8 EINSTEIN’S UNIVERSEAS

百度搜索 A Short History of Nearly Everything 天涯 或 A Short History of Nearly Everything 天涯在线书库 即可找到本书最新章节.

    THE EENTH tury drew to a close, stists could reflect with satisfa thatthey had pinned down most of the mysteries of the physical world: electricity, magism,gases, optics, acoustics, kiics, and statistical meics, to name just a few, all had falleninto order before them. They had discovered the X ray, the cathode ray, the ele, andradioactivity, ied the ohm, the watt, the Kelvin, the joule, the amp, and the little erg.

    If a thing could be oscillated, accelerated, perturbed, distilled, bined, weighed, or madegaseous they had do, and in the process produced a body of universal laws so weightyand majestic that we still tend to write them out in capitals: the Eleagic Field Theoryof Light, Richter’s Law of Reciprocal Proportions, Charles’s Law of Gases, the Law ofbining Volumes, the Zeroth Law, the Valence cept, the Laws of Mass As, andothers beyond ting. The whole world ged and chuffed with the maery andinstruments that their iy had produced. Many wise people believed that there wasnothing much left for sce to do.

    In 1875, when a young German in Kiel named Max Planck was deg whether to devotehis life to mathematics or to physics, he was urged most heartily not to choose physicsbecause the breakthroughs had all been made there. The iury, he was assured,would be one of solidation and refi, not revolution. Planck didn’t listeudiedtheoretical physid threw himself body and soul into work oropy, a process at theheart of thermodynamics, which seemed to hold much promise for an ambitious young man.

    1In 1891 he produced his results and learo his dismay that the important work oropyhad in fact been done already, in this instance by a retiring scholar at Yale Uy namedJ. Willard Gibbs.

    Gibbs is perhaps the most brilliant person that most people have never heard of. Modest tothe point of near invisibility, he passed virtually the whole of his life, apart from three yearsspent studying in Europe, within a three-block area bounded by his house and the Yalecampus in New Haven, ecticut. For his first ten years at Yale he didn’t even bother todraw a salary. (He had indepe means.) From 1871, when he joihe uy as aprofessor, to his death in 1903, his courses attracted an average of slightly over oudent asemester. His written work was difficult to follow and employed a private form of notationthat many found inprehensible. But buried among his are formulations were insightsof the loftiest brilliance.

    In 1875–78, Gibbs produced a series of papers, collectively titledOn the Equilibrium ofHeterogeneous Substances , that dazzlingly elucidated the thermodynamic principles of, well,1Specifically it is a measure of randomness or disorder in a system. Darrell Ebbing, iextbook GeneralChemistry, very usefully suggests thinking of a deck of cards. A new pack fresh out of the box, arranged by suitand in sequence from ace to king,  be said to be in its ordered state. Shuffle the cards and you put them in adisordered state. Entropy is a way of measuring just how disordered that state is and of determining thelikelihood of particular outes with further shuffles. Of course, if you wish to have any observationspublished in a respectable journal you will need also to uand additional cepts such as thermalnonuniformities, lattice distances, and stoietric relationships, but thats the general idea.

    nearly everything—“gases, mixtures, surfaces, solids, phase ges . . . chemical reas,eleical cells, sedimentation, and osmosis,” to quote William H. Cropper. In esse Gibbs did was show that thermodynamics didn’t apply simply to heat and energy at thesort of large and noisy scale of the steam engine, but was also present and iial at theatomic level of chemical reas. Gibbs’s Equilibrium has been called “the Principia ofthermodynamics,” but for reasons that defy speculation Gibbs chose to publish theselandmark observations iransas of the ecticut Academy of Arts and Sces,a journal that mao be obscure even in ecticut, which is why Planck did not hearof him until too late.

    Undaunted—well, perhaps mildly daunted—Planck turo other matters.

    2We shall turnto these ourselves in a moment, but first we must make a slight (but relevant!) detour toCleveland, Ohio, and an institution then known as the Case School of Applied Sce. There,in the 1880s, a physicist of early middle years named Albert Michelson, assisted by his friendthe chemist Edward Morley, embarked on a series of experiments that produced curious anddisturbis that would have great ramifications for much of what followed.

