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hildebrand traveled to the site and decided fairly swiftly that they had their crater。 by early1991 it had been established to nearly everyone’s satisfaction that chicxulub was the impactsite。
still； many people didn’t quite grasp what an impact could do。 as stephen jay gouldrecalled in one of his essays： “i remember harboring some strong initial doubts about theefficacy of such an event 。 。 。 ＇w＇hy should an object only six miles across wreak such havocupon a planet with a diameter of eight thousand miles？”
conveniently a natural test of the theory arose when the shoemakers and levy discoveredet shoemaker…levy 9； which they soon realized was headed for jupiter。 for the first time；humans would be able to witness a cosmic collision—and witness it very well thanks to thenew hubble space telescope。 most astronomers； according to curtis peebles； expected little；particularly as the et was not a coherent sphere but a string of twenty…one fragments。 “mysense；” wrote one； “is that jupiter will swallow these ets up without so much as a burp。”
one week before the impact； nature ran an article； “the big fizzle is ing；” predictingthat the impact would constitute nothing more than a meteor shower。
the impacts began on july 16； 1994； went on for a week and were bigger by far thananyone—with the possible exception of gene shoemaker—expected。 one fragment； knownas nucleus g； struck with the force of about six million megatons—seventy…five times morethan all the nuclear weaponry in existence。 nucleus g was only about the size of a smallmountain； but it created wounds in the jovian surface the size of earth。 it was the final blowfor critics of the alvarez theory。
luis alvarez never knew of the discovery of the chicxulub crater or of the shoemaker…levy et； as he died in 1988。 shoemaker also died early。 on the third anniversary of theshoemaker…levy impact； he and his wife were in the australian outback； where they wentevery year to search for impact sites。 on a dirt track in the tanami desert—normally one ofthe emptiest places on earth—they came over a slight rise just as another vehicle wasapproaching。 shoemaker was killed instantly； his wife injured。 part of his ashes were sent tothe moon aboard the lunar prospector spacecraft。 the rest were scattered around meteorcrater。
anderson and witzke no longer had the crater that killed the dinosaurs； “but we still hadthe largest and most perfectly preserved impact crater in the mainland united states；”
anderson said。 （a little verbal dexterity is required to keep manson’s superlative status。 othercraters are larger—notably； chesapeake bay； which was recognized as an impact site in1994—but they are either offshore or deformed。） “chicxulub is buried under two to threekilometers of limestone and mostly offshore； which makes it difficult to study；” andersonwent on； “while manson is really quite accessible。 it’s because it is buried that it is actuallyparatively pristine。”
i asked them how much warning we would receive if a similar hunk of rock was ingtoward us today。
“oh； probably none；” said anderson breezily。 “it wouldn’t be visible to the naked eye untilit warmed up； and that wouldn’t happen until it hit the atmosphere； which would be about onesecond before it hit the earth。 you’re talking about something moving many tens of timesfaster than the fastest bullet。 unless it had been seen by someone with a telescope； and that’sby no means a certainty； it would take us pletely by surprise。”
how hard an impactor hits depends on a lot of variables—angle of entry； velocity andtrajectory； whether the collision is head…on or from the side； and the mass and density of theimpacting object； among much else—none of which we can know so many millions of yearsafter the fact。 but what scientists can do—and anderson and witzke have done—is measurethe impact site and calculate the amount of energy released。 from that they can work out plausible scenarios of what it must have been like—or； more chillingly； would be like if ithappened now。
an asteroid or et traveling at cosmic velocities would enter the earth’s atmosphere atsuch a speed that the air beneath it couldn’t get out of the way and would be pressed； as ina bicycle pump。 as anyone who has used such a pump knows； pressed air grows swiftlyhot； and the temperature below it would rise to some 60；000 kelvin； or ten times the surfacetemperature of the sun。 in this instant of its arrival in our atmosphere； everything in themeteor’s path—people； houses； factories； cars—would crinkle and vanish like cellophane in aflame。
one second after entering the atmosphere； the meteorite would slam into the earth’ssurface； where the people of manson had a moment before been going about their business。
the meteorite itself would vaporize instantly； but the blast would blow out a thousand cubickilometers of rock； earth； and superheated gases。 every living thing within 150 miles thathadn’t been killed by the heat of entry would now be killed by the blast。 radiating outward atalmost the speed of light would be the initial shock wave； sweeping everything before it。
for those outside the zone of immediate devastation； the first inkling of catastrophe wouldbe a flash of blinding light—the brightest ever seen by human eyes—followed an instant to aminute or two later by an apocalyptic sight of unimaginable grandeur： a roiling wall ofdarkness reaching high into the heavens； filling an entire field of view and traveling atthousands of miles an hour。 its approach would be eerily silent since it would be moving farbeyond the speed of sound。 anyone in a tall building in omaha or des moines； say； whochanced to look in the right direction would see a bewildering veil of turmoil followed byinstantaneous oblivion。
within minutes； over an area stretching from denver to detroit and enpassing what hadonce been chicago； st。 louis； kansas city； the twin cities—the whole of the midwest； inshort—nearly every standing thing would be flattened or on fire； and nearly every living thingwould be dead。 people up to a thousand miles away would be knocked off their feet and slicedor clobbered by a blizzard of flying projec