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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 moreplicated。 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。
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10 GETTING THE LEAD OUT
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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鈥攗sually 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 pound 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鈥檛 bring a little lead into consumers鈥櫋ives。 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 a and death。 you really don鈥檛 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鈥攁nd tetraethyl lead did indubitably stop engines from knocking。 so in1923 three of america鈥檚 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 鈥渆thyl鈥�
because it sounded friendlier and less toxic than 鈥渓ead鈥潯nd 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： 鈥渢hese men probably went insane because theyworked too hard。鈥潯ltogether 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 pany 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鈥檚 ebullient inventor；thomas midgley； decided to hold a demonstration for reporters to allay their concerns。 as hechatted away about the pany鈥檚 mitment 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鈥檛 take long to bee critical。
chlorofluorocarbons are also not very abundant鈥攖hey constitute only about one part perbillion of the atmosphere as a whole鈥攂ut they are extravagantly destructive。 one pound ofcfcs can capture and annihilate seventy thousand pounds of atmospheric ozone。 cfcs alsohang around for a long time鈥攁bout a century on average鈥攚reaking 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鈥攁nd 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 being 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鈥檚 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鈥攖hat is； the time it takes for half of any sample to disappear1鈥攐f 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鈥攖hough 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 being widespread； certain flaws within it becameapparent。 to begin with； it was discovered that one of the basic ponents of libby鈥檚formula； 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