    What Michelson and Morley did, without actually intending to, was undermine alongstanding belief in something called the luminiferous ether, a stable, invisible, weightless,friless, and unfortunately wholly imaginary medium that was thought to permeate theuniverse. ceived by Descartes, embraced by on, and veed by nearly everyoneever sihe ether held a position of absolute trality in eenth-tury physics as away of explaining how light traveled across the emptiness of space. It was especially neededin the 1800s because light aromagism were now seen as waves, which is to saytypes of vibrations. Vibrations must occur in something; hehe need for, and lastiion to, aher. As late as 1909, the great British physicist J. J. Thomson was insisting:

    “The ether is not a fantastic creation of the<var></var> speculative philosopher; it is as essential to us asthe air we breathe”—this more than four years after it retty intestably establishedthat it did. People, in short, were really attached to the ether.

    If you o illustrate the idea of eenth-tury America as a land of opportunity,you could hardly improve on the life of Albert Michelson. Born in 1852 on the German–Polish border to a family of poor Jewish merts, he came to the Uates with hisfamily as an infant and grew up in a mining camp in California’s gold rush try, where hisfather ran a dry goods business. Too poor to pay for college, he traveled to Washington, D.d took to l by the front door of the White House so that he could fall in besidePresident Ulysses S. Grant when the President emerged for his daily stitutional. (It wasclearly a more i age.) In the course of these walks, Michelson so ingratiated himself tothe President that Grant agreed to secure for him a free place at the U.S. Naval Academy. Itwas there that Michelson learned his physics.

    Ten years later, by norofessor at the Case School in Cleveland, Michelson becameied in trying to measure something called the ether drift—a kind of head windproduced by moving objects as they plowed through space. One of the predis ofonian physics was that the speed of light as it pushed through the ether should vary with2Planck was often unlucky in life. His beloved first wife died early, in 1909, and the younger of his two sonswas killed in the First World War. He also had twin daughters whom he adored. One died giving birth. Thesurviving twio look after the baby and fell in love with her sisters husband. They married and two yearslater she died in childbirth. In 1944, when Planck was eighty-five, an Allied bomb fell on his house and he losteverything-papers, diaries, a lifetime of accumulations. The following year his surviving son was caught in aspiracy to assassiler and executed.

    respect to an observer depending oher the observer was moving toward the source oflight or away from it, but no one had figured out a way to measure this. It occurred toMichelson that for half the year the Earth is traveling toward the Sun and for half the year it ismoving away from it, and he reasohat if you took careful enough measurements atopposite seasons and pared light’s travel time betweewo, you would have youranswer.

    Michelson talked Alexander Graham Bell, newly enriched ior of the telephone, intoproviding the funds to build an ingenious aive instrument of Michelson’s owndevising called an interferometer, which could measure the velocity of light with greatprecision. Then, assisted by the genial but shadowy Morley, Michelson embarked on years offastidious measurements. The work was delicate and exhausting, and had to be suspended fora time to permit Michelson a brief but prehensive nervous breakdown, but by 1887 theyhad their results. They were not at all what the two stists had expected to find.

    As Caltech astrophysicist Kip S. Thorne has written: “The speed of light turned out to bethe same inall dires and at all seasons.” It was the first hint in two hundred years—ily two hundred years, in fact—that on’s laws might not apply all the timeeverywhere. The Michelson-Morley oute became, in the words of William H. Cropper,“probably the most famous ive result in the history of physics.” Michelson was awardeda Nobel Prize in physics for the work—the first Ameri so honored—but not for twentyyears. Meanwhile, the Michelson-Morley experiments would hover unpleasantly, like a mustysmell, in the background of stific thought.

    Remarkably, ae his findings, wheweh tury dawned Michelsonted himself among those who believed that the work of sce was nearly at an end,with “only a few turrets and pino be added, a few roof bosses to be carved,” in thewords of a writer in Nature.

    In fact, of course, the world was about to enter a tury of sce where many peoplewouldn’t uand anything and none would uand everything. Stists would soonfind themselves adrift in a bewildering realm of particles and antiparticles, where things popin and out of existen spans of time that make nanoseds look plodding and uful,where everything is strange. Sce was moving from a world of macrophysics, whereobjects could be seen and held and measured, to one of microphysics, where events transpirewith unimaginable swiftness on scales far below the limits of imagining. We were about toehe quantum age, and the first person to push on the door was the so-far unfortunateMax Planck.

