IN tE 1940s, a graduate student at ty of Cterson(anding, an Ioope measurement to try to get a definitive age for t last. Unfortunatelyall aminated—usually    tained somet ed to occur. Many years terson realized t ttable Oorhomas Midgley, Jr.

        Midgley raining, and t ayed so. Instead, erest in trial applications ofcry. In 1921, on,Oigated a pound called tetraetetraet it signifitly reduced tion known asengine knock.

        Even to be dangerous, by tietury it could be found in all manner of er products. Food came in s sealed er en stored in lead-lianks. It o fruit as a pesticidei even came as part of toote tubes.    existed t didn’t bring a little lead into ers’ lives. a greater and more lasting intimacy ts addition to gasoline.

        Lead is a oxioo mud you    irreparably damage tral nervous system. Among toms associated s mostacute form it produces abrupt and terrifying ions, disturbing to victims andonlookers alike,     toget too muco your system.

        On to extrad    embarrassingly profitableto produdustrially—araetably stop engines from knog. So in1923 t corporations, General Motors, Du Pont, and Standard Oil oferprise called tion (later seo simply Etion) o making as mucetraeto buy, and t proved to be a very great deal. tive “ethyl”

        because it sounded friendlier aoxic troduced it for publiption (in more    people realized) on February 1, 1923.

        Almost at once produ o ex taggered gait and fusedfaculties t mark tly poisoned. Also almost at oionembarked on a policy of calm but unyielding denial t    rial cry,Promet one plant developed irreversible delusions, aspokesman blandly informed reporters: “t insane because too oget least fifteen ion ofleaded gasoline, and untold numbers of oten violently so; tnumbers are unknoo    times,    notably in 1924 ion y-five more urned into perma staggering    a single ill-ventilated facility.

        As rumors circulated about t, et ior,to ration for reporters to allay tted a tment to safety, etraet to y seds, claiming all t    t , Midgley kneoo     uff if .

        Buoyed by turo anotecors in ten appallingly risky because t sometimes leaked. One leak from a refrigerator at a al inCleveland, O out to create a gast able, nonflammable, noncorrosive, and safe to breatinct for ttable t    uny, ed chlorofluorocarbons, or CFCs.

        Seldom rial product been more sly or unfortunately embraced. CFto produ in tions iioo deodorant sprays before it iced, ury later, t tratosp a good thing.

        Ozone is a form of oxygen in ead oft is a bit of a    t at ground level it is a pollutant, osp is beneficial, si soaks up dangerous ultraviolet radiation. Beneficial ozoneis not terribly abundant,    ributed evenly t tratosp one eig is urbed,and    take long to bee critical.

        C very abundant—titute only about one part perbillion of tmosp travagantly destructive. One pound ofCFCs    capture and annie seventy tmospime—about a tury on average—wreaking he while.

        t    sponges. A single CFC molecule is about ten times moreeffit at exacerbating greens tself as a green, cimately prove to be just about t iion of tietury.

        Midgley never kiveCFCs er being crippled ed a traption involving a series of motorized pulleys t automaticallyraised or turned angled in tinto a and rangled.

        If you erested in finding out ty of Co be. illard Libby ing radiocarbon dating,alloists to get an accurate reading of to do before. Up to time, t reliable dates bao furt Dynasty i from about 3000B.o one couldfidently say, for instance, ed or at ime ihe caves of Lascaux in France.

        Libby’s idea     in 1960. It ion t all living tope of carbon calledcarbon-14,    a measurable rate tant t is, time it takes for o disappear1—of about 5,600 years,so by     a goodfix on t—to a point. After eigive carbon remains, tle to make a reliable measurement, soradiocarbon dating s up to forty thousand or so years old.

        Curiously, just as te fla becameapparent. to begin     one of ts of Libby’sformula, knoant,    3 pert. By time, s aken t tate everyone, stists decided to keep te stant. “tim Flannery notes, “everyrae you read today is given as too young by around 3 pert.” t quite stop t    carbon-14 samples    beeasily inated iny scrap of vegetable matter, forinsta ed    noticed. For younger samples—ty t ination does not alter somuc for older samples it    be a serious problem because so feoms arebeing ted. In t instao borro is like misting by a dollaro a t is more like misting by a dollar o t.

        Libby’s metion t t of carbon-14 in tmospe at t ory. In fact it    been. e no tmosp Eartism is defleg ic rays,and t t    vary signifitly over time. t some carbon-14 dates are more1If you oms determine    session, t t a statistical venience-a kind ofactuarial table for elemental terial    isntt every atom in t for exactly 30 seds or 60 seds or 90 seds or some otidilyordained period. Ea    survive for airely random lengtime t o do iples of 30; it mig until t mige auries to e. No one    say. But    for te ofdisappearance s an average rate, in ot to any large sampling. Someone once , for insta dimes    30 years.

        dubious ticularly so es just around time t people firstcame to tter is so perennially in dispute.

        Finally, ale uedly, readings    be t by seeminglyued external factors—sucs of tested. O case involved te over s in    monks in amonastery graveyard    tial clusion t t into doubt by tion t ten alot of fiso be older t t    got to tantalizinglyunresolved.

        Because of ted sings of carbon-14, stists devised oting a materials, among trons trappedin clays, aron spin resonance, is of trons. But even t oft date anyt 200,000 years, and t date inanicmaterials like rocks at all, ermi.

        ting rocks    one point almost everyone in t not been for a determined Englis migo abeyaogether.

        acles s he achieved.

