Absolute Zero and the Conquest of Cold
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While this exciting development was invigorating research into subatomic particles, an astonishing advance was made in the field of superconductivity. Since the time of Onnes, scientists had been trying to find materials that became superconductive at temperatures higher than that of liquid helium, believing that only when superconductivity could be produced easily and economically could it be put to the tremendous practical uses Onnes and every subsequent thinker in the field had envisioned—free-flowing electric currents, more powerful magnets, a world with a near-infinite capacity to conserve and distribute its energy supply. Onnes had discovered superconductivity in mercury at 4.19 K; in the ensuing seventy years, the record for the "critical temperature" at which superconductivity commenced had been raised only 19 degrees, to 23.2 K for a compound of niobium, a rare metal. At IBM's Zurich laboratory, in the early 1980s Karl Alex Müller and his junior associate Johann Georg Bednorz began working with metallic oxides to see if they could be made superconductive; oxides—combinations of oxygen with other elements—were a bit of an odd choice, since some were used as insulators, and many had no electrical conductivity at all, although a few had been shown capable of becoming superconductors. Working more like chemists than physicists, Bednorz and Müller mixed compounds, baked the mixtures in ovens, and then chilled them to liquid-hydrogen temperatures. They did their work without lab assistants, and without much encouragement from their colleagues in the laboratory; Bednorz even had to steal time from his regular assignments to perform the oxide experiments. After two and a half years of trying various compounds, on January 27,1986, they succeeded in making an oxide of barium, lathanum, copper, and oxygen that became superconducting at 35 K. Being cautious, telling almost no one of their accomplishment, they prepared an article in April for publication in September 1986 in Zeitschrift fur Physik.
An explosion of research and excitement followed that publication, as laboratories in Japan, China, England, Switzerland, and the United States jumped into the chase for a compound that would become superconducting above 77 K, the temperature at which nitrogen liquefied. Since the liquefaction of nitrogen had become routine and inexpensive, if liquid nitrogen could be used to produce superconductivity, scientists reasoned, there ought to be no limit to employing superconductivity for the profit of whatever entity could patent the compound having the highest "critical temperature." A frantic six-month scramble among the laboratories led to the jam-packed "Woodstock of Physics" meeting in New York City on March 18,1987, at which the major groups reported their recent research—some accomplishments so new that the ink was not yet dry on articles about them. The winner of the chase for the compound that was the easiest to create, and that had the highest critical tempera ture, was Paul Chu's laboratory at the University of Houston, whose "1-2-3" compound became superconductive at an astounding 93 K.
A media frenzy followed, reaching and involving the uppermost levels of governments on several continents, as superconductivity achieved at liquid-nitrogen temperatures (above 77 K) was touted as the key to everything from Star Wars missile defense systems to superfast computers to energy storage and transmission devices that would drastically lower the price of electric power. In the delirium over what seemed the ultimate use of the extreme cold, an eighth-grade science teacher—the daughter of an IBM physicist—used the "Shake 'n Bake" method to cook a wafer of the new compound in a regular oven, then placed it in a dish of liquid nitrogen and magically floated above the dish a tiny magnet. Cornelis Drebbel would have been pleased.
Müller and Bednorz were awarded the 1987 Nobel Prize in physics, and there were high hopes that the 1990s would be the decade in which "high-temperature superconductivity" (HTS) would revolutionize the world. When these overblown expectations were disappointed by the difficulty of fashioning the new compounds into electrically conductive wires, and of constructing ways to maintain them at liquid-nitrogen temperatures, it seemed as though a balloon had burst. However, sure and steady progress in utilization was made in the decade after the 1987 Woodstock of Physics—an industry journal claimed that the "pace of utilization" of HTS was on a par with that achieved by other high-tech "overnight sensations" such as microprocessor chips. More than one hundred new HTS compounds have been created, with onset temperatures as high as 134 K, nearly twice as warm as liquid nitrogen.
