IN 1911, A Britisist named C. t. R. ilson udying cloud formations bytramping regularly to t of Ben Nevis, a famously damp Scottisain, o    t be an easier o study clouds. Ba t an artificial cloud    ting a reasonable model of a cloud in laboratory ditions.

        t    ional, ued be. ed an alpicle to seed    left avisible trail—like trails of a passing airliner.    ied ticle detector.

        It provided ving evide subatomic particles did indeed exist.

        Eventually tists ied a more poon-beam device, Berkeley produced ron, or atom smasingly knoraptions ill o accelerate a proton or oticle to aremely raetimes circular, sometimes linear), t into anoticle and see ’s    sce at its subtlest, but it ive.

        As ps built bigger and more ambitious maco find or postulateparticles or particle families seemingly    number: muons, pions, ermediate vector bosons, baryons, tacs beganto grotle unfortable. “Young man,” Enrico Fermi replied    asked icular particle, “if I could remember ticles, I .”

        today accelerators    sound like somettle: ton Syn, tron-Positron Collider, tivistic s of energy (some operateonly at nig people in neigo o s fadingicles into sucate of liveli asingle ele    do forty-seven tunnel in a sed. Fears in tists migently create a black range quarks,” eraic particles and propagate untrollably. If you are reading t happened.

        Finding particles takes a certain amount of tration. t just tiny and sbut also often tantalizingly eva. Particles    e into being and be gone again in aslittle as 0.000000000000000000000001 sed (10-24). Even t sluggisableparticles han 0.0000001 sed (10-7).

        Some particles are almost ludicrously slippery. Every sed ted by 10,000trillion trillion tiny, all but massless rinos (mostly s out by tually all of t t and everyt is on it,including you and me, as if it    to trap just a feists ankso 12.5 million gallons of er (t is, er ive abundance ofdeuterium in it) in underground c be interferedypes of radiation.

        Very occasionally, a passirino o one of tomiuclei in terand produce a little puff of energy. Stists t take us verysligo uanding tal properties of ted t rinos do    not a great deal—about oen-milliont of aron.

        it really takes to find particles ts of it. tionsininess of t and ties required to do tion for NuclearResearctle city. Straddling tzerland, it employste t is measured in square miles.    boasts astring of mag unnel oversixteen miles around.

        Breaking up atoms, as James trefil ed, is easy; you do it eacime you sc ligomiuclei, e a lot of money and agenerous supply of electricity. Getting doo ticles t make upparticles—requires still more: trillions of volts of electricity and t of a small tralAmeriation. ’s neions in 2005,rillion volts of energy and cost sometostruct.

        1But t could    upon, t and nounately o-be Superdug Supercollider, ed near axaexas, in ts oed States gress. tention of tolet stists probe “timate nature of matter,” as it is al, by re-creating as nearlyas possible tions in ts first ten ths of a sed.

        to fling particles tunnel fifty-taggering y-rillion volts of energy. It o build (a figure t eventually rose to $10 billion) and o run.

        In per example in ory of p money into a    $2 billion on t, t in 1993 after fourteen miles oftunnel exas nos t expensive eis, I am told by my friend Jeff Guinn of t ortar-telegram, “essentially a vast,cleared field dotted along ted small towns.”

        1tical side effects to all tly effort. t. It ed by a    stist, tim Berners-Lee, in 1989.

        Siicle ps    ts a little loeven paratively modest projects    be quite breatly rino observatory at take Mine in Lead,Souta,    $500 million to build—t is already dug—beforeyou even look at ts. ts.” A particle accelerator at Fermilab in Illinois, mea.

        Particle p, is a erprise—but it is a productive one.

        today ticle t is ed, butunfortunately, in t is very difficult to uand tionsicles, and ure s t tionsare from oo anotably eacime o unlock a box,    ticles called tacravel faster t. Oto find gravitons—t of gravity. At om is not easy to say. Carl Sagan in os raised ty t if you traveled doo aron, you mig it tained auniverse of its oion stories of ties. “it,anized into t of galaxies and smaller structures, are an immense numberof otinier elementary particles,    leveland so on forever—an infinite dohin universes, endlessly.