        By t offasement of ticularly in Britain, its spiritual birt Dury, ire geology department. Often o bet io pursue ric dating of rocks. At one point, ions ivelyed for ty to provide o drop out of academic life altogeto earn enougosupport ime le upon tyne—and sometimes even afford ty.

        tecically straiglyfrom t observed by Er Rutoms decayfrom one element into anot a rate predictable enoug you    use t takes for potassium-40 to bee argon-40, and you measure ts of eac erial is. ributiono measure te of uranium into lead to calculate th.

        But tecies to overe.    leasted gadgetry of a sort t could make veryfine measurements from tiny samples, and as    asimple adding mac e an ac    t least tunately,    yet anot to acceptaiveness of ists. Alto praise ai    t merely terials fromwh had been formed.

        It    at time t y of g lead isotopes in igneous rocks ( edting, as opposed to ts). Realizing t tedious,    to young Clair Patterson as ation project.

        Famously terson t determining t, it ake years.

        Patterson began    in 1948. pared ributions to tterson’s discovery of touciclimactic. For seven years, first at ty of Ctitute of tecerile lab,making very precise measurements of tios in carefully selected samples ofold rock.

        t you needed rocks t remely a, taining lead- and uranium-bearing crystals t    as old as t itself—anytes—but really a rocks are only rarely found oe 1940s no oogetood o t for e teics, o.) Pattersoime,    to try to make sense of ted materials. Eventually, andingeniously, it occurred to     tage by using rocksfrom beyouro meteorites.

        tion    correct as it turned out— maeorites are essentially leftover building materials from tem,and to preserve a more or less pristierior cry. Measure th.

        As alraigio sound. Meteorites are not abundant aeoritic samples not especially easy to get tecreme andneeded muc. Above all, t Patterson’s samples inuously and unatably inated mospo air. It    eventually led o create a sterile laboratory—t, acc to at least one at.

        It took Patterson seven years of patient    to assemble suitable samples for fiing. In traveled to tional Laboratory in Illinois,ime on a late-model mass spectrograpegand measuring te quantities of uranium and lead locked up in a crystals.    last s, Patterso raigo o a al because     attack.

        Soon after a meeting in issin, Patterson announced a definitive age for t standsuncer,” as McGrayne admiringly notes. After th finally had an age.

        terson nourention to tion of all tlead in tmospouo find t tle    tsof lead on    invariably    surprisingly, y years every study of lead’s effects urers of lead additives.

        In one sucudy, a doctor o breated quantities. tested. Unfortunately, as torappears not to    excreted as a e product. Rat accumulates int’s    so dangerous—aested. In sequence, lead was given a    bill of h.

        Patterson quickly establis mospill do, in fact,since lead never goes a about 90 pert of it appeared to e fromautomobile ex pipes, but    prove it.    o parelead levels in tmosp existed before 1923, raetroduced. It occurred to    ice cores could provide the answer.

        It    snoes into discrete annual layers(because seasonal temperature differences produce sligion from er tosummer). By ting back t of lead in eac global lead trations at any time for ion became tion of ice core studies, on wological work is based.

        Patterson found    before 1923 t no lead in tmosp siime its level eadily and dangerously.     to get lead taken out of gasolio t end, ant and often vocalcritic of try and its is.

        It o be a ion s directors    Justice Le Grosvenor of tional Geograpy.) Patterson suddenly foundresearc to acquire. troleum Instituteceled a researcract ed States Public ral gover institution.

        As Patterson increasingly became a liability to itution, trustees edly pressed by lead industry officials to s    o JamieLin Kitman, ing in tion in 2000, Etives allegedly offered to eerson    pag.” Absurdly, ional Researced to iigate tmospionably t on atmospheric lead.

        to    credit, Patterson never ually s led to trodu of t of 1970 and finally to ted States in 1986. Almost immediately lead levels in t. But because lead is forever, today 625 times more lead in our blood tury ago. t of lead in tmospio groe legally, by about a ris ayear, mostly from mining, smelting, and industrial activities. ted States also bannedlead in indoor paint, “forty-four years after most of Europe,” as McGrayes.

        Remarkably, sidering its startling toxicity, lead solder    removed from Amerifood tainers until 1993.

        As for tion, it’s still going strong, tandard Oil, and Du Pontno longer akes in t to a pany called Albemarle Paper in1962.) Acc to McGrayne, as late as February 2001 Etio tend “tresearco s leaded gasoline poses a t to .” On its e, a ory of tion of lead—or indeedof t simply refers to t as taining “a certainbination of chemicals.”

        Eto its 2001 pany ats,tetraetEL as it calls it) still ated for $25.1 million in sales in 2000 (out ofoverall sales of $795 million), up from $24.1 million in 1999, but dos report tated its determination to “maximize ted bytEL as its usage tio ps tEL t ed Octel of England.

        As for t to us by ted States, but tenacious little devils and any t youloosed into tmosps or ance)    certainly be around and dev ozone long after you ill introdug s of CFto tmospoayne Biddle, 60 million pounds of tuff, ill finds its o t every year. So    is to say, many of our largecorporations are still making it at ts overseas. It    be banned in tries until 2010.

        Clair Patterson died in 1995.    ention from ury ofsistent and increasingly selfless ac. A good case could be made t    iial geologist of tietury. Yet wterson?

        Most geology textbooks don’t mention    popular books on tory of ting of Eartually mao misspell ure made tional, ratounding error of tterson was a woman.

        At all events, to tterson by 1953 t last    tai.
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