Nothing stops them
Terrific pop-science book recounts search for strange and elusive subatomic particles
IN the world of subatomic particles — where neutrinos reside — there is much strange behaviour, but perhaps that of neutrinos is the strangest. At least a million times smaller than electrons, neutrinos coming from our sun are right now passing through your body, about 100 trillion every second. They do no harm, for they do not bump into anything inside you. Even a block of lead a light-year thick can barely stop a neutrino. How could such an elusive particle be found, let alone even be conceived? For why would we need it? Covering similar ground as Neutrino by Frank Close (Oxford, 2010), but written in a style addressed to a wider audience, Neutrino Hunters, by physicist Ray Jayawardhana of the University of Toronto, tracks this tale in considerable detail right up to the present. Writing in a clear and breezy style, he weaves in biographical tidbits from scientists’ lives, but always comes back to the important topic — the ideas and work, the interplay between theory and experiment. Neutrino Hunters is a fine piece of popularscience literature. It all began in December 1930 when the brilliant, witty and abrasive Austrian physicist Wolfgang Pauli proposed a solution to a problem around a particular experiment involving radioactivity. The energy of the subatomic particles before the experiment did not equal the energy after the experiment. There was some missing energy. Pauli postulated that the missing energy was carried by a new little particle. This was a radical idea and was widely rejected, because at the time there were only three known subatomic particles: electrons, protons, and photons. tomp Electrons and protons were the material basis of matter (atoms) and photons were the stuff of light. Such wasw the nature of the entire universe in 1930: a nice trinity of particles. Addingin any more was heresy — the sort of thingt fitting Pauli’s snarky personality. One important physicist who nonethelesst took the idea seriously was EnricoE Fermi, who bestowed the name neutrino, from an Italian word meaning “little neutral thing.” Whereas electrons were charged negativity and protons positively, the neutrino was neutral with no electrical charge. A name alone was not enough to induce belief in the existence of the neutrino. Indeed, it was not until June 1956 that experimental evidence for neutrinos produced by nuclear processes was found by physicists Fred Reines and Clyde Cowan at the Savannah River nuclear reactor site in South Carolina. They quickly dispatched a telegram to Pauli announcing the news, much to his delight (actually, he got drunk). The next step was to find neutrinos created naturally. The closest case of a natural neutrino maker is our sun. A series of various neutrino detectors were built around the world, such as Kamiokande (Japan), IceCube (Antarctica) and SNOLAB (the Sudbury Neutrino Observatory Laboratory, north of Toronto, buried two kilometres deep underground in an old nickel mine, in order to filter out “noise”). These and other sites carry on in the detection and study of neutrinos coming from the sun, and elsewhere. There is another Canadian connection to this story: the astronomer Ian Shelton (from Winnipeg, too) discovered an exploding supernova on Feb. 23, 1987, using a U of T telescope in Chile. News spread quickly and neutrinos emitted from that explosion were detected in several places. This was the first case of finding neutrinos coming something other than our sun. Further work continues for various applications of neutrinos: (geology) probing deep into the earth; (cosmology), understanding what happened at the Big Bang; (astrophysics) explaining the growth and death of stars; and (particle physics) revealing why there is more matter than antimatter in the universe.
David Topper is senior scholar in history at the University of Winnipeg. His latest book, How Einstein Created Relativity, received a “highly recommended”
rating by the American Library Association.
Technicians check magnets that direct protons to the target for the CERN (European Organization for Nuclear Research) neutrinos project in Geneva.
Neutrino Hunters The Thrilling Chase for a Ghostly Particle to Unlock the Secrets
of the Universe By Ray Jayawardhana Harper Collins, 232 pages, $30