part  iii   a new age dawns

a physicist is the atoms’ way of thinking about atoms. -anonymous

8    EINSTEIN’S UNIVERSEAS

the nineteenth century drew to a close, scientists could reflect with satisfaction thatthey had pinned down most of the mysteries of the physical world: electricity, magnetism,gases, optics, acoustics, kinetics, and statistical mechanics, to name just a few, all had falleninto order before them. they had discovered the x ray, the cathode ray, the electron, andradioactivity, invented the ohm, the watt, the kelvin, the joule, the amp, and the little erg.

if a thing could be oscillated, accelerated, perturbed, distilled, combined, weighed, or madegaseous they had done it, and in the process produced a body of universal laws so weightyand majestic that we still tend to write them out in capitals: the electromagnetic field theoryof light, richter’s law of reciprocal proportions, charles’s law of gases, the law ofcombining volumes, the zeroth law, the valence concept, the laws of mass actions, andothers beyond counting. the whole world clanged and chuffed with the machinery andinstruments that their ingenuity had produced. many wise people believed that there wasnothing much left for science to do.

in 1875, when a young german in kiel named max planck was deciding whether to devotehis life to mathematics or to physics, he was urged most heartily not to choose physicsbecause the breakthroughs had all been made there. the coming century, he was assured,would be one of consolidation and refinement, not revolution. planck didn’t listen. he studiedtheoretical physics and threw himself body and soul into work on entropy, a process at theheart of thermodynamics, which seemed to hold much promise for an ambitious young man.

1in 1891 he produced his results and learned to his dismay that the important work on entropyhad in fact been done already, in this instance by a retiring scholar at yale university namedj. willard gibbs.

gibbs is perhaps the most brilliant person that most people have never heard of. modest tothe point of near invisibility, he passed virtually the whole of his life, apart from three yearsspent studying in europe, within a three-block area bounded by his house and the yalecampus in new haven, connecticut. for his first ten years at yale he didn’t even bother todraw a salary. (he had independent means.) from 1871, when he joined the university as aprofessor, to his death in 1903, his courses attracted an average of slightly over one student asemester. his written work was difficult to follow and employed a private form of notationthat many found incomprehensible. but buried among his arcane formulations were insightsof the loftiest brilliance.

in 1875–78, gibbs produced a series of papers, collectively titledon the equilibrium ofheterogeneous substances , that dazzlingly elucidated the thermodynamic principles of, well,1specifically it is a measure of randomness or disorder in a system. darrell ebbing, in the textbook generalchemistry, very usefully suggests thinking of a deck of cards. a new pack fresh out of the box, arranged by suitand in sequence from ace to king, can be said to be in its ordered state. shuffle the cards and you put them in adisordered state. entropy is a way of measuring just how disordered that state is and of determining thelikelihood of particular outcomes with further shuffles. of course, if you wish to have any observationspublished in a respectable journal you will need also to understand additional concepts such as thermalnonuniformities, lattice distances, and stoichiometric relationships, but thats the general idea.

nearly everything—“gases, mixtures, surfaces, solids, phase changes . . . chemical reactions,electrochemical cells, sedimentation, and osmosis,” to quote william h. cropper. in essencewhat gibbs did was show that thermodynamics didn’t apply simply to heat and energy at thesort of large and noisy scale of the steam engine, but was also present and influential at theatomic level of chemical reactions. gibbs’s equilibrium has been called “the principia ofthermodynamics,” but for reasons that defy speculation gibbs chose to publish theselandmark observations in the transactions of the connecticut academy of arts and sciences,a journal that managed to be obscure even in connecticut, which is why planck did not hearof him until too late.

undaunted—well, perhaps mildly daunted—planck turned to other matters.

2we shall turnto these ourselves in a moment, but first we must make a slight (but relevant!) detour tocleveland, ohio, and an institution then known as the case school of applied science. there,in the 1880s, a physicist of early middle years named albert michelson, assisted by his friendthe chemist edward morley, embarked on a series of experiments that produced curious anddisturbing results that would have great ramifications for much of what followed.

what michelson and morley did, without actually intending to, was undermine alongstanding belief in something called the luminiferous ether, a stable, invisible, weightless,frictionless, and unfortunately wholly imaginary medium that was thought to permeate theuniverse. conceived by descartes, embraced by newton, and venerated by nearly everyoneever since, the ether held a position of absolute centrality in nineteenth-century physics as away of explaining how light traveled across the emptiness of space. it was especially neededin the 1800s because light and electromagnetism were now seen as waves, which is to saytypes of vibrations. vibrations must occur in something; hence the need for, and lastingdevotion to, an ether. as late as 1909, the great british physicist j. j. thomson was insisting:

“the ether is not a fantastic creation of the speculative philosopher; it is as essential to us asthe air we breathe”—this more than four years after it was pretty incontestably establishedthat it didn’t exist. people, in short, were really attached to the ether.

if you needed to illustrate the idea of nineteenth-century america as a land of opportunity,you could hardly improve on the life of albert michelson. born in 1852 on the german–polish border to a family of poor jewish merchants, he came to the united states with hisfamily as an infant and grew up in a mining camp in california’s gold rush country, where hisfather ran a dry goods business. too poor to pay for college, he traveled to washington, d.c.,and took to loitering by the front door of the white house so that he could fall in besidepresident ulysses s. grant when the president emerged for his daily constitutional. (it wasclearly a more innocent age.) in the course of these walks, michelson so ingratiated himself tothe president that grant agreed to secure for him a free place at the u.s. naval academy. itwas there that michelson learned his physics.

ten years later, by now a professor at the case school in cleveland, michelson becameinterested in trying to measure something called the ether drift—a kind of head windproduced by moving objects as they plowed through space. one of the predictions ofnewtonian physics was that the speed of light as it pushed through the ether should vary with2planck was often unlucky in life. his beloved first wife died early, in 1909, and the younger of his two sonswas killed in the first world war. he also had twin daughters whom he adored. one died giving birth. thesurviving twin went to look after the baby and fell in love with her sisters husband. they married and two yearslater she died in childbirth. in 1944, when planck was eighty-five, an allied bomb fell on his house and he losteverything-papers, diaries, a lifetime of accumulations. the following year his surviving son was caught in aconspiracy to assassinate hitler and executed.

respect to an observer depending on whether the observer was moving toward the source oflight or away from it, but no one had figured out a way to measure this. it occurred tomichelson that for half the year the earth is traveling toward the sun and for half the year it ismoving away from it, and he reasoned that if you took careful enough measurements atopposite seasons and compared light’s travel time between the two, you would have youranswer.

michelson talked alexander graham bell, newly enriched inventor of the telephone, intoproviding the funds to build an ingenious and sensitive instrument of michelson’s owndevising called an interferometer, which could measure the velocity of light with greatprecision. then, assisted by the genial but shadowy morley, michelson embarked on years offastidious measurements. the work was delicate and exhausting, and had to be suspended fora time to permit michelson a brief but comprehensive nervous breakdown, but by 1887 theyhad their results. they were not at all what the two scientists had expected to find.

as caltech astrophysicist kip s. thorne has written: “the speed of light turned out to bethe same inall directions and at all seasons.” it was the first hint in two hundred years—inexactly two hundred years, in fact—that newton’s laws might not apply all the timeeverywhere. the michelson-morley outcome became, in the words of william h. cropper,“probably the most famous negative result in the history of physics.” michelson was awardeda nobel prize in physics for the work—the first american so honored—but not for twentyyears. meanwhile, the michelson-morley experiments would hover unpleasantly, like a mustysmell, in the background of scientific thought.

remarkably, and despite his findings, when the twentieth century dawned michelsoncounted himself among those who believed that the work of science was nearly at an end,with “only a few turrets and pinnacles to be added, a few roof bosses to be carved,” in thewords of a writer in nature.

in fact, of course, the world was about to enter a century of science where many peoplewouldn’t understand anything and none would understand everything. scientists would soonfind themselves adrift in a bewildering realm of particles and antiparticles, where things popin and out of existence in spans of time that make nanoseconds look plodding and uneventful,where everything is strange. science was moving from a world of macrophysics, whereobjects could be seen and held and measured, to one of microphysics, where events transpirewith unimaginable swiftness on scales far below the limits of imagining. we were about toenter the quantum age, and the first person to push on the door was the so-far unfortunatemax planck.

in 1900, now a theoretical physicist at the university of berlin and at the somewhatadvanced age of forty-two, planck unveiled a new “quantum theory,” which posited thatenergy is not a continuous thing like flowing water but comes in individualized packets,which he called quanta. this was a novel concept, and a good one. in the short term it wouldhelp to provide a solution to the puzzle of the michelson-morley experiments in that itdemonstrated that light needn’t be a wave after all. in the longer term it would lay thefoundation for the whole of modern physics. it was, at all events, the first clue that the worldwas about to change.

but the landmark event—the dawn of a new age—came in 1905, when there appeared inthe german physics journal annalen der physik a series of papers by a young swissbureaucrat who had no university affiliation, no access to a laboratory, and the regular use of
no library greater than that of the national patent office in bern, where he was employed as atechnical examiner third class. (an application to be promoted to technical examiner secondclass had recently been rejected.)his name was albert einstein, and in that one eventful year he submitted to annalen derphysik five papers, of which three, according to c. p. snow, “were among the greatest in thehistory of physics”—one examining the photoelectric effect by means of planck’s newquantum theory, one on the behavior of small particles in suspension (what is known asbrownian motion), and one outlining a special theory of relativity.

the first won its author a nobel prize and explained the nature of light (and also helped tomake television possible, among other things).

3the second provided proof that atoms doindeed exist—a fact that had, surprisingly, been in some dispute. the third merely changedthe world.

einstein was born in ulm, in southern germany, in 1879, but grew up in munich. little inhis early life suggested the greatness to come. famously he didn’t learn to speak until he wasthree. in the 1890s, his father’s electrical business failing, the family moved to milan, butalbert, by now a teenager, went to switzerland to continue his education—though he failedhis college entrance exams on the first try. in 1896 he gave up his german citizenship toavoid military conscription and entered the zurich polytechnic institute on a four-year coursedesigned to churn out high school science teachers. he was a bright but not outstandingstudent.

in 1900 he graduated and within a few months was beginning to contribute papers toannalen der physik. his very first paper, on the physics of fluids in drinking straws (of allthings), appeared in the same issue as planck’s quantum theory. from 1902 to 1904 heproduced a series of papers on statistical mechanics only to discover that the quietlyproductive j. willard gibbs in connecticut had done that work as well, in his elementaryprinciples of statistical mechanics of 1901.

at the same time he had fallen in love with a fellow student, a hungarian named milevamaric. in 1901 they had a child out of wedlock, a daughter, who was discreetly put up foradoption. einstein never saw his child. two years later, he and maric were married. inbetween these events, in 1902, einstein took a job with the swiss patent office, where hestayed for the next seven years. he enjoyed the work: it was challenging enough to engage hismind, but not so challenging as to distract him from his physics. this was the backgroundagainst which he produced the special theory of relativity in 1905.

called “on the electrodynamics of moving bodies,” it is one of the most extraordinaryscientific papers ever published, as much for how it was presented as for what it said. it hadno footnotes or citations, contained almost no mathematics, made no mention of any workthat had influenced or preceded it, and acknowledged the help of just one individual, a3einstein was honored, somewhat vaguely, “for services to theoretical physics.” he had to wait sixteen years, till1921, to receive the award-quite a long time, all things considered, but nothing at all compared with frederickreines, who detected the neutrino in 1957 but wasnt honored with a nobel until 1995, thirty-eight years later, orthe german ernst ruska, who invented the electron microscope in 1932 and received his nobel prize in 1986,more than half a century after the fact. since nobel prizes are never awarded posthumously, longevity can be asimportant a factor as ingenuity for prizewinners.

colleague at the patent office named michele besso. it was, wrote c. p. snow, as if einstein“had reached the conclusions by pure thought, unaided, without listening to the opinions ofothers. to a surprisingly large extent, that is precisely what he had done.”

his famous equation, e =mc2, did not appear with the paper, but came in a brief supplementthat followed a few months later. as you will recall from school days, e in the equation standsfor energy, m for mass, and c2for the speed of light squared.

in simplest terms, what the equation says is that mass and energy have an equivalence.

they are two forms of the same thing: energy is liberated matter; matter is energy waiting tohappen. since c2(the speed of light times itself) is a truly enormous number, what theequation is saying is that there is a huge amount—a really huge amount—of energy bound upin every material thing.

4you may not feel outstandingly robust, but if you are an average-sized adult you willcontain within your modest frame no less than 7 x 1018joules of potential energy—enough toexplode with the force of thirty very large hydrogen bombs, assuming you knew how toliberate it and really wished to make a point. everything has this kind of energy trappedwithin it. we’re just not very good at getting it out. even a uranium bomb—the mostenergetic thing we have produced yet—releases less than 1 percent of the energy it couldrelease if only we were more cunning.

among much else, einstein’s theory explained how radiation worked: how a lump ofuranium could throw out constant streams of high-level energy without melting away like anice cube. (it could do it by converting mass to energy extremely efficiently à lae =mc2.) itexplained how stars could burn for billions of years without racing through their fuel. (ditto.)at a stroke, in a simple formula, einstein endowed geologists and astronomers with theluxury of billions of years. above all, the special theory showed that the speed of light wasconstant and supreme. nothing could overtake it. it brought light (no pun intended, exactly) tothe very heart of our understanding of the nature of the universe. not incidentally, it alsosolved the problem of the luminiferous ether by making it clear that it didn’t exist. einsteingave us a universe that didn’t need it.

physicists as a rule are not overattentive to the pronouncements of swiss patent officeclerks, and so, despite the abundance of useful tidings, einstein’s papers attracted little notice.

having just solved several of the deepest mysteries of the universe, einstein applied for a jobas a university lecturer and was rejected, and then as a high school teacher and was rejectedthere as well. so he went back to his job as an examiner third class, but of course he keptthinking. he hadn’t even come close to finishing yet.

when the poet paul valéry once asked einstein if he kept a notebook to record his ideas,einstein looked at him with mild but genuine surprise. “oh, that’s not necessary,” he replied.

“it’s so seldom i have one.” i need hardly point out that when he did get one it tended to begood. einstein’s next idea was one of the greatest that anyone has ever had—indeed, the verygreatest, according to boorse, motz, and weaver in their thoughtful history of atomic science.

4how c came to be the symbol for the speed of light is something of a mystery, but david bodanis suggests itprobably came from the latin celeritas, meaning swiftness. the relevant volume of the oxford englishdictionary, compiled a decade before einsteins theory, recognizes c as a symbol for many things, from carbonto cricket, but makes no mention of it as a symbol for light or swiftness.

“as the creation of a single mind,” they write, “it is undoubtedly the highest intellectualachievement of humanity,” which is of course as good as a compliment can get.

in 1907, or so it has sometimes been written, albert einstein saw a workman fall off a roofand began to think about gravity. alas, like many good stories this one appears to beapocryphal. according to einstein himself, he was simply sitting in a chair when the problemof gravity occurred to him.

actually, what occurred to einstein was something more like the beginning of a solution tothe problem of gravity, since it had been evident to him from the outset that one thing missingfrom the special theory was gravity. what was “special” about the special theory was that itdealt with things moving in an essentially unimpeded state. but what happened when a thingin motion—light, above all—encountered an obstacle such as gravity? it was a question thatwould occupy his thoughts for most of the next decade and lead to the publication in early1917 of a paper entitled “cosmological considerations on the general theory of relativity.”

the special theory of relativity of 1905 was a profound and important piece of work, ofcourse, but as c. p. snow once observed, if einstein hadn’t thought of it when he did someoneelse would have, probably within five years; it was an idea waiting to happen. but the generaltheory was something else altogether. “without it,” wrote snow in 1979, “it is likely that weshould still be waiting for the theory today.”

with his pipe, genially self-effacing manner, and electrified hair, einstein was too splendida figure to remain permanently obscure, and in 1919, the war over, the world suddenlydiscovered him. almost at once his theories of relativity developed a reputation for beingimpossible for an ordinary person to grasp. matters were not helped, as david bodanis pointsout in his superb book e=mc2, when the new york times decided to do a story, and—forreasons that can never fail to excite wonder—sent the paper’s golfing correspondent, onehenry crouch, to conduct the interview.

crouch was hopelessly out of his depth, and got nearly everything wrong. among the morelasting errors in his report was the assertion that einstein had found a publisher daring enoughto publish a book that only twelve men “in all the world could comprehend.” there was nosuch book, no such publisher, no such circle of learned men, but the notion stuck anyway.

soon the number of people who could grasp relativity had been reduced even further in thepopular imagination—and the scientific establishment, it must be said, did little to disturb themyth.

when a journalist asked the british astronomer sir arthur eddington if it was true that hewas one of only three people in the world who could understand einstein’s relativity theories,eddington considered deeply for a moment and replied: “i am trying to think who the thirdperson is.” in fact, the problem with relativity wasn’t that it involved a lot of differentialequations, lorentz transformations, and other complicated mathematics (though it did—eveneinstein needed help with some of it), but that it was just so thoroughly nonintuitive.

in essence what relativity says is that space and time are not absolute, but relative to boththe observer and to the thing being observed, and the faster one moves the more pronouncedthese effects become. we can never accelerate ourselves to the speed of light, and the harderwe try (and faster we go) the more distorted we will become, relative to an outside observer.

almost at once popularizers of science tried to come up with ways to make these conceptsaccessible to a general audience. one of the more successful attempts—commercially at
least—was the abc of relativity by the mathematician and philosopher bertrand russell. init, russell employed an image that has been used many times since. he asked the reader toenvision a train one hundred yards long moving at 60 percent of the speed of light. tosomeone standing on a platform watching it pass, the train would appear to be only eightyyards long and everything on it would be similarly compressed. if we could hear thepassengers on the train speak, their voices would sound slurred and sluggish, like a recordplayed at too slow a speed, and their movements would appear similarly ponderous. even theclocks on the train would seem to be running at only four-fifths of their normal speed.

however—and here’s the thing—people on the train would have no sense of thesedistortions. to them, everything on the train would seem quite normal. it would be we on theplatform who looked weirdly compressed and slowed down. it is all to do, you see, with yourposition relative to the moving object.

this effect actually happens every time you move. fly across the united states, and youwill step from the plane a quinzillionth of a second, or something, younger than those you leftbehind. even in walking across the room you will very slightly alter your own experience oftime and space. it has been calculated that a baseball thrown at a hundred miles an hour willpick up 0.000000000002 grams of mass on its way to home plate. so the effects of relativityare real and have been measured. the problem is that such changes are much too small tomake the tiniest detectable difference to us. but for other things in the universe—light,gravity, the universe itself—these are matters of consequence.

so if the ideas of relativity seem weird, it is only because we don’t experience these sorts ofinteractions in normal life. however, to turn to bodanis again, we all commonly encounterother kinds of relativity—for instance with regard to sound. if you are in a park and someoneis playing annoying music, you know that if you move to a more distant spot the music willseem quieter. that’s not because the musicis quieter, of course, but simply that your positionrelative to it has changed. to something too small or sluggish to duplicate this experience—asnail, say—the idea that a boom box could seem to two observers to produce two differentvolumes of music simultaneously might seem incredible.

the most challenging and nonintuitive of all the concepts in the general theory of relativityis the idea that time is part of space. our instinct is to regard time as eternal, absolute,immutable—nothing can disturb its steady tick. in fact, according to einstein, time is variableand ever changing. it even has shape. it is bound up—“inextricably interconnected,” instephen hawking’s expression—with the three dimensions of space in a curious dimensionknown as spacetime.

spacetime is usually explained by asking you to imagine something flat but pliant—amattress, say, or a sheet of stretched rubber—on which is resting a heavy round object, suchas an iron ball. the weight of the iron ball causes the material on which it is sitting to stretchand sag slightly. this is roughly analogous to the effect that a massive object such as the sun(the iron ball) has on spacetime (the material): it stretches and curves and warps it. now ifyou roll a smaller ball across the sheet, it tries to go in a straight line as required by newton’slaws of motion, but as it nears the massive object and the slope of the sagging fabric, it rollsdownward, ineluctably drawn to the more massive object. this is gravity—a product of thebending of spacetime.

every object that has mass creates a little depression in the fabric of the cosmos. thus theuniverse, as dennis overbye has put it, is “the ultimate sagging mattress.” gravity on this
view is no longer so much a thing as an outcome—“not a ‘force’ but a byproduct of thewarping of spacetime,” in the words of the physicist michio kaku, who goes on: “in somesense, gravity does not exist; what moves the planets and stars is the distortion of space andtime.”

of course the sagging mattress analogy can take us only so far because it doesn’tincorporate the effect of time. but then our brains can take us only so far because it is sonearly impossible to envision a dimension comprising three parts space to one part time, allinterwoven like the threads in a plaid fabric. at all events, i think we can agree that this wasan awfully big thought for a young man staring out the window of a patent office in thecapital of switzerland.

among much else, einstein’s general theory of relativity suggested that the universe mustbe either expanding or contracting. but einstein was not a cosmologist, and he accepted theprevailing wisdom that the universe was fixed and eternal. more or less reflexively, hedropped into his equations something called the cosmological constant, which arbitrarilycounterbalanced the effects of gravity, serving as a kind of mathematical pause button. bookson the history of science always forgive einstein this lapse, but it was actually a fairlyappalling piece of science and he knew it. he called it “the biggest blunder of my life.”

coincidentally, at about the time that einstein was affixing a cosmological constant to histheory, at the lowell observatory in arizona, an astronomer with the cheerily intergalacticname of vesto slipher (who was in fact from indiana) was taking spectrographic readings ofdistant stars and discovering that they appeared to be moving away from us. the universewasn’t static. the stars slipher looked at showed unmistakable signs of a doppler shift5—thesame mechanism behind that distinctive stretched-out yee-yummm sound cars make as theyflash past on a racetrack. the phenomenon also applies to light, and in the case of recedinggalaxies it is known as a red shift (because light moving away from us shifts toward the redend of the spectrum; approaching light shifts to blue).

slipher was the first to notice this effect with light and to realize its potential importancefor understanding the motions of the cosmos. unfortunately no one much noticed him. thelowell observatory, as you will recall, was a bit of an oddity thanks to percival lowell’sobsession with martian canals, which in the 1910s made it, in every sense, an outpost ofastronomical endeavor. slipher was unaware of einstein’s theory of relativity, and the worldwas equally unaware of slipher. so his finding had no impact.

glory instead would pass to a large mass of ego named edwin hubble. hubble was born in1889, ten years after einstein, in a small missouri town on the edge of the ozarks and grewup there and in wheaton, illinois, a suburb of chicago. his father was a successful insuranceexecutive, so life was always comfortable, and edwin enjoyed a wealth of physicalendowments, too. he was a strong and gifted athlete, charming, smart, and immensely good-looking—“handsome almost to a fault,” in the description of william h. cropper, “an5named for johann christian doppler, an austrian physicist, who first noticed the effect in 1842. briefly, whathappens is that as a moving object approaches a stationary one its sound waves become bunched up as they cramup against whatever device is receiving them (your ears, say), just as you would expect of anything that is beingpushed from behind toward an immobile object. this bunching is perceived by the listener as a kind of pinchedand elevated sound (the yee). as the sound source passes, the sound waves spread out and lengthen, causing thepitch to drop abruptly (the yummm).

adonis” in the words of another admirer. according to his own accounts, he also managed tofit into his life more or less constant acts of valor—rescuing drowning swimmers, leadingfrightened men to safety across the battlefields of france, embarrassing world-championboxers with knockdown punches in exhibition bouts. it all seemed too good to be true. it was.

for all his gifts, hubble was also an inveterate liar.

this was more than a little odd, for hubble’s life was filled from an early age with a levelof distinction that was at times almost ludicrously golden. at a single high school track meetin 1906, he won the pole vault, shot put, discus, hammer throw, standing high jump, andrunning high jump, and was on the winning mile-relay team—that is seven first places in onemeet—and came in third in the broad jump. in the same year, he set a state record for the highjump in illinois.

as a scholar he was equally proficient, and had no trouble gaining admission to studyphysics and astronomy at the university of chicago (where, coincidentally, the head of thedepartment was now albert michelson). there he was selected to be one of the first rhodesscholars at oxford. three years of english life evidently turned his head, for he returned towheaton in 1913 wearing an inverness cape, smoking a pipe, and talking with a peculiarlyorotund accent—not quite british but not quite not—that would remain with him for life.

though he later claimed to have passed most of the second decade of the century practicinglaw in kentucky, in fact he worked as a high school teacher and basketball coach in newalbany, indiana, before belatedly attaining his doctorate and passing briefly through thearmy. (he arrived in france one month before the armistice and almost certainly never hearda shot fired in anger.)in 1919, now aged thirty, he moved to california and took up a position at the mountwilson observatory near los angeles. swiftly, and more than a little unexpectedly, hebecame the most outstanding astronomer of the twentieth century.

it is worth pausing for a moment to consider just how little was known of the cosmos at thistime. astronomers today believe there are perhaps 140 billion galaxies in the visible universe.

that’s a huge number, much bigger than merely saying it would lead you to suppose. ifgalaxies were frozen peas, it would be enough to fill a large auditorium—the old bostongarden, say, or the royal albert hall. (an astrophysicist named bruce gregory has actuallycomputed this.) in 1919, when hubble first put his head to the eyepiece, the number of thesegalaxies that were known to us was exactly one: the milky way. everything else was thoughtto be either part of the milky way itself or one of many distant, peripheral puffs of gas.

hubble quickly demonstrated how wrong that belief was.

over the next decade, hubble tackled two of the most fundamental questions of theuniverse: how old is it, and how big? to answer both it is necessary to know two things—howfar away certain galaxies are and how fast they are flying away from us (what is known astheir recessional velocity). the red shift gives the speed at which galaxies are retiring, butdoesn’t tell us how far away they are to begin with. for that you need what are known as“standard candles”—stars whose brightness can be reliably calculated and used asbenchmarks to measure the brightness (and hence relative distance) of other stars.

hubble’s luck was to come along soon after an ingenious woman named henrietta swanleavitt had figured out a way to do so. leavitt worked at the harvard college observatory asa computer, as they were known. computers spent their lives studying photographic plates ofstars and making computations—hence the name. it was little more than drudgery by another
name, but it was as close as women could get to real astronomy at harvard—or indeed prettymuch anywhere—in those days. the system, however unfair, did have certain unexpectedbenefits: it meant that half the finest minds available were directed to work that wouldotherwise have attracted little reflective attention, and it ensured that women ended up with anappreciation of the fine structure of the cosmos that often eluded their male counterparts.

one harvard computer, annie jump cannon, used her repetitive acquaintance with thestars to devise a system of stellar classifications so practical that it is still in use today.

leavitt’s contribution was even more profound. she noticed that a type of star known as acepheid variable (after the constellation cepheus, where it first was identified) pulsated witha regular rhythm—a kind of stellar heartbeat. cepheids are quite rare, but at least one of themis well known to most of us. polaris, the pole star, is a cepheid.

we now know that cepheids throb as they do because they are elderly stars that havemoved past their “main sequence phase,” in the parlance of astronomers, and become redgiants. the chemistry of red giants is a little weighty for our purposes here (it requires anappreciation for the properties of singly ionized helium atoms, among quite a lot else), but putsimply it means that they burn their remaining fuel in a way that produces a very rhythmic,very reliable brightening and dimming. leavitt’s genius was to realize that by comparing therelative magnitudes of cepheids at different points in the sky you could work out where theywere in relation to each other. they could be used as “standard candles”—a term she coinedand still in universal use. the method provided only relative distances, not absolute distances,but even so it was the first time that anyone had come up with a usable way to measure thelarge-scale universe.