Equally important, the practical use of superconducting wires has begun. In Geneva, the public utility now has a transformer wound with HTS-compound superconducting wires to step down the voltage from the country's power grid; since the new transformer runs without oil, the likelihood of the fires and pollution that often occur with regular transformers is drastically decreased. In Detroit, a contract has been awarded to the American Superconductor Corporation to produce a 400-foot-long superconducting line for that city's public utility by the year 2000; the line's 250 pounds of superconducting wire will carry as much current as 18,000 pounds of the existing copper wire. Among the costs saved are significant environmental ones, since the creation of 250 pounds of superconducting wire uses up considerably fewer natural resources than does the extraction, refining, and manufacture of 18,000 pounds of copper wire.
In North Carolina, the public utility offers superconducting magnetic-storage devices to commercial customers for use in countering unexpected power surges and dips. Other projects nationally include a superconducting generator coil, a 125-horsepower motor, many times smaller than usual motors, and improved SMES (superconducting magnetic energy storage) systems, in which the magnets are charged during off-peak hours when demand is low, enabling them to make more power available to the grid when demand rises. The U.S. Department of Energy estimates that if all public utilities switched to superconducting transmission and distribution lines, they would be 50 percent more efficient. Expected for the future is a shift from generating plants in and near cities to ones in remote locations, or ones that use less expensive solar or geothermal energy sources to produce electric power, which can then be cheaply and efficiently transmitted for use in population centers. An added bonus expected from these sources is that more efficient transmission of power will diminish pollution.
The new HTS superconductors show equal promise for electronic equipment: they are being used to filter signals from noise in cellular-phone base stations, improving cell-phone reception; they are reducing imaging time, improving resolution, and lowering the costs of MRIs. Perhaps the most unexpected use is in sewer and water-purification systems: iron compounds are salted into the liquids, where they bond with undesirable bacteria and viruses, form ing substances that superconducting magnets can then attract and remove. A similar "magnetic separation" process is being used in portable devices to clear contaminated soil sites, including sites that contain the radioactive compounds called actinides. Other high-tech applications are on the drawing board. Superconductivity applications seem likely to become the sixth major industry based on mastery of the cold.
In terms of numbers of people and industries served the technologies of cold are at an all-time high. Virtually all American homes have refrigerators, and most have air conditioners, as do all modern business buildings from factories to warehouses to corporate headquarters. In the Far East, the major source of energy for electric power is rapidly becoming LNG. Oxygen transported in liquefied form is in use in all hospitals. Other liquefied gases are critical to dozens of manufacturing processes; worldwide, annual sales of such gases total $10 billion, with the American-based company Praxair accounting for about half of that. Throughout the industrialized countries, most people daily use electronic devices made with, food preserved by, or chemicals manufactured by means of liquefied gases and the cold they produce. Increasingly, what separates the "have" from the "have-not" nations of the world is that the first group makes more use of the cold.
Still more uses are coming. In 1998 two milestones were reached in the use of superconducting magnets. In one, the first 18.4 kilometers (11.4 miles) of track for Japan's "maglev"—magnetic levitation�
��train was opened. The sets of magnets in the train, the tracks, and the ancillary equipment float the train millimeters above the guide track and serve to accelerate it along the track at speeds much faster than can be achieved by any system in which the train and track are in contact. In the second milestone, superconducting magnets were employed in brain surgery; in St. Louis, in December 1998, the magnets were used to direct a surgical instrument around corners and on a curved path through the brain, avoiding vital sections, to perform a tumor biopsy. The process was considerably less invasive than conventional methods and is expected to be used in the near future to treat motor disorders such as Parkinson's disease that are centered in the brain, as well as to treat cancer and heart disease in other areas of the body.
The new Kamerlingh Onnes Laboratory at Leiden opened in late 1998, and while it, too, works with HTS materials, its main mandate is to explore many frontiers of physics at temperatures capable of being generated by liquid helium. At one end of the research "factory," an automated production facility manufactures large quantities of liquid helium, which is then held in 5,000-liter containers and siphoned off into smaller ones. A screen saver on the computer in the production facility asks, as Onnes might have done, "How much helium have you wasted today?" Containers of the precious fluid are wheeled down corridors to the other end of the building, where a dozen cryostats and associated measuring equipment are located on concrete-and-steel platforms specially constructed to eliminate all vibrations.
