Absolute Zero and the Conquest of Cold by Tom Shachtman, Houghton Mifflin,
$25, ISBN 0395938880
IN A QUEST for the ultimate chill, Tom Shachtman leads us on a whistle-stop
tour of the conquest of cold. From the early attempts of Cornelis Drebbel to air
condition Westminster Abbey nearly 500 years ago to modern low-temperature
physics, Shachtman describes the discovery and search for the holy grail of
absolute zero, where strange things happen.
On the way he takes in the comfortable indulgences of modern air conditioning
and refrigerators, and shows how achieving these was a challenge in itself. The
first portable refrigerator was built by Thomas Moore in 1800鈥攊ts
insulation consisted of a lining of rabbit fur. Indeed, cold and its measurement
are as useful for physicists as finding longitude is for mariners. So is
Shachtman鈥檚 account of the search for the certainties of cold as riveting a
tale as, for example, Dava Sobel鈥檚 best-selling Longitude?
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Unlike Sobel, describing her lone hero John Harrison, Shachtman chooses to
deal with a whole array of stars in his book. There鈥檚 Sweden鈥檚 Anders Celsius,
who devised the thermometer scale that now bears his name, James Joule, who
discovered the mechanical equivalent of heat and showed along with others that a
rapidly expanding gas cools.
Shachtman begins his tale in 1620 with Drebbel鈥檚 struggle to keep a
congregation cool, and travels slowly down the centuries dealing with events
such as Robert Boyle鈥檚 observations 鈥渢ouching cold鈥� in 1665, the formulation of
the laws of thermodynamics, and Kelvin鈥檚 discovery of the absolute zero point of
temperature in 1848.
Perhaps it鈥檚 because Shachtman has so much ground to cover that he
occasionally misses out some of the fun of cold鈥檚 history. For example, chemist
Antoine Lavoisier and Count Rumford both had the idea that heat is a form of
energy. In Absolute Zero, they appear almost on the same page. What
Shachtman fails to tell us is that this is not all they had in
common鈥擱umford was married Lavoisier鈥檚 widow for a while.
It takes him three-quarters of the book to reach the modern world, and tell
us about one of the most significant steps in the exploration of low temperature
physics: the liquefaction of helium by Heike Kamerlingh Onnes in 1908.
Schachtman tackles superconductivity, an array of unusual electric and
magnetic phenomena that occurs at low temperatures in many materials.
In 1911, only three years after liquefying helium, Kamerlingh Onnes found
that mercury suddenly loses all its electrical resistance when cooled below 4.2
kelvin. He had discovered a new state. As the temperature nears absolute zero,
other strange things start to happen too. Super-cooled gases liquefy and begin
to flow uphill. Solids also defy gravity as they float in the air. He would need
more room, of course, to do full justice to this fascinating subject.
But he does introduce us briefly to Bose-Einstein condensates. There are two
sorts of particles in matter, fermions and bosons, with different
quantum-mechanical properties. Electrons are fermions, but drop the temperature
low enough, and they combine to form single entities known as Cooper pairs,
which are bosons. A new state of matter at ultra-low temperatures had been
predicted in 1925 by Albert Einstein and Satyenda Bose, but was not achieved
until much later: in due course the temperature was lowered to within 170
billionths of a degree above absolute zero.
Exactly what was going on was revealed by the Bardeen-Cooper-Schrieffer
theory, developed in 1957. It revolutionised our understanding of
superconductivity by offering the first fully quantum-mechanical explanation for
its existence. It had taken nearly half a century since the discovery of the
properties of supercooled helium to reach that point.
From superconductors, Shachtman naturally moves on to Josephson junctions,
which lie between superconductors kept apart by a thin insulating barrier. These
allow the passage, or tunnelling, of paired electrons, thus enabling the
measurement of tiny changes in electrical voltages and magnetic fields. And he
does deal, albeit briefly, with the isotopes of helium and the phenomenon known
as superfluidity.
Turning from the quantum world, Shachtman flips to the other extreme of size,
when he reminds us that fuels to boost space shots into orbit combine oxygen and
hydrogen stored in ultra-cold liquid form.
Entertaining details add life to the story. I did not know that on the way to
solving some of the superconductivity puzzle, physicist Leon Cooper, who shared
the 1972 physics Nobel, worked in an enclave labelled 鈥淭he Institute of Retarded
厂迟耻诲颈别蝉鈥�.
For deeper insights, and for physicists reading his book, Shachtman might
have done well to introduce the Fermi-Dirac system, which explains some of the
phenomena of superconductivity, but in different terms. It鈥檚 pretty, it鈥檚
important鈥攁nd it offers a good supplement to the Bose-Einstein system. He
also missed a vivid demonstration of the association of heat flow and material
flow at low temperatures: the fountain effect, which occurs when superfluid
liquid helium spurts out of the end of a capillary. It was first reported in
1938 by John Allen of St Andrews University and my former supervisor, the late
Harry Jones.
Shachtman already has three novels, six children鈥檚 books and nine non-fiction
books under his belt. His search for the story of the hunt for absolute zero has
taken him from New York and Washington libraries to London鈥檚 Royal Institution
and the British Library. Did he do it justice? Has he outdone Longitude
in telling his story? Not quite. But this is a readable and well-researched
history of an interesting field squeezed into a little space. He does not always
get all scientific details right, but it is fun.