Absolute Zero and the Conquest of Cold (13 page)

His next article was somewhat clearer. In it, he tried to "answer the question of what we are to understand by 'forces,' and of how such [forces] are related to each other." This provincial doctor, untrained in physics, proceeded to cast doubt on the foundations of the clockwork universe by contending that Newton had misperceived gravity. Gravity was not a force but a property of matter, Mayer said, and Newton had confused the two concepts. The qualities of a force were "indestructibility and transformability," and gravity had neither of these; nor could gravity cause motion, because movement also required spatial separation of objects. That spatial separation of bodies, which Mayer labeled "fallforce," was the real force. Motion, heat, and fallforce, Mayer wrote, were different configurations of the same "indestructible, transformable, imponderable" substance.
^*
He tried to come up with a numerical measurement of that substance by analyzing others' experiments, and deduced a figure: "the warming of a given weight of water from o° to i°C corresponds to the fall of an equal weight from the height of about 365 meters [1,200 feet]." This seemed to most readers like a comparison of apples and oranges.

This article was published, but it was ignored by serious students. Years later, Rudolf Clausius would confess to Mayer that he had not bothered to read it because its title did not include the word
heat
or
motion.
When Mayer produced another article in 1845, he had to pay for its printing himself. In it he equated heat with mechanical effect and contended that both were independent of whatever fluid or gas was being used, since the fluid or gas "serves only as a tool for effecting the transformation of the one force into the other." C. A. Truesdell, III, another modern historian of thermodynamics, has called this a major theoretical insight, the interconvertibility of heat and work. Carnot had crept up on it but had not stated it very well; Mayer did it better. Within a decade, this idea—expressed by others—would lead to advances in producing seriously cold temperatures. Truesdell adds that because Mayer was "virginally innocent" of the theories and experiments of mainstream scientists, he did not properly frame his interconvertibility insight in mathematical terms, which resulted in its remaining unknown and unheralded.

Steam engines, boilers, locomotives, and factories based on steam power were the elements of the workaday world of Manchester, England, and Glasgow, Scotland, in the first half of the nineteenth century, when these cities were at the center of the Industrial Revolution. The leading scientists born and raised in those cities in those years—James Prescott Joule, William and James Thomson, W. J. M. Rankine—thought in ways that combined the practicality of engineers with the mathematical adroitness of the best natural scientists, and they were better able than their solely Oxford- and Cambridge-trained contemporaries to elucidate the basic laws of heat, and to apply them to the study of cold.

The work of Joule would eventually lead directly to the elimination of caloric and to the "dynamical" theory of heat, which defined heat or cold as a state of motion measurable by its kinetic energy. But that accomplishment did not come easy or quickly. Joule was born on Christmas Eve in 1818, the second son of a wealthy Manchester industrialist. In poor health from age five to twelve, confined to bed, he became a prodigious reader. He emerged from his sickness with a permanent spinal weakness that gave him something of a hunchback and with a personality universally described as unassertive and shy.

Already in this chronicle we have encountered an unusual number of scientists who were sickly in their childhood and who contended throughout life with chronic illnesses. Studying mid-twentieth-century scientists, psychologist Bernice T. Eiduson found a disproportionate number who had been confined to their beds for large amounts of time by childhood illnesses. During these travails, they "searched for resources within themselves and became comfortable being by themselves"; most turned to reading, and through reading they developed a bent for intellectual work. Not very good at sports, unfit by illness to compete in childhood games, they remained emotionally fragile throughout life, deriving satisfaction mostly from intense involvement in science.

James Joule and his older brother, Benjamin, who became a noted musician, were tutored at home and then, under the auspices of the Manchester Literary and Philosophical Society, by one of England's most illustrious scientists, John Dalton. A Fellow of the Royal Society, Dalton had produced such milestones as the basic explanation for atomic weights, and verification that all gases have the same coefficient of expansion. "It was from his instruction," James Joule later wrote, "that I first formed a desire to increase my knowledge by original research." The teenaged Joule shot off a pistol, to measure the recoil, and burned away his eyebrows; he gave himself and his friends shocks from electric kites and Leiden jars; he sent electricity through an old cart-horse and also through a servant girl, recording her observations on the effects until she passed out.

