one of the things that endears him to me.
Kelvin figured out the physics of sending telegraph signals thousands of miles through wires that are underwater. It isn’t so easy to do this if you don’t understand the fundamentals of electromagnetism. That is, if the wire is in air, you can send in your series of dots and dashes at one end, and you get the same thing out the other almost regardless of how long the wire is. But with many miles of your wire underwater, the signal that emerges at the far end will be both delayed and mostly noise. The difference is that sea water is a conductor rather than an insulator. It came as quite a shock to early proponents of undersea telegraphy when the first test cables behaved so differently from their in-air counterparts.
Faraday, when asked for an explanation, noted that the higher capacitance of the cable when in water was likely the cause, but he couldn’t do the math. In fact, in those days, inventors simply didn’t do the math anyway–they experimented to see what worked. Kelvin was asked, essentially, to explain Faraday’s explanation. Though he had to infer from a brief account what Faraday said, as Lindley describes: ". . . that was all he needed . . . In several pages of calculations, Thompson worked out, as no one had done before, the theory of transmission of a pulse of electricity down an insulated underwater cable."
Kelvin was one of the first to apply science to the problems of technology! And he enjoyed doing it so much that it probably cost him permanent fame, and led to his current obscurity. Though Kelvin did groundbreaking work in so many fields, even including the establishment of that most cherished of physical laws, conservation of energy, his distraction with technological matters kept him from "finishing up" his pure scientific work. His genius is evident in many fields of classical physics to those who look into the origins of things, but as Lindley put it: "(Kelvin) never quite finished things off in a way that would allow history to judge him the true creator of any of the subjects he tackled." (Lindley, p. 155) So while others were doing the work that would ultimately bring them lasting scientific fame, Kelvin might, for instance, be found at sea on a ship laying cable.
Another thing that led to Kelvin disappearing from the history of physics was his dislike for the way mathematical formalism was taking the place of genuine physical understanding. In Sir Edmund Whittaker’s landmark work History of the Theories of Aether and Electricity (2), he says: "In that power to which Gauss attached so much importance, of devising dynamical models and analogies for obscure physical phenomena, perhaps no one has ever excelled W. Thompson." At this point, Whittaker includes a footnote where he says: "The value of a dynamical model is, that it will have properties other than those which suggested its construction; the question then arises as to whether these properties are found in nature." Kelvin, though an exceptional mathematician in his own right, was always driven to "finding the right model." Getting the mathematics right was an important thing, but Kelvin always wanted to have a picture in his mind of what was "really happening." Otherwise the job wasn’t finished.
So while the Maxwellians (those electrodynamicists who came after Maxwell) were busy exploring the mathematical implications of Maxwell’s theory (including Oliver Heaviside who, via vector calculus, reduced the theory to the set of equations seen on T-shirts today), Kelvin busied himself with trying to work out the correct model of the aether demanded by the mathematics.
This pursuit eventually led Kelvin to develop the "vortex sponge" model of the aether. You can think of it as hollow vortices in a perfect fluid, a sort of "froth theory of the aether," as Rayleigh derisively called it. (Lindley p. 286) Nowadays it’s suspiciously reminiscent of the "spacetime foam" we read about so often. Of this model, Whittaker says: ". . . among the many mechanical schemes which were devised in the nineteenth century to represent electrical and optical phenomena, none possesses greater interest than that which pictures the aether as a vortex sponge." (Whittaker, p. 303)
Unfortunately for Kelvin, the vortex sponge model was analytically intractable without a computer, and Kelvin couldn’t get it to work. This is similar to the way Einstein finished out his life, working on a unified field theory he, too, couldn’t finish. Nevertheless, neither of these pursuits should be considered either failures or wastes of time. Much of value continues to come out of Einstein’s later work, and I’m confident that Kelvin’s vortex modeling will earn its proper respectable place in history, several decades hence. But explaining why I feel that way would take a whole bunch of future columns.
In the end, perhaps it can best be said that though Kelvin remained brilliant and inventive until the very end of his life, as the exemplar of nineteenth-century physics, his fame suffered all the more when his way of doing physics went out of style.
References
1) Lindley, David. Degrees Kelvin. Joseph Henry Press, 2004. ISBN 0-309-09073-3
2) Whittaker, Sir Edmund. History of the Theories of Aether and Electricity, Vol. 1. Thomas Nelson and Sons LTD., 1951.
