Chapter 10 Chapter 8 Einstein's Universe

As the nineteenth century wore on, scientists could look back with satisfaction on having solved most of the mysteries of physics. Let us give a few examples: electricity, magnetism, gas science, optics, acoustics, dynamics and statistical mechanics have all bowed before them.They had discovered x-rays, cathode rays, electrons, and the phenomena of radiation, and invented the units of measurement, the ohm, the watt, the kelvin, the joule, the ampere, and the tiny erg. Anything that can be oscillated, accelerated, disturbed, distilled, combined, weighed, or turned into a gas, they have done it; in the process, They came up with a whole bunch of general laws.These laws are very important and very grand, until today we often write them in capital letters: "Electromagnetic Field Theory of Light", "Liskov's Law of Mutual Ratio", "Charlie's Law of Gases", "Law of Combination of Volumes", "Zeroth Law" , "Concept of Atomic Valence", "Law of Mass Action" and so on, there are too many to count.The whole world tinkled and clicked to the sound of the machines and instruments they invented.Many smart people think that scientists don't have much left to do.

In 1875, a young man named Max Planck in Kiel, Germany was hesitant about whether he should pursue mathematics or physics in his life.People sincerely advised him not to choose physics, because the big problems of physics have already been solved.They told him categorically that the next century would be one of consolidation and improvement, not revolution.Planck refused to listen, he delved into theoretical physics, and devoted himself to the core problem of thermodynamics--the research work of entropy. To an ambitious young man, research on this problem seemed promising. In 1891, he made the result, only to find to his surprise that this important work on entropy had actually been done.He was a reclusive scholar at Yale called J. Willard Gibbs.

Gibbs is a remarkable figure, but one that most people probably haven't heard of.He behaved poorly and seldom appeared in public. Except for three years of research in Europe, he spent almost his entire life within a three-block radius: his home on one side and the Yale University campus in New Haven, Connecticut, on the other.For the first ten years at Yale, he didn't even bother to collect his salary. (He had additional income.) He was a professor at the university from 1871 until his death in 1903.During this period, an average of only one student took his class each semester.What he wrote was obscure and difficult to understand, and he often used symbols invented by himself, which many people thought was a bible.But deep within those arcane formulas lie the wisest and deepest insights.

During 1875-1878, Gibbs wrote a series of papers, compiled into a collection of "On the Equilibrium of Multiphase Matter". The book is an excellent account of nearly all the principles of thermodynamics -- including, in the words of William H. Cooper, "gases, mixtures, planes, solids, phase shifts...chemical reactions, electrochemical cells, precipitation, and osmosis ".Ultimately, Gibbs wanted to show that thermodynamics didn't just apply to heat and energy on the vast and noisy scale of a steam engine, but that it existed at the atomic level of chemical reactions as well, and to a great extent.Gibbs' "Equilibrium" has always been called "The Principles of Thermodynamics," but for reasons beyond guesswork, Gibbs was willing to publish these epoch-making insights in the "Proceedings of the Connecticut Academy of Arts and Sciences," a A magazine that was unknown even in Connecticut.That's why Planck didn't hear his name until much later.

Undeterred—well, perhaps a little timidly, Planck began to turn his attention to other problems. 1 On that front, we shall wait a moment, with a slight (and appropriate) diversion to Cleveland, Ohio, to an institution then known as the Case School of Applied Science. There was a middle-aged physicist there in the 1880s named Albert Michelson.He carried out a series of experiments with the assistance of his friend the chemist Edward Morey.Those experiments yielded very interesting and surprising results that will have a major impact on many things to come. What Michelson and Morey did -- inadvertently, indeed -- undermined long-held beliefs in something called a light ether.It is a medium that is stable, invisible, weightless, frictionless, and unfortunately entirely imaginary.It is believed that this medium fills the universe.Hypothesized by Descartes, embraced by Newton and revered by almost everyone thereafter, the aether occupies an absolutely central place in nineteenth-century physics as an explanation of why light travels through the emptiness of space.It was especially necessary at the beginning of the 19th century, when light and electromagnetism were considered to be waves, that is to say vibrations of sorts.The vibrations have to be in something for that to happen, so an ether is needed and long believed to exist.Until 1909, the great British physicist JJ Thomson still insisted: "Ether is not the imagination of some thinking philosopher, it is as indispensable to us as the air we breathe." --He After more than 4 years of saying this, it is indisputably certain that the ether does not exist.All in all, people really cannot do without ether.

