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add one grain of salt to any table and let bob evans walk amongthem。 at a glance he will spot it。 that grain of salt is the supernova。
evans鈥檚 is a talent so exceptional that oliver sacks； in an anthropologist on mars； devotesa passage to him in a chapter on autistic savants鈥攓uickly adding that 鈥渢here is no suggestionthat he is autistic。鈥潯vans； who has not met sacks； laughs at the suggestion that he might beeither autistic or a savant； but he is powerless to explain quite where his talent es from。
鈥渋 just seem to have a knack for memorizing star fields；鈥潯e told me； with a franklyapologetic look； when i visited him and his wife； elaine； in their picture…book bungalow on atranquil edge of the village of hazelbrook； out where sydney finally ends and the boundlessaustralian bush begins。 鈥渋鈥檓 not particularly good at other things；鈥潯e added。 鈥渋 don鈥檛remember names well。鈥�
鈥渙r where he鈥檚 put things；鈥潯alled elaine from the kitchen。
he nodded frankly again and grinned； then asked me if i鈥檇 like to see his telescope。 i hadimagined that evans would have a proper observatory in his backyard鈥攁 scaled…downversion of a mount wilson or palomar； with a sliding domed roof and a mechanized chair thatwould be a pleasure to maneuver。 in fact； he led me not outside but to a crowded storeroomoff the kitchen where he keeps his books and papers and where his telescope鈥攁 whitecylinder that is about the size and shape of a household hot…water tank鈥攔ests in a homemade；swiveling plywood mount。 when he wishes to observe； he carries them in two trips to a smalldeck off the kitchen。 between the overhang of the roof and the feathery tops of eucalyptustrees growing up from the slope below； he has only a letter…box view of the sky； but he says itis more than good enough for his purposes。 and there； when the skies are clear and the moonnot too bright； he finds his supernovae。
the term supernova was coined in the 1930s by a memorably odd astrophysicist namedfritz zwicky。 born in bulgaria and raised in switzerland； zwicky came to the californiainstitute of technology in the 1920s and there at once distinguished himself by his abrasivepersonality and erratic talents。 he didn鈥檛 seem to be outstandingly bright； and many of hiscolleagues considered him little more than 鈥渁n irritating buffoon。鈥潯 fitness buff； he wouldoften drop to the floor of the caltech dining hall or other public areas and do one…armedpushups to demonstrate his virility to anyone who seemed inclined to doubt it。 he wasnotoriously aggressive； his manner eventually being so intimidating that his closestcollaborator； a gentle man named walter baade； refused to be left alone with him。 amongother things； zwicky accused baade； who was german； of being a nazi； which he was not。 onat least one occasion zwicky threatened to kill baade； who worked up the hill at the mountwilson observatory； if he saw him on the caltech campus。
but zwicky was also capable of insights of the most startling brilliance。 in the early 1930s；he turned his attention to a question that had long troubled astronomers： the appearance in thesky of occasional unexplained points of light； new stars。 improbably he wondered if theneutron鈥攖he subatomic particle that had just been discovered in england by jameschadwick； and was thus both novel and rather fashionable鈥攎ight be at the heart of things。 itoccurred to him that if a star collapsed to the sort of densities found in the core of atoms； theresult would be an unimaginably pacted core。 atoms would literally be crushed together；their electrons forced into the nucleus； forming neutrons。 you would have a neutron star。
imagine a million really weighty cannonballs squeezed down to the size of a marble and鈥攚ell； you鈥檙e still not even close。 the core of a neutron star is so dense that a single spoonfulof matter from it would weigh 200 billion pounds。 a spoonful！ but there was more。 zwickyrealized that after the collapse of such a star there would be a huge amount of energy leftover鈥攅nough to make the biggest bang in the universe。 he called these resultant explosionssupernovae。 they would be鈥攖hey are鈥攖he biggest events in creation。
