gasoline 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； 鈥渇orty…four years after most of europe；鈥潯s mcgrayne notes。
remarkably； considering its startling toxicity； lead solder was not removed from americanfood containers until 1993。
as for the ethyl corporation； it鈥檚 still going strong； though gm； standard oil； and du pontno longer have stakes in the pany。 （they sold out to a pany called albemarle paper in1962。） according to mcgrayne； as late as february 2001 ethyl continued to contend 鈥渢hatresearch has failed to show that leaded gasoline poses a threat to human health or theenvironment。鈥潯n its website； a history of the pany makes no mention of lead鈥攐r indeedof thomas midgley鈥攂ut simply refers to the original product as containing 鈥渁 certainbination of chemicals。鈥�
ethyl no longer makes leaded gasoline； although； according to its 2001 pany 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 pany stated its determination to 鈥渕aximize the cash generated bytel as its usage continues to phase down around the world。鈥潯thyl 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鈥攖hat 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鈥檛 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鈥檛 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。
w w w。x iaoshu otx t。c o m
11 MUSTER MARK鈥橲 QUARKS
灏忥紝璇达紝t锛寈t锛屽ぉ锛屽爞
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鈥攁 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鈥攍ike 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鈥攁nd indeed still work鈥攐n 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鈥檚 why they were called atom smashers。 it wasn鈥檛 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 unfortable。 鈥測oung man；鈥潯nrico fermi replied when a student asked himthe name of a particular particle； 鈥渋f i could remember the names of these particles； i wouldhave been a botanist。鈥�
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鈥檛 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 鈥渟trange quarks；鈥潯hich could； theoretically； interact with othersubatomic particles and propagate uncontrollably。 if you are reading this； that hasn鈥檛happened。
finding particles takes a certain amount of concentration。 they are not just tiny and swiftbut also often tantalizingly evanescent。 particles can e 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鈥檛 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鈥檛 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鈥攁bout 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 ele