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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 plicated。 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 inplete。 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 leastinplete。”
in an attempt to draw everything together； physicists have e 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