    In 1900, now a theoretical physicist at the Uy of Berlin and at the somewhatadvanced age of forty-two, Planveiled a new “quantum theory,” which posited thatenergy is not a tinuous thing like flowing water but es in individualized packets,which he called quanta. This was a novel cept, and a ?good one. In the short term it wouldhelp to provide a solution to the puzzle of the Michelson-Morley experiments in that itdemonstrated that light  be a wave after all. In the loerm it would lay thefoundation for the whole of modern physics. It was, at all events, the first clue that the worldwas about to ge.

    But the landmark event—the dawn of a new age—came in 1905, when there appeared inthe German physics journal Annalen der Physik a series of papers by a young Swissbureaucrat who had no uy affiliation, no access to a laboratory, and the regular use ofno library greater than that of the national patent offi Bern, where he was employed as ateical examihird class. (An application to be promoted to teical examiner sedclass had retly beeed.)His name was Albert Einstein, and in that oful year he submitted to Annalen derPhysik five papers, of which three, acc to C. P. Snow, “were among the greatest iory of physics”—one examining the photoelectric effect by means of Planck’s newquantum theory, one on the behavior of small particles in suspension (what is known asBrownian motion), and olining a special theory of relativity.

    The first won its author a Nobel Prize and explaihe nature of light (and also helped tomake television possible, among other things).

    3The sed provided proof that atoms doindeed exist—a fact that had, surprisingly, been in some dispute. The third merely gedthe world.

    Einstein was born in Ulm, in southern Germany, in 1879, but grew up in Munich. Little inhis early life suggested the greato e. Famously he didn’t learn to speak until he wasthree. In the 1890s, his father’s electrical business failing, the family moved to Milan, butAlbert, by now a teenager, went to Switzerland to tinue his education—though he failedhis college entrance exams on the first try. In 1896 he gave up his German citizenship toavoid military scription aered the Zurich Polyteistitute on a four-year coursedesigo  out high school sce teachers. He was a bright but not outstandingstudent.

    In 1900 he graduated and within a few months was beginning to tribute papers toAnnalen der Physik. His very first paper, on the physics of fluids in drinking straws (of allthings), appeared in the same issue as Planck’s quantum theory. From 1902 to 1904 heproduced a series of papers on statistical meily to discover that the quietlyproductive J. Willard Gibbs in ecticut had dohat work as well, in his ElementaryPrinciples of Statistical Meics of 1901.

    At the same time he had fallen in love with a fellow student, a Hungarian named MilevaMari 1901 they had a child out of wedlock, a daughter, who was discreetly put up foradoptioein never saw his child. Two years later, he and Maric were married. Iween these events, in 1902, Eiook a job with the Swiss patent office, where hestayed for the  seven years. He ehe work: it was challenging enough to engage hismind, but not so challenging as to distract him from his physics. This was the backgroundagainst which he produced the special theory of relativity in 1905.

    Called “On the Electrodynamioving Bodies,” it is one of the most extraordinarystific papers ever published, as much for how it resented as for what it said. It hadno footnotes or citations, tained almost no mathematics, made ion of any workthat had influenced or preceded it, and aowledged the help of just one individual, a3Einstein was honored, somewhat vaguely, &quot;for services to theoretical physics.&quot; He had to wait sixteen years, till1921, to receive the award-quite a long time, all things sidered, but nothing at all pared with FrederickReines, who detected the rino in 1957 but wasnt honored with a Nobel until 1995, thirty-eight years later, orthe Germa Ruska, who ied the eleicroscope in 1932 and received his Nobel Prize in 1986,more than half a tury after the fact. Sinobel Prizes are never awarded posthumously, loy  be asimportant a factor as iy for prizewinners.

    colleague at the patent offiamed Michele Besso. It was, wrote C. P. Snow, as if Einstein“had reached the clusions by pure thought, unaided, without listening to the opinions ofothers. To a surprisingly large extent, that is precisely what he had done.”

