Noth­ing stops them

Ter­rific pop-sci­ence book re­counts search for strange and elu­sive sub­atomic par­ti­cles

Winnipeg Free Press - Section G - - BOOKS - Re­viewed by David Top­per

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.

CERN / THE AS­SO­CI­ATED PRESS FILES

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

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