(just to put these insights into perspective, it is perhaps worth noting that at the time leavittand cannon were inferring fundamental properties of the cosmos from dim smudges onphotographic plates, the harvard astronomer william h. pickering, who could of course peerinto a first-class telescope as often as he wanted, was developing his seminal theory that darkpatches on the moon were caused by swarms of seasonally migrating insects.)combining leavitt’s cosmic yardstick with vesto slipher’s handy red shifts, edwin hubblenow began to measure selected points in space with a fresh eye. in 1923 he showed that a puffof distant gossamer in the andromeda constellation known as m31 wasn’t a gas cloud at allbut a blaze of stars, a galaxy in its own right, a hundred thousand light-years across and atleast nine hundred thousand light-years away. the universe was vaster—vastly vaster—thananyone had ever supposed. in 1924 he produced a landmark paper, “cepheids in spiralnebulae” (nebulae,from the latin for “clouds,” was his word for galaxies), showing that theuniverse consisted not just of the milky way but of lots of independent galaxies—“islanduniverses”—many of them bigger than the milky way and much more distant.

this finding alone would have ensured hubble’s reputation, but he now turned to thequestion of working out just how much vaster the universe was, and made an even morestriking discovery. hubble began to measure the spectra of distant galaxies—the business thatslipher had begun in arizona. using mount wilson’s new hundred-inch hooker telescopeand some clever inferences, he worked out that all the galaxies in the sky (except for our ownlocal cluster) are moving away from us. moreover, their speed and distance were neatlyproportional: the further away the galaxy, the faster it was moving.

this was truly startling. the universe was expanding, swiftly and evenly in all directions. itdidn’t take a huge amount of imagination to read backwards from this and realize that it must
therefore have started from some central point. far from being the stable, fixed, eternal voidthat everyone had always assumed, this was a universe that had a beginning. it mighttherefore also have an end.

the wonder, as stephen hawking has noted, is that no one had hit on the idea of theexpanding universe before. a static universe, as should have been obvious to newton andevery thinking astronomer since, would collapse in upon itself. there was also the problemthat if stars had been burning indefinitely in a static universe they’d have made the wholeintolerably hot—certainly much too hot for the likes of us. an expanding universe resolvedmuch of this at a stroke.

hubble was a much better observer than a thinker and didn’t immediately appreciate thefull implications of what he had found. partly this was because he was woefully ignorant ofeinstein’s general theory of relativity. this was quite remarkable because, for one thing,einstein and his theory were world famous by now. moreover, in 1929 albert michelson—now in his twilight years but still one of the world’s most alert and esteemed scientists—accepted a position at mount wilson to measure the velocity of light with his trustyinterferometer, and must surely have at least mentioned to him the applicability of einstein’stheory to his own findings.

at all events, hubble failed to make theoretical hay when the chance was there. instead, itwas left to a belgian priest-scholar (with a ph.d. from mit) named georges lema?tre tobring together the two strands in his own “fireworks theory,” which suggested that theuniverse began as a geometrical point, a “primeval atom,” which burst into glory and hadbeen moving apart ever since. it was an idea that very neatly anticipated the modernconception of the big bang but was so far ahead of its time that lema?tre seldom gets morethan the sentence or two that we have given him here. the world would need additionaldecades, and the inadvertent discovery of cosmic background radiation by penzias and wilsonat their hissing antenna in new jersey, before the big bang would begin to move frominteresting idea to established theory.

neither hubble nor einstein would be much of a part of that big story. though no onewould have guessed it at the time, both men had done about as much as they were ever goingto do.

in 1936 hubble produced a popular book called the realm of the nebulae, whichexplained in flattering style his own considerable achievements. here at last he showed thathe had acquainted himself with einstein’s theory—up to a point anyway: he gave it four pagesout of about two hundred.

hubble died of a heart attack in 1953. one last small oddity awaited him. for reasonscloaked in mystery, his wife declined to have a funeral and never revealed what she did withhis body. half a century later the whereabouts of the century’s greatest astronomer remainunknown. for a memorial you must look to the sky and the hubble space telescope,launched in 1990 and named in his honor.

9    THE MIGHTY ATOM

while einstein and hubble were productively unraveling the large-scale structure ofthe cosmos, others were struggling to understand something closer to hand but in its way justas remote: the tiny and ever- mysterious atom.

the great caltech physicist richard feynman once observed that if you had to reducescientific history to one important statement it would be “all things are made of atoms.” theyare everywhere and they constitute every thing. look around you. it is all atoms. not just thesolid things like walls and tables and sofas, but the air in between. and they are there innumbers that you really cannot conceive.

the basic working arrangement of atoms is the molecule (from the latin for “little mass”).

a molecule is simply two or more atoms working together in a more or less stablearrangement: add two atoms of hydrogen to one of oxygen and you have a molecule of water.

chemists tend to think in terms of molecules rather than elements in much the way thatwriters tend to think in terms of words and not letters, so it is molecules they count, and theseare numerous to say the least. at sea level, at a temperature of 32 degrees fahrenheit, onecubic centimeter of air (that is, a space about the size of a sugar cube) will contain 45 billionbillion molecules. and they are in every single cubic centimeter you see around you. thinkhow many cubic centimeters there are in the world outside your window—how many sugarcubes it would take to fill that view. then think how many it would take to build a universe.

atoms, in short, are very abundant.

they are also fantastically durable. because they are so long lived, atoms really get around.

every atom you possess has almost certainly passed through several stars and been part ofmillions of organisms on its way to becoming you. we are each so atomically numerous andso vigorously recycled at death that a significant number of our atoms—up to a billion foreach of us, it has been suggested—probably once belonged to shakespeare. a billion moreeach came from buddha and genghis khan and beethoven, and any other historical figureyou care to name. (the personages have to be historical, apparently, as it takes the atomssome decades to become thoroughly redistributed; however much you may wish it, you arenot yet one with elvis presley.)so we are all reincarnations—though short-lived ones. when we die our atoms willdisassemble and move off to find new uses elsewhere—as part of a leaf or other human beingor drop of dew. atoms, however, go on practically forever. nobody actually knows how longan atom can survive, but according to martin rees it is probably about 1035years—a numberso big that even i am happy to express it in notation.

above all, atoms are tiny—very tiny indeed. half a million of them lined up shoulder toshoulder could hide behind a human hair. on such a scale an individual atom is essentiallyimpossible to imagine, but we can of course try.

start with a millimeter, which is a line this long: -. now imagine that line divided into athousand equal widths. each of those widths is a micron. this is the scale of microorganisms.

a typical paramecium, for instance, is about two microns wide, 0.002 millimeters, which isreally very small. if you wanted to see with your naked eye a paramecium swimming in adrop of water, you would have to enlarge the drop until it was some forty feet across.

however, if you wanted to see the atoms in the same drop, you would have to make the dropfifteen miles across.

atoms, in other words, exist on a scale of minuteness of another order altogether. to getdown to the scale of atoms, you would need to take each one of those micron slices and shaveit into ten thousand finer widths. that’s the scale of an atom: one ten-millionth of amillimeter. it is a degree of slenderness way beyond the capacity of our imaginations, but youcan get some idea of the proportions if you bear in mind that one atom is to the width of amillimeter line as the thickness of a sheet of paper is to the height of the empire statebuilding.

it is of course the abundance and extreme durability of atoms that makes them so useful,and the tininess that makes them so hard to detect and understand. the realization that atomsare these three things—small, numerous, practically indestructible—and that all things aremade from them first occurred not to antoine-laurent lavoisier, as you might expect, or evento henry cavendish or humphry davy, but rather to a spare and lightly educated englishquaker named john dalton, whom we first encountered in the chapter on chemistry.

dalton was born in 1766 on the edge of the lake district near cockermouth to a family ofpoor but devout quaker weavers. (four years later the poet william wordsworth would alsojoin the world at cockermouth.) he was an exceptionally bright student—so very brightindeed that at the improbably youthful age of twelve he was put in charge of the local quakerschool. this perhaps says as much about the school as about dalton’s precocity, but perhapsnot: we know from his diaries that at about this time he was reading newton’s principia in theoriginal latin and other works of a similarly challenging nature. at fifteen, stillschoolmastering, he took a job in the nearby town of kendal, and a decade after that hemoved to manchester, scarcely stirring from there for the remaining fifty years of his life. inmanchester he became something of an intellectual whirlwind, producing books and paperson subjects ranging from meteorology to grammar. color blindness, a condition from whichhe suffered, was for a long time called daltonism because of his studies. but it was a plumpbook called a new system of chemical philosophy, published in 1808, that established hisreputation.

there, in a short chapter of just five pages (out of the book’s more than nine hundred),people of learning first encountered atoms in something approaching their modernconception. dalton’s simple insight was that at the root of all matter are exceedingly tiny,irreducible particles. “we might as well attempt to introduce a new planet into the solarsystem or annihilate one already in existence, as to create or destroy a particle of hydrogen,”he wrote.

neither the idea of atoms nor the term itself was exactly new. both had been developed bythe ancient greeks. dalton’s contribution was to consider the relative sizes and characters ofthese atoms and how they fit together. he knew, for instance, that hydrogen was the lightestelement, so he gave it an atomic weight of one. he believed also that water consisted of sevenparts of oxygen to one of hydrogen, and so he gave oxygen an atomic weight of seven. bysuch means was he able to arrive at the relative weights of the known elements. he wasn’talways terribly accurate—oxygen’s atomic weight is actually sixteen, not seven—but theprinciple was sound and formed the basis for all of modern chemistry and much of the rest ofmodern science.

the work made dalton famous—albeit in a low-key, english quaker sort of way. in 1826,the french chemist p .j. pelletier traveled to manchester to meet the atomic hero. pelletierexpected to find him attached to some grand institution, so he was astounded to discover himteaching elementary arithmetic to boys in a small school on a back street. according to the
scientific historian e. j. holmyard, a confused pelletier, upon beholding the great man,stammered:

“est-ce que j’ai l’honneur de m’addresser à monsieur dalton?” for he couldhardly believe his eyes that this was the chemist of european fame, teaching a boyhis first four rules. “yes,” said the matter-of-fact quaker. “wilt thou sit downwhilst i put this lad right about his arithmetic?”

although dalton tried to avoid all honors, he was elected to the royal society against hiswishes, showered with medals, and given a handsome government pension. when he died in1844, forty thousand people viewed the coffin, and the funeral cortege stretched for twomiles. his entry in the dictionary of national biography is one of the longest, rivaled inlength only by those of darwin and lyell among nineteenth-century men of science.

for a century after dalton made his proposal, it remained entirely hypothetical, and a feweminent scientists—notably the viennese physicist ernst mach, for whom is named the speedof sound—doubted the existence of atoms at all. “atoms cannot be perceived by the senses . .

. they are things of thought,” he wrote. the existence of atoms was so doubtfully held in thegerman-speaking world in particular that it was said to have played a part in the suicide of thegreat theoretical physicist, and atomic enthusiast, ludwig boltzmann in 1906.

it was einstein who provided the first incontrovertible evidence of atoms’ existence withhis paper on brownian motion in 1905, but this attracted little attention and in any caseeinstein was soon to become consumed with his work on general relativity. so the first realhero of the atomic age, if not the first personage on the scene, was ernest rutherford.

rutherford was born in 1871 in the “back blocks” of new zealand to parents who hademigrated from scotland to raise a little flax and a lot of children (to paraphrase stevenweinberg). growing up in a remote part of a remote country, he was about as far from themainstream of science as it was possible to be, but in 1895 he won a scholarship that took himto the cavendish laboratory at cambridge university, which was about to become the hottestplace in the world to do physics.

physicists are notoriously scornful of scientists from other fields. when the wife of thegreat austrian physicist wolfgang pauli left him for a chemist, he was staggered withdisbelief. “had she taken a bullfighter i would have understood,” he remarked in wonder to afriend. “but a chemist . . .”

it was a feeling rutherford would have understood. “all science is either physics or stampcollecting,” he once said, in a line that has been used many times since. there is a certainengaging irony therefore that when he won the nobel prize in 1908, it was in chemistry, notphysics.

rutherford was a lucky man—lucky to be a genius, but even luckier to live at a time whenphysics and chemistry were so exciting and so compatible (his own sentimentsnotwithstanding). never again would they quite so comfortably overlap.

for all his success, rutherford was not an especially brilliant man and was actually prettyterrible at mathematics. often during lectures he would get so lost in his own equations thathe would give up halfway through and tell the students to work it out for themselves.

according to his longtime colleague james chadwick, discoverer of the neutron, he wasn’teven particularly clever at experimentation. he was simply tenacious and open-minded. forbrilliance he substituted shrewdness and a kind of daring. his mind, in the words of onebiographer, was “always operating out towards the frontiers, as far as he could see, and thatwas a great deal further than most other men.” confronted with an intractable problem, hewas prepared to work at it harder and longer than most people and to be more receptive tounorthodox explanations. his greatest breakthrough came because he was prepared to spendimmensely tedious hours sitting at a screen counting alpha particle scintillations, as they wereknown—the sort of work that would normally have been farmed out. he was one of the firstto see—possibly the very first—that the power inherent in the atom could, if harnessed, makebombs powerful enough to “make this old world vanish in smoke.”

physically he was big and booming, with a voice that made the timid shrink. once whentold that rutherford was about to make a radio broadcast across the atlantic, a colleague drilyasked: “why use radio?” he also had a huge amount of good-natured confidence. whensomeone remarked to him that he seemed always to be at the crest of a wave, he responded,“well, after all, i made the wave, didn’t i?” c. p. snow recalled how once in a cambridgetailor’s he overheard rutherford remark: “every day i grow in girth. and in mentality.”

but both girth and fame were far ahead of him in 1895 when he fetched up at thecavendish.

1it was a singularly eventful period in science. in the year of his arrival incambridge, wilhelm roentgen discovered x rays at the university of würzburg in germany,and the next year henri becquerel discovered radioactivity. and the cavendish itself wasabout to embark on a long period of greatness. in 1897, j. j. thomson and colleagues woulddiscover the electron there, in 1911 c. t. r. wilson would produce the first particle detectorthere (as we shall see), and in 1932 james chadwick would discover the neutron there.

further still in the future, james watson and francis crick would discover the structure ofdna at the cavendish in 1953.

in the beginning rutherford worked on radio waves, and with some distinction—hemanaged to transmit a crisp signal more than a mile, a very reasonable achievement for thetime—but gave it up when he was persuaded by a senior colleague that radio had little future.

on the whole, however, rutherford didn’t thrive at the cavendish. after three years there,feeling he was going nowhere, he took a post at mcgill university in montreal, and there hebegan his long and steady rise to greatness. by the time he received his nobel prize (for“investigations into the disintegration of the elements, and the chemistry of radioactivesubstances,” according to the official citation) he had moved on to manchester university,and it was there, in fact, that he would do his most important work in determining thestructure and nature of the atom.

1the name comes from the same cavendishes who producec henry. this one was william cavendish, seventhduke of devonshire, who was a gifted mathematician and steel baron in victoriar england. in 1870, he gave theuniversity ￡6,300 to build an experimental lab.

by the early twentieth century it was known that atoms were made of parts—thomson’sdiscovery of the electron had established that—but it wasn’t known how many parts therewere or how they fit together or what shape they took. some physicists thought that atomsmight be cube shaped, because cubes can be packed together so neatly without any wastedspace. the more general view, however, was that an atom was more like a currant bun or aplum pudding: a dense, solid object that carried a positive charge but that was studded withnegatively charged electrons, like the currants in a currant bun.

in 1910, rutherford (assisted by his student hans geiger, who would later invent theradiation detector that bears his name) fired ionized helium atoms, or alpha particles, at asheet of gold foil.

2to rutherford’s astonishment, some of the particles bounced back. it wasas if, he said, he had fired a fifteen-inch shell at a sheet of paper and it rebounded into his lap.

this was just not supposed to happen. after considerable reflection he realized there could beonly one possible explanation: the particles that bounced back were striking something smalland dense at the heart of the atom, while the other particles sailed through unimpeded. anatom, rutherford realized, was mostly empty space, with a very dense nucleus at the center.

this was a most gratifying discovery, but it presented one immediate problem. by all the lawsof conventional physics, atoms shouldn’t therefore exist.

let us pause for a moment and consider the structure of the atom as we know it now. everyatom is made from three kinds of elementary particles: protons, which have a positiveelectrical charge; electrons, which have a negative electrical charge; and neutrons, which haveno charge. protons and neutrons are packed into the nucleus, while electrons spin aroundoutside. the number of protons is what gives an atom its chemical identity. an atom with oneproton is an atom of hydrogen, one with two protons is helium, with three protons is lithium,and so on up the scale. each time you add a proton you get a new element. (because thenumber of protons in an atom is always balanced by an equal number of electrons, you willsometimes see it written that it is the number of electrons that defines an element; it comes tothe same thing. the way it was explained to me is that protons give an atom its identity,electrons its personality.)neutrons don’t influence an atom’s identity, but they do add to its mass. the number ofneutrons is generally about the same as the number of protons, but they can vary up and downslightly. add a neutron or two and you get an isotope. the terms you hear in reference todating techniques in archeology refer to isotopes—carbon-14, for instance, which is an atomof carbon with six protons and eight neutrons (the fourteen being the sum of the two).

neutrons and protons occupy the atom’s nucleus. the nucleus of an atom is tiny—only onemillionth of a billionth of the full volume of the atom—but fantastically dense, since itcontains virtually all the atom’s mass. as cropper has put it, if an atom were expanded to thesize of a cathedral, the nucleus would be only about the size of a fly—but a fly manythousands of times heavier than the cathedral. it was this spaciousness—this resounding,unexpected roominess—that had rutherford scratching his head in 1910.

it is still a fairly astounding notion to consider that atoms are mostly empty space, and thatthe solidity we experience all around us is an illusion. when two objects come together in the2geiger would also later become a loyal nazi, unhesitatingly betraying jewish colleagues, including many whohad helped him.

real world—billiard balls are most often used for illustration—they don’t actually strike eachother. “rather,” as timothy ferris explains, “the negatively charged fields of the two ballsrepel each other . . . were it not for their electrical charges they could, like galaxies, pass rightthrough each other unscathed.” when you sit in a chair, you are not actually sitting there, butlevitating above it at a height of one angstrom (a hundred millionth of a centimeter), yourelectrons and its electrons implacably opposed to any closer intimacy.

the picture that nearly everybody has in mind of an atom is of an electron or two flyingaround a nucleus, like planets orbiting a sun. this image was created in 1904, based on littlemore than clever guesswork, by a japanese physicist named hantaro nagaoka. it iscompletely wrong, but durable just the same. as isaac asimov liked to note, it inspiredgenerations of science fiction writers to create stories of worlds within worlds, in which atomsbecome tiny inhabited solar systems or our solar system turns out to be merely a mote in somemuch larger scheme. even now cern, the european organization for nuclear research, usesnagaoka’s image as a logo on its website. in fact, as physicists were soon to realize, electronsare not like orbiting planets at all, but more like the blades of a spinning fan, managing to fillevery bit of space in their orbits simultaneously (but with the crucial difference that the bladesof a fan only seem to be everywhere at once; electrons are ).

needless to say, very little of this was understood in 1910 or for many years afterward.

rutherford’s finding presented some large and immediate problems, not least that no electronshould be able to orbit a nucleus without crashing. conventional electrodynamic theorydemanded that a flying electron should very quickly run out of energy—in only an instant orso—and spiral into the nucleus, with disastrous consequences for both. there was also theproblem of how protons with their positive charges could bundle together inside the nucleuswithout blowing themselves and the rest of the atom apart. clearly whatever was going ondown there in the world of the very small was not governed by the laws that applied in themacro world where our expectations reside.

as physicists began to delve into this subatomic realm, they realized that it wasn’t merelydifferent from anything we knew, but different from anything ever imagined. “becauseatomic behavior is so unlike ordinary experience,” richard feynman once observed, “it isvery difficult to get used to and it appears peculiar and mysterious to everyone, both to thenovice and to the experienced physicist.” when feynman made that comment, physicists hadhad half a century to adjust to the strangeness of atomic behavior. so think how it must havefelt to rutherford and his colleagues in the early 1910s when it was all brand new.

one of the people working with rutherford was a mild and affable young dane namedniels bohr. in 1913, while puzzling over the structure of the atom, bohr had an idea soexciting that he postponed his honeymoon to write what became a landmark paper. becausephysicists couldn’t see anything so small as an atom, they had to try to work out its structurefrom how it behaved when they did things to it, as rutherford had done by firing alphaparticles at foil. sometimes, not surprisingly, the results of these experiments were puzzling.

one puzzle that had been around for a long time had to do with spectrum readings of thewavelengths of hydrogen. these produced patterns showing that hydrogen atoms emittedenergy at certain wavelengths but not others. it was rather as if someone under surveillancekept turning up at particular locations but was never observed traveling between them. no onecould understand why this should be.

it was while puzzling over this problem that bohr was struck by a solution and dashed offhis famous paper. called “on the constitutions of atoms and molecules,” the paper explainedhow electrons could keep from falling into the nucleus by suggesting that they could occupyonly certain well-defined orbits. according to the new theory, an electron moving betweenorbits would disappear from one and reappear instantaneously in another without visiting thespace between. this idea—the famous “quantum leap”—is of course utterly strange, but itwas too good not to be true. it not only kept electrons from spiraling catastrophically into thenucleus; it also explained hydrogen’s bewildering wavelengths. the electrons only appearedin certain orbits because they only existed in certain orbits. it was a dazzling insight, and itwon bohr the 1922 nobel prize in physics, the year after einstein received his.

meanwhile the tireless rutherford, now back at cambridge as j. j. thomson’s successor ashead of the cavendish laboratory, came up with a model that explained why the nuclei didn’tblow up. he saw that they must be offset by some type of neutralizing particles, which hecalled neutrons. the idea was simple and appealing, but not easy to prove. rutherford’sassociate, james chadwick, devoted eleven intensive years to hunting for neutrons beforefinally succeeding in 1932. he, too, was awarded with a nobel prize in physics, in 1935. asboorse and his colleagues point out in their history of the subject, the delay in discovery wasprobably a very good thing as mastery of the neutron was essential to the development of theatomic bomb. (because neutrons have no charge, they aren’t repelled by the electrical fields atthe heart of an atom and thus could be fired like tiny torpedoes into an atomic nucleus, settingoff the destructive process known as fission.) had the neutron been isolated in the 1920s, theynote, it is “very likely the atomic bomb would have been developed first in europe,undoubtedly by the germans.”

as it was, the europeans had their hands full trying to understand the strange behavior ofthe electron. the principal problem they faced was that the electron sometimes behaved like aparticle and sometimes like a wave. this impossible duality drove physicists nearly mad. forthe next decade all across europe they furiously thought and scribbled and offered competinghypotheses. in france, prince louis-victor de broglie, the scion of a ducal family, found thatcertain anomalies in the behavior of electrons disappeared when one regarded them as waves.

the observation excited the attention of the austrian erwin schr?dinger, who made some deftrefinements and devised a handy system called wave mechanics. at almost the same time thegerman physicist werner heisenberg came up with a competing theory called matrixmechanics. this was so mathematically complex that hardly anyone really understood it,including heisenberg himself (“i do not even know what a matrix is ,” heisenberg despairedto a friend at one point), but it did seem to solve certain problems that schr?dinger’s wavesfailed to explain. the upshot is that physics had two theories, based on conflicting premises,that produced the same results. it was an impossible situation.

finally, in 1926, heisenberg came up with a celebrated compromise, producing a newdiscipline that came to be known as quantum mechanics. at the heart of it was heisenberg’suncertainty principle, which states that the electron is a particle but a particle that can bedescribed in terms of waves. the uncertainty around which the theory is built is that we canknow the path an electron takes as it moves through a space or we can know where it is at agiven instant, but we cannot know both.