    His famous equation, E =mc2, did not appear with the paper, but came in a brief supplementthat followed a few months later. As you will recall from school days, E in the equation standsfor energy, m for mass, and c2for the speed of light squared.

    In simplest terms, what the equation says is that mass and energy have an equivalence.

    They are two forms of the same thing: energy is liberated matter; matter is energy waiting tohappen. Since c2(the speed of light times itself) is a truly enormous number, what theequation is saying is that there is a huge amount—a really huge amount—of energy bound upin every material thing.

    4You may not feel outstandingly robust, but if you are an average-sized adult you willtain within your modest frame han 7 x 1018joules of potential energy—enough toexplode with the force of thirty very large hydrogen bombs, assuming you knew how toliberate it and really wished to make a point. Everything has this kind of energy trappedwithin it. We’re just not very good at getting it out. Even a uranium bomb—the mosteic thing roduced yet—releases less than 1 pert of the energy it couldrelease if only we were more ing.

    Among much else, Einstein’s theory explained how radiation worked: how a lump ofuranium could throw out stant streams of high-level energy without melting away like anice cube. (It could do it by verting mass to energy extremely effitly à laE =mc2.) Itexplained how stars could burn for billions of years without rag through their fuel. (Ditto.)At a stroke, in a simple formula, Einstein endowed geologists and astronomers with theluxury of billions of years. Above all, the special theory showed that the speed of light wasstant and supreme. Nothing could overtake it. It brought light (no pun intended, exactly) tothe very heart of our uanding of the nature of the universe. Not ially, it alsosolved the problem of the luminiferous ether by making it clear that it did. Einsteingave us a universe that didn’t .

    Physicists as a rule are not overatteo the pronous of Swiss patent officeclerks, and so, despite the abundance of useful tidings, Einstein’s papers attracted little notice.

    Having just solved several of the deepest mysteries of the universe, Einstein applied for a jobas a uy lecturer and was rejected, and then as a high school teacher and was rejectedthere as well. So he went back to his job as an examihird class, but of course he keptthinking. He hadn’t even e close to finishi.

    When the poet Paul Valéry once asked Einstein if he kept a notebook to record his ideas,Einstein looked at him with mild but genuine surprise. “Oh, that’s not necessary,” he replied.

    “It’s so seldom I have one.” I need hardly point out that when he did get o teo begood. Einstein’s  idea was one of the greatest that anyone has ever had—indeed.he verygreatest, acc to Boorse, Motz, and Weaver ihoughtful history of atomic sce.

    4How c came to be the symbol for the speed of light is something of a mystery, but David Bodanis suggests itprobably came from the Latin celeritas, meaning swiftness. The relevant volume of the Oxford EnglishDiary, piled a decade before Einsteins theory, reizes c as a symbol for many things, from carbonto cricket, but makes ion of it as a symbol fht or swiftness.

    “As the creation of a single mind,” they write, “it is undoubtedly the highest intellectualachievement of humanity,” which is of course as good as a pliment  get.

    In 1907, or so it has sometimes been written, Albert Einstein saw a workman fall off a roofand began to think about gravity. Alas, like many good stories this one appears to beapocryphal. Acc to Einstein himself, he was simply sitting in a chair when the problemof gravity occurred to him.

    Actually, what occurred to Einstein was something more like the beginning of a solution tothe problem of gravity, si had been evident to him from the outset that ohing missingfrom the special theory was gravity. What was “special” about the special theory was that itdealt with things moving in an essentially unimpeded state. But what happened when a thingin motion—light, above all—entered an obstacle such as gravity? It was a question thatwould occupy his thoughts for most of the  decade ao the publication in early1917 of a paper entitled “ological siderations on the General Theory of Relativity.”

    The special theory of relativity of 1905 rofound and important piece of work, ofcourse, but as C. P. Snow once observed, if Einstein hadn’t thought of it when he did someoneelse would have, probably within five years; it was an idea waiting to happen. But the geheory was something else altogether. “Without it,” wrote Snow in 1979, “it is likely that weshould still be waiting for the theory today.”

