Really, Really Cold
By the time you read this, the odds are very good that a record will have been set for the lowest temperature ever recorded in the United States. No Alaska town will hold it, and it won't belong to any of our usual rivals, like International Falls or Alamosa or Jackson Hole. The new low will be recorded in Gainesville. That's Gainesville, Florida.
Well, that's not strictly true. The low temperature, if they do achieve it, actually will be a world record--and possibly the coldest temperature anywhere in the universe. The would-be record breakers aren't Gainesville's weathermen; they're scientists at the Microkelvin Research Laboratory at the University of Florida. And the new low won't be recorded at the Gainesville airport, but in a nuclear demagnetization refrigerator.
Had you going there for a minute, didn't I?
Though the Gainesville low won't produce any frostbitten fingers, or even increased parka sales, the temperatures expected are unimaginably colder than what Alaskans encounter in the worst of winters. Physicists measure them on the Kelvin scale (after the Victorian-era mathematician and physicist William Thomson, Lord Kelvin). The unit of measurement is the degree Celsius or centigrade; that is, on the Kelvin scale as on the centigrade scale, one hundred degrees separate the boiling and freezing points of water.
Unlike the centigrade scale, though, the Kelvin scale has no degrees below zero. It starts at the theoretical point wholly devoid of heat, of motion, perhaps of time itself: zero degrees Kelvin (0oK) is absolute zero. If it did exist and were measurable, thermometers would record minus 273.15oC or minus 459.67oF.
Expert opinion now holds that absolute zero can never be achieved---and even if it could be, quantum mechanics demands that it would be a realm of orderly motion rather than utter stillness. But laboratory efforts have come close.
By the early 20th century, physicists competing to liquefy all the gases had achieved temperatures well below 2 degrees Kelvin. That outdid nature. The chilliest places naturally occurring in the universe, the intergalactic empty zones, are at about 2.7K. By 1933, the low temperature record in earthly laboratories was 0.25K.
That last degree is being sliced steadily finer. Physicists now consider work in millikelvins---thousandths of a degree Kelvin---nearly routine. As its name implies, the Gainesville lab deals in microkelvins---millionths of that last degree. With new equipment just now beginning to function, the ultralow-temperature facility is expecting nanokelvins (billionths of a degree) and aiming for picokelvins, just trillionths of a degree above absolute zero.
Achieving such low temperatures is tricky and expensive work, but the physicists think the rewards are worth it. According to Mosaic, the National Science Foundation publication from which this information came, among them are "superconductors that carry electricity eternally without resistance; superfluids that flow eerily without friction; and macroscopic volumes of solids or liquids that behave in many ways like single molecules"---for example, systems in which electrons follow orbits exactly as they would in single atoms, but over centimeter-plus diameters. This will provide a new tool or studying the generation of magnetic fields, which are normally the product of electrons orbiting in nuclear shells.
Yet the scientists engaged in this work can't really predict where it will lead; they can only be sure it won't be dull. Nobel Prizes for work leading to high-temperature superconductors and the scanning tunneling microscope have been won by researchers at laboratories for low-temperature research.
Until the new Florida equipment bears out its promise, a northern site will hold the record for coldest temperature known. Working at the Helsinki University of Technology in Finland, Pertti Hakonen and Shi Yin reduced the temperature of nuclei of silver atoms to 0.8 nanokelvin---eight-tenths of a billionth of a degree above absolute zero.