3any attempt to measure one will unavoidably3there is a little uncertainty about the use of the word uncertainty in regard to heisenbergs principle. michaelfrayn, in an afterword to his play copenhagen, notes that several words in german-unsicherheit, unscharfe,unbestimmtheit-have been used by various translators, but that none quite equates to the english uncertainty.

frayn suggests that indeterminacy would be a better word for the principle and indeterminability would be betterstill.

disturb the other. this isn’t a matter of simply needing more precise instruments; it is animmutable property of the universe.

what this means in practice is that you can never predict where an electron will be at anygiven moment. you can only list its probability of being there. in a sense, as dennis overbyehas put it, an electron doesn’t exist until it is observed. or, put slightly differently, until it isobserved an electron must be regarded as being “at once everywhere and nowhere.”

if this seems confusing, you may take some comfort in knowing that it was confusing tophysicists, too. overbye notes: “bohr once commented that a person who wasn’t outraged onfirst hearing about quantum theory didn’t understand what had been said.” heisenberg, whenasked how one could envision an atom, replied: “don’t try.”

so the atom turned out to be quite unlike the image that most people had created. theelectron doesn’t fly around the nucleus like a planet around its sun, but instead takes on themore amorphous aspect of a cloud. the “shell” of an atom isn’t some hard shiny casing, asillustrations sometimes encourage us to suppose, but simply the outermost of these fuzzyelectron clouds. the cloud itself is essentially just a zone of statistical probability marking thearea beyond which the electron only very seldom strays. thus an atom, if you could see it,would look more like a very fuzzy tennis ball than a hard-edged metallic sphere (but not muchlike either or, indeed, like anything you’ve ever seen; we are, after all, dealing here with aworld very different from the one we see around us).

it seemed as if there was no end of strangeness. for the first time, as james trefil has put it,scientists had encountered “an area of the universe that our brains just aren’t wired tounderstand.” or as feynman expressed it, “things on a small scale behave nothing like thingson a large scale.” as physicists delved deeper, they realized they had found a world where notonly could electrons jump from one orbit to another without traveling across any interveningspace, but matter could pop into existence from nothing at all—“provided,” in the words ofalan lightman of mit, “it disappears again with sufficient haste.”

perhaps the most arresting of quantum improbabilities is the idea, arising from wolfgangpauli’s exclusion principle of 1925, that the subatomic particles in certain pairs, even whenseparated by the most considerable distances, can each instantly “know” what the other isdoing. particles have a quality known as spin and, according to quantum theory, the momentyou determine the spin of one particle, its sister particle, no matter how distant away, willimmediately begin spinning in the opposite direction and at the same rate.

it is as if, in the words of the science writer lawrence joseph, you had two identical poolballs, one in ohio and the other in fiji, and the instant you sent one spinning the other wouldimmediately spin in a contrary direction at precisely the same speed. remarkably, thephenomenon was proved in 1997 when physicists at the university of geneva sent photonsseven miles in opposite directions and demonstrated that interfering with one provoked aninstantaneous response in the other.

things reached such a pitch that at one conference bohr remarked of a new theory that thequestion was not whether it was crazy, but whether it was crazy enough. to illustrate thenonintuitive nature of the quantum world, schr?dinger offered a famous thought experimentin which a hypothetical cat was placed in a box with one atom of a radioactive substanceattached to a vial of hydrocyanic acid. if the particle degraded within an hour, it would triggera mechanism that would break the vial and poison the cat. if not, the cat would live. but we
could not know which was the case, so there was no choice, scientifically, but to regard thecat as 100 percent alive and 100 percent dead at the same time. this means, as stephenhawking has observed with a touch of understandable excitement, that one cannot “predictfuture events exactly if one cannot even measure the present state of the universe precisely!”

because of its oddities, many physicists disliked quantum theory, or at least certain aspectsof it, and none more so than einstein. this was more than a little ironic since it was he, in hisannus mirabilis of 1905, who had so persuasively explained how photons of light couldsometimes behave like particles and sometimes like waves—the notion at the very heart of thenew physics. “quantum theory is very worthy of regard,” he observed politely, but he reallydidn’t like it. “god doesn’t play dice,” he said.

4einstein couldn’t bear the notion that god could create a universe in which some thingswere forever unknowable. moreover, the idea of action at a distance—that one particle couldinstantaneously influence another trillions of miles away—was a stark violation of the specialtheory of relativity. this expressly decreed that nothing could outrace the speed of light andyet here were physicists insisting that, somehow, at the subatomic level, information could.

(no one, incidentally, has ever explained how the particles achieve this feat. scientists havedealt with this problem, according to the physicist yakir aharanov, “by not thinking aboutit.”)above all, there was the problem that quantum physics introduced a level of untidiness thathadn’t previously existed. suddenly you needed two sets of laws to explain the behavior ofthe universe—quantum theory for the world of the very small and relativity for the largeruniverse beyond. the gravity of relativity theory was brilliant at explaining why planetsorbited suns or why galaxies tended to cluster, but turned out to have no influence at all at theparticle level. to explain what kept atoms together, other forces were needed, and in the1930s two were discovered: the strong nuclear force and weak nuclear force. the strong forcebinds atoms together; it’s what allows protons to bed down together in the nucleus. the weakforce engages in more miscellaneous tasks, mostly to do with controlling the rates of certainsorts of radioactive decay.

the weak nuclear force, despite its name, is ten billion billion billion times stronger thangravity, and the strong nuclear force is more powerful still—vastly so, in fact—but theirinfluence extends to only the tiniest distances. the grip of the strong force reaches out only toabout 1/100,000 of the diameter of an atom. that’s why the nuclei of atoms are so compactedand dense and why elements with big, crowded nuclei tend to be so unstable: the strong forcejust can’t hold on to all the protons.

the upshot of all this is that physics ended up with two bodies of laws—one for the worldof the very small, one for the universe at large—leading quite separate lives. einstein dislikedthat, too. he devoted the rest of his life to searching for a way to tie up these loose ends byfinding a grand unified theory, and always failed. from time to time he thought he had it, butit always unraveled on him in the end. as time passed he became increasingly marginalizedand even a little pitied. almost without exception, wrote snow, “his colleagues thought, andstill think, that he wasted the second half of his life.”

4or at least that is how it is nearly always rendered. the actual quote was: “it seems hard to sneak a look atgod’s cards. but that he plays dice and uses ‘telepathic’ methods. . . is something that i cannot believe for asingle moment.”

elsewhere, however, real progress was being made. by the mid-1940s scientists hadreached a point where they understood the atom at an extremely profound level—as they alltoo effectively demonstrated in august 1945 by exploding a pair of atomic bombs over japan.

by this point physicists could be excused for thinking that they had just about conqueredthe atom. in fact, everything in particle physics was about to get a whole lot morecomplicated. but before we take up that slightly exhausting story, we must bring anotherstraw of our history up to date by considering an important and salutary tale of avarice, deceit,bad science, several needless deaths, and the final determination of the age of the earth.

10    GETTING THE LEAD OUT

in the late 1940s, a graduate student at the university of chicago named clair patterson(who was, first name notwithstanding, an iowa farm boy by origin) was using a new methodof lead isotope measurement to try to get a definitive age for the earth at last. unfortunatelyall his samples came up contaminated—usually wildly so. most contained something like twohundred times the levels of lead that would normally be expected to occur. many years wouldpass before patterson realized that the reason for this lay with a regrettable ohio inventornamed thomas midgley, jr.

midgley was an engineer by training, and the world would no doubt have been a safer placeif he had stayed so. instead, he developed an interest in the industrial applications ofchemistry. in 1921, while working for the general motors research corporation in dayton,ohio, he investigated a compound called tetraethyl lead (also known, confusingly, as leadtetraethyl), and discovered that it significantly reduced the juddering condition known asengine knock.

even though lead was widely known to be dangerous, by the early years of the twentiethcentury it could be found in all manner of consumer products. food came in cans sealed withlead solder. water was often stored in lead-lined tanks. it was sprayed onto fruit as a pesticidein the form of lead arsenate. it even came as part of the packaging of toothpaste tubes. hardlya product existed that didn’t bring a little lead into consumers’ lives. however, nothing gave ita greater and more lasting intimacy than its addition to gasoline.

lead is a neurotoxin. get too much of it and you can irreparably damage the brain andcentral nervous system. among the many symptoms associated with overexposure areblindness, insomnia, kidney failure, hearing loss, cancer, palsies, and convulsions. in its mostacute form it produces abrupt and terrifying hallucinations, disturbing to victims andonlookers alike, which generally then give way to coma and death. you really don’t want toget too much lead into your system.

on the other hand, lead was easy to extract and work, and almost embarrassingly profitableto produce industrially—and tetraethyl lead did indubitably stop engines from knocking. so in1923 three of america’s largest corporations, general motors, du pont, and standard oil ofnew jersey, formed a joint enterprise called the ethyl gasoline corporation (later shortenedto simply ethyl corporation) with a view to making as much tetraethyl lead as the world waswilling to buy, and that proved to be a very great deal. they called their additive “ethyl”

because it sounded friendlier and less toxic than “lead” and introduced it for publicconsumption (in more ways than most people realized) on february 1, 1923.

almost at once production workers began to exhibit the staggered gait and confusedfaculties that mark the recently poisoned. also almost at once, the ethyl corporationembarked on a policy of calm but unyielding denial that would serve it well for decades. assharon bertsch mcgrayne notes in her absorbing history of industrial chemistry,prometheans in the lab, when employees at one plant developed irreversible delusions, a
spokesman blandly informed reporters: “these men probably went insane because theyworked too hard.” altogether at least fifteen workers died in the early days of production ofleaded gasoline, and untold numbers of others became ill, often violently so; the exactnumbers are unknown because the company nearly always managed to hush up news ofembarrassing leakages, spills, and poisonings. at times, however, suppressing the newsbecame impossible, most notably in 1924 when in a matter of days five production workersdied and thirty-five more were turned into permanent staggering wrecks at a single ill-ventilated facility.

as rumors circulated about the dangers of the new product, ethyl’s ebullient inventor,thomas midgley, decided to hold a demonstration for reporters to allay their concerns. as hechatted away about the company’s commitment to safety, he poured tetraethyl lead over hishands, then held a beaker of it to his nose for sixty seconds, claiming all the while that hecould repeat the procedure daily without harm. in fact, midgley knew only too well the perilsof lead poisoning: he had himself been made seriously ill from overexposure a few monthsearlier and now, except when reassuring journalists, never went near the stuff if he could helpit.

buoyed by the success of leaded gasoline, midgley now turned to another technologicalproblem of the age. refrigerators in the 1920s were often appallingly risky because they useddangerous gases that sometimes leaked. one leak from a refrigerator at a hospital incleveland, ohio, in 1929 killed more than a hundred people. midgley set out to create a gasthat was stable, nonflammable, noncorrosive, and safe to breathe. with an instinct for theregrettable that was almost uncanny, he invented chlorofluorocarbons, or cfcs.

seldom has an industrial product been more swiftly or unfortunately embraced. cfcs wentinto production in the early 1930s and found a thousand applications in everything from carair conditioners to deodorant sprays before it was noticed, half a century later, that they weredevouring the ozone in the stratosphere. as you will be aware, this was not a good thing.

ozone is a form of oxygen in which each molecule bears three atoms of oxygen instead oftwo. it is a bit of a chemical oddity in that at ground level it is a pollutant, while way up in thestratosphere it is beneficial, since it soaks up dangerous ultraviolet radiation. beneficial ozoneis not terribly abundant, however. if it were distributed evenly throughout the stratosphere, itwould form a layer just one eighth of an inch or so thick. that is why it is so easily disturbed,and why such disturbances don’t take long to become critical.

chlorofluorocarbons are also not very abundant—they constitute only about one part perbillion of the atmosphere as a whole—but they are extravagantly destructive. one pound ofcfcs can capture and annihilate seventy thousand pounds of atmospheric ozone. cfcs alsohang around for a long time—about a century on average—wreaking havoc all the while.

they are also great heat sponges. a single cfc molecule is about ten thousand times moreefficient at exacerbating greenhouse effects than a molecule of carbon dioxide—and carbondioxide is of course no slouch itself as a greenhouse gas. in short, chlorofluorocarbons mayultimately prove to be just about the worst invention of the twentieth century.

midgley never knew this because he died long before anyone realized how destructivecfcs were. his death was itself memorably unusual. after becoming crippled with polio,midgley invented a contraption involving a series of motorized pulleys that automatically
raised or turned him in bed. in 1944, he became entangled in the cords as the machine wentinto action and was strangled.

if you were interested in finding out the ages of things, the university of chicago in the1940s was the place to be. willard libby was in the process of inventing radiocarbon dating,allowing scientists to get an accurate reading of the age of bones and other organic remains,something they had never been able to do before. up to this time, the oldest reliable dateswent back no further than the first dynasty in egypt from about 3000b.c. no one couldconfidently say, for instance, when the last ice sheets had retreated or at what time in the pastthe cro-magnon people had decorated the caves of lascaux in france.

libby’s idea was so useful that he would be awarded a nobel prize for it in 1960. it wasbased on the realization that all living things have within them an isotope of carbon calledcarbon-14, which begins to decay at a measurable rate the instant they die. carbon-14 has ahalf-life—that is, the time it takes for half of any sample to disappear1—of about 5,600 years,so by working out how much a given sample of carbon had decayed, libby could get a goodfix on the age of an object—though only up to a point. after eight half-lives, only 1/256 of theoriginal radioactive carbon remains, which is too little to make a reliable measurement, soradiocarbon dating works only for objects up to forty thousand or so years old.

curiously, just as the technique was becoming widespread, certain flaws within it becameapparent. to begin with, it was discovered that one of the basic components of libby’sformula, known as the decay constant, was off by about 3 percent. by this time, however,thousands of measurements had been taken throughout the world. rather than restate everyone, scientists decided to keep the inaccurate constant. “thus,” tim flannery notes, “everyraw radiocarbon date you read today is given as too young by around 3 percent.” theproblems didn’t quite stop there. it was also quickly discovered that carbon-14 samples can beeasily contaminated with carbon from other sources—a tiny scrap of vegetable matter, forinstance, that has been collected with the sample and not noticed. for younger samples—those under twenty thousand years or so—slight contamination does not always matter somuch, but for older samples it can be a serious problem because so few remaining atoms arebeing counted. in the first instance, to borrow from flannery, it is like miscounting by a dollarwhen counting to a thousand; in the second it is more like miscounting by a dollar when youhave only two dollars to count.

libby’s method was also based on the assumption that the amount of carbon-14 in theatmosphere, and the rate at which it has been absorbed by living things, has been consistentthroughout history. in fact it hasn’t been. we now know that the volume of atmosphericcarbon-14 varies depending on how well or not earth’s magnetism is deflecting cosmic rays,and that that can vary significantly over time. this means that some carbon-14 dates are more1if you have ever wondered how the atoms determine which 50 percent will die and which 50 percent willsurvive for the next session, the answer is that the half-life is really just a statistical convenience-a kind ofactuarial table for elemental things. imagine you had a sample of material with a half-life of 30 seconds. it isntthat every atom in the sample will exist for exactly 30 seconds or 60 seconds or 90 seconds or some other tidilyordained period. each atom will in fact survive for an entirely random length of time that has nothing to do withmultiples of 30; it might last until two seconds from now or it might oscillate away for years or decades orcenturies to come. no one can say. but what we can say is that for the sample as a whole the rate ofdisappearance will be such that half the atoms will disappear every 30 seconds. its an average rate, in otherwords, and you can apply it to any large sampling. someone once worked out, for instance, that dimes have ahalf-life of about 30 years.

dubious than others. this is particularly so with dates just around the time that people firstcame to the americas, which is one of the reasons the matter is so perennially in dispute.

finally, and perhaps a little unexpectedly, readings can be thrown out by seeminglyunrelated external factors—such as the diets of those whose bones are being tested. onerecent case involved the long-running debate over whether syphilis originated in the newworld or the old. archeologists in hull, in the north of england, found that monks in amonastery graveyard had suffered from syphilis, but the initial conclusion that the monks haddone so before columbus’s voyage was cast into doubt by the realization that they had eaten alot of fish, which could make their bones appear to be older than in fact they were. the monksmay well have had syphilis, but how it got to them, and when, remain tantalizinglyunresolved.

because of the accumulated shortcomings of carbon-14, scientists devised other methods ofdating ancient materials, among them thermoluminesence, which measures electrons trappedin clays, and electron spin resonance, which involves bombarding a sample withelectromagnetic waves and measuring the vibrations of the electrons. but even the best ofthese could not date anything older than about 200,000 years, and they couldn’t date inorganicmaterials like rocks at all, which is of course what you need if you wish to determine the ageof your planet.

the problems of dating rocks were such that at one point almost everyone in the world hadgiven up on them. had it not been for a determined english professor named arthur holmes,the quest might well have fallen into abeyance altogether.

holmes was heroic as much for the obstacles he overcame as for the results he achieved.

by the 1920s, when holmes was in the prime of his career, geology had slipped out offashion—physics was the new excitement of the age—and had become severely underfunded,particularly in britain, its spiritual birthplace. at durham university, holmes was for manyyears the entire geology department. often he had to borrow or patch together equipment inorder to pursue his radiometric dating of rocks. at one point, his calculations were effectivelyheld up for a year while he waited for the university to provide him with a simple addingmachine. occasionally, he had to drop out of academic life altogether to earn enough tosupport his family—for a time he ran a curio shop in newcastle upon tyne—and sometimeshe could not even afford the ￡5 annual membership fee for the geological society.

the technique holmes used in his work was theoretically straightforward and arose directlyfrom the process, first observed by ernest rutherford in 1904, in which some atoms decayfrom one element into another at a rate predictable enough that you can use them as clocks. ifyou know how long it takes for potassium-40 to become argon-40, and you measure theamounts of each in a sample, you can work out how old a material is. holmes’s contributionwas to measure the decay rate of uranium into lead to calculate the age of rocks, and thus—hehoped—of the earth.

but there were many technical difficulties to overcome. holmes also needed—or at leastwould very much have appreciated—sophisticated gadgetry of a sort that could make veryfine measurements from tiny samples, and as we have seen it was all he could do to get asimple adding machine. so it was quite an achievement when in 1946 he was able toannounce with some confidence that the earth was at least three billion years old and possiblyrather more. unfortunately, he now met yet another formidable impediment to acceptance: theconservativeness of his fellow scientists. although happy to praise his methodology, many
maintained that he had found not the age of the earth but merely the age of the materials fromwhich the earth had been formed.

it was just at this time that harrison brown of the university of chicago developed a newmethod for counting lead isotopes in igneous rocks (which is to say those that were createdthrough heating, as opposed to the laying down of sediments). realizing that the work wouldbe exceedingly tedious, he assigned it to young clair patterson as his dissertation project.

famously he promised patterson that determining the age of the earth with his new methodwould be “duck soup.” in fact, it would take years.

patterson began work on the project in 1948. compared with thomas midgley’s colorfulcontributions to the march of progress, patterson’s discovery of the age of the earth feelsmore than a touch anticlimactic. for seven years, first at the university of chicago and then atthe california institute of technology (where he moved in 1952), he worked in a sterile lab,making very precise measurements of the lead/uranium ratios in carefully selected samples ofold rock.

the problem with measuring the age of the earth was that you needed rocks that wereextremely ancient, containing lead- and uranium-bearing crystals that were about as old as theplanet itself—anything much younger would obviously give you misleadingly youthfuldates—but really ancient rocks are only rarely found on earth. in the late 1940s no onealtogether understood why this should be. indeed, and rather extraordinarily, we would bewell into the space age before anyone could plausibly account for where all the earth’s oldrocks went. (the answer was plate tectonics, which we shall of course get to.) patterson,meantime, was left to try to make sense of things with very limited materials. eventually, andingeniously, it occurred to him that he could circumvent the rock shortage by using rocksfrom beyond earth. he turned to meteorites.

the assumption he made—rather a large one, but correct as it turned out—was that manymeteorites are essentially leftover building materials from the early days of the solar system,and thus have managed to preserve a more or less pristine interior chemistry. measure the ageof these wandering rocks and you would have the age also (near enough) of the earth.

as always, however, nothing was quite as straightforward as such a breezy descriptionmakes it sound. meteorites are not abundant and meteoritic samples not especially easy to gethold of. moreover, brown’s measurement technique proved finicky in the extreme andneeded much refinement. above all, there was the problem that patterson’s samples werecontinuously and unaccountably contaminated with large doses of atmospheric lead wheneverthey were exposed to air. it was this that eventually led him to create a sterile laboratory—theworld’s first, according to at least one account.

it took patterson seven years of patient work just to assemble suitable samples for finaltesting. in the spring of 1953 he traveled to the argonne national laboratory in illinois,where he was granted time on a late-model mass spectrograph, a machine capable of detectingand measuring the minute quantities of uranium and lead locked up in ancient crystals. whenat last he had his results, patterson was so excited that he drove straight to his boyhood homein iowa and had his mother check him into a hospital because he thought he was having aheart attack.

soon afterward, at a meeting in wisconsin, patterson announced a definitive age for theearth of 4,550 million years (plus or minus 70 million years)—“a figure that stands
unchanged 50 years later,” as mcgrayne admiringly notes. after two hundred years of trying,the earth finally had an age.