    With his pipe, genially self-effag manner, arified hair, Einstein was too splendida figure to remain permaly obscure, and in 1919, the war over, the world suddenlydiscovered him. Almost at once his theories of relativity developed a reputation for beingimpossible for an ordinary person to grasp. Matters were not helped, as David Bodanis pointsout in his superb book E=mc2, when the New York Times decided to do a story, and—forreasons that ever fail to excite wonder—sent the paper’s golfing correspo, oneHenry Crouch, to duct the interview.

    Crouch was hopelessly out of his depth, and got nearly everything wrong. Among the morelasting errors in his report was the assertion that Einstein had found a publisher daring enoughto publish a book that only twelve men “in all the world could prehend.” There was nosuch book, no such publisher, no such circle of learned men, but the notion stuyway.

    Soon the number of people who could grasp relativity had been reduced even further in thepopular imagination—and the stific establishment, it must be said, did little to disturb themyth.

    When a journalist asked the British astronomer Sir Arthur Eddington if it was true that hewas one of only three people in the world who could uaein’s relativity theories,Eddington sidered deeply for a moment and replied: “I am trying to think who the thirdperson is.” In fact, the problem with relativity wasn’t that it involved a lot of differentialequations, Lorentz transformations, and other plicated mathematics (though it did—eveein needed help with some of it), but that it was just so thhly nonintuitive.

    In essence what relativity says is that spad time are not absolute, but relative to boththe observer and to the thing being observed, and the faster one moves the more pronouhese effects bee. We ever accelerate ourselves to the speed of light, and the harderwe try (and faster we go) the more distorted we will bee, relative to an outside observer.

    Almost at once popularizers of sce tried to e up with ways to make these ceptsaccessible to a general audience. One of the more successful attempts—ercially atleast—was The ABC of Relativity by the mathemati and philosopher Bertrand Russell. Init, Russell employed an image that has been used many times since. He asked the reader toenvision a train one hundred yards long moving at 60 pert of the speed of light. Tosomeoanding on a platform watg it pass, the train would appear to be oyyards long and everything on it would be similarly pressed. If we could hear thepassengers orain speak, their voices would sound slurred and sluggish, like a recordplayed at too sloeed, and their movements would appear similarly ponderous. Even theclocks orain would seem to be running at only four-fifths of their normal speed.

    However—and here’s the thing—people orain would have no sense of thesedistortions. To them, everything orain would seem quite normal. It would be we oform who looked weirdly pressed and slowed down. It is all to do, you see, with yourpositioive to the moving object.

    This effect actually happens every time you move. Fly across the Uates, and youwill step from the plane a quinzillionth of a sed, or something, youhan those you leftbehind. Even in walking across the room you will very slightly alter your own experieime and space. It has been calculated that a baseball thrown at a hundred miles an hour willpick up 0.000000000002 grams of mass on its way to home plate. So the effects of relativityare real and have been measured. The problem is that such ges are muall tomake the ti detectable differeo us. But for other things in the universe—light,gravity, the universe itself—these are matters of sequence.

    So if the ideas of relativity seem weird, it is only because we don’t experiehese sorts ofiions in normal life. However, to turn to Bodanis again, we all only enterother kinds of relativity—for instah regard to sound. If you are in a park and someoneis playing annoying music, you know that if you move to a more distant spot the music willseem quieter. That’s not because the musicis quieter, of course, but simply that your positioive to it has ged. To something too small or sluggish to duplicate this experience—asnail, say—the idea that a boom box could seem to two observers to produce two differentvolumes of music simultaneously might seem incredible.

    The most challenging and nonintuitive of all the cepts in the general theory of relativityis the idea that time is part of space. Our instinct is tard time as eternal, absolute,immutable—nothing  disturb its steady tick. In fact, acc to Einstein, time is variableand ever ging. It even has shape. It is bound up—“iricably interected,” inStephen Hawking’s expression—with the three dimensions of spa a curious dimensionknoacetime.

    Spacetime is usually explained by asking you to imagine something flat but pliant—amattress, say, or a sheet of stretched rubber—on which is resting a heavy round object, suchas an iron ball. The weight of the iron ball causes the material on which it is sitting to stretd sag slightly. This is roughly analogous to the effect that a massive object such as the Sun(the iron ball) has on spacetime (the material): it stretches and curves and s it. Now ifyou roll a smaller ball across the sheet, it tries to go in a straight line as required by on’slaws of motion, but as it nears the massive objed the slope of the sagging fabric, it rollsdownward, iably drawn to the more massive object. This is gravity—a product of thebending of spacetime.