on january 15； 1934； the journal physical review published a very concise abstract of apresentation that had been conducted by zwicky and baade the previous month at stanforduniversity。 despite its extreme brevity鈥攐ne paragraph of twenty…four lines鈥攖he abstractcontained an enormous amount of new science： it provided the first reference to supernovaeand to neutron stars； convincingly explained their method of formation； correctly calculatedthe scale of their explosiveness； and； as a kind of concluding bonus； connected supernovaexplosions to the production of a mysterious new phenomenon called cosmic rays； which hadrecently been found swarming through the universe。 these ideas were revolutionary to say theleast。 neutron stars wouldn鈥檛 be confirmed for thirty…four years。 the cosmic rays notion； though considered plausible； hasn鈥檛 been verified yet。 altogether； the abstract was； in thewords of caltech astrophysicist kip s。 thorne； 鈥渙ne of the most prescient documents in thehistory of physics and astronomy。鈥�
interestingly； zwicky had almost no understanding of why any of this would happen。
according to thorne； 鈥渉e did not understand the laws of physics well enough to be able tosubstantiate his ideas。鈥潯wicky鈥檚 talent was for big ideas。 others鈥攂aade mostly鈥攚ere leftto do the mathematical sweeping up。
zwicky also was the first to recognize that there wasn鈥檛 nearly enough visible mass in theuniverse to hold galaxies together and that there must be some other gravitational influence鈥攚hat we now call dark matter。 one thing he failed to see was that if a neutron star shrankenough it would bee so dense that even light couldn鈥檛 escape its immense gravitationalpull。 you would have a black hole。 unfortunately； zwicky was held in such disdain by mostof his colleagues that his ideas attracted almost no notice。 when； five years later； the greatrobert oppenheimer turned his attention to neutron stars in a landmark paper； he made not asingle reference to any of zwicky鈥檚 work even though zwicky had been working for years onthe same problem in an office just down the hall。 zwicky鈥檚 deductions concerning dark matterwouldn鈥檛 attract serious attention for nearly four decades。 we can only assume that he did alot of pushups in this period。
surprisingly little of the universe is visible to us when we incline our heads to the sky。 onlyabout 6；000 stars are visible to the naked eye from earth； and only about 2；000 can be seenfrom any one spot。 with binoculars the number of stars you can see from a single locationrises to about 50；000； and with a small two…inch telescope it leaps to 300；000。 with a sixteen…inch telescope； such as evans uses； you begin to count not in stars but in galaxies。 from hisdeck； evans supposes he can see between 50；000 and 100；000 galaxies； each containing tensof billions of stars。 these are of course respectable numbers； but even with so much to take in；supernovae are extremely rare。 a star can burn for billions of years； but it dies just once andquickly； and only a few dying stars explode。 most expire quietly； like a campfire at dawn。 in atypical galaxy； consisting of a hundred billion stars； a supernova will occur on average onceevery two or three hundred years。 finding a supernova therefore was a little bit like standingon the observation platform of the empire state building with a telescope and searchingwindows around manhattan in the hope of finding； let us say； someone lighting a twenty…first…birthday cake。
so when a hopeful and softspoken minister got in touch to ask if they had any usable fieldcharts for hunting supernovae； the astronomical munity thought he was out of his mind。
at the time evans had a ten…inch telescope鈥攁 very respectable size for amateur stargazingbut hardly the sort of thing with which to do serious cosmology鈥攁nd he was proposing tofind one of the universe鈥檚 rarer phenomena。 in the whole of astronomical history before evansstarted looking in 1980； fewer than sixty supernovae had been found。 （at the time i visitedhim； in august of 2001； he had just recorded his thirty…fourth visual discovery； a thirty…fifthfollowed three months later and a thirty…sixth in early 2003。）evans； however； had certain advantages。 most observers； like most people generally； are inthe northern hemisphere； so he had a lot of sky largely to himself； especially at first。 he alsohad speed and his uncanny memory。 large telescopes are cumbersome things； and much oftheir operational time is consumed with being maneuvered into position。 evans could swing his little sixteen…inch telescope around like a tail gunner in a dogfight； spending no more thana couple of seconds on any particular point in the sky。 in consequence； he could observeperhaps four hundred galaxies in an evening while a large professional telescope would belucky to do fifty or sixty。
looking for supernovae is mostly a matter of not finding them。 from 1980 to 1996 heaveraged two discoveries a year鈥攏ot a huge payoff for hundreds of nights of peering andpeering。 once he found three in