his main work done, patterson now turned his attention to the nagging question of all thatlead in the atmosphere. he was astounded to find that what little was known about the effectsof lead on humans was almost invariably wrong or misleading—and not surprisingly, hediscovered, since for forty years every study of lead’s effects had been funded exclusively bymanufacturers of lead additives.

in one such study, a doctor who had no specialized training in chemical pathologyundertook a five-year program in which volunteers were asked to breathe in or swallow leadin elevated quantities. then their urine and feces were tested. unfortunately, as the doctorappears not to have known, lead is not excreted as a waste product. rather, it accumulates inthe bones and blood—that’s what makes it so dangerous—and neither bone nor blood wastested. in consequence, lead was given a clean bill of health.

patterson quickly established that we had a lot of lead in the atmosphere—still do, in fact,since lead never goes away—and that about 90 percent of it appeared to come fromautomobile exhaust pipes, but he couldn’t prove it. what he needed was a way to comparelead levels in the atmosphere now with the levels that existed before 1923, when tetraethyllead was introduced. it occurred to him that ice cores could provide the answer.

it was known that snowfall in places like greenland accumulates into discrete annual layers(because seasonal temperature differences produce slight changes in coloration from winter tosummer). by counting back through these layers and measuring the amount of lead in each, hecould work out global lead concentrations at any time for hundreds, or even thousands, ofyears. the notion became the foundation of ice core studies, on which much modernclimatological work is based.

what patterson found was that before 1923 there was almost no lead in the atmosphere, andthat since that time its level had climbed steadily and dangerously. he now made it his life’squest to get lead taken out of gasoline. to that end, he became a constant and often vocalcritic of the lead industry and its interests.

it would prove to be a hellish campaign. ethyl was a powerful global corporation withmany friends in high places. (among its directors have been supreme court justice lewispowell and gilbert grosvenor of the national geographic society.) patterson suddenly foundresearch funding withdrawn or difficult to acquire. the american petroleum institutecanceled a research contract with him, as did the united states public health service, asupposedly neutral government institution.

as patterson increasingly became a liability to his institution, the school trustees wererepeatedly pressed by lead industry officials to shut him up or let him go. according to jamielincoln kitman, writing in the nation in 2000, ethyl executives allegedly offered to endow achair at caltech “if patterson was sent packing.” absurdly, he was excluded from a 1971national research council panel appointed to investigate the dangers of atmospheric leadpoisoning even though he was by now unquestionably the leading expert on atmospheric lead.

to his great credit, patterson never wavered or buckled. eventually his efforts led to theintroduction of the clean air act of 1970 and finally to the removal from sale of all leadedgasoline in the united states in 1986. almost immediately lead levels in the blood ofamericans fell by 80 percent. but because lead is forever, those of us alive today have about625 times more lead in our blood than people did a century ago. the amount of lead in theatmosphere also continues to grow, quite legally, by about a hundred thousand metric tons ayear, mostly from mining, smelting, and industrial activities. the united states also bannedlead in indoor paint, “forty-four years after most of europe,” as mcgrayne notes.

remarkably, considering its startling toxicity, lead solder was not removed from americanfood containers until 1993.

as for the ethyl corporation, it’s still going strong, though gm, standard oil, and du pontno longer have stakes in the company. (they sold out to a company called albemarle paper in1962.) according to mcgrayne, as late as february 2001 ethyl continued to contend “thatresearch has failed to show that leaded gasoline poses a threat to human health or theenvironment.” on its website, a history of the company makes no mention of lead—or indeedof thomas midgley—but simply refers to the original product as containing “a certaincombination of chemicals.”

ethyl no longer makes leaded gasoline, although, according to its 2001 company accounts,tetraethyl lead (or tel as it calls it) still accounted for $25.1 million in sales in 2000 (out ofoverall sales of $795 million), up from $24.1 million in 1999, but down from $117 million in1998. in its report the company stated its determination to “maximize the cash generated bytel as its usage continues to phase down around the world.” ethyl markets tel through anagreement with associated octel of england.

as for the other scourge left to us by thomas midgley, chlorofluorocarbons, they werebanned in 1974 in the united states, but they are tenacious little devils and any that youloosed into the atmosphere before then (in your deodorants or hair sprays, for instance) willalmost certainly be around and devouring ozone long after you have shuffled off. worse, weare still introducing huge amounts of cfcs into the atmosphere every year. according towayne biddle, 60 million pounds of the stuff, worth $1.5 billion, still finds its way onto themarket every year. so who is making it? we are—that is to say, many of our largecorporations are still making it at their plants overseas. it will not be banned in third worldcountries until 2010.

clair patterson died in 1995. he didn’t win a nobel prize for his work. geologists neverdo. nor, more puzzlingly, did he gain any fame or even much attention from half a century ofconsistent and increasingly selfless achievement. a good case could be made that he was themost influential geologist of the twentieth century. yet who has ever heard of clair patterson?

most geology textbooks don’t mention him. two recent popular books on the history of thedating of earth actually manage to misspell his name. in early 2001, a reviewer of one ofthese books in the journal nature made the additional, rather astounding error of thinkingpatterson was a woman.

at all events, thanks to the work of clair patterson by 1953 the earth at last had an ageeveryone could agree on. the only problem now was it was older than the universe thatcontained it.

11    MUSTER MARK’S QUARKS

in 1911, a british scientist named c. t. r. wilson was studying cloud formations bytramping regularly to the summit of ben nevis, a famously damp scottish mountain, when itoccurred to him that there must be an easier way to study clouds. back in the cavendish labin cambridge he built an artificial cloud chamber—a simple device in which he could cooland moisten the air, creating a reasonable model of a cloud in laboratory conditions.

the  device  worked  very  well,  but  had  an additional, unexpected benefit. when heaccelerated an alpha particle through the chamber to seed his make-believe clouds, it left avisible trail—like the contrails of a passing airliner. he had just invented the particle detector.

it provided convincing evidence that subatomic particles did indeed exist.

eventually two other cavendish scientists invented a more powerful proton-beam device,while in california ernest lawrence at berkeley produced his famous and impressivecyclotron, or atom smasher, as such devices were long excitingly known. all of thesecontraptions worked—and indeed still work—on more or less the same principle, the ideabeing to accelerate a proton or other charged particle to an extremely high speed along a track(sometimes circular, sometimes linear), then bang it into another particle and see what fliesoff. that’s why they were called atom smashers. it wasn’t science at its subtlest, but it wasgenerally effective.

as physicists built bigger and more ambitious machines, they began to find or postulateparticles or particle families seemingly without number: muons, pions, hyperons, mesons, k-mesons, higgs bosons, intermediate vector bosons, baryons, tachyons. even physicists beganto grow a little uncomfortable. “young man,” enrico fermi replied when a student asked himthe name of a particular particle, “if i could remember the names of these particles, i wouldhave been a botanist.”

today accelerators have names that sound like something flash gordon would use inbattle: the super proton synchrotron, the large electron-positron collider, the large hadroncollider, the relativistic heavy ion collider. using huge amounts of energy (some operateonly at night so that people in neighboring towns don’t have to witness their lights fadingwhen the apparatus is fired up), they can whip particles into such a state of liveliness that asingle electron can do forty-seven thousand laps around a four-mile tunnel in a second. fearshave been raised that in their enthusiasm scientists might inadvertently create a black hole oreven something called “strange quarks,” which could, theoretically, interact with othersubatomic particles and propagate uncontrollably. if you are reading this, that hasn’thappened.

finding particles takes a certain amount of concentration. they are not just tiny and swiftbut also often tantalizingly evanescent. particles can come into being and be gone again in aslittle as 0.000000000000000000000001 second (10-24). even the most sluggish of unstableparticles hang around for no more than 0.0000001 second (10-7).

some particles are almost ludicrously slippery. every second the earth is visited by 10,000trillion trillion tiny, all but massless neutrinos (mostly shot out by the nuclear broilings of thesun), and virtually all of them pass right through the planet and everything that is on it,including you and me, as if it weren’t there. to trap just a few of them, scientists need tanksholding up to 12.5 million gallons of heavy water (that is, water with a relative abundance ofdeuterium in it) in underground chambers (old mines usually) where they can’t be interferedwith by other types of radiation.

very occasionally, a passing neutrino will bang into one of the atomic nuclei in the waterand produce a little puff of energy. scientists count the puffs and by such means take us veryslightly closer to understanding the fundamental properties of the universe. in 1998, japaneseobservers reported that neutrinos do have mass, but not a great deal—about one ten-millionththat of an electron.

what it really takes to find particles these days is money and lots of it. there is a curiousinverse relationship in modern physics between the tininess of the thing being sought and thescale of facilities required to do the searching. cern, the european organization for nuclearresearch, is like a little city. straddling the border of france and switzerland, it employsthree thousand people and occupies a site that is measured in square miles. cern boasts astring of magnets that weigh more than the eiffel tower and an underground tunnel oversixteen miles around.

breaking up atoms, as james trefil has noted, is easy; you do it each time you switch on afluorescent light. breaking up atomic nuclei, however, requires quite a lot of money and agenerous supply of electricity. getting down to the level of quarks—the particles that make upparticles—requires still more: trillions of volts of electricity and the budget of a small centralamerican nation. cern’s new large hadron collider, scheduled to begin operations in 2005,will achieve fourteen trillion volts of energy and cost something over $1.5 billion toconstruct.

1but these numbers are as nothing compared with what could have been achieved by, andspent upon, the vast and now unfortunately never-to-be superconducting supercollider, whichbegan being constructed near waxahachie, texas, in the 1980s, before experiencing asupercollision of its own with the united states congress. the intention of the collider was tolet scientists probe “the ultimate nature of matter,” as it is always put, by re-creating as nearlyas possible the conditions in the universe during its first ten thousand billionths of a second.

the plan was to fling particles through a tunnel fifty-two miles long, achieving a trulystaggering ninety-nine trillion volts of energy. it was a grand scheme, but would also havecost $8 billion to build (a figure that eventually rose to $10 billion) and hundreds of millionsof dollars a year to run.

in perhaps the finest example in history of pouring money into a hole in the ground,congress spent $2 billion on the project, then canceled it in 1993 after fourteen miles oftunnel had been dug. so texas now boasts the most expensive hole in the universe. the siteis, i am told by my friend jeff guinn of the fort worth star-telegram, “essentially a vast,cleared field dotted along the circumference by a series of disappointed small towns.”

1there are practical side effects to all this costly effort. the world wide web is a cern offshoot. it wasinvented by a cern scientist, tim berners-lee, in 1989.

since the supercollider debacle particle physicists have set their sights a little lower, buteven comparatively modest projects can be quite breathtakingly costly when compared with,well, almost anything. a proposed neutrino observatory at the old homestake mine in lead,south dakota, would cost $500 million to build—this in a mine that is already dug—beforeyou even look at the annual running costs. there would also be $281 million of “generalconversion costs.” a particle accelerator at fermilab in illinois, meanwhile, cost $260 millionmerely to refit.

particle physics, in short, is a hugely expensive enterprise—but it is a productive one.

today the particle count is well over 150, with a further 100 or so suspected, butunfortunately, in the words of richard feynman, “it is very difficult to understand therelationships of all these particles, and what nature wants them for, or what the connectionsare from one to another.” inevitably each time we manage to unlock a box, we find that thereis another locked box inside. some people think there are particles called tachyons, which cantravel faster than the speed of light. others long to find gravitons—the seat of gravity. atwhat point we reach the irreducible bottom is not easy to say. carl sagan in cosmos raised thepossibility that if you traveled downward into an electron, you might find that it contained auniverse of its own, recalling all those science fiction stories of the fifties. “within it,organized into the local equivalent of galaxies and smaller structures, are an immense numberof other, much tinier elementary particles, which are themselves universes at the next leveland so on forever—an infinite downward regression, universes within universes, endlessly. and upward as well.”

for most of us it is a world that surpasses understanding. to read even an elementary guideto particle physics nowadays you must now find your way through lexical thickets such asthis: “the charged pion and antipion decay respectively into a muon plus antineutrino and anantimuon plus neutrino with an average lifetime of 2.603 x 10-8seconds, the neutral piondecays into two photons with an average lifetime of about 0.8 x 10-16seconds, and the muonand antimuon decay respectively into . . .” and so it runs on—and this from a book for thegeneral reader by one of the (normally) most lucid of interpreters, steven weinberg.

in the 1960s, in an attempt to bring just a little simplicity to matters, the caltech physicistmurray gell-mann invented a new class of particles, essentially, in the words of stevenweinberg, “to restore some economy to the multitude of hadrons”—a collective term used byphysicists for protons, neutrons, and other particles governed by the strong nuclear force.

gell-mann’s theory was that all hadrons were made up of still smaller, even morefundamental particles. his colleague richard feynman wanted to call these new basicparticles partons, as in dolly, but was overruled. instead they became known as quarks.

gell-mann took the name from a line in finnegans wake: “three quarks for mustermark!” (discriminating physicists rhyme the word with storks, not larks, even though thelatter is almost certainly the pronunciation joyce had in mind.) the fundamental simplicity ofquarks was not long lived. as they became better understood it was necessary to introducesubdivisions. although quarks are much too small to have color or taste or any other physicalcharacteristics we would recognize, they became clumped into six categories—up, down,strange, charm, top, and bottom—which physicists oddly refer to as their “flavors,” and theseare further divided into the colors red, green, and blue. (one suspects that it was not altogethercoincidental that these terms were first applied in california during the age of psychedelia.)
eventually out of all this emerged what is called the standard model, which is essentially asort of parts kit for the subatomic world. the standard model consists of six quarks, sixleptons, five known bosons and a postulated sixth, the higgs boson (named for a scottishscientist, peter higgs), plus three of the four physical forces: the strong and weak nuclearforces and electromagnetism.

the arrangement essentially is that among the basic building blocks of matter are quarks;these are held together by particles called gluons; and together quarks and gluons formprotons and neutrons, the stuff of the atom’s nucleus. leptons are the source of electrons andneutrinos. quarks and leptons together are called fermions. bosons (named for the indianphysicist s. n. bose) are particles that produce and carry forces, and include photons andgluons. the higgs boson may or may not actually exist; it was invented simply as a way ofendowing particles with mass.

it is all, as you can see, just a little unwieldy, but it is the simplest model that can explainall that happens in the world of particles. most particle physicists feel, as leon ledermanremarked in a 1985 pbs documentary, that the standard model lacks elegance and simplicity.

“it is too complicated. it has too many arbitrary parameters,” lederman said. “we don’t reallysee the creator twiddling twenty knobs to set twenty parameters to create the universe as weknow it.” physics is really nothing more than a search for ultimate simplicity, but so far all wehave is a kind of elegant messiness—or as lederman put it: “there is a deep feeling that thepicture is not beautiful.”

the standard model is not only ungainly but incomplete. for one thing, it has nothing at allto say about gravity. search through the standard model as you will, and you won’t findanything to explain why when you place a hat on a table it doesn’t float up to the ceiling. nor,as we’ve just noted, can it explain mass. in order to give particles any mass at all we have tointroduce the notional higgs boson; whether it actually exists is a matter for twenty-first-century physics. as feynman cheerfully observed: “so we are stuck with a theory, and we donot know whether it is right or wrong, but we do know that it is a little wrong, or at leastincomplete.”

in an attempt to draw everything together, physicists have come up with something calledsuperstring theory. this postulates that all those little things like quarks and leptons that wehad previously thought of as particles are actually “strings”—vibrating strands of energy thatoscillate in eleven dimensions, consisting of the three we know already plus time and sevenother dimensions that are, well, unknowable to us. the strings are very tiny—tiny enough topass for point particles.

by introducing extra dimensions, superstring theory enables physicists to pull togetherquantum laws and gravitational ones into one comparatively tidy package, but it also meansthat anything scientists say about the theory begins to sound worryingly like the sort ofthoughts that would make you edge away if conveyed to you by a stranger on a park bench.

here, for example, is the physicist michio kaku explaining the structure of the universe froma superstring perspective: “the heterotic string consists of a closed string that has two types ofvibrations, clockwise and counterclockwise, which are treated differently. the clockwisevibrations live in a ten-dimensional space. the counterclockwise live in a twenty-six-dimensional space, of which sixteen dimensions have been compactified. (we recall that inkaluza’s original five-dimensional, the fifth dimension was compactified by being wrappedup into a circle.)” and so it goes, for some 350 pages.

string theory has further spawned something called “m theory,” which incorporatessurfaces known as membranes—or simply “branes” to the hipper souls of the world ofphysics. i’m afraid this is the stop on the knowledge highway where most of us must get off.

here is a sentence from the new york times, explaining this as simply as possible to a generalaudience: “the ekpyrotic process begins far in the indefinite past with a pair of flat emptybranes sitting parallel to each other in a warped five-dimensional space. . . . the two branes,which form the walls of the fifth dimension, could have popped out of nothingness as aquantum fluctuation in the even more distant past and then drifted apart.” no arguing withthat. no understanding it either. ekpyrotic, incidentally, comes from the greek word for“conflagration.”

matters in physics have now reached such a pitch that, as paul davies noted in nature, it is“almost impossible for the non-scientist to discriminate between the legitimately weird andthe outright crackpot.” the question came interestingly to a head in the fall of 2002 when twofrench physicists, twin brothers igor and grickha bogdanov, produced a theory of ambitiousdensity involving such concepts as “imaginary time” and the “kubo-schwinger-martincondition,” and purporting to describe the nothingness that was the universe before the bigbang—a period that was always assumed to be unknowable (since it predated the birth ofphysics and its properties).

almost at once the bogdanov paper excited debate among physicists as to whether it wastwaddle, a work of genius, or a hoax. “scientifically, it’s clearly more or less completenonsense,” columbia university physicist peter woit told the new york times, “but thesedays that doesn’t much distinguish it from a lot of the rest of the literature.”

karl popper, whom steven weinberg has called “the dean of modern philosophers ofscience,” once suggested that there may not be an ultimate theory for physics—that, rather,every explanation may require a further explanation, producing “an infinite chain of more andmore fundamental principles.” a rival possibility is that such knowledge may simply bebeyond us. “so far, fortunately,” writes weinberg in dreams of a final theory, “we do notseem to be coming to the end of our intellectual resources.”

almost certainly this is an area that will see further developments of thought, and almostcertainly these thoughts will again be beyond most of us.

while physicists in the middle decades of the twentieth-century were looking perplexedlyinto the world of the very small, astronomers were finding no less arresting an incompletenessof understanding in the universe at large.

when we last met edwin hubble, he had determined that nearly all the galaxies in our fieldof view are flying away from us, and that the speed and distance of this retreat are neatlyproportional: the farther away the galaxy, the faster it is moving. hubble realized that thiscould be expressed with a simple equation, ho = v/d (where ho is the constant, v is therecessional velocity of a flying galaxy, andd its distance away from us). ho has been knownever since as the hubble constant and the whole as hubble’s law. using his formula, hubblecalculated that the universe was about two billion years old, which was a little awkwardbecause even by the late 1920s it was fairly obvious that many things within the universe—not least earth itself—were probably older than that. refining this figure has been an ongoingpreoccupation of cosmology.

almost the only thing constant about the hubble constant has been the amount ofdisagreement over what value to give it. in 1956, astronomers discovered that cepheidvariables were more variable than they had thought; they came in two varieties, not one. thisallowed them to rework their calculations and come up with a new age for the universe offrom 7 to 20 billion years—not terribly precise, but at least old enough, at last, to embrace theformation of the earth.

in the years that followed there erupted a long-running dispute between allan sandage, heirto hubble at mount wilson, and gérard de vaucouleurs, a french-born astronomer based atthe university of texas. sandage, after years of careful calculations, arrived at a value for thehubble constant of 50, giving the universe an age of 20 billion years. de vaucouleurs wasequally certain that the hubble constant was 100.

2this would mean that the universe wasonly half the size and age that sandage believed—ten billion years. matters took a furtherlurch into uncertainty when in 1994 a team from the carnegie observatories in california,using measures from the hubble space telescope, suggested that the universe could be as littleas eight billion years old—an age even they conceded was younger than some of the starswithin the universe. in february 2003, a team from nasa and the goddard space flightcenter in maryland, using a new, far-reaching type of satellite called the wilkinsonmicrowave anistropy probe, announced with some confidence that the age of the universe is13.7 billion years, give or take a hundred million years or so. there matters rest, at least forthe moment.

the difficulty in making final determinations is that there are often acres of room forinterpretation. imagine standing in a field at night and trying to decide how far away twodistant electric lights are. using fairly straightforward tools of astronomy you can easilyenough determine that the bulbs are of equal brightness and that one is, say, 50 percent moredistant than the other. but what you can’t be certain of is whether the nearer light is, let ussay, a 58-watt bulb that is 122 feet away or a 61-watt light that is 119 feet, 8 inches away. ontop of that you must make allowances for distortions caused by variations in the earth’satmosphere, by intergalactic dust, contaminating light from foreground stars, and many otherfactors. the upshot is that your computations are necessarily based on a series of nestedassumptions, any of which could be a source of contention. there is also the problem thataccess to telescopes is always at a premium and historically measuring red shifts has beennotably costly in telescope time. it could take all night to get a single exposure. inconsequence, astronomers have sometimes been compelled (or willing) to base conclusionson notably scanty evidence. in cosmology, as the journalist geoffrey carr has suggested, wehave “a mountain of theory built on a molehill of evidence.” or as martin rees has put it:

“our present satisfaction [with our state of understanding] may reflect the paucity of the datarather than the excellence of the theory.”

this uncertainty applies, incidentally, to relatively nearby things as much as to the distantedges of the universe. as donald goldsmith notes, when astronomers say that the galaxy m87is 60 million light-years away, what they really mean (“but do not often stress to the generalpublic”) is that it is somewhere between 40 million and 90 million light-years away—not2you are of course entitled to wonder what is meant exactly by “a constant of 50” or “a constant of 100.” theanswer lies in astronomical units of measure. except conversationally, astronomers dont use light-years. theyuse a distance called the parsec (a contraction of parallax and second), based on a universal measure called thestellar parallax and equivalent to 3.26 light-years. really big measures, like the size of a universe, are measuredin megaparsecs: a million parsecs. the constant is expressed in terms of kilometers per second per megaparsec.

thus when astronomers refer to a hubble constant of 50, what they really mean is “50 kilometers per second permegaparsec.” for most of us that is of course an utterly meaningless measure, but then with astronomicalmeasures most distances are so huge as to be utterly meaningless.

quite the same thing. for the universe at large, matters are naturally magnified. bearing allthat in mind, the best bets these days for the age of the universe seem to be fixed on a range ofabout 12 billion to 13.5 billion years, but we remain a long way from unanimity.

one interesting recently suggested theory is that the universe is not nearly as big as wethought, that when we peer into the distance some of the galaxies we see may simply bereflections, ghost images created by rebounded light.

the fact is, there is a great deal, even at quite a fundamental level, that we don’t know—notleast what the universe is made of. when scientists calculate the amount of matter needed tohold things together, they always come up desperately short. it appears that at least 90 percentof the universe, and perhaps as much as 99 percent, is composed of fritz zwicky’s “darkmatter”—stuff that is by its nature invisible to us. it is slightly galling to think that we live ina universe that, for the most part, we can’t even see, but there you are. at least the names forthe two main possible culprits are entertaining: they are said to be either wimps (for weaklyinteracting massive particles, which is to say specks of invisible matter left over from the bigbang) or machos (for massive compact halo objects—really just another name for blackholes, brown dwarfs, and other very dim stars).

particle physicists have tended to favor the particle explanation of wimps, astrophysiciststhe stellar explanation of machos. for a time machos had the upper hand, but not nearlyenough of them were found, so sentiment swung back toward wimps but with the problemthat no wimp has ever been found. because they are weakly interacting, they are (assumingthey even exist) very hard to detect. cosmic rays would cause too much interference. soscientists must go deep underground. one kilometer underground cosmic bombardmentswould be one millionth what they would be on the surface. but even when all these are addedin, “two-thirds of the universe is still missing from the balance sheet,” as one commentatorhas put it. for the moment we might very well call them dunnos (for dark unknownnonreflective nondetectable objects somewhere).

recent evidence suggests that not only are the galaxies of the universe racing away fromus, but that they are doing so at a rate that is accelerating. this is counter to all expectations. itappears that the universe may not only be filled with dark matter, but with dark energy.

scientists sometimes also call it vacuum energy or, more exotically, quintessence. whatever itis, it seems to be driving an expansion that no one can altogether account for. the theory isthat empty space isn’t so empty at all—that there are particles of matter and antimatterpopping into existence and popping out again—and that these are pushing the universeoutward at an accelerating rate. improbably enough, the one thing that resolves all this iseinstein’s cosmological constant—the little piece of math he dropped into the general theoryof relativity to stop the universe’s presumed expansion, and called “the biggest blunder of mylife.” it now appears that he may have gotten things right after all.

the upshot of all this is that we live in a universe whose age we can’t quite compute,surrounded by stars whose distances we don’t altogether know, filled with matter we can’tidentify, operating in conformance with physical laws whose properties we don’t trulyunderstand.

and on that rather unsettling note, let’s return to planet earth and consider something thatwe do understand—though by now you perhaps won’t be surprised to hear that we don’tunderstand it completely and what we do understand we haven’t understood for long.