In 1837 Dalton had a stroke and retired from teaching. Joule was nineteen and went to work as a manager in the family brewery between nine and six each day. He spent his other waking hours performing experiments and writing them up. His first articles were about electricity; in one, signed only with an initial, he correctly identified the compound nature of lightning, many years before photography was able to document it. An 1839 paper was rejected for publication by the Royal Society, though an abstract was published in a secondary journal. Many years afterward, Joule told a biographer he had not been surprised by the rejection of his early paper, because "I could imagine those gentlemen in London sitting round a table and saying to each other, 'What good can come out of a town where they dine in the middle of the day?'" A more recent biographer discounts this as Joule's idea of a joke, but it probably contains more than a grain of emotional truth.

Joule continued his experiments, moving from electricity to the study of the heat produced by an electromagnetic engine. He proved that Ohm's law governing the relationship between electric current and resistance held, "whatever the length, thickness, shape or kind of metallic conductor," and that the heating effect of a current is proportional to the resistance of the circuit and to the square of the amount of current. This work did command the attention of the Royal Society, which printed his article about it. But lacking a champion other than Dalton, himself somewhat of an outsider, Joule appears to have been judged as a throwback to the days of amateurs whose contributions only incrementally added to scientific knowledge.

Lyon Playfair, a chemistry professor in Manchester in the 1840s, remembered Joule then as "a man of singular simplicity and earnestness," who once proposed to Playfair that they take a trip together to Niagara Falls, not to enjoy the beauty of the natural wonder "but to ascertain the difference of temperature of the water at the top and bottom of the fall." They would meet over supper to discuss the progress of their research, and Joule also brought Playfair to the brewery, where he had a small laboratory; there, Playfair recalled with perfect hindsight, "I, of course, quickly recognized that my young friend, the brewer, was a great philosopher."

Joule was a philosopher undergoing a change of heart. In 1839 he had confidently predicted that electromagnetic machines would replace steam engines and had tried one out in his brewery expressly for that purpose. In 1841, though, he publicly admitted his inability to perfect an electromagnetic machine that could do better than a Cornish steam engine that raised 1.5 million pounds to a height of 1 foot by the combustion of 1 pound of coal. A third historian of thermodynamics, Crosbie Smith, suggests that Joule's attempt to understand the failure of the electric machine to match the economy of heat engines led him to his most important research, measuring the amount of work obtainable from various amounts of heat.

As frequently happens in science, the scientist's private circumstances changed just when Joule was altering his experimental focus. In 1842 Benjamin Joule married the family governess, disturbing the closeness of the brothers, and in 1843 Joule's father moved the family to a new home and built a laboratory there for his son James. That year, James Joule finished a paper entitled
On the Caloric Effects of Magneto-Electricity, and on the Mechanical Value of Heat,
in which he overturned nearly everything previous researchers thought true about heat. By experiment, he refuted the theory—related to caloric—that what an electric current did was transfer heat from one part of a circuit to another. Joule showed that the current (and only the current) generated the heat, and he argued that heat was not a substance but a "
state of vibration
" that could be "induced by an action of a simply mechanical character." This was actually a revolutionary idea that in another ten years would become the basis for the "dynamical" theory of heat that enabled a proper understanding of cold and how it could be produced.

In 1843 Joule readied this paper for a meeting of the British Association for the Advancement of Science, held in Cork, Ireland, but for various reasons, including his own lack of assertiveness, he was assigned to deliver it to the Chemical section, rather than to the section on Physics. Most listeners ignored it.

This third rejection of a demonstration of a basic principle of thermodynamics—and the articulation of a reasonable new theory of heat—was even less appropriate than the receptions given to Carnot and Mayer, since this seminal paper was written by a man whose work had been previously published by the Royal Society, was composed in proper scientific language that used good mathematics and cited relevant prior research, and was presented to a high-level audience ostensibly capable of appreciating its importance.

