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to 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 pany’s 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’t take long to bee 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 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’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 being widespread； certain flaws within it becameapparent。 to begin with； it was discovered that one of the basic ponents 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 e。 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 s