12    THE EARTH MOVES

in one of his last professional acts before his death in 1955, albert einstein wrote a shortbut glowing foreword to a book by a geologist named charles hapgood entitled earth’sshifting crust: a key to some basic problems of earth science. hapgood’s book was asteady demolition of the idea that continents were in motion. in a tone that all but invited thereader to join him in a tolerant chuckle, hapgood observed that a few gullible souls hadnoticed “an apparent correspondence in shape between certain continents.” it would appear,he went on, “that south america might be fitted together with africa, and so on. . . . it is evenclaimed that rock formations on opposite sides of the atlantic match.”

1. hapgood briskly dismissed any such notions, noting that the geologists k. e. casterand j. c. mendes had done extensive fieldwork on both sides of the atlantic and hadestablished beyond question that no such similarities existed. goodness knows what outcropsmessrs. caster and mendes had looked at, beacuse in fact many of the rock formations onboth sides of the atlanticare the same—not just very similar but the same.

this was not an idea that flew with mr. hapgood, or many other geologists of his day. thetheory hapgood alluded to was one first propounded in 1908 by an amateur americangeologist named frank bursley taylor. taylor came from a wealthy family and had both themeans and freedom from academic constraints to pursue unconventional lines of inquiry. hewas one of those struck by the similarity in shape between the facing coastlines of africa andsouth america, and from this observation he developed the idea that the continents had onceslid around. he suggested—presciently as it turned out—that the crunching together ofcontinents could have thrust up the world’s mountain chains. he failed, however, to producemuch in the way of evidence, and the theory was considered too crackpot to merit seriousattention.

in germany, however, taylor’s idea was picked up, and effectively appropriated, by atheorist named alfred wegener, a meteorologist at the university of marburg. wegenerinvestigated the many plant and fossil anomalies that did not fit comfortably into the standardmodel of earth history and realized that very little of it made sense if conventionallyinterpreted. animal fossils repeatedly turned up on opposite sides of oceans that were clearlytoo wide to swim. how, he wondered, did marsupials travel from south america to australia?

how did identical snails turn up in scandinavia and new england? and how, come to that,did one account for coal seams and other semi-tropical remnants in frigid spots likespitsbergen, four hundred miles north of norway, if they had not somehow migrated therefrom warmer climes?

wegener developed the theory that the world’s continents had once come together in asingle landmass he called pangaea, where flora and fauna had been able to mingle, before thecontinents had split apart and floated off to their present positions. all this he put together in abook called die entstehung der kontinente und ozeane, or the origin of continents and
oceans, which was published in german in 1912 and—despite the outbreak of the firstworld war in the meantime—in english three years later.

because of the war, wegener’s theory didn’t attract much notice at first, but by 1920, whenhe produced a revised and expanded edition, it quickly became a subject of discussion.

everyone agreed that continents moved—but up and down, not sideways. the process ofvertical movement, known as isostasy, was a foundation of geological beliefs for generations,though no one had any good theories as to how or why it happened. one idea, which remainedin textbooks well into my own school days, was the baked apple theory propounded by theaustrian eduard suess just before the turn of the century. this suggested that as the moltenearth had cooled, it had become wrinkled in the manner of a baked apple, creating oceanbasins and mountain ranges. never mind that james hutton had shown long before that anysuch static arrangement would eventually result in a featureless spheroid as erosion leveledthe bumps and filled in the divots. there was also the problem, demonstrated by rutherfordand soddy early in the century, that earthly elements hold huge reserves of heat—much toomuch to allow for the sort of cooling and shrinking suess suggested. and anyway, if suess’stheory was correct then mountains should be evenly distributed across the face of the earth,which patently they were not, and of more or less the same ages; yet by the early 1900s it wasalready evident that some ranges, like the urals and appalachians, were hundreds of millionsof years older than others, like the alps and rockies. clearly the time was ripe for a newtheory. unfortunately, alfred wegener was not the man that geologists wished to provide it.

for a start, his radical notions questioned the foundations of their discipline, seldom aneffective way to generate warmth in an audience. such a challenge would have been painfulenough coming from a geologist, but wegener had no background in geology. he was ameteorologist, for goodness sake. a weatherman—a german weatherman. these were notremediable deficiencies.

and so geologists took every pain they could think of to dismiss his evidence and belittlehis suggestions. to get around the problems of fossil distributions, they posited ancient “landbridges” wherever they were needed. when an ancient horse named hipparion was found tohave lived in france and florida at the same time, a land bridge was drawn across theatlantic. when it was realized that ancient tapirs had existed simultaneously in southamerica and southeast asia a land bridge was drawn there, too. soon maps of prehistoricseas were almost solid with hypothesized land bridges—from north america to europe, frombrazil to africa, from southeast asia to australia, from australia to antarctica. theseconnective tendrils had not only conveniently appeared whenever it was necessary to move aliving organism from one landmass to another, but then obligingly vanished without leaving atrace of their former existence. none of this, of course, was supported by so much as a grainof actual evidence—nothing so wrong could be—yet it was geological orthodoxy for the nexthalf century.

even land bridges couldn’t explain some things. one species of trilobite that was wellknown in europe was also found to have lived on newfoundland—but only on one side. noone could persuasively explain how it had managed to cross two thousand miles of hostileocean but then failed to find its way around the corner of a 200-mile-wide island. even moreawkwardly anomalous was another species of trilobite found in europe and the pacificnorthwest but nowhere in between, which would have required not so much a land bridge as aflyover. yet as late as 1964 when the encyclopaedia britannica discussed the rival theories, itwas wegener’s that was held to be full of “numerous grave theoretical difficulties.”

to be sure, wegener made mistakes. he asserted that greenland is drifting west by about amile a year, which is clearly nonsense. (it’s more like half an inch.) above all, he could offerno convincing explanation for how the landmasses moved about. to believe in his theory youhad to accept that massive continents somehow pushed through solid crust, like a plowthrough soil, without leaving any furrow in their wake. nothing then known could plausiblyexplain what motored these massive movements.

it was arthur holmes, the english geologist who did so much to determine the age of theearth, who suggested a possible way. holmes was the first scientist to understand thatradioactive warming could produce convection currents within the earth. in theory thesecould be powerful enough to slide continents around on the surface. in his popular andinfluential textbook principles of physical geology , first published in 1944, holmes laid outa continental drift theory that was in its fundamentals the theory that prevails today. it wasstill a radical proposition for the time and widely criticized, particularly in the united states,where resistance to drift lasted longer than elsewhere. one reviewer there fretted, without anyevident sense of irony, that holmes presented his arguments so clearly and compellingly thatstudents might actually come to believe them.

elsewhere, however, the new theory drew steady if cautious support. in 1950, a vote at theannual meeting of the british association for the advancement of science showed that abouthalf of those present now embraced the idea of continental drift. (hapgood soon after citedthis figure as proof of how tragically misled british geologists had become.) curiously,holmes himself sometimes wavered in his conviction. in 1953 he confessed: “i have neversucceeded in freeing myself from a nagging prejudice against continental drift; in mygeological bones, so to speak, i feel the hypothesis is a fantastic one.”

continental drift was not entirely without support in the united states. reginald daly ofharvard spoke for it, but he, you may recall, was the man who suggested that the moon hadbeen formed by a cosmic impact, and his ideas tended to be considered interesting, evenworthy, but a touch too exuberant for serious consideration. and so most american academicsstuck to the belief that the continents had occupied their present positions forever and thattheir surface features could be attributed to something other than lateral motions.

interestingly, oil company geologists had known for years that if you wanted to find oil youhad to allow for precisely the sort of surface movements that were implied by plate tectonics.

but oil geologists didn’t write academic papers; they just found oil.

there was one other major problem with earth theories that no one had resolved, or evencome close to resolving. that was the question of where all the sediments went. every yearearth’s rivers carried massive volumes of eroded material—500 million tons of calcium, forinstance—to the seas. if you multiplied the rate of deposition by the number of years it hadbeen going on, it produced a disturbing figure: there should be about twelve miles ofsediments on the ocean bottoms—or, put another way, the ocean bottoms should by now bewell above the ocean tops. scientists dealt with this paradox in the handiest possible way.

they ignored it. but eventually there came a point when they could ignore it no longer.

in the second world war, a princeton university mineralogist named harry hess was putin charge of an attack transport ship, the uss cape johnson. aboard this vessel was a fancynew depth sounder called a fathometer, which was designed to facilitate inshore maneuvers
during beach landings, but hess realized that it could equally well be used for scientificpurposes and never switched it off, even when far out at sea, even in the heat of battle. whathe found was entirely unexpected. if the ocean floors were ancient, as everyone assumed, theyshould be thickly blanketed with sediments, like the mud on the bottom of a river or lake. buthess’s readings showed that the ocean floor offered anything but the gooey smoothness ofancient silts. it was scored everywhere with canyons, trenches, and crevasses and dotted withvolcanic seamounts that he called guyots after an earlier princeton geologist named arnoldguyot. all this was a puzzle, but hess had a war to take part in, and put such thoughts to theback of his mind.

after the war, hess returned to princeton and the preoccupations of teaching, but themysteries of the seafloor continued to occupy a space in his thoughts. meanwhile, throughoutthe 1950s oceanographers were undertaking more and more sophisticated surveys of theocean floors. in so doing, they found an even bigger surprise: the mightiest and mostextensive mountain range on earth was—mostly—underwater. it traced a continuous pathalong the world’s seabeds, rather like the stitching on a baseball. if you began at iceland, youcould follow it down the center of the atlantic ocean, around the bottom of africa, and acrossthe indian and southern oceans, below australia; there it angled across the pacific as ifmaking for baja california before shooting up the west coast of the united states to alaska.

occasionally its higher peaks poked above the water as an island or archipelago—the azoresand canaries in the atlantic, hawaii in the pacific, for instance—but mostly it was buriedunder thousands of fathoms of salty sea, unknown and unsuspected. when all its brancheswere added together, the network extended to 46,600 miles.

a very little of this had been known for some time. people laying ocean-floor cables in thenineteenth century had realized that there was some kind of mountainous intrusion in the mid-atlantic from the way the cables ran, but the continuous nature and overall scale of the chainwas a stunning surprise. moreover, it contained physical anomalies that couldn’t be explained.

down the middle of the mid-atlantic ridge was a canyon—a rift—up to a dozen miles widefor its entire 12,000-mile length. this seemed to suggest that the earth was splitting apart atthe seams, like a nut bursting out of its shell. it was an absurd and unnerving notion, but theevidence couldn’t be denied.

then in 1960 core samples showed that the ocean floor was quite young at the mid-atlanticridge but grew progressively older as you moved away from it to the east or west. harry hessconsidered the matter and realized that this could mean only one thing: new ocean crust wasbeing formed on either side of the central rift, then being pushed away from it as new crustcame along behind. the atlantic floor was effectively two large conveyor belts, one carryingcrust toward north america, the other carrying crust toward europe. the process becameknown as seafloor spreading.

when the crust reached the end of its journey at the boundary with continents, it plungedback into the earth in a process known as subduction. that explained where all the sedimentwent. it was being returned to the bowels of the earth. it also explained why ocean floorseverywhere were so comparatively youthful. none had ever been found to be older than about175 million years, which was a puzzle because continental rocks were often billions of yearsold. now hess could see why. ocean rocks lasted only as long as it took them to travel toshore. it was a beautiful theory that explained a great deal. hess elaborated his ideas in animportant paper, which was almost universally ignored. sometimes the world just isn’t readyfor a good idea.

meanwhile, two researchers, working independently, were making some startling findingsby drawing on a curious fact of earth history that had been discovered several decades earlier.

in 1906, a french physicist named bernard brunhes had found that the planet’s magnetic fieldreverses itself from time to time, and that the record of these reversals is permanently fixed incertain rocks at the time of their birth. specifically, tiny grains of iron ore within the rockspoint to wherever the magnetic poles happen to be at the time of their formation, then staypointing in that direction as the rocks cool and harden. in effect they “remember” where themagnetic poles were at the time of their creation. for years this was little more than acuriosity, but in the 1950s patrick blackett of the university of london and s. k. runcorn ofthe university of newcastle studied the ancient magnetic patterns frozen in british rocks andwere startled, to say the very least, to find them indicating that at some time in the distant pastbritain had spun on its axis and traveled some distance to the north, as if it had somehowcome loose from its moorings. moreover, they also discovered that if you placed a map ofeurope’s magnetic patterns alongside an american one from the same period, they fit togetheras neatly as two halves of a torn letter. it was uncanny.

their findings were ignored too.

it finally fell to two men from cambridge university, a geophysicist named drummondmatthews and a graduate student of his named fred vine, to draw all the strands together. in1963, using magnetic studies of the atlantic ocean floor, they demonstrated conclusively thatthe seafloors were spreading in precisely the manner hess had suggested and that thecontinents were in motion too. an unlucky canadian geologist named lawrence morley cameup with the same conclusion at the same time, but couldn’t find anyone to publish his paper.

in what has become a famous snub, the editor of the journal of geophysical research toldhim: “such speculations make interesting talk at cocktail parties, but it is not the sort of thingthat ought to be published under serious scientific aegis.” one geologist later described it as“probably the most significant paper in the earth sciences ever to be denied publication.”

at all events, mobile crust was an idea whose time had finally come. a symposium ofmany of the most important figures in the field was convened in london under the auspices ofthe royal society in 1964, and suddenly, it seemed, everyone was a convert. the earth, themeeting agreed, was a mosaic of interconnected segments whose various stately jostlingsaccounted for much of the planet’s surface behavior.

the name “continental drift” was fairly swiftly discarded when it was realized that thewhole crust was in motion and not just the continents, but it took a while to settle on a namefor the individual segments. at first people called them “crustal blocks” or sometimes “pavingstones.” not until late 1968, with the publication of an article by three americanseismologists in the journal of geophysical research , did the segments receive the name bywhich they have since been known: plates. the same article called the new science platetectonics.

old ideas die hard, and not everyone rushed to embrace the exciting new theory. well intothe 1970s, one of the most popular and influential geological textbooks, the earth by thevenerable harold jeffreys, strenuously insisted that plate tectonics was a physicalimpossibility, just as it had in the first edition way back in 1924. it was equally dismissive ofconvection and seafloor spreading. and in basin and range, published in 1980, john mcpheenoted that even then one american geologist in eight still didn’t believe in plate tectonics.

today we know that earth’s surface is made up of eight to twelve big plates (depending onhow you define big) and twenty or so smaller ones, and they all move in different directionsand at different speeds. some plates are large and comparatively inactive, others small butenergetic. they bear only an incidental relationship to the landmasses that sit upon them. thenorth american plate, for instance, is much larger than the continent with which it isassociated. it roughly traces the outline of the continent’s western coast (which is why thatarea is so seismically active, because of the bump and crush of the plate boundary), butignores the eastern seaboard altogether and instead extends halfway across the atlantic to themid-ocean ridge. iceland is split down the middle, which makes it tectonically half americanand half european. new zealand, meanwhile, is part of the immense indian ocean plate eventhough it is nowhere near the indian ocean. and so it goes for most plates.

the connections between modern landmasses and those of the past were found to beinfinitely more complex than anyone had imagined. kazakhstan, it turns out, was onceattached to norway and new england. one corner of staten island, but only a corner, iseuropean. so is part of newfoundland. pick up a pebble from a massachusetts beach, and itsnearest kin will now be in africa. the scottish highlands and much of scandinavia aresubstantially american. some of the shackleton range of antarctica, it is thought, may oncehave belonged to the appalachians of the eastern u.s. rocks, in short, get around.

the constant turmoil keeps the plates from fusing into a single immobile plate. assumingthings continue much as at present, the atlantic ocean will expand until eventually it is muchbigger than the pacific. much of california will float off and become a kind of madagascar ofthe pacific. africa will push northward into europe, squeezing the mediterranean out ofexistence and thrusting up a chain of mountains of himalayan majesty running from paris tocalcutta. australia will colonize the islands to its north and connect by some isthmianumbilicus to asia. these are future outcomes, but not future events. the events are happeningnow. as we sit here, continents are adrift, like leaves on a pond. thanks to global positioningsystems we can see that europe and north america are parting at about the speed a fingernailgrows—roughly two yards in a human lifetime. if you were prepared to wait long enough,you could ride from los angeles all the way up to san francisco. it is only the brevity oflifetimes that keeps us from appreciating the changes. look at a globe and what you areseeing really is a snapshot of the continents as they have been for just one-tenth of 1 percentof the earth’s history.

earth is alone among the rocky planets in having tectonics, and why this should be is a bitof a mystery. it is not simply a matter of size or density—venus is nearly a twin of earth inthese respects and yet has no tectonic activity. it is thought—though it is really nothing morethan a thought—that tectonics is an important part of the planet’s organic well-being. as thephysicist and writer james trefil has put it, “it would be hard to believe that the continuousmovement of tectonic plates has no effect on the development of life on earth.” he suggeststhat the challenges induced by tectonics—changes in climate, for instance—were animportant spur to the development of intelligence. others believe the driftings of thecontinents may have produced at least some of the earth’s various extinction events. innovember of 2002, tony dickson of cambridge university in england produced a report,published in the journal science, strongly suggesting that there may well be a relationshipbetween the history of rocks and the history of life. what dickson established was that thechemical composition of the world’s oceans has altered abruptly and vigorously throughoutthe past half billion years and that these changes often correlate with important events inbiological history—the huge outburst of tiny organisms that created the chalk cliffs ofengland’s south coast, the sudden fashion for shells among marine organisms during the
cambrian period, and so on. no one can say what causes the oceans’ chemistry to change sodramatically from time to time, but the opening and shutting of ocean ridges would be anobvious possible culprit.

at all events, plate tectonics not only explained the surface dynamics of the earth—how anancient hipparion got from france to florida, for example—but also many of its internalactions. earthquakes, the formation of island chains, the carbon cycle, the locations ofmountains, the coming of ice ages, the origins of life itself—there was hardly a matter thatwasn’t directly influenced by this remarkable new theory. geologists, as mcphee has noted,found themselves in the giddying position that “the whole earth suddenly made sense.”

but only up to a point. the distribution of continents in former times is much less neatlyresolved than most people outside geophysics think. although textbooks give confident-looking representations of ancient landmasses with names like laurasia, gondwana, rodinia,and pangaea, these are sometimes based on conclusions that don’t altogether hold up. asgeorge gaylord simpson observes in fossils and the history of life, species of plants andanimals from the ancient world have a habit of appearing inconveniently where they shouldn’tand failing to be where they ought.

the outline of gondwana, a once-mighty continent connecting australia, africa,antarctica, and south america, was based in large part on the distribution of a genus ofancient tongue fern called glossopteris, which was found in all the right places. however,much later glossopteris was also discovered in parts of the world that had no knownconnection to gondwana. this troubling discrepancy was—and continues to be—mostlyignored. similarly a triassic reptile called lystrosaurus has been found from antarctica allthe way to asia, supporting the idea of a former connection between those continents, but ithas never turned up in south america or australia, which are believed to have been part ofthe same continent at the same time.

there are also many surface features that tectonics can’t explain. take denver. it is, aseveryone knows, a mile high, but that rise is comparatively recent. when dinosaurs roamedthe earth, denver was part of an ocean bottom, many thousands of feet lower. yet the rockson which denver sits are not fractured or deformed in the way they would be if denver hadbeen pushed up by colliding plates, and anyway denver was too far from the plate edges to besusceptible to their actions. it would be as if you pushed against the edge of a rug hoping toraise a ruck at the opposite end. mysteriously and over millions of years, it appears thatdenver has been rising, like baking bread. so, too, has much of southern africa; a portion ofit a thousand miles across has risen nearly a mile in 100 million years without any knownassociated tectonic activity. australia, meanwhile, has been tilting and sinking. over the past100 million years as it has drifted north toward asia, its leading edge has sunk by some sixhundred feet. it appears that indonesia is very slowly drowning, and dragging australia downwith it. nothing in the theories of tectonics can explain any of this.

alfred wegener never lived to see his ideas vindicated. on an expedition to greenland in1930, he set out alone, on his fiftieth birthday, to check out a supply drop. he never returned.

he was found a few days later, frozen to death on the ice. he was buried on the spot and liesthere yet, but about a yard closer to north america than on the day he died.

einstein also failed to live long enough to see that he had backed the wrong horse. in fact,he died at princeton, new jersey, in 1955 before charles hapgood’s rubbishing of continentaldrift theories was even published.

the other principal player in the emergence of tectonics theory, harry hess, was also atprinceton at the time, and would spend the rest of his career there. one of his students was abright young fellow named walter alvarez, who would eventually change the world ofscience in a quite different way.

as for geology itself, its cataclysms had only just begun, and it was young alvarez whohelped to start the process.

part iv  dangerous planet

the history of any one part of the earth, like the life of a soldier, consists of long periods of boredom and short periods of terror.

-british geologist derek v. ager

13    BANG!

people knew for a long time that there was something odd about the earth beneath manson, iowa. in 1912, a man drilling a well for the town water supply reported bringing up alot of strangely deformed rock—“crystalline clast breccia with a melt matrix” and “overturnedejecta flap,” as it was later described in an official report. the water was odd too. it wasalmost as soft as rainwater. naturally occurring soft water had never been found in iowabefore.

though manson’s strange rocks and silken waters were matters of curiosity, forty-oneyears would pass before a team from the university of iowa got around to making a trip to thecommunity, then as now a town of about two thousand people in the northwest part of thestate. in 1953, after sinking a series of experimental bores, university geologists agreed thatthe site was indeed anomalous and attributed the deformed rocks to some ancient, unspecifiedvolcanic action. this was in keeping with the wisdom of the day, but it was also about aswrong as a geological conclusion can get.

the trauma to manson’s geology had come not from within the earth, but from at least 100million miles beyond. sometime in the very ancient past, when manson stood on the edge of ashallow sea, a rock about a mile and a half across, weighing ten billion tons and traveling atperhaps two hundred times the speed of sound ripped through the atmosphere and punchedinto the earth with a violence and suddenness that we can scarcely imagine. where mansonnow stands became in an instant a hole three miles deep and more than twenty miles across.

the limestone that elsewhere gives iowa its hard mineralized water was obliterated andreplaced by the shocked basement rocks that so puzzled the water driller in 1912.

the manson impact was the biggest thing that has ever occurred on the mainland unitedstates. of any type. ever. the crater it left behind was so colossal that if you stood on oneedge you would only just be able to see the other side on a good day. it would make the grandcanyon look quaint and trifling. unfortunately for lovers of spectacle, 2.5 million years ofpassing ice sheets filled the manson crater right to the top with rich glacial till, then graded itsmooth, so that today the landscape at manson, and for miles around, is as flat as a tabletop.

which is of course why no one has ever heard of the manson crater.

at the library in manson they are delighted to show you a collection of newspaper articlesand a box of core samples from a 1991–92 drilling program—indeed, they positively bustle toproduce them—but you have to ask to see them. nothing permanent is on display, andnowhere in the town is there any historical marker.

to most people in manson the biggest thing ever to happen was a tornado that rolled upmain street in 1979, tearing apart the business district. one of the advantages of all thatsurrounding flatness is that you can see danger from a long way off. virtually the whole townturned out at one end of main street and watched for half an hour as the tornado came toward
them, hoping it would veer off, then prudently scampered when it did not. four of them, alas,didn’t move quite fast enough and were killed. every june now manson has a weeklong eventcalled crater days, which was dreamed up as a way of helping people forget that unhappyanniversary. it doesn’t really have anything to do with the crater. nobody’s figured out a wayto capitalize on an impact site that isn’t visible.