Disappointed, Joule kept on, taking heart from the fact that his earlier work on electricity had been confirmed by French and German scientists. He shortly developed an obsession: designing a beautifully structured series of experiments to prove once and for all that heat and mechanical work were equivalent and that the relationship between them was fixed and measurable.

If heat and work were equivalent, Joule reasoned, that would be true even if the heat was generated by something not usually thought of as a heat source. Using a perforated cylinder, he pushed water through its pin-sized holes and found that this slightly raised the temperature of the water; computing the foot-pounds involved in pushing the water through, he came up with a figure that was close to those he had deduced in other experiments.

Since heat was also generated by compressing a gas, Joule tried to measure the work associated with that, placing a copper vessel inside a calorimeter (a device used to measure quantities of heat) filled with water, introducing compressed gas into the vessel, and measuring the resulting rise in the water temperature. The results further validated his earlier experiments.

As had Boyle two centuries earlier, Joule realized there would be objections to his results from people who still believed in an outmoded theory, so he carefully designed further experiments to withstand their objections. Among the calorist critics Joule hoped to refute was Clapeyron. Joule was incensed by Clapeyron's contention, derived from Carnot, that in the transfer of heat from furnace to boiler in a steam engine, large amounts of heat were lost. "Believing that the power to destroy belongs to the Creator alone," Joule wrote, "I entirely coincide with ... the opinion that any theory which, when carried out, demands the annihilation of force, is necessarily erroneous." This was a religious objection to the idea—actually, the same objection that had troubled Carnot. But Joule knew that his experiments, even if they did not prove or disprove that "force" could be annihilated, did prove some things of equal importance: that heat and work were measurable, and that when air expanded without doing work, no heat was lost or transferred. The implication of the last result was clear: caloric had nothing to do with heat.

Fifty years later, the consummate experimenter James Dewar would deem Joule's success at proving his contentions about heat and cold through experiment "simply astonishing," given that such nimble minds as von Rumford's and Davy's had worked in the same area but had entirely missed the proper understanding. Joule's article put science on the verge of casting away the mechanistic worldview that depended on vague substances such as caloric and of substituting a more mature concept in which heat was the product of molecular motion. Shortly, such understandings would lead to the concept of energy, the transformations of which would explain the production of heat and cold, and also (though tangential to this story) the character and propagation of light, sound, electricity, and magnetic fields.

In 1844, though, when a distinguished older scientist sent Joule's article to the Royal Society for consideration by the
Philosophical Transactions,
it was turned down. At that moment in time, it appeared that the scientific establishments of the three leading experimentalist countries—France, Germany, and Great Britain—would continue to refuse to acknowledge the new understandings of heat, and the lack of heat known as cold, and thereby serve to keep the country of the cold unknown and unexplored.

T
HE MAN WHO WOULD DO THE MOST
to complete the conquest of cold by reaching an understanding of heat, William Thomson, was twenty-one years old in 1845, the author of a half-dozen interesting papers on physics, the possessor of a recent advanced degree in that field, and was working in Paris at the laboratory of one of France's most respected scientists, Victor Regnault. Thomson's brilliance, already widely acknowledged by his peers, was manifest in everything he did and touched: sitting in a Paris café, he wrote to his friend Gabriel Stokes that he noted in "a cup of thick chocolate au lait" an instance of elasticity in an incompressible liquid when he stirred the liquid with a spoon, then removed the spoon, producing "oscillations" and "eddies." He saw connections everywhere. Examining rival theories of electricity, Thomson tried to synthesize them, and in the attempt he showed there was no need to consider electricity as a weightless, "imponderable" fluid. But he continued to believe that heat depended on that other imponderable fluid, caloric, as did Regnault, who had devoted his life to the measurement of heat. However, while Regnault would never get beyond mere measurements and his attachments to old concepts such as caloric, the young Thomson would soon be able to leave both behind.