Scientists working at the cutting edge of physics increasingly choose to investigate all sorts of physical phenomena by means of low temperatures, says the Leiden lab's current director, Jos de Jongh, because at micro- and millikelvin temperatures "you can eliminate all the extraneous influences," such as radiation and vibration, and be more certain that the only variable is the phenomenon under study. For instance, de Jongh, his graduate students, and visiting researchers from several countries recently completed studies of how large a metallic cluster must be before it stops behaving like a collection of atoms and starts behaving like a bulk object; the answer was in the range of 150 atoms. Other studies in the lab have used special cameras operating at ultra-low temperatures to observe the crystallization of helium-3 at millikelvin levels.
The use of ultra-low temperatures in basic research on the structure of matter entered a new phase in early June 1995, when a team of physicists at a research coalition of the National Institute of Standards and Technology and the University of Colorado, led by Carl E. Wieman and Eric A. Cornell, had an experience paralleling those of Faraday in 1823, Cailletet in 1877, and Onnes in 1911. While conducting an experiment at the lowest temperatures they could reach, they produced a blob of material never seen before. In this instance, the blob was what had eluded scientists for seventy years, a Bose-Einstein condensate (BEC)—that gas of atoms whose existence had been postulated by Einstein in the 1920s but that had not been definitively known to exist until 1995. The temperature was 170-billionths of a degree above absolute zero, and the blob was not even seen directly, since it was immediately destroyed by a laser probe flashing through it, but its image remained on a computer screen. Further experiment reduced the temperature to 2-billionths of a degree Kelvin, more than a million times colder than interstellar space.
This was a highly significant event—combining the production of a form of matter that no one before this had been certain could be generated on Earth with the reaching of the deepest and most profound cold, a cold almost beyond imagining.
Only weeks later, another BEC was created at Rice University, and within months, others were brought into existence at Stanford and at MIT. Physicists were elated over the possibilities of using BECs to study the mechanisms behind superconductivity and superfluidity—superfluid helium was believed to have some of the characteristics of a BEC—and to examine other aspects of atoms and elementary particles. "If you want to speculate wildly," Cornell told a reporter, "you could imagine an atomic beam analogous to a laser beam—one that could move or deposit single atoms to build a molecule-size structure."
That wild conjecture became reality in less than two years, in January 1997, when a team headed by Wolfgang Ketterle at MIT created an "atom laser" from a BEC. In 1998 Ketterle's group was able to magnetically manipulate a BEC-based atomic laser to do what Cornell had predicted: move atoms around, and form complex molecules. It was an indication that whatever could be postulated in terms of subatomic particles at ultracold temperatures might well be realized in the near future.
In February 1999 a team at Harvard headed by Lene Vestergaard Hau used the BEC and laser-cooling techniques to produce an environment only 50-billionths of a degree above absolute zero and to slow the speed of light to a mere 38 miles per hour. As with Ketterle's atomic laser, no immediate applications were expected from the Hau group's feat, but it was believed that in ten years' time, many practical uses might be developed. In mid-June of 1999, the MIT group announced another breakthrough. For the first time, the scientists had quantitatively measured zero-point motion in a BEC.
As the research on subatomic particles goes forth in the coldest temperatures imaginable, opening up possibilities for studying and manipulating the subatomic building blocks of matter, so do projects in other scientific fields that rely on mastery of the cold, among them some of the most advanced projects now being conducted. To study the farthest reaches of the universe from Earth, electronic detectors chilled by liquid helium have recently been set up near the South Pole, in an ambitious astronomical project, AST/RO, the Antarctic Submillimeter Telescope and Remote Observatory. And to study asteroids and other solid bodies in deep space, an unmanned probe has been launched, powered by a new propulsion system inspired by science fiction, an engine that moves the ship through space by means of squeezing the energy out of the ions of a rare gas, xenon—a gas obtained through air-separation processes, and maintained on board the spacecraft as an ultracold liquid.