“very occasionally we get people coming in and asking where they should go to see thecrater and we have to tell them that there is nothing to see,” says anna schlapkohl, the town’sfriendly librarian. “then they go away kind of disappointed.” however, most people,including most iowans, have never heard of the manson crater. even for geologists it barelyrates a footnote. but for one brief period in the 1980s, manson was the most geologicallyexciting place on earth.

the story begins in the early 1950s when a bright young geologist named eugeneshoemaker paid a visit to meteor crater in arizona. today meteor crater is the most famousimpact site on earth and a popular tourist attraction. in those days, however, it didn’t receivemany visitors and was still often referred to as barringer crater, after a wealthy miningengineer named daniel m. barringer who had staked a claim on it in 1903. barringer believedthat the crater had been formed by a ten-million-ton meteor, heavily freighted with iron andnickel, and it was his confident expectation that he would make a fortune digging it out.

unaware that the meteor and everything in it would have been vaporized on impact, hewasted a fortune, and the next twenty-six years, cutting tunnels that yielded nothing.

by the standards of today, crater research in the early 1900s was a trifle unsophisticated, tosay the least. the leading early investigator, g. k. gilbert of columbia university, modeledthe effects of impacts by flinging marbles into pans of oatmeal. (for reasons i cannot supply,gilbert conducted these experiments not in a laboratory at columbia but in a hotel room.)somehow from this gilbert concluded that the moon’s craters were indeed formed byimpacts—in itself quite a radical notion for the time—but that the earth’s were not. mostscientists refused to go even that far. to them, the moon’s craters were evidence of ancientvolcanoes and nothing more. the few craters that remained evident on earth (most had beeneroded away) were generally attributed to other causes or treated as fluky rarities.

by the time shoemaker came along, a common view was that meteor crater had beenformed by an underground steam explosion. shoemaker knew nothing about undergroundsteam explosions—he couldn’t: they don’t exist—but he did know all about blast zones. oneof his first jobs out of college was to study explosion rings at the yucca flats nuclear test sitein nevada. he concluded, as barringer had before him, that there was nothing at meteorcrater to suggest volcanic activity, but that there were huge distributions of other stuff—anomalous fine silicas and magnetites principally—that suggested an impact from space.

intrigued, he began to study the subject in his spare time.

working first with his colleague eleanor helin and later with his wife, carolyn, andassociate david levy, shoemaker began a systematic survey of the inner solar system. theyspent one week each month at the palomar observatory in california looking for objects,asteroids primarily, whose trajectories carried them across earth’s orbit.

“at the time we started, only slightly more than a dozen of these things had ever beendiscovered in the entire course of astronomical observation,” shoemaker recalled some yearslater in a television interview. “astronomers in the twentieth century essentially abandonedthe solar system,” he added. “their attention was turned to the stars, the galaxies.”

what shoemaker and his colleagues found was that there was more risk out there—a greatdeal more—than anyone had ever imagined.

asteroids, as most people know, are rocky objects orbiting in loose formation in a beltbetween mars and jupiter. in illustrations they are always shown as existing in a jumble, butin fact the solar system is quite a roomy place and the average asteroid actually will be abouta million miles from its nearest neighbor. nobody knows even approximately how manyasteroids there are tumbling through space, but the number is thought to be probably not lessthan a billion. they are presumed to be planets that never quite made it, owing to theunsettling gravitational pull of jupiter, which kept—and keeps—them from coalescing.

when asteroids were first detected in the 1800s—the very first was discovered on the firstday of the century by a sicilian named giuseppi piazzi—they were thought to be planets, andthe first two were named ceres and pallas. it took some inspired deductions by theastronomer william herschel to work out that they were nowhere near planet sized but muchsmaller. he called them asteroids—latin for “starlike”—which was slightly unfortunate asthey are not like stars at all. sometimes now they are more accurately called planetoids.

finding asteroids became a popular activity in the 1800s, and by the end of the centuryabout a thousand were known. the problem was that no one was systematically recordingthem. by the early 1900s, it had often become impossible to know whether an asteroid thatpopped into view was new or simply one that had been noted earlier and then lost track of. bythis time, too, astrophysics had moved on so much that few astronomers wanted to devotetheir lives to anything as mundane as rocky planetoids. only a few astronomers, notablygerard kuiper, the dutch-born astronomer for whom the kuiper belt of comets is named,took any interest in the solar system at all. thanks to his work at the mcdonald observatoryin texas, followed later by work done by others at the minor planet center in cincinnati andthe spacewatch project in arizona, a long list of lost asteroids was gradually whittled downuntil by the close of the twentieth century only one known asteroid was unaccounted for—anobject called 719 albert. last seen in october 1911, it was finally tracked down in 2000 afterbeing missing for eighty-nine years.

so from the point of view of asteroid research the twentieth century was essentially just along exercise in bookkeeping. it is really only in the last few years that astronomers havebegun to count and keep an eye on the rest of the asteroid community. as of july 2001,twenty-six thousand asteroids had been named and identified—half in just the previous twoyears. with up to a billion to identify, the count obviously has barely begun.

in a sense it hardly matters. identifying an asteroid doesn’t make it safe. even if everyasteroid in the solar system had a name and known orbit, no one could say what perturbationsmight send any of them hurtling toward us. we can’t forecast rock disturbances on our ownsurface. put them adrift in space and what they might do is beyond guessing. any asteroid outthere that has our name on it is very likely to have no other.

think of the earth’s orbit as a kind of freeway on which we are the only vehicle, but whichis crossed regularly by pedestrians who don’t know enough to look before stepping off thecurb. at least 90 percent of these pedestrians are quite unknown to us. we don’t know wherethey live, what sort of hours they keep, how often they come our way. all we know is that atsome point, at uncertain intervals, they trundle across the road down which we are cruising atsixty-six thousand miles an hour. as steven ostro of the jet propulsion laboratory has put it,“suppose that there was a button you could push and you could light up all the earth-crossing
asteroids larger than about ten meters, there would be over 100 million of these objects in thesky.” in short, you would see not a couple of thousand distant twinkling stars, but millionsupon millions upon millions of nearer, randomly moving objects—“all of which are capableof colliding with the earth and all of which are moving on slightly different courses throughthe sky at different rates. it would be deeply unnerving.” well, be unnerved because it isthere. we just can’t see it.

altogether it is thought—though it is really only a guess, based on extrapolating fromcratering rates on the moon—that some two thousand asteroids big enough to imperilcivilized existence regularly cross our orbit. but even a small asteroid—the size of a house,say—could destroy a city. the number of these relative tiddlers in earth-crossing orbits isalmost certainly in the hundreds of thousands and possibly in the millions, and they are nearlyimpossible to track.

the first one wasn’t spotted until 1991, and that was after it had already gone by. named1991 ba, it was noticed as it sailed past us at a distance of 106,000 miles—in cosmic termsthe equivalent of a bullet passing through one’s sleeve without touching the arm. two yearslater, another, somewhat larger asteroid missed us by just 90,000 miles—the closest pass yetrecorded. it, too, was not seen until it had passed and would have arrived without warning.

according to timothy ferris, writing in the new yorker, such near misses probably happentwo or three times a week and go unnoticed.

an object a hundred yards across couldn’t be picked up by any earth-based telescope untilit was within just a few days of us, and that is only if a telescope happened to be trained on it,which is unlikely because even now the number of people searching for such objects ismodest. the arresting analogy that is always made is that the number of people in the worldwho are actively searching for asteroids is fewer than the staff of a typical mcdonald’srestaurant. (it is actually somewhat higher now. but not much.)while gene shoemaker was trying to get people galvanized about the potential dangers ofthe inner solar system, another development—wholly unrelated on the face of it—was quietlyunfolding in italy with the work of a young geologist from the lamont doherty laboratory atcolumbia university. in the early 1970s, walter alvarez was doing fieldwork in a comelydefile known as the bottaccione gorge, near the umbrian hill town of gubbio, when he grewcurious about a thin band of reddish clay that divided two ancient layers of limestone—onefrom the cretaceous period, the other from the tertiary. this is a point known to geology asthe kt boundary,1and it marks the time, sixty-five million years ago, when the dinosaurs androughly half the world’s other species of animals abruptly vanish from the fossil record.

alvarez wondered what it was about a thin lamina of clay, barely a quarter of an inch thick,that could account for such a dramatic moment in earth’s history.

at the time the conventional wisdom about the dinosaur extinction was the same as it hadbeen in charles lyell’s day a century earlier—namely that the dinosaurs had died out overmillions of years. but the thinness of the clay layer clearly suggested that in umbria, if1it is kt rather than ct because c had already been appropriated for cambrian. depending on which sourceyou credit, the k comes either from the greek kreta or german kreide. both conveniently mean “chalk,” whichis also what cretaceous means.

nowhere else, something rather more abrupt had happened. unfortunately in the 1970s notests existed for determining how long such a deposit might have taken to accumulate.

in the normal course of things, alvarez almost certainly would have had to leave theproblem at that, but luckily he had an impeccable connection to someone outside hisdiscipline who could help—his father, luis. luis alvarez was an eminent nuclear physicist;he had won the nobel prize for physics the previous decade. he had always been mildlyscornful of his son’s attachment to rocks, but this problem intrigued him. it occurred to himthat the answer might lie in dust from space.

every year the earth accumulates some thirty thousand metric tons of “cosmicspherules”—space dust in plainer language—which would be quite a lot if you swept it intoone pile, but is infinitesimal when spread across the globe. scattered through this thin dustingare exotic elements not normally much found on earth. among these is the element iridium,which is a thousand times more abundant in space than in the earth’s crust (because, it isthought, most of the iridium on earth sank to the core when the planet was young).

alvarez knew that a colleague of his at the lawrence berkeley laboratory in california,frank asaro, had developed a technique for measuring very precisely the chemicalcomposition of clays using a process called neutron activation analysis. this involvedbombarding samples with neutrons in a small nuclear reactor and carefully counting thegamma rays that were emitted; it was extremely finicky work. previously asaro had used thetechnique to analyze pieces of pottery, but alvarez reasoned that if they measured the amountof one of the exotic elements in his son’s soil samples and compared that with its annual rateof deposition, they would know how long it had taken the samples to form. on an octoberafternoon in 1977, luis and walter alvarez dropped in on asaro and asked him if he wouldrun the necessary tests for them.

it was really quite a presumptuous request. they were asking asaro to devote months tomaking the most painstaking measurements of geological samples merely to confirm whatseemed entirely self-evident to begin with—that the thin layer of clay had been formed asquickly as its thinness suggested. certainly no one expected his survey to yield any dramaticbreakthroughs.

“well, they were very charming, very persuasive,” asaro recalled in an interview in 2002.

“and it seemed an interesting challenge, so i agreed to try. unfortunately, i had a lot of otherwork on, so it was eight months before i could get to it.” he consulted his notes from theperiod. “on june 21, 1978, at 1:45 p.m., we put a sample in the detector. it ran for 224minutes and we could see we were getting interesting results, so we stopped it and had alook.”

the results were so unexpected, in fact, that the three scientists at first thought they had tobe wrong. the amount of iridium in the alvarez sample was more than three hundred timesnormal levels—far beyond anything they might have predicted. over the following monthsasaro and his colleague helen michel worked up to thirty hours at a stretch (“once youstarted you couldn’t stop,” asaro explained) analyzing samples, always with the same results.

tests on other samples—from denmark, spain, france, new zealand, antarctica—showedthat the iridium deposit was worldwide and greatly elevated everywhere, sometimes by asmuch as five hundred times normal levels. clearly something big and abrupt, and probablycataclysmic, had produced this arresting spike.

after much thought, the alvarezes concluded that the most plausible explanation—plausible to them, at any rate—was that the earth had been struck by an asteroid or comet.

the idea that the earth might be subjected to devastating impacts from time to time was notquite as new as it is now sometimes presented. as far back as 1942, a northwesternuniversity astrophysicist named ralph b. baldwin had suggested such a possibility in anarticle in popular astronomy magazine. (he published the article there because no academicpublisher was prepared to run it.) and at least two well-known scientists, the astronomerernst ?pik and the chemist and nobel laureate harold urey, had also voiced support for thenotion at various times. even among paleontologists it was not unknown. in 1956 a professorat oregon state university, m. w. de laubenfels, writing in the journal of paleontology, hadactually anticipated the alvarez theory by suggesting that the dinosaurs may have been dealt adeath blow by an impact from space, and in 1970 the president of the americanpaleontological society, dewey j. mclaren, proposed at the group’s annual conference thepossibility that an extraterrestrial impact may have been the cause of an earlier event knownas the frasnian extinction.

as if to underline just how un-novel the idea had become by this time, in 1979 ahollywood studio actually produced a movie called meteor (“it’s five miles wide . . . it’scoming at 30,000 m.p.h.—and there’s no place to hide!”) starring henry fonda, nataliewood, karl malden, and a very large rock.

so when, in the first week of 1980, at a meeting of the american association for theadvancement of science, the alvarezes announced their belief that the dinosaur extinctionhad not taken place over millions of years as part of some slow inexorable process, butsuddenly in a single explosive event, it shouldn’t have come as a shock.

but it did. it was received everywhere, but particularly in the paleontological community,as an outrageous heresy.

“well, you have to remember,” asaro recalls, “that we were amateurs in this field. walterwas a geologist specializing in paleomagnetism, luis was a physicist and i was a nuclearchemist. and now here we were telling paleontologists that we had solved a problem that hadeluded them for over a century. it’s not terribly surprising that they didn’t embrace itimmediately.” as luis alvarez joked: “we were caught practicing geology without alicense.”

but there was also something much deeper and more fundamentally abhorrent in the impacttheory. the belief that terrestrial processes were gradual had been elemental in natural historysince the time of lyell. by the 1980s, catastrophism had been out of fashion for so long that ithad become literally unthinkable. for most geologists the idea of a devastating impact was, aseugene shoemaker noted, “against their scientific religion.”

nor did it help that luis alvarez was openly contemptuous of paleontologists and theircontributions to scientific knowledge. “they’re really not very good scientists. they’re morelike stamp collectors,” he wrote in the new york times in an article that stings yet.

opponents of the alvarez theory produced any number of alternative explanations for theiridium deposits—for instance, that they were generated by prolonged volcanic eruptions inindia called the deccan traps—and above all insisted that there was no proof that thedinosaurs disappeared abruptly from the fossil record at the iridium boundary. one of the
most vigorous opponents was charles officer of dartmouth college. he insisted that theiridium had been deposited by volcanic action even while conceding in a newspaper interviewthat he had no actual evidence of it. as late as 1988 more than half of all americanpaleontologists contacted in a survey continued to believe that the extinction of the dinosaurswas in no way related to an asteroid or cometary impact.

the one thing that would most obviously support the alvarezes’ theory was the one thingthey didn’t have—an impact site. enter eugene shoemaker. shoemaker had an iowaconnection—his daughter-in-law taught at the university of iowa—and he was familiar withthe manson crater from his own studies. thanks to him, all eyes now turned to iowa.

geology is a profession that varies from place to place. in iowa, a state that is flat andstratigraphically uneventful, it tends to be comparatively serene. there are no alpine peaks orgrinding glaciers, no great deposits of oil or precious metals, not a hint of a pyroclastic flow.

if you are a geologist employed by the state of iowa, a big part of the work you do is toevaluate manure management plans, which all the state’s “animal confinement operators”—hog farmers to the rest of us—are required to file periodically. there are fifteen million hogsin iowa, so a lot of manure to manage. i’m not mocking this at all—it’s vital and enlightenedwork; it keeps iowa’s water clean—but with the best will in the world it’s not exactly dodginglava bombs on mount pinatubo or scrabbling over crevasses on the greenland ice sheet insearch of ancient life-bearing quartzes. so we may well imagine the flutter of excitement thatswept through the iowa department of natural resources when in the mid-1980s the world’sgeological attention focused on manson and its crater.

trowbridge hall in iowa city is a turn-of-the-century pile of red brick that houses theuniversity of iowa’s earth sciences department and—way up in a kind of garret—thegeologists of the iowa department of natural resources. no one now can remember quitewhen, still less why, the state geologists were placed in an academic facility, but you get theimpression that the space was conceded grudgingly, for the offices are cramped and low-ceilinged and not very accessible. when being shown the way, you half expect to be taken outonto a roof ledge and helped in through a window.

ray anderson and brian witzke spend their working lives up here amid disordered heapsof papers, journals, furled charts, and hefty specimen stones. (geologists are never at a lossfor paperweights.) it’s the kind of space where if you want to find anything—an extra chair, acoffee cup, a ringing telephone—you have to move stacks of documents around.

“suddenly we were at the center of things,” anderson told me, gleaming at the memory ofit, when i met him and witzke in their offices on a dismal, rainy morning in june. “it was awonderful time.”

i asked them about gene shoemaker, a man who seems to have been universally revered.

“he was just a great guy,” witzke replied without hesitation. “if it hadn’t been for him, thewhole thing would never have gotten off the ground. even with his support, it took two yearsto get it up and running. drilling’s an expensive business—about thirty-five dollars a footback then, more now, and we needed to go down three thousand feet.”

“sometimes more than that,” anderson added.

“sometimes more than that,” witzke agreed. “and at several locations. so you’re talking alot of money. certainly more than our budget would allow.”

so  a  collaboration  was  formed  between the Iowa geological survey and the u.s. geological survey.

“at least we thought it was a collaboration,” said Anderson, producing a small pained smile.

“it was a real learning curve for us,” witzke went on. “there was actually quite a lot of badscience going on throughout the period—people rushing in with results that didn’t alwaysstand up to scrutiny.” one of those moments came at the annual meeting of the americangeophysical union in 1985, when glenn izett and c. l. pillmore of the u.s. geologicalsurvey announced that the manson crater was of the right age to have been involved with thedinosaurs’ extinction. the declaration attracted a good deal of press attention but wasunfortunately premature. a more careful examination of the data revealed that manson wasnot only too small, but also nine million years too early.

the first anderson or witzke learned of this setback to their careers was when they arrivedat a conference in south dakota and found people coming up to them with sympathetic looksand saying: “we hear you lost your crater.” it was the first they knew that izett and the otherusgs scientists had just announced refined figures revealing that manson couldn’t after allhave been the extinction crater.

“it was pretty stunning,” recalls anderson. “i mean, we had this thing that was reallyimportant and then suddenly we didn’t have it anymore. but even worse was the realizationthat the people we thought we’d been collaborating with hadn’t bothered to share with us theirnew findings.”

“why not?”

he shrugged. “who knows? anyway, it was a pretty good insight into how unattractivescience can get when you’re playing at a certain level.”

the search moved elsewhere. by chance in 1990 one of the searchers, alan hildebrand ofthe university of arizona, met a reporter from the houston chronicle who happened to knowabout a large, unexplained ring formation, 120 miles wide and 30 miles deep, under mexico’syucatán peninsula at chicxulub, near the city of progreso, about 600 miles due south of neworleans. the formation had been found by pemex, the mexican oil company, in 1952—theyear, coincidentally, that gene shoemaker first visited meteor crater in arizona—but thecompany’s geologists had concluded that it was volcanic, in line with the thinking of the day.

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 discoveredcomet 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 comet was not a coherent sphere but a string of twenty-one fragments. “mysense,” wrote one, “is that jupiter will swallow these comets up without so much as a burp.”

one week before the impact, nature ran an article, “the big fizzle is coming,” 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 comet, 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 actuallycomparatively pristine.”

i asked them how much warning we would receive if a similar hunk of rock was comingtoward 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 completely 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 comet 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 compressed, as ina bicycle pump. as anyone who has used such a pump knows, compressed 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 encompassing 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 projectiles. beyond a thousand miles the devastation fromthe blast would gradually diminish.

but that’s just the initial shockwave. no one can do more than guess what the associateddamage would be, other than that it would be brisk and global. the impact would almostcertainly set off a chain of devastating earthquakes. volcanoes across the globe would beginto rumble and spew. tsunamis would rise up and head devastatingly for distant shores. withinan hour, a cloud of blackness would cover the planet, and burning rock and other debriswould be pelting down everywhere, setting much of the planet ablaze. it has been estimatedthat at least a billion and a half people would be dead by the end of the first day. the massivedisturbances to the ionosphere would knock out communications systems everywhere, sosurvivors would have no idea what was happening elsewhere or where to turn. it would hardlymatter. as one commentator has put it, fleeing would mean “selecting a slow death over aquick one. the death toll would be very little affected by any plausible relocation effort, sinceearth’s ability to support life would be universally diminished.”

the amount of soot and floating ash from the impact and following fires would blot out thesun, certainly for months, possibly for years, disrupting growing cycles. in 2001 researchers atthe california institute of technology analyzed helium isotopes from sediments left from thelater kt impact and concluded that it affected earth’s climate for about ten thousand years.

this was actually used as evidence to support the notion that the extinction of dinosaurs wasswift and emphatic—and so it was in geological terms. we can only guess how well, orwhether, humanity would cope with such an event.

and in all likelihood, remember, this would come without warning, out of a clear sky.

but let’s assume we did see the object coming. what would we do? everyone assumes wewould send up a nuclear warhead and blast it to smithereens. the idea has some problems,however. first, as john s. lewis notes, our missiles are not designed for space work. theyhaven’t the oomph to escape earth’s gravity and, even if they did, there are no mechanisms toguide them across tens of millions of miles of space. still less could we send up a shipload ofspace cowboys to do the job for us, as in the movie armageddon; we no longer possess arocket powerful enough to send humans even as far as the moon. the last rocket that could,saturn 5, was retired years ago and has never been replaced. nor could we quickly build anew one because, amazingly, the plans for saturn launchers were destroyed as part of anasa housecleaning exercise.

even if we did manage somehow to get a warhead to the asteroid and blasted it to pieces,the chances are that we would simply turn it into a string of rocks that would slam into us oneafter the other in the manner of comet shoemaker-levy on jupiter—but with the differencethat now the rocks would be intensely radioactive. tom gehrels, an asteroid hunter at theuniversity of arizona, thinks that even a year’s warning would probably be insufficient totake appropriate action. the greater likelihood, however, is that we wouldn’t see any object—even a comet—until it was about six months away, which would be much too late.

shoemaker-levy 9 had been orbiting jupiter in a fairly conspicuous manner since 1929, but ittook over half a century before anyone noticed.

interestingly, because these things are so difficult to compute and must incorporate such asignificant margin of error, even if we knew an object was heading our way we wouldn’tknow until nearly the end—the last couple of weeks anyway—whether collision was certain.

for most of the time of the object’s approach we would exist in a kind of cone of uncertainty.

it would certainly be the most interesting few months in the history of the world. and imaginethe party if it passed safely.

“so how often does something like the manson impact happen?” i asked anderson andwitzke before leaving.

“oh, about once every million years on average,” said witzke.

“and remember,” added anderson, “this was a relatively minor event. do you know howmany extinctions were associated with the manson impact?”

“no idea,” i replied.

“none,” he said, with a strange air of satisfaction. “not one.”

of course, witzke and anderson added hastily and more or less in unison, there wouldhave been terrible devastation across much of the earth, as just described, and completeannihilation for hundreds of miles around ground zero. but life is hardy, and when the smokecleared there were enough lucky survivors from every species that none permanentlyperished.

the good news, it appears, is that it takes an awful lot to extinguish a species. the badnews is that the good news can never be counted on. worse still, it isn’t actually necessary tolook to space for petrifying danger. as we are about to see, earth can provide plenty of dangerof its own.

14    THE FIRE BELOW

in the summer of 1971, a young geologist named mike voorhies was scouting around onsome grassy farmland in eastern nebraska, not far from the little town of orchard, where hehad grown up. passing through a steep-sided gully, he spotted a curious glint in the brushabove and clambered up to have a look. what he had seen was the perfectly preserved skull ofa young rhinoceros, which had been washed out by recent heavy rains.

a few yards beyond, it turned out, was one of the most extraordinary fossil beds everdiscovered in north america, a dried-up water hole that had served as a mass grave for scoresof animals—rhinoceroses, zebra-like horses, saber-toothed deer, camels, turtles. all had diedfrom some mysterious cataclysm just under twelve million years ago in the time known togeology as the miocene. in those days nebraska stood on a vast, hot plain very like theserengeti of africa today. the animals had been found buried under volcanic ash up to tenfeet deep. the puzzle of it was that there were not, and never had been, any volcanoes innebraska.

today, the site of voorhies’s discovery is called ashfall fossil beds state park, and it has astylish new visitors’ center and museum, with thoughtful displays on the geology of nebraskaand the history of the fossil beds. the center incorporates a lab with a glass wall throughwhich visitors can watch paleontologists cleaning bones. working alone in the lab on themorning i passed through was a cheerfully grizzled-looking fellow in a blue work shirt whomi recognized as mike voorhies from a bbc television documentary in which he featured.

they don’t get a huge number of visitors to ashfall fossil beds state park—it’s slightly inthe middle of nowhere—and voorhies seemed pleased to show me around. he took me to thespot atop a twenty-foot ravine where he had made his find.