        And upward as well.”

        For most of us it is a    surpasses uanding. to read even aary guideto particle p nos sucipion decay respectively into a muon plus arino and anantimuon plus rino ime of 2.603 x 10-8seds, tral piondecays into time of about 0.8 x 10-16seds, and timuon decay respectively into . . .” And so it runs on—and t lucid of interpreters, Steven einberg.

        I t just a little simplicity to matters, tecMurray Gell-Mann ied a neicles, essentially, in teveneinberg, “to restore some ey to titude of ive term used byps for protons, rons, and oticles governed by trong nuclear force.

        Gell-Mann’s t all ill smaller, even morefual particles. ed to call ticles partons, as in Dolly, but ead they became known as quarks.

        Gell-Mann took terMark!” (Discriminating ps rorks, not larks, even tter is almost certainly tion Joyce al simplicity ofquarks    long lived. As tter uood it o introducesubdivisions. Altoo small to aste or any oteristics o six categories—up, de, cop, and bottom—o as to ts t it    altogetal t terms    applied in California during tually out of all t is called tandard Model,    of parts kit for tomidard Model sists of six quarks, sixleptons, five knoulated sixttisist, Peter rong and romagism.

        t essentially is t among tter are quarks;togeticles called gluons; and togetons arons, tuff of tom’s nucleus. Leptons are trons arinos. Quarks aons toget S. N. Bose) are particles t produd carry forces, and include pons andgluons. t actually exist; it ed simply as a icles h mass.

        It is all, as you    see, just a little un it is t model t    explainall t icles. Most particle ps feel, as Leon Ledermanremarked in a 1985 PBS dotary, t tandard Model lacks elegand simplicity.

        “It is too plicated. It oo many arbitrary parameters,” Lederman said. “e don’t reallysee tor ty knobs to set ty parameters to create t.” Pimate simplicity, but so far all    it: “t ture is not beautiful.”

        tandard Model is not only ungainly but inplete. For o    allto say about gravity. Seardard Model as you    findanyto explain able it doesn’t float up to t noted,    it explain mass. In order to give particles any mass at all roduce tional    actually exists is a matter for ty-first-tury puck    kno it is a little    leastinplete.”

        In an attempt tets ring tulates t all ttle tons t icles are actually “strings”—vibrating strands of energy toscillate in eleven dimensions, sisting of time and sevenot are, o us. trings are very tiny—tiny enougopass for point particles.

        By introdug extra dimensions, superstring ts to pull togetum laational ones into one paratively tidy package, but it also meanst anytists say about to sound    ofts t o you by a stranger on a park bench.

        Micructure    perspective: “terotic string sists of a closed string t ypes ofvibrations, clockerclocked differently. tions live in a ten-dimensional space. terclocky-six-dimensional space, of    inKaluza’s inal five-dimensional, tified by being o a circle.)” And so it goes, for some 350 pages.

        String tessurfaces knoo top on t of us must get off.

        ence from times, explaining to a generalaudieic process begins far in te past    emptybranes sitting parallel to eacum fluctuation in tant past and ted apart.” Nuing . No uanding it eititally, es from tion.”

        Matters in pc, as Paul Davies noted in Nature, it is“almost impossible for tist to discrimiimately rig.” tion came iingly to a iousdensity involving sucs as “imaginary time” and tindition,” and purp to describe t    o be unkno predated ts properties).

        Almost at oed debate among ps as to ’s clearly more or less pletenonsense,” bia Uy p Peter oit told times, “but t doesn’t muguis from a lot of t of terature.”

        Karl Popper,    t be an ultimate t, ration may require a furtion, produg “an infinite cal principles.” A rival possibility is t suately,” es einberg in Dreams of a Final tseem to be ing to tellectual resources.”