    Every object that has mass creates a little depression in the fabric of the os. Thus theuniverse, as Dennis Overbye has put it, is “the ultimate sagging mattress.” Gravity on thisview is no longer so much a thing as an oute—“not a ‘force’ but a byproduct of theing of spacetime,” in the words of the physicist Michio Kaku, who goes on: “In somesense, gravity does ; what moves the plas and stars is the distortion of spadtime.”

    Of course the sagging mattress analogy  take us only so far because it doesn’tincorporate the effect of time. But then our brains  take us only so far because it is sonearly impossible to envision a dimension prising three parts space to one part time, allinterwoven like the threads in a plaid fabric. At all events, I think we  agree that this wasan awfully big thought for a young man staring out the window of a patent offi thecapital of Switzerland.

    Among much else, Einstein’s general theory of relativity suggested that the universe mustbe either expanding or trag. But Einstein was not a ologist, and he accepted theprevailing wisdom that the universe was fixed aernal. More or less reflexively, hedropped into his equations something called the ological stant, which arbitr<u>.</u>arilyterbalahe effects of gravity, serving as a kind of mathematical pause button. Bookson the history of sce always five Eihis lapse, but it was actually a fairlyappalling piece of sd he k. He called it “the biggest blunder of my life.”

    tally, at about the time that Einstein was affixing a ological stant to histheory, at the Lowell Observatory in Arizona, an astronomer with the cheerily intergalaame of Vesto Slipher (who was in fact from Indiana) was taking spectrographic readings ofdistant stars and disc that they appeared to be moving away from us. The universewasn’t static. The stars Slipher looked at showed unmistakable signs of a Doppler shift5—thesame meism behind that distinctive stretched-out yee-yummm sound cars make as theyflash past on a racetrack. The phenomenon also applies to light, and in the case of reggalaxies it is known as a red shift (because light moving away from us shifts toward the redend of the spectrum; approag light shifts to blue).

    Slipher was the first to notice this effect with light and to realize its potential importancefor uanding the motions of the os. Unfortunately no one muoticed him. TheLowell Observatory, as you will recall, was a bit of an oddity thanks to Percival Lowell’sobsession with Martian als, whi the 1910s made it, in every sense, an outpost ofastronomical endeavor. Slipher was unaware of Einstein’s theory of relativity, and the worldwas equally unaware of Slipher. So his finding had no impact.

    Glory instead would pass to a large mass of ego named Edwin Hubble. Hubble was born in1889, ten years after Einstein, in a small Missouri town on the edge of the Ozarks and grewup there and ion, Illinois, a suburb of Chicago. His father was a successful insuranceexecutive, so life was always fortable, and Edwin enjoyed a wealth of physidowments, too. He was a strong and gifted athlete, charming, smart, and immensely good-looking—“handsome almost to a fault,” in the description of William H. Cropper, “an5Named for Johann Christian Doppler, an Austrian physicist, who first noticed the effe 1842. Briefly, pens is that as a moving object approaches a stationary os sound waves bee bunched up as they cramup against whatever device is receiving them (your ears, say), just as you would expect of anything that is beingpushed from behind toward an immobile object. This bung is perceived by the listener as a kind of pinchedand elevated sound (the yee). As the sound source passes, the sound waves spread out ahen, causing thepitch to drop abruptly (the yummm).

    Adonis” in the words of another admirer. Acc to his own ats, he also maofit into his life more or less stant acts of valor—resg drowning swimmers, leadingfrightened men to safety across the battlefields of France, embarrassing world-championboxers with knockdown punches in exhibition bouts. It all seemed too good to be true. It was.

    For all his gifts, Hubble was also an ie liar.

    This was more than a little odd, for Hubble’s life was filled from an early age with a levelof distin that was at times almost ludicrously golden. At a single high school track meetin 1906, he won the pole vault, shot put, discus, hammer throw, standing high jump, andrunning high jump, and was on the winning mile-relay team—that is seven first places i—and came in third in the broad jump. In the same year, he set a state record for the highjump in Illinois.