If the present direction and volume of research are any guide, a large proportion of tomorrow's technological advances, and of tomorrow's discoveries about the composition of matter and the nature of the universe, will be made in the vicinity of absolute zero and will be based on our mastery and manipulation of the cold.
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Acknowledgments
Notes
Index
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Acknowledgments
I wish to thank the Alfred P. Sloan Foundation for a generous grant enabling me to complete this book. The Writers Room in New York City afforded me shelter through this project, as it has through others; my colleagues and the staff there have been a source of unflagging support and encouragement. Much of the research was conducted at the main branch of the New York Public Library at 42nd Street and in the recently opened Science, Industry and Business Library (SIBL) at 34th Street; the library also provided me with facilities in its Wertheim Room. Other American libraries consulted include those at Columbia and New York universities, the Library of Congress, the Scoville Library in Salisbury, Connecticut, and the Alfred H. Lane Library at The Writers Room.
In London, I worked extensively in the unrivaled historical collections of the British Library and of the Science and Technology Library connected to the Victoria and Albert Museum; in the Netherlands, my research centered on the collections of the Boerhaave Museum in Leiden and of the free library of Amsterdam. Visits to the Royal Institution in London, arranged by Dr. Frank James, and to the Kamerlingh Onnes Laboratory at Leiden, arranged by director Dr. Jos de Jongh and emeritus director Dr. Rudolf de Bruyn Ouboter, were especially helpful in gleaning details about the settings in which James Dewar and Heike Kamerlingh Onnes worked.
I owe debts of gratitude to Coleman Hough for basic research and insights, to editor Laura van Dam for her enthusiasm and her ability to ask the best questions, to Steve Fraser for getting me going on the book, and to my wife, Harriet Shelare, and sons, Noah and Daniel, for putting up with my obsession with an esoteric topic
. Rudolf de Bruyn Ouboter, Russell Donnelly, and other physicists read portions of the manuscript and made helpful suggestions. The errors that may remain are, of course, mine alone.
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Notes
The sections that follow report the major published and unpublished sources for the material in the book, with a few comments on them. The list is cumulative; that is, sources used in earlier chapters are also used in later ones, but I have omitted second references to them to make it easier to read. Though the listing does not constitute a complete bibliography, I hope it will provide ample fodder for readers who want to find out more about the people, events, history, and science of the cold.
Chapter 1
Any science-history research begins with the multivolume Dictionary of Scientific Biography, in whose pages the work of most (though not all) of the people discussed in this book are profiled. Gerrit Tierie's brief Cornelius Drebbel (1572–1633), 1932, collects all the comments made by Drebbel's contemporaries and quotes liberally from his works. Thomas Tymme's A Dialogue Philosophicall..., 1612, provides the best description of Drebbel's fabled perpetual-motion machine. Two thoughtful articles are L. E. Harris's "Cornelius Drebbel: A Neglected Genius of Seventeenth Century Technology," Newcomen Society, 1958; and Rosalie L. Colie's "Cornelius Drebbel and Salomon de Caus: Two Jacobean Models for Salomon's House," Huntington Library Quarterly, 1954–1955. Fascinating references for the period are Lynn Thorndike's monumental History of Magic and Experimental Science, 1923; William Eamon's study of books of secrets, Science and the Secrets of Nature, 1994; and Elizabeth David's Harvest of the Cold Months, 1994. The last traces the work of della Porta and other alchemists and engineers mentioned in the chapter. Material about James I is provided in Robert Ashton's compilation James I by His Contemporaries, 1969, and in biogra phies, the most useful being Antonia Fraser's King James VI of Scotland and I of England, 1974. Westminster Abbey is interestingly traced in Edward Carpenter's A House of Kings, 1966.