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looking into the past is of course the easy part。 glance at the night sky and what you see ishistory and lots of it—the stars not as they are now but as they were when their light leftthem。 for all we know； the north star； our faithful panion； might actually have burnedout last january or in 1854 or at any time since the early fourteenth century and news of it justhasn’t reached us yet。 the best we can say—can ever say—is that it was still burning on thisdate 680 years ago。 stars die all the time。 what bob evans does better than anyone else whohas ever tried is spot these moments of celestial farewell。
by day； evans is a kindly and now semiretired minister in the uniting church in australia；who does a bit of freelance work and researches the history of nineteenth…century religiousmovements。 but by night he is； in his unassuming way； a titan of the skies。 he huntssupernovae。
supernovae occur when a giant star； one much bigger than our own sun； collapses and thenspectacularly explodes； releasing in an instant the energy of a hundred billion suns； burningfor a time brighter than all the stars in its galaxy。 “it’s like a trillion hydrogen bombs going offat once；” says evans。 if a supernova explosion happened within five hundred light…years of us；we would be goners； according to evans—“it would wreck the show；” as he cheerfully puts it。
but the universe is vast； and supernovae are normally much too far away to harm us。 in fact；most are so unimaginably distant that their light reaches us as no more than the faintesttwinkle。 for the month or so that they are visible； all that distinguishes them from the otherstars in the sky is that they occupy a point of space that wasn’t filled before。 it is theseanomalous； very occasional pricks in the crowded dome of the night sky that the reverendevans finds。
to understand what a feat this is； imagine a standard dining room table covered in a blacktablecloth and someone throwing a handful of salt across it。 the scattered grains can bethought of as a galaxy。 now imagine fifteen hundred more tables like the first one—enough tofill a wal…mart parking lot； say； or to make a single line two miles long—each with a randomarray of salt across it。 now 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’s is a talent so exceptional that oliver sacks； in an anthropologist on mars； devotesa passage to him in a chapter on autistic savants—quickly adding that “there is no suggestionthat he is autistic。” evans； 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。
“i just seem to have a knack for memorizing star fields；” he 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。 “i’m not particularly good at other things；” he added。 “i don’tremember names well。”
“or where he’s put things；” called elaine from the kitchen。
he nodded frankly again and grinned； then asked me if i’d like to see his telescope。 i hadimagined that evans would have a proper observatory in his backyard—a 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—a whitecylinder that is about the size and shape of a household hot…water tank—rests 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’t seem to be outstandingly bright； and many of hiscolleagues considered him little more than “an irritating buffoon。” a 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—the subatomic particle that had just been discovered in england by jameschadwick； and was thus both novel and rather fashionable—might 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—well； you’re 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