“it was a dumb place to look for bones,” he said happily. “but i wasn’t looking for bones. iwas thinking of making a geological map of eastern nebraska at the time, and really just kindof poking around. if i hadn’t gone up this ravine or the rains hadn’t just washed out that skull,i’d have walked on by and this would never have been found.” he indicated a roofedenclosure nearby, which had become the main excavation site. some two hundred animalshad been found lying together in a jumble.

i asked him in what way it was a dumb place to hunt for bones. “well, if you’re looking forbones, you really need exposed rock. that’s why most paleontology is done in hot, dry places.

it’s not that there are more bones there. it’s just that you have some chance of spotting them.

in a setting like this”—he made a sweeping gesture across the vast and unvarying prairie—“you wouldn’t know where to begin. there could be really magnificent stuff out there, butthere’s no surface clues to show you where to start looking.”

at first they thought the animals were buried alive, and voorhies stated as much in anational geographic article in 1981. “the article called the site a ‘pompeii of prehistoric
animals,’ ” he told me, “which was unfortunate because just afterward we realized that theanimals hadn’t died suddenly at all. they were all suffering from something calledhypertrophic pulmonary osteodystrophy, which is what you would get if you were breathing alot of abrasive ash—and they must have been breathing a lot of it because the ash was feetthick for hundreds of miles.” he picked up a chunk of grayish, claylike dirt and crumbled itinto my hand. it was powdery but slightly gritty. “nasty stuff to have to breathe,” he went on,“because it’s very fine but also quite sharp. so anyway they came here to this watering hole,presumably seeking relief, and died in some misery. the ash would have ruined everything. itwould have buried all the grass and coated every leaf and turned the water into an undrinkablegray sludge. it couldn’t have been very agreeable at all.”

the bbc documentary had suggested that the existence of so much ash in nebraska was asurprise. in fact, nebraska’s huge ash deposits had been known about for a long time. foralmost a century they had been mined to make household cleaning powders like comet andajax. but curiously no one had ever thought to wonder where all the ash came from.

“i’m a little embarrassed to tell you,” voorhies said, smiling briefly, “that the first i thoughtabout it was when an editor at the national geographic asked me the source of all the ash andi had to confess that i didn’t know. nobody knew.”

voorhies sent samples to colleagues all over the western united states asking if there wasanything about it that they recognized. several months later a geologist named billbonnichsen from the idaho geological survey got in touch and told him that the ash matcheda volcanic deposit from a place called bruneau-jarbidge in southwest idaho. the event thatkilled the plains animals of nebraska was a volcanic explosion on a scale previouslyunimagined—but big enough to leave an ash layer ten feet deep almost a thousand miles awayin eastern nebraska. it turned out that under the western united states there was a hugecauldron of magma, a colossal volcanic hot spot, which erupted cataclysmically every600,000 years or so. the last such eruption was just over 600,000 years ago. the hot spot isstill there. these days we call it yellowstone national park.

we know amazingly little about what happens beneath our feet. it is fairly remarkable tothink that ford has been building cars and baseball has been playing world series for longerthan we have known that the earth has a core. and of course the idea that the continents moveabout on the surface like lily pads has been common wisdom for much less than a generation.

“strange as it may seem,” wrote richard feynman, “we understand the distribution of matterin the interior of the sun far better than we understand the interior of the earth.”

the distance from the surface of earth to the center is 3,959 miles, which isn’t so very far.

it has been calculated that if you sunk a well to the center and dropped a brick into it, it wouldtake only forty-five minutes for it to hit the bottom (though at that point it would beweightless since all the earth’s gravity would be above and around it rather than beneath it).

our own attempts to penetrate toward the middle have been modest indeed. one or two southafrican gold mines reach to a depth of two miles, but most mines on earth go no more thanabout a quarter of a mile beneath the surface. if the planet were an apple, we wouldn’t yethave broken through the skin. indeed, we haven’t even come close.

until slightly under a century ago, what the best-informed scientific minds knew aboutearth’s interior was not much more than what a coal miner knew—namely, that you could dig
down through soil for a distance and then you’d hit rock and that was about it. then in 1906,an irish geologist named r. d. oldham, while examining some seismograph readings from anearthquake in guatemala, noticed that certain shock waves had penetrated to a point deepwithin the earth and then bounced off at an angle, as if they had encountered some kind ofbarrier. from this he deduced that the earth has a core. three years later a croatianseismologist named andrija mohorovi?i′c was studying graphs from an earthquake in zagrebwhen he noticed a similar odd deflection, but at a shallower level. he had discovered theboundary between the crust and the layer immediately below, the mantle; this zone has beenknown ever since as the mohorovi?i′c discontinuity, or moho for short.

we were beginning to get a vague idea of the earth’s layered interior—though it really wasonly vague. not until 1936 did a danish scientist named inge lehmann, studyingseismographs of earthquakes in new zealand, discover that there were two cores—an innerone that we now believe to be solid and an outer one (the one that oldham had detected) thatis thought to be liquid and the seat of magnetism.

at just about the time that lehmann was refining our basic understanding of the earth’sinterior by studying the seismic waves of earthquakes, two geologists at caltech in californiawere devising a way to make comparisons between one earthquake and the next. they werecharles richter and beno gutenberg, though for reasons that have nothing to do with fairnessthe scale became known almost at once as richter’s alone. (it has nothing to do with richtereither. a modest fellow, he never referred to the scale by his own name, but always called it“the magnitude scale.”)the richter scale has always been widely misunderstood by nonscientists, though perhapsa little less so now than in its early days when visitors to richter’s office often asked to seehis celebrated scale, thinking it was some kind of machine. the scale is of course more anidea than an object, an arbitrary measure of the earth’s tremblings based on surfacemeasurements. it rises exponentially, so that a 7.3 quake is fifty times more powerful than a6.3 earthquake and 2,500 times more powerful than a 5.3 earthquake.

at least theoretically, there is no upper limit for an earthquake—nor, come to that, a lowerlimit. the scale is a simple measure of force, but says nothing about damage. a magnitude 7quake happening deep in the mantle—say, four hundred miles down—might cause no surfacedamage at all, while a significantly smaller one happening just four miles under the surfacecould wreak widespread devastation. much, too, depends on the nature of the subsoil, thequake’s duration, the frequency and severity of aftershocks, and the physical setting of theaffected area. all this means that the most fearsome quakes are not necessarily the mostforceful, though force obviously counts for a lot.

the largest earthquake since the scale’s invention was (depending on which source youcredit) either one centered on prince william sound in alaska in march 1964, whichmeasured 9.2 on the richter scale, or one in the pacific ocean off the coast of chile in 1960,which was initially logged at 8.6 magnitude but later revised upward by some authorities(including the united states geological survey) to a truly grand-scale 9.5. as you will gatherfrom this, measuring earthquakes is not always an exact science, particularly wheninterpreting readings from remote locations. at all events, both quakes were whopping. the1960 quake not only caused widespread damage across coastal south america, but also set offa giant tsunami that rolled six thousand miles across the pacific and slapped away much ofdowntown hilo, hawaii, destroying five hundred buildings and killing sixty people. similarwave surges claimed yet more victims as far away as japan and the philippines.

for pure, focused, devastation, however, probably the most intense earthquake in recordedhistory was one that struck—and essentially shook to pieces—lisbon, portugal, on all saintsday (november 1), 1755. just before ten in the morning, the city was hit by a suddensideways lurch now estimated at magnitude 9.0 and shaken ferociously for seven full minutes.

the convulsive force was so great that the water rushed out of the city’s harbor and returnedin a wave fifty feet high, adding to the destruction. when at last the motion ceased, survivorsenjoyed just three minutes of calm before a second shock came, only slightly less severe thanthe first. a third and final shock followed two hours later. at the end of it all, sixty thousandpeople were dead and virtually every building for miles reduced to rubble. the san franciscoearthquake of 1906, for comparison, measured an estimated 7.8 on the richter scale andlasted less than thirty seconds.

earthquakes are fairly common. every day on average somewhere in the world there aretwo of magnitude 2.0 or greater—that’s enough to give anyone nearby a pretty good jolt.

although they tend to cluster in certain places—notably around the rim of the pacific—theycan occur almost anywhere. in the united states, only florida, eastern texas, and the uppermidwest seem—so far—to be almost entirely immune. new england has had two quakes ofmagnitude 6.0 or greater in the last two hundred years. in april 2002, the region experienceda 5.1 magnitude shaking in a quake near lake champlain on the new york–vermont border,causing extensive local damage and (i can attest) knocking pictures from walls and childrenfrom beds as far away as new hampshire.

the most common types of earthquakes are those where two plates meet, as in californiaalong the san andreas fault. as the plates push against each other, pressures build up untilone or the other gives way. in general, the longer the interval between quakes, the greater thepent-up pressure and thus the greater the scope for a really big jolt. this is a particular worryfor tokyo, which bill mcguire, a hazards specialist at university college london, describesas “the city waiting to die” (not a motto you will find on many tourism leaflets). tokyo standson the boundary of three tectonic plates in a country already well known for its seismicinstability. in 1995, as you will remember, the city of kobe, three hundred miles to the west,was struck by a magnitude 7.2 quake, which killed 6,394 people. the damage was estimatedat $99 billion. but that was as nothing—well, as comparatively little—compared with whatmay await tokyo.

tokyo has already suffered one of the most devastating earthquakes in modern times. onseptember 1, 1923, just before noon, the city was hit by what is known as the great kantoquake—an event more than ten times more powerful than kobe’s earthquake. two hundredthousand people were killed. since that time, tokyo has been eerily quiet, so the strainbeneath the surface has been building for eighty years. eventually it is bound to snap. in 1923,tokyo had a population of about three million. today it is approaching thirty million. nobodycares to guess how many people might die, but the potential economic cost has been put ashigh as $7 trillion.

even more unnerving, because they are less well understood and capable of occurringanywhere at any time, are the rarer type of shakings known as intraplate quakes. thesehappen away from plate boundaries, which makes them wholly unpredictable. and becausethey come from a much greater depth, they tend to propagate over much wider areas. themost notorious such quakes ever to hit the united states were a series of three in newmadrid, missouri, in the winter of 1811–12. the adventure started just after midnight on
december 16 when people were awakened first by the noise of panicking farm animals (therestiveness of animals before quakes is not an old wives’ tale, but is in fact well established,though not at all understood) and then by an almighty rupturing noise from deep within theearth. emerging from their houses, locals found the land rolling in waves up to three feet highand opening up in fissures several feet deep. a strong smell of sulfur filled the air. theshaking lasted for four minutes with the usual devastating effects to property. among thewitnesses was the artist john james audubon, who happened to be in the area. the quakeradiated outward with such force that it knocked down chimneys in cincinnati four hundredmiles away and, according to at least one account, “wrecked boats in east coast harbors and .

. . even collapsed scaffolding erected around the capitol building in washington, d.c.” onjanuary 23 and february 4 further quakes of similar magnitude followed. new madrid hasbeen silent ever since—but not surprisingly, since such episodes have never been known tohappen in the same place twice. as far as we know, they are as random as lightning. the nextone could be under chicago or paris or kinshasa. no one can even begin to guess. and whatcauses these massive intraplate rupturings? something deep within the earth. more than thatwe don’t know.

by the 1960s scientists had grown sufficiently frustrated by how little they understood ofthe earth’s interior that they decided to try to do something about it. specifically, they got theidea to drill through the ocean floor (the continental crust was too thick) to the mohodiscontinuity and to extract a piece of the earth’s mantle for examination at leisure. thethinking was that if they could understand the nature of the rocks inside the earth, they mightbegin to understand how they interacted, and thus possibly be able to predict earthquakes andother unwelcome events.

the project became known, all but inevitably, as the mohole and it was pretty welldisastrous. the hope was to lower a drill through 14,000 feet of pacific ocean water off thecoast of mexico and drill some 17,000 feet through relatively thin crustal rock. drilling froma ship in open waters is, in the words of one oceanographer, “like trying to drill a hole in thesidewalks of new york from atop the empire state building using a strand of spaghetti.”

every attempt ended in failure. the deepest they penetrated was only about 600 feet. themohole became known as the no hole. in 1966, exasperated with ever-rising costs and noresults, congress killed the project.

four years later, soviet scientists decided to try their luck on dry land. they chose a spot onrussia’s kola peninsula, near the finnish border, and set to work with the hope of drilling toa depth of fifteen kilometers. the work proved harder than expected, but the soviets werecommendably persistent. when at last they gave up, nineteen years later, they had drilled to adepth of 12,262 meters, or about 7.6 miles. bearing in mind that the crust of the earthrepresents only about 0.3 percent of the planet’s volume and that the kola hole had not cuteven one-third of the way through the crust, we can hardly claim to have conquered theinterior.

interestingly, even though the hole was modest, nearly everything about it was surprising.

seismic wave studies had led the scientists to predict, and pretty confidently, that they wouldencounter sedimentary rock to a depth of 4,700 meters, followed by granite for the next 2,300meters and basalt from there on down. in the event, the sedimentary layer was 50 percentdeeper than expected and the basaltic layer was never found at all. moreover, the world downthere was far warmer than anyone had expected, with a temperature at 10,000 meters of 180
degrees centigrade, nearly twice the forecasted level. most surprising of all was that the rockat that depth was saturated with water—something that had not been thought possible.

because we can’t see into the earth, we have to use other techniques, which mostly involvereading waves as they travel through the interior. we also know a little bit about the mantlefrom what are known as kimberlite pipes, where diamonds are formed. what happens is thatdeep in the earth there is an explosion that fires, in effect, a cannonball of magma to thesurface at supersonic speeds. it is a totally random event. a kimberlite pipe could explode inyour backyard as you read this. because they come up from such depths—up to 120 milesdown—kimberlite pipes bring up all kinds of things not normally found on or near thesurface: a rock called peridotite, crystals of olivine, and—just occasionally, in about one pipein a hundred—diamonds. lots of carbon comes up with kimberlite ejecta, but most isvaporized or turns to graphite. only occasionally does a hunk of it shoot up at just the rightspeed and cool down with the necessary swiftness to become a diamond. it was such a pipethat made johannesburg the most productive diamond mining city in the world, but there maybe others even bigger that we don’t know about. geologists know that somewhere in thevicinity of northeastern indiana there is evidence of a pipe or group of pipes that may be trulycolossal. diamonds up to twenty carats or more have been found at scattered sites throughoutthe region. but no one has ever found the source. as john mcphee notes, it may be buriedunder glacially deposited soil, like the manson crater in iowa, or under the great lakes.

so how much do we know about what’s inside the earth? very little. scientists aregenerally agreed that the world beneath us is composed of four layers—rocky outer crust, amantle of hot, viscous rock, a liquid outer core, and a solid inner core.

1we know that thesurface is dominated by silicates, which are relatively light and not heavy enough to accountfor the planet’s overall density. therefore there must be heavier stuff inside. we know that togenerate our magnetic field somewhere in the interior there must be a concentrated belt ofmetallic elements in a liquid state. that much is universally agreed upon. almost everythingbeyond that—how the layers interact, what causes them to behave in the way they do, whatthey will do at any time in the future—is a matter of at least some uncertainty, and generallyquite a lot of uncertainty.

even the one part of it we can see, the crust, is a matter of some fairly strident debate.

nearly all geology texts tell you that continental crust is three to six miles thick under theoceans, about twenty-five miles thick under the continents, and forty to sixty miles thickunder big mountain chains, but there are many puzzling variabilities within thesegeneralizations. the crust beneath the sierra nevada mountains, for instance, is only aboutnineteen to twenty-five miles thick, and no one knows why. by all the laws of geophysics thesierra nevadas should be sinking, as if into quicksand. (some people think they may be.)1for those who crave a more detailed picture of the earths interior, here are the dimensions of the variouslayers, using average figures: from 0 to 40 km (25 mi) is the crust. from 40 to 400 km (25 to 250 mi) is theupper mantle. from 400 to 650 km (250 to 400 mi) is a transition zone between the upper and lower mantle.

from 650 to 2,700 km (400 to 1,700 mi) is the lower mantle. from 2,700 to 2,890 km (1,700 to 1,900 mi) is the”d” layer. from 2,890 to 5,150 km (1,900 to 3,200 mi) is the outer core, and from 5,150 to 6,378 km (3,200 to3,967 mi) is the inner core.

how and when the earth got its crust are questions that divide geologists into two broadcamps—those who think it happened abruptly early in the earth’s history and those who thinkit happened gradually and rather later. strength of feeling runs deep on such matters. richardarmstrong of yale proposed an early-burst theory in the 1960s, then spent the rest of hiscareer fighting those who did not agree with him. he died of cancer in 1991, but shortlybefore his death he “lashed out at his critics in a polemic in an australian earth science journalthat charged them with perpetuating myths,” according to a report inearth magazine in 1998.

“he died a bitter man,” reported a colleague.

the crust and part of the outer mantle together are called the lithosphere (from the greeklithos, meaning “stone”), which in turn floats on top of a layer of softer rock called theasthenosphere (from greek words meaning “without strength”), but such terms are neverentirely satisfactory. to say that the lithosphere floats on top of the asthenosphere suggests adegree of easy buoyancy that isn’t quite right. similarly it is misleading to think of the rocksas flowing in anything like the way we think of materials flowing on the surface. the rocksare viscous, but only in the same way that glass is. it may not look it, but all the glass on earthis flowing downward under the relentless drag of gravity. remove a pane of really old glassfrom the window of a european cathedral and it will be noticeably thicker at the bottom thanat the top. that is the sort of “flow” we are talking about. the hour hand on a clock movesabout ten thousand times faster than the “flowing” rocks of the mantle.

the movements occur not just laterally as the earth’s plates move across the surface, but upand down as well, as rocks rise and fall under the churning process known as convection.

convection as a process was first deduced by the eccentric count von rumford at the end ofthe eighteenth century. sixty years later an english vicar named osmond fisher prescientlysuggested that the earth’s interior might well be fluid enough for the contents to move about,but that idea took a very long time to gain support.

in about 1970, when geophysicists realized just how much turmoil was going on downthere, it came as a considerable shock. as shawna vogel put it in the book naked earth: thenew geophysics: “it was as if scientists had spent decades figuring out the layers of theearth’s atmosphere—troposphere, stratosphere, and so forth—and then had suddenly foundout about wind.”

how deep the convection process goes has been a matter of controversy ever since. somesay it begins four hundred miles down, others two thousand miles below us. the problem, asdonald trefil has observed, is that “there are two sets of data, from two different disciplines,that cannot be reconciled.” geochemists say that certain elements on earth’s surface cannothave come from the upper mantle, but must have come from deeper within the earth.

therefore the materials in the upper and lower mantle must at least occasionally mix.

seismologists insist that there is no evidence to support such a thesis.

so all that can be said is that at some slightly indeterminate point as we head toward thecenter of earth we leave the asthenosphere and plunge into pure mantle. considering that itaccounts for 82 percent of the earth’s volume and 65 percent of its mass, the mantle doesn’tattract a great deal of attention, largely because the things that interest earth scientists andgeneral readers alike happen either deeper down (as with magnetism) or nearer the surface (aswith earthquakes). we know that to a depth of about a hundred miles the mantle consistspredominantly of a type of rock known as peridotite, but what fills the space beyond isuncertain. according to a nature report, it seems not to be peridotite. more than this we donot know.

beneath the mantle are the two cores—a solid inner core and a liquid outer one. needless tosay, our understanding of the nature of these cores is indirect, but scientists can make somereasonable assumptions. they know that the pressures at the center of the earth aresufficiently high—something over three million times those found at the surface—to turn anyrock there solid. they also know from earth’s history (among other clues) that the inner coreis very good at retaining its heat. although it is little more than a guess, it is thought that inover four billion years the temperature at the core has fallen by no more than 200°f. no oneknows exactly how hot the earth’s core is, but estimates range from something over 7,000°fto 13,000°f—about as hot as the surface of the sun.

the outer core is in many ways even less well understood, though everyone is in agreementthat it is fluid and that it is the seat of magnetism. the theory was put forward by e. c.

bullard of cambridge university in 1949 that this fluid part of the earth’s core revolves in away that makes it, in effect, an electrical motor, creating the earth’s magnetic field. theassumption is that the convecting fluids in the earth act somehow like the currents in wires.

exactly what happens isn’t known, but it is felt pretty certain that it is connected with the corespinning and with its being liquid. bodies that don’t have a liquid core—the moon and mars,for instance—don’t have magnetism.

we know that earth’s magnetic field changes in power from time to time: during the age ofthe dinosaurs, it was up to three times as strong as now. we also know that it reverses itselfevery 500,000 years or so on average, though that average hides a huge degree ofunpredictability. the last reversal was about 750,000 years ago. sometimes it stays put formillions of years—37 million years appears to be the longest stretch—and at other times it hasreversed after as little as 20,000 years. altogether in the last 100 million years it has reverseditself about two hundred times, and we don’t have any real idea why. it has been called “thegreatest unanswered question in the geological sciences.”

we may be going through a reversal now. the earth’s magnetic field has diminished byperhaps as much as 6 percent in the last century alone. any diminution in magnetism is likelyto be bad news, because magnetism, apart from holding notes to refrigerators and keeping ourcompasses pointing the right way, plays a vital role in keeping us alive. space is full ofdangerous cosmic rays that in the absence of magnetic protection would tear through ourbodies, leaving much of our dna in useless tatters. when the magnetic field is working,these rays are safely herded away from the earth’s surface and into two zones in near spacecalled the van allen belts. they also interact with particles in the upper atmosphere to createthe bewitching veils of light known as the auroras.

a big part of the reason for our ignorance, interestingly enough, is that traditionally therehas been little effort to coordinate what’s happening on top of the earth with what’s going oninside. according to shawna vogel: “geologists and geophysicists rarely go to the samemeetings or collaborate on the same problems.”

perhaps nothing better demonstrates our inadequate grasp of the dynamics of the earth’sinterior than how badly we are caught out when it acts up, and it would be hard to come upwith a more salutary reminder of the limitations of our understanding than the eruption ofmount st. helens in washington in 1980.

at that time, the lower forty-eight united states had not seen a volcanic eruption for oversixty-five years. therefore the government volcanologists called in to monitor and forecast st.

helens’s behavior primarily had seen only hawaiian volcanoes in action, and they, it turnedout, were not the same thing at all.