        Almost certainly t s of t, and almostcertainly ts    of us.

        s iury o tronomers ing an inpletenessof uanding in t large.

        met Ed nearly all t tance of treat are lyproportional: ter it is moving.    tion, ant, v is ty of a flying galaxy, andd its distance a a t tle ae 1920s it    many t least Eartself—. Refining tion of ology.

        Almost tant about tant    ofdisagreement ive it. In 1956, astronomers discovered t Cep; ties, not oo reions and e up o 20 billion years—not terribly precise, but at least old enoug last, to embrace tion of th.

        In t folloed a long-running dispute bet ilson, and Gérard de Vaucouleurs, a Frener based atty of texas. Sandage, after years of careful calculations, arrived at a value for tant of 50, giving tain t tant was 100.

        2t t Sandage believed—ten billion years. Matters took a furto uainty ories in California,using measures from telescope, suggested t ttleas eigarseam from NASA and tter in Maryland, using a e called tropy Probe, annouake a ters rest, at least fort.

        ty in making final determinations is t ten acres of room forinterpretation. Imagianding in a field at nigrying to decide aric ligraigools of astronomy you    easilyenougerminess and t one is, say, 50 pert moredistant t    be certain of is    ussay, a 58-t bulb t is 122 feet at lig is 119 feet, 8 incop of t you must make alloortions caused by variations in tmalactic dust, inating ligars, and many otors. t is t your putations are necessarily based on a series of edassumptions, any of ion. taccess to telescopes is al a premium and orically measuring red ss ably costly in telescope time. It could take all nigo get a single exposure. Insequence, astronomers imes been pelled (or o base clusionson notably sty evidence. In ology, as t Geoffrey Carr ed,    on a molein Rees    it:

        “Our present satisfa [ate of uanding] may reflect ty of taratheory.”

        tainty applies, ially, to relatively nearby to tantedges of tes,    t-years a do not often stress to t it is someitled to    exactly by "a stant of 50" or "a stant of 100." tronomical units of measure. Except versationally, astronomers dont use ligance called tra of parallax and sed), based on a universal measure called tellar parallax and equivalent to 3.26 ligant is expressed in terms of kilometers per sed per megaparsec.

        tronomers refer to a ant of 50, ;50 kilometers per sed permegaparsec." For most of us t is of course an utterly meaningless measure, but tronomicalmeasures most distances are so o be utterly meaningless.

        quite t large, matters are naturally magnified. Bearing allt in mind, t bets to be fixed on a range ofabout 12 billion to 13.5 billion years, but y.

        Oerestily suggested t t nearly as big as , t ane of tions, g images created by rebounded light.

        t is, t deal, even at quite a fual level, t    k ists calculate t of matter oogetely s. It appears t at least 90 pertof t, is posed of Fritz Zter”—stuff t is by its nature invisible to us. It is sligo t , for t part,    even see, but t least ts are eaining: to be eiterag Massive Particles, ter left over from t s—really just anotars).

        Particle ps eo favor ticle explanation of IMPs, astropstellar explanation of MACime MAot nearlyenougiment so    no IMP erag, t) very o detect. ic rays oo mucerference. Sostists must go deep underground. One kilometer underground ibardments t even ill missing from t,” as one entator it. For t ectable Objects Somewhere).

        Ret evidence suggests t not only are t t t a rate t is accelerating. ter to all expectations. Itappears t t only be filled ter, but h dark energy.

        Stists sometimes also call it vacuum energy or, more exotically, quintessence. ever itis, it seems to be driving an expansion t no one    altoget for. t empty space isn’t so empty at all—t ticles of matter and antimatterpopping iend popping out again—and t t an accelerating rate. Improbably enoug resolves all tein’s ological stant—ttle pieato tivity to stop t blunder of mylife.” It    after all.

        t of all t e pute,surrounded by stars    altogetter identify, operating in ance ies    trulyuand.

        And on t rattling note, let’s return to Plaand—t be surprised to    uand it pletely and and ood for long.
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