    As a scholar he was equally profit, and had no trouble gaining admission to studyphysid astronomy at the Uy of Chicago (where, tally, the head of thedepartment was now Albert Michelson). There he was selected to be one of the first Rhodesscholars at Oxford. Three years of English life evidently turned his head, for he returoWheaton in 1913 wearing an Inverness cape, smoking a pipe, and talking with a peculiarlyorotund at—not quite British but not quite not—that would remain with him for life.

    Though he later claimed to have passed most of the sed decade of the tury practiglaw iucky, in fact he worked as a high school teacher and basketball coa NewAlbany, Indiana, before belatedly attaining his doctorate and passing briefly through theArmy. (He arrived in Franonth before the Armistid almost certainly never hearda shot fired in anger.)In 1919, now aged thirty, he moved to California and took up a position at the MountWilson Observatory near Los Angeles. Swiftly, and more than a little uedly, hebecame the most outstanding astronomer of the tweh tury.

    I藏书网t is worth pausing for a moment to sider just how little was known of the os at thistime. Astrooday believe there are perhaps 140 billion galaxies in the visible universe.

    That’s a huge number, much bigger than merely saying it would lead you to suppose. Ifgalaxies were frozen peas, it would be enough to fill a large auditorium—the old BostonGarden, say, or the Royal Albert Hall. (An astrophysicist named Bruce Gregory has actuallyputed this.) In 1919, when Hubble first put his head to the eyepiece, the number of thesegalaxies that were known to us was exactly ohe Milky Way. Everything else was thoughtto be either part of the Milky Way itself or one of many distant, peripheral puffs of gas.

    Hubble quickly demonstrated h that belief was.

    Over the  decade, Hubble tackled two of the most fual questions of theuniverse: how old is it, and how big? To answer both it is necessary to know two things—howfar away certain galaxies are and how fast they are flying away from us (what is known astheir recessional velocity). The red shift gives the speed at which galaxies are retiring, butdoesn’t tell us how far away they are to begin with. For that you need what are known as“standard dles”—stars whose brightness  be reliably calculated and used asbenchmarks to measure the brightness (and hence relative distance) of other stars.

    Hubble’s luck was to e along soon after an ingenious woman named Hea Swat had figured out a way to do so. Leavitt worked at the Harvard College Observatory asa puter, as they were known. puters spent their lives studying photographic plates ofstars and making putations—hehe  was little more than drudgery by anothername, but it was as close as women could get to real astronomy at Harvard—or indeed prettymuywhere—in those days. The system, however unfair, did have certain uedbes: it meant that half the fi minds available were directed to work that wouldotherwise have attracted little reflective attention, and it ehat women ended up with anappreciation of the firucture of the os that often eluded their male terparts.

    One Harvard puter, Annie Jump on, used her repetitive acquaintah thestars to devise a system of stellar classifications so practical that it is still ioday.

    Leavitt’s tribution was even more profound. She noticed that a type of star known as aCepheid variable (after the stellation Cepheus, where it first was identified) pulsated witha regular rhythm—a kind of stellar heartbeat. Cepheids are quite rare, but at least one of themis well known to most of us. Polaris, the Pole Star, is a Cepheid.

    We now know that Cepheids throb as they do because they are elderly stars that havemoved past their “main sequence phase,” in the parlance of astronomers, and bee redgiants. The chemistry iants is a little weighty for our purposes here (it requires anappreciation for the properties of singly ionized helium atoms, among quite a lot else), but putsimply it means that they burn their remaining fuel in a way that produces a very rhythmic,very reliable brightening and dimming. Leavitt’s genius was to realize that by paring therelative magnitudes of Cepheids at different points in the sky you could work out where theywere iion to each other. They could be used as “standard dles”—a term she edand still in universal use. The method provided only relative distances, not absolute distances,but even so it was the first time that anyone had e up with a usable way to measure thelarge-scale universe.