20. helens started its ominous rumblings on march 20. within a week it was eruptingmagma, albeit in modest amounts, up to a hundred times a day, and being constantly shakenwith earthquakes. people were evacuated to what was assumed to be a safe distance of eightmiles. as the mountain’s rumblings grew st. helens became a tourist attraction for the world.

newspapers gave daily reports on the best places to get a view. television crews repeatedlyflew in helicopters to the summit, and people were even seen climbing over the mountain. onone day, more than seventy copters and light aircraft circled the summit. but as the dayspassed and the rumblings failed to develop into anything dramatic, people grew restless, andthe view became general that the volcano wasn’t going to blow after all.

on april 19 the northern flank of the mountain began to bulge conspicuously. remarkably,no one in a position of responsibility saw that this strongly signaled a lateral blast. theseismologists resolutely based their conclusions on the behavior of hawaiian volcanoes,which don’t blow out sideways. almost the only person who believed that something reallybad might happen was jack hyde, a geology professor at a community college in tacoma. hepointed out that st. helens didn’t have an open vent, as hawaiian volcanoes have, so anypressure building up inside was bound to be released dramatically and probablycatastrophically. however, hyde was not part of the official team and his observationsattracted little notice.

we all know what happened next. at 8:32 a.m. on a sunday morning, may 18, the northside of the volcano collapsed, sending an enormous avalanche of dirt and rock rushing downthe mountain slope at 150 miles an hour. it was the biggest landslide in human history andcarried enough material to bury the whole of manhattan to a depth of four hundred feet. aminute later, its flank severely weakened, st. helens exploded with the force of five hundredhiroshima-sized atomic bombs, shooting out a murderous hot cloud at up to 650 miles anhour—much too fast, clearly, for anyone nearby to outrace. many people who were thought tobe in safe areas, often far out of sight of the volcano, were overtaken. fifty-seven people werekilled. twenty-three of the bodies were never found. the toll would have been much higherexcept that it was a sunday. had it been a weekday many lumber workers would have beenworking within the death zone. as it was, people were killed eighteen miles away.

the luckiest person on that day was a graduate student named harry glicken. he had beenmanning an observation post 5.7 miles from the mountain, but he had a college placementinterview on may 18 in california, and so had left the site the day before the eruption. hisplace was taken by david johnston. johnston was the first to report the volcano exploding;moments later he was dead. his body was never found. glicken’s luck, alas, was temporary.

eleven years later he was one of forty-three scientists and journalists fatally caught up in alethal outpouring of superheated ash, gases, and molten rock—what is known as a pyroclasticflow—at mount unzen in japan when yet another volcano was catastrophically misread.

volcanologists may or may not be the worst scientists in the world at making predictions,but they are without question the worst in the world at realizing how bad their predictions are.

less than two years after the unzen catastrophe another group of volcano watchers, led bystanley williams of the university of arizona, descended into the rim of an active volcanocalled galeras in colombia. despite the deaths of recent years, only two of the sixteenmembers of williams’s party wore safety helmets or other protective gear. the volcano
erupted, killing six of the scientists, along with three tourists who had followed them, andseriously injuring several others, including williams himself.

in an extraordinarily unself-critical book called surviving galeras, williams said he could“only shake my head in wonder” when he learned afterward that his colleagues in the worldof volcanology had suggested that he had overlooked or disregarded important seismic signalsand behaved recklessly. “how easy it is to snipe after the fact, to apply the knowledge wehave now to the events of 1993,” he wrote. he was guilty of nothing worse, he believed, thanunlucky timing when galeras “behaved capriciously, as natural forces are wont to do. i wasfooled, and for that i will take responsibility. but i do not feel guilty about the deaths of mycolleagues. there is no guilt. there was only an eruption.”

but to return to washington. mount st. helens lost thirteen hundred feet of peak, and 230square miles of forest were devastated. enough trees to build 150,000 homes (or 300,000 insome reports) were blown away. the damage was placed at $2.7 billion. a giant column ofsmoke and ash rose to a height of sixty thousand feet in less than ten minutes. an airlinersome thirty miles away reported being pelted with rocks.

ninety  minutes  after  the  blast, ash  began to rain down on yakima, washington, acommunity of fifty thousand people about eighty miles away. as you would expect, the ashturned day to night and got into everything, clogging motors, generators, and electricalswitching equipment, choking pedestrians, blocking filtration systems, and generally bringingthings to a halt. the airport shut down and highways in and out of the city were closed.

all this was happening, you will note, just downwind of a volcano that had been rumblingmenacingly for two months. yet yakima had no volcano emergency procedures. the city’semergency broadcast system, which was supposed to swing into action during a crisis, did notgo on the air because “the sunday-morning staff did not know how to operate the equipment.”

for three days, yakima was paralyzed and cut off from the world, its airport closed, itsapproach roads impassable. altogether the city received just five-eighths of an inch of ashafter the eruption of mount st. helens. now bear that in mind, please, as we consider what ayellowstone blast would do.

15    DANGEROUS BEAUTY

in the 1960s, while studying the volcanic history of yellowstone national park, bobchristiansen of the united states geological survey became puzzled about something that,oddly, had not troubled anyone before: he couldn’t find the park’s volcano. it had been knownfor a long time that yellowstone was volcanic in nature—that’s what accounted for all itsgeysers and other steamy features—and the one thing about volcanoes is that they aregenerally pretty conspicuous. but christiansen couldn’t find the yellowstone volcanoanywhere. in particular what he couldn’t find was a structure known as a caldera.

most of us, when we think of volcanoes, think of the classic cone shapes of a fuji orkilimanjaro, which are created when erupting magma accumulates in a symmetrical mound.

these can form remarkably quickly. in 1943, at parícutin in mexico, a farmer was startled tosee smoke rising from a patch on his land. in one week he was the bemused owner of a conefive hundred feet high. within two years it had topped out at almost fourteen hundred feet andwas more than half a mile across. altogether there are some ten thousand of these intrusivelyvisible volcanoes on earth, all but a few hundred of them extinct. but there is a second, lesscelebrated type of volcano that doesn’t involve mountain building. these are volcanoes soexplosive that they burst open in a single mighty rupture, leaving behind a vast subsided pit,the caldera (from a latin word for cauldron). yellowstone obviously was of this second type,but christiansen couldn’t find the caldera anywhere.

by coincidence just at this time nasa decided to test some new high-altitude cameras bytaking photographs of yellowstone, copies of which some thoughtful official passed on to thepark authorities on the assumption that they might make a nice blow-up for one of thevisitors’ centers. as soon as christiansen saw the photos he realized why he had failed to spotthe caldera: virtually the whole park—2.2 million acres—was caldera. the explosion had lefta crater more than forty miles across—much too huge to be perceived from anywhere atground level. at some time in the past yellowstone must have blown up with a violence farbeyond the scale of anything known to humans.

yellowstone, it turns out, is a supervolcano. it sits on top of an enormous hot spot, areservoir of molten rock that rises from at least 125 miles down in the earth. the heat fromthe hot spot is what powers all of yellowstone’s vents, geysers, hot springs, and popping mudpots. beneath the surface is a magma chamber that is about forty-five miles across—roughlythe same dimensions as the park—and about eight miles thick at its thickest point. imagine apile of tnt about the size of rhode island and reaching eight miles into the sky, to about theheight of the highest cirrus clouds, and you have some idea of what visitors to yellowstoneare shuffling around on top of. the pressure that such a pool of magma exerts on the crustabove has lifted yellowstone and about three hundred miles of surrounding territory about1,700 feet higher than they would otherwise be. if it blew, the cataclysm is pretty well beyondimagining. according to professor bill mcguire of university college london, “youwouldn’t be able to get within a thousand kilometers of it” while it was erupting. theconsequences that followed would be even worse.

superplumes of the type on which yellowstone sits are rather like martini glasses—thin onthe way up, but spreading out as they near the surface to create vast bowls of unstable magma.

some of these bowls can be up to 1,200 miles across. according to theories, they don’talways erupt explosively but sometimes burst forth in a vast, continuous outpouring—aflood—of molten rock, such as with the deccan traps in india sixty-five million years ago.

(trap in this context comes from a swedish word for a type of lava; deccan is simply anarea.) these covered an area of 200,000 square miles and probably contributed to the demiseof the dinosaurs—they certainly didn’t help—with their noxious outgassings. superplumesmay also be responsible for the rifts that cause continents to break up.

such plumes are not all that rare. there are about thirty active ones on the earth at themoment, and they are responsible for many of the world’s best-known islands and islandchains—iceland, hawaii, the azores, canaries, and galápagos archipelagos, little pitcairn inthe middle of the south pacific, and many others—but apart from yellowstone they are alloceanic. no one has the faintest idea how or why yellowstone’s ended up beneath acontinental plate. only two things are certain: that the crust at yellowstone is thin and that theworld beneath it is hot. but whether the crust is thin because of the hot spot or whether the hotspot is there because the crust is thin is a matter of heated (as it were) debate. the continentalnature of the crust makes a huge difference to its eruptions. where the other supervolcanoestend to bubble away steadily and in a comparatively benign fashion, yellowstone blowsexplosively. it doesn’t happen often, but when it does you want to stand well back.

since its first known eruption 16.5 million years ago, it has blown up about a hundredtimes, but the most recent three eruptions are the ones that get written about. the last eruptionwas a thousand times greater than that of mount st. helens; the one before that was 280 timesbigger, and the one before was so big that nobody knows exactly how big it was. it was atleast twenty-five hundred times greater than st. helens, but perhaps eight thousand timesmore monstrous.

we have absolutely nothing to compare it to. the biggest blast in recent times was that ofkrakatau in indonesia in august 1883, which made a bang that reverberated around the worldfor nine days, and made water slosh as far away as the english channel. but if you imaginethe volume of ejected material from krakatau as being about the size of a golf ball, then thebiggest of the yellowstone blasts would be the size of a sphere you could just about hidebehind. on this scale, mount st. helens’s would be no more than a pea.

the yellowstone eruption of two million years ago put out enough ash to bury new yorkstate to a depth of sixty-seven feet or california to a depth of twenty. this was the ash thatmade mike voorhies’s fossil beds in eastern nebraska. that blast occurred in what is nowidaho, but over millions of years, at a rate of about one inch a year, the earth’s crust hastraveled over it, so that today it is directly under northwest wyoming. (the hot spot itselfstays in one place, like an acetylene torch aimed at a ceiling.) in its wake it leaves the sort ofrich volcanic plains that are ideal for growing potatoes, as idaho’s farmers long agodiscovered. in another two million years, geologists like to joke, yellowstone will beproducing french fries for mcdonald’s, and the people of billings, montana, will be steppingaround geysers.

the ash fall from the last yellowstone eruption covered all or parts of nineteen westernstates (plus parts of canada and mexico)—nearly the whole of the united states west of themississippi. this, bear in mind, is the breadbasket of america, an area that produces roughlyhalf the world’s cereals. and ash, it is worth remembering, is not like a big snowfall that will melt in the spring. if you wanted to grow crops again, you would have to find some place toput all the ash. it took thousands of workers eight months to clear 1.8 billion tons of debrisfrom the sixteen acres of the world trade center site in new york. imagine what it wouldtake to clear kansas.

and that’s not even to consider the climatic consequences. the last supervolcano eruptionon earth was at toba, in northern sumatra, seventy-four thousand years ago. no one knowsquite how big it was other than that it was a whopper. greenland ice cores show that the tobablast was followed by at least six years of “volcanic winter” and goodness knows how manypoor growing seasons after that. the event, it is thought, may have carried humans right to thebrink of extinction, reducing the global population to no more than a few thousandindividuals. that means that all modern humans arose from a very small population base,which would explain our lack of genetic diversity. at all events, there is some evidence tosuggest that for the next twenty thousand years the total number of people on earth was nevermore than a few thousand at any time. that is, needless to say, a long time to recover from asingle volcanic blast.

all this was hypothetically interesting until 1973, when an odd occurrence made itsuddenly momentous: water in yellowstone lake, in the heart of the park, began to run overthe banks at the lake’s southern end, flooding a meadow, while at the opposite end of the lakethe water mysteriously flowed away. geologists did a hasty survey and discovered that a largearea of the park had developed an ominous bulge. this was lifting up one end of the lake andcausing the water to run out at the other, as would happen if you lifted one side of a child’swading pool. by 1984, the whole central region of the park—several dozen square miles—was more than three feet higher than it had been in 1924, when the park was last formallysurveyed. then in 1985, the whole of the central part of the park subsided by eight inches. itnow seems to be swelling again.

the geologists realized that only one thing could cause this—a restless magma chamber.

yellowstone wasn’t the site of an ancient supervolcano; it was the site of an active one. it wasalso at about this time that they were able to work out that the cycle of yellowstone’seruptions averaged one massive blow every 600,000 years. the last one, interestingly enough,was 630,000 years ago. yellowstone, it appears, is due.

“it may not feel like it, but you’re standing on the largest active volcano in the world,” pauldoss, yellowstone national park geologist, told me soon after climbing off an enormousharley-davidson motorcycle and shaking hands when we met at the park headquarters atmammoth hot springs early on a lovely morning in june. a native of indiana, doss is anamiable, soft-spoken, extremely thoughtful man who looks nothing like a national parkservice employee. he has a graying beard and hair tied back in a long ponytail. a smallsapphire stud graces one ear. a slight paunch strains against his crisp park service uniform.

he looks more like a blues musician than a government employee. in fact, he is a bluesmusician (harmonica). but he sure knows and loves geology. “and i’ve got the best place inthe world to do it,” he says as we set off in a bouncy, battered four-wheel-drive vehicle in thegeneral direction of old faithful. he has agreed to let me accompany him for a day as he goesabout doing whatever it is a park geologist does. the first assignment today is to give anintroductory talk to a new crop of tour guides.

yellowstone, i hardly need point out, is sensationally beautiful, with plump, statelymountains, bison-specked meadows, tumbling streams, a sky-blue lake, wildlife beyondcounting. “it really doesn’t get any better than this if you’re a geologist,” doss says. “you’vegot rocks up at beartooth gap that are nearly three billion years old—three-quarters of theway back to earth’s beginning—and then you’ve got mineral springs here”—he points at thesulfurous hot springs from which mammoth takes its title—“where you can see rocks as theyare being born. and in between there’s everything you could possibly imagine. i’ve neverbeen any place where geology is more evident—or prettier.”

“so you like it?” i say.

“oh, no, i love it,” he answers with profound sincerity. “i mean i really love it here. thewinters are tough and the pay’s not too hot, but when it’s good, it’s just—”

he interrupted himself to point out a distant gap in a range of mountains to the west, whichhad just come into view over a rise. the mountains, he told me, were known as the gallatins.

“that gap is sixty or maybe seventy miles across. for a long time nobody could understandwhy that gap was there, and then bob christiansen realized that it had to be because themountains were just blown away. when you’ve got sixty miles of mountains just obliterated,you know you’re dealing with something pretty potent. it took christiansen six years to figureit all out.”

i asked him what caused yellowstone to blow when it did.

“don’t know. nobody knows. volcanoes are strange things. we really don’t understandthem at all. vesuvius, in italy, was active for three hundred years until an eruption in 1944and then it just stopped. it’s been silent ever since. some volcanologists think that it isrecharging in a big way, which is a little worrying because two million people live on oraround it. but nobody knows.”

“and how much warning would you get if yellowstone was going to go?”

he shrugged. “nobody was around the last time it blew, so nobody knows what thewarning signs are. probably you would have swarms of earthquakes and some surface upliftand possibly some changes in the patterns of behavior of the geysers and steam vents, butnobody really knows.”

“so it could just blow without warning?”

he nodded thoughtfully. the trouble, he explained, is that nearly all the things that wouldconstitute warning signs already exist in some measure at yellowstone. “earthquakes aregenerally a precursor of volcanic eruptions, but the park already has lots of earthquakes—1,260 of them last year. most of them are too small to be felt, but they are earthquakesnonetheless.”

a change in the pattern of geyser eruptions might also be taken as a clue, he said, but thesetoo vary unpredictably. once the most famous geyser in the park was excelsior geyser. itused to erupt regularly and spectacularly to heights of three hundred feet, but in 1888 it juststopped. then in 1985 it erupted again, though only to a height of eighty feet. steamboatgeyser is the biggest geyser in the world when it blows, shooting water four hundred feet intothe air, but the intervals between its eruptions have ranged from as little as four days to almost
fifty years. “if it blew today and again next week, that wouldn’t tell us anything at all aboutwhat it might do the following week or the week after or twenty years from now,” doss says.

“the whole park is so volatile that it’s essentially impossible to draw conclusions from almostanything that happens.”

evacuating yellowstone would never be easy. the park gets some three million visitors ayear, mostly in the three peak months of summer. the park’s roads are comparatively few andthey are kept intentionally narrow, partly to slow traffic, partly to preserve an air ofpicturesqueness, and partly because of topographical constraints. at the height of summer, itcan easily take half a day to cross the park and hours to get anywhere within it. “wheneverpeople see animals, they just stop, wherever they are,” doss says. “we get bear jams. we getbison jams. we get wolf jams.”

in the autumn of 2000, representatives from the u.s. geological survey and national parkservice, along with some academics, met and formed something called the yellowstonevolcanic observatory. four such bodies were in existence already—in hawaii, california,alaska, and washington—but oddly none in the largest volcanic zone in the world. the yvois not actually a thing, but more an idea—an agreement to coordinate efforts at studying andanalyzing the park’s diverse geology. one of their first tasks, doss told me, was to draw up an“earthquake and volcano hazards plan”—a plan of action in the event of a crisis.

“there isn’t one already?” i said.

“no. afraid not. but there will be soon.”

“isn’t that just a little tardy?”

he smiled. “well, let’s just say that it’s not any too soon.”

once it is in place, the idea is that three people—christiansen in menlo park, california,professor robert b. smith at the university of utah, and doss in the park—would assess thedegree of danger of any potential cataclysm and advise the park superintendent. thesuperintendent would take the decision whether to evacuate the park. as for surroundingareas, there are no plans. if yellowstone were going to blow in a really big way, you would beon your own once you left the park gates.

of course it may be tens of thousands of years before that day comes. doss thinks such aday may not come at all. “just because there was a pattern in the past doesn’t mean that it stillholds true,” he says. “there is some evidence to suggest that the pattern may be a series ofcatastrophic explosions, then a long period of quiet. we may be in that now. the evidencenow is that most of the magma chamber is cooling and crystallizing. it is releasing itsvolatiles; you need to trap volatiles for an explosive eruption.”

in the meantime there are plenty of other dangers in and around yellowstone, as was madedevastatingly evident on the night of august 17, 1959, at a place called hebgen lake justoutside the park. at twenty minutes to midnight on that date, hebgen lake suffered acatastrophic quake. it was magnitude 7.5, not vast as earthquakes go, but so abrupt andwrenching that it collapsed an entire mountainside. it was the height of the summer season,though fortunately not so many people went to yellowstone in those days as now. eighty
million tons of rock, moving at more than one hundred miles an hour, just fell off themountain, traveling with such force and momentum that the leading edge of the landslide ranfour hundred feet up a mountain on the other side of the valley. along its path lay part of therock creek campground. twenty-eight campers were killed, nineteen of them buried toodeep ever to be found again. the devastation was swift but heartbreakingly fickle. threebrothers, sleeping in one tent, were spared. their parents, sleeping in another tent besidethem, were swept away and never seen again.

“a big earthquake—and i mean big—will happen sometime,” doss told me. “you cancount on that. this is a big fault zone for earthquakes.”

despite the hebgen lake quake and the other known risks, yellowstone didn’t getpermanent seismometers until the 1970s.

if you needed a way to appreciate the grandeur and inexorable nature of geologic processes,you could do worse than to consider the tetons, the sumptuously jagged range that stands justto the south of yellowstone national park. nine million years ago, the tetons didn’t exist.

the land around jackson hole was just a high grassy plain. but then a forty-mile-long faultopened within the earth, and since then, about once every nine hundred years, the tetonsexperience a really big earthquake, enough to jerk them another six feet higher. it is theserepeated jerks over eons that have raised them to their present majestic heights of seventhousand feet.

that nine hundred years is an average—and a somewhat misleading one. according torobert b. smith and lee j. siegel in windows into the earth , a geological history of theregion, the last major teton quake was somewhere between about five and seven thousandyears ago. the tetons, in short, are about the most overdue earthquake zone on the planet.

hydrothermal explosions are also a significant risk. they can happen anytime, pretty muchanywhere, and without any predictability. “you know, by design we funnel visitors intothermal basins,” doss told me after we had watched old faithful blow. “it’s what they cometo see. did you know there are more geysers and hot springs at yellowstone than in all therest of the world combined?”

“i didn’t know that.”

he nodded. “ten thousand of them, and nobody knows when a new vent might open.” wedrove to a place called duck lake, a body of water a couple of hundred yards across. “it lookscompletely innocuous,” he said. “it’s just a big pond. but this big hole didn’t used to be here.

at some time in the last fifteen thousand years this blew in a really big way. you’d have hadseveral tens of millions of tons of earth and rock and superheated water blowing out athypersonic speeds. you can imagine what it would be like if this happened under, say, theparking lot at old faithful or one of the visitors’ centers.” he made an unhappy face.

“would there be any warning?”

“probably not. the last significant explosion in the park was at a place called pork chopgeyser in 1989. that left a crater about five meters across—not huge by any means, but bigenough if you happened to be standing there at the time. fortunately, nobody was around so
nobody was hurt, but that happened without warning. in the very ancient past there have beenexplosions that have made holes a mile across. and nobody can tell you where or when thatmight happen again. you just have to hope that you’re not standing there when it does.”

big rockfalls are also a danger. there was a big one at gardiner canyon in 1999, but againfortunately no one was hurt. late in the afternoon, doss and i stopped at a place where therewas a rock overhang poised above a busy park road. cracks were clearly visible. “it could goat any time,” doss said thoughtfully.

“you’re kidding,” i said. there wasn’t a moment when there weren’t two cars passingbeneath it, all filled with, in the most literal sense, happy campers.

“oh, it’s not likely,” he added. “i’m just saying it could. equally it could stay like that fordecades. there’s just no telling. people have to accept that there is risk in coming here. that’sall there is to it.”

as we walked back to his vehicle to head back to mammoth hot springs, doss added: “butthe thing is, most of the time bad things don’t happen. rocks don’t fall. earthquakes don’toccur. new vents don’t suddenly open up. for all the instability, it’s mostly remarkably andamazingly tranquil.”

“like earth itself,” i remarked.

“precisely,” he agreed.

the risks at yellowstone apply to park employees as much as to visitors. doss got ahorrific sense of that in his first week on the job five years earlier. late one night, three youngsummer employees engaged in an illicit activity known as “hot-potting”—swimming orbasking in warm pools. though the park, for obvious reasons, doesn’t publicize it, not all thepools in yellowstone are dangerously hot. some are extremely agreeable to lie in, and it wasthe habit of some of the summer employees to have a dip late at night even though it wasagainst the rules to do so. foolishly the threesome had failed to take a flashlight, which wasextremely dangerous because much of the soil around the warm pools is crusty and thin andone can easily fall through into a scalding vent below. in any case, as they made their wayback to their dorm, they came across a stream that they had had to leap over earlier. theybacked up a few paces, linked arms and, on the count of three, took a running jump. in fact, itwasn’t the stream at all. it was a boiling pool. in the dark they had lost their bearings. none ofthe three survived.

i thought about this the next morning as i made a brief call, on my way out of the park, at aplace called emerald pool, in the upper geyser basin. doss hadn’t had time to take me therethe day before, but i thought i ought at least to have a look at it, for emerald pool is a historicsite.

in 1965, a husband-and-wife team of biologists named thomas and louise brock, while ona summer study trip, had done a crazy thing. they had scooped up some of the yellowy-brown scum that rimmed the pool and examined it for life. to their, and eventually the widerworld’s, deep surprise, it was full of living microbes. they had found the world’s firstextremophiles—organisms that could live in water that had previously been assumed to be
much too hot or acid or choked with sulfur to bear life. emerald pool, remarkably, was allthese things, yet at least two types of living things, sulpholobus acidocaldarius andthermophilus aquaticus as they became known, found it congenial. it had always beensupposed that nothing could survive above temperatures of 50°c (122°f), but here wereorganisms basking in rank, acidic waters nearly twice that hot.

for almost twenty years, one of the brocks’ two new bacteria, thermophilus aquaticus,remained a laboratory curiosity until a scientist in california named kary b. mullis realizedthat heat-resistant enzymes within it could be used to create a bit of chemical wizardry knownas a polymerase chain reaction, which allows scientists to generate lots of dna from verysmall amounts—as little as a single molecule in ideal conditions. it’s a kind of geneticphotocopying, and it became the basis for all subsequent genetic science, from academicstudies to police forensic work. it won mullis the nobel prize in chemistry in 1993.

meanwhile,  scientists  were  finding even hardier microbes, now known ashyperthermophiles, which demand temperatures of 80°c (176°f) or more. the warmestorganism found so far, according to frances ashcroft in life at the extremes, is pyrolobusfumarii, which dwells in the walls of ocean vents where the temperature can reach 113°c(235.4°f). the upper limit for life is thought to be about 120°c (248°f), though no oneactually knows. at all events, the brocks’ findings completely changed our perception of theliving world. as nasa scientist jay bergstralh has put it: “wherever we go on earth—eveninto what’s seemed like the most hostile possible environments for life—as long as there is liquid water and some source of chemical energy we find life.”

life, it turns out, is infinitely more clever and adaptable than anyone had ever supposed.

this is a very good thing, for as we are about to see, we live in a world that doesn’t altogether seem to want us here.