    (Just to put these insights into perspective, it is perhaps worth noting that at the time Leavittand on were inferring fual properties of the os from dim smudges onphotographic plates, the Harvard astronomer William H. Pickering, who could of course peerinto a first-class telescope as often as he wanted, was developing his seminal theory that darkpatches on the Moon were caused by swarms of seasonally migrating is.)binit’s ic yardstick with Vesto Slipher’s handy red shifts, Edwin Hubblenow began to measure selected points in space with a fresh eye. In 1923 he showed that a puffof distant gossamer in the Andromeda stellation known as M31 wasn’t a gas cloud at allbut a blaze of stars, a galaxy in its ht, a huhousand light-years across and atleast nine huhousand light-years away. The universe was vaster—vastly vaster—thananyone had ever supposed. In 1924 he produced a landmark paper, “Cepheids in SpiralNebulae” (nebulae,from the Latin for “clouds,” was his word falaxies), showing that theuniverse sisted not just of the Milky Way but of lots of indepe galaxies—“islanduniverses”—many of them bigger than the Milky Way and much more distant.

    This finding alone would have ensured Hubble’s reputation, but he now turo thequestion of w out just how much vaster the universe was, and made an even morestriking discovery. Hubble began to measure the spectra of distant galaxies—the busihatSlipher had begun in Arizona. Using Mount Wilson’s new hundred-inch Hooker telescopeand some clever inferences, he worked out that all the galaxies in the sky (except for our ownlocal cluster) are moving away from us. Moreover, their speed and distance were lyproportional: the further away the galaxy, the faster it was moving.

    This was truly startling. The universe was expanding, swiftly and evenly in all dires. Itdidn’t take a huge amount of imagination to read backwards from this and realize that it musttherefore have started from some tral point. Far from being the stable, fixed, eternal voidthat everyone had always assumed, this was a universe that had a beginning. It mighttherefore also have an end.

    The wonder, as Stephen Hawking has noted, is that no one had hit on the idea of theexpanding universe before. A statiiverse, as should have been obvious to on ahinking astronomer since, would collapse in upon itself. There was also the problemthat if stars had been burning indefinitely in a statiiverse they’d have made the wholeintolerably hot—certainly much too hot for the likes of us. An expanding universe resolvedmuch of this at a stroke.

    Hubble was a much better observer than a thinker and didn’t immediately appreciate thefull implications of what he had found. Partly this was because he was woefully ignorant ofEinstein’s General Theory of Relativity. This was quite remarkable because, for ohiein and his theory were world famous by now. Moreover, in 1929 Albert Michelson—now in his twilight years but still one of the world’s most alert aeemed stists—accepted a position at Mount Wilson to measure the velocity of light with his trustyinterferometer, and must surely have at least mentioo him the applicability of Einstein’stheory to his own findings.

    At all events, Hubble failed to make theoretical hay when the ce was there. Instead, itwas left to a Belgian priest-scholar (with a Ph.D. from MIT) named Gees Lema?tre t together the two strands in his own “fireworks theory,” which suggested that theuniverse began as a geometrical point, a “primeval atom,” which burst into glory and hadbeen moving apart ever si was ahat very ly anticipated the modernception of the Big Bang but was so far ahead of its time that Lema?tre seldom gets morethan the sentence or two that we have given him here. The world would need additionaldecades, and the ient discovery of ic background radiation by Penzias and Wilsonat their hissing antenna in New Jersey, before the Big Bang would begin to move fromiing idea to established theory.

    her Hubble ein would be much of a part of that big story. Though no onewould have guessed it at the time, both men had done about as much as they were ever goingto do.

    In 1936 Hubble produced a popular book called The Realm of the Nebulae, whichexplained in flattering style his own siderable achievements. Here at last he showed thathe had acquainted himself with Einstein’s theory—up to a point anyway: he gave it fesout of about two hundred.

    Hubble died of a heart atta 1953. One last small oddity awaited him. For reasonscloaked in mystery, his wife deed to have a funeral and never revealed what she did withhis body. Half a tury later the whereabouts of the tury’s greatest astronomer remainunknown. For a memorial you must look to the sky and the Hubble Space Telescope,launched in 1990 and named in his honor.

百度搜索 A Short History of Nearly Everything 天涯 或 A Short History of Nearly Everything 天涯在线书库 即可找到本书最新章节.