If you need to illustrate the idea that 19th-century America was the land of opportunity, you'd be hard-pressed to find another example like Albert Michelson.Born in 1852 in a poor Jewish merchant family on the border between Germany and Poland, he came to the United States with his family as a child and grew up in a mining village in a gold rush area in California.His father ran a dry goods business there.His family was too poor to afford college, so he came to Washington, the capital, and wandered around the main entrance of the White House, hoping to meet Ulysses S. Grant when he went out for a walk every day. (Apparently it was a more modest era.) Michelson so won the president's favor during such walks that Grant even agreed to send him to the U.S. Naval Academy for free.It was there that Michelson studied physics.

A decade later, Michelson, now a professor at the Case School in Cleveland, became interested in measuring something called ether drift -- a headwind produced by moving objects through space.One of the predictions of Newtonian physics is that light appears to the observer to travel at different speeds as it travels through the ether, depending on whether the observer is moving toward or against the light source.But no one could figure out a way to measure this.It occurred to Michelson that the earth moves toward the sun for half a year, and moves against the sun for half a year.He thought the answer could be found by making careful measurements in opposite seasons, comparing the speed of light between the two.

Michelson persuaded the inventor of the telephone, the newly rich Alexander Graham Bell, to finance the construction of an ingenious and sensitive instrument of Michelson's own design, called an interferometer, to measure light with great precision. speed.Then, with the assistance of the affable and mysterious Morey, Michelson took several years of careful measurements.It was such delicate and laborious work that Michelson's spirits were so broken that the work had to be interrupted for some time. However, by 1887, they had results.Moreover, this result was completely beyond the expectations of the two scientists.

"It turns out that the speed of light is the same in all directions and in all seasons," writes Caltech astrophysicist Kip S. Thorne. This is 200 years -- exactly 200 years, actually -- The first indication that Newton's laws might not hold true everywhere and everywhere.In the words of William H. Cropper, the Michelson-Morley result became "quite possibly the most negative result in the history of physics".For this, Michelson was awarded the Nobel Prize in Physics -- thus becoming the first American to do so -- but not for 20 years.Meanwhile, the Michelson-Morley experiment floated uncomfortably in the back of scientists' minds like a musty smell.

Remarkably, despite his discovery, when the 20th century rolled around, Michelson felt like everyone else that scientific work was drawing to a close -- in the words of one author in the journal Nature Said: "It is enough to add a few turrets and spires, and carve a few reliefs on the roof." In reality, of course, the world is about to enter a scientific century.At that time, everyone will understand a little, and no one will understand everything.Scientists are about to find themselves floating in a sea of ​​particles and antiparticles, moments of being and disappearing that make nanoseconds seem so sluggish, ordinarily, everything is so weird.Science is moving from macrophysics to microphysics.In the former, objects can be seen, touched, and measured; in the latter, things happen suddenly and unimaginably quickly, completely beyond the scope of imagination.We are on the verge of entering a quantum age, and the first person to push the door on it was the hitherto unlucky Max Planck.

In 1900, at the age of 42, Planck was already a theoretical physicist at the University of Berlin.He revealed a new "quantum theory" , the theory is that energy is not a stream-like continuum, but something that travels in packets, which he calls quanta.It's really a novel concept, and a good one at that.In the short term, it could provide an explanation for the Michelson-Morley puzzle, because it shows that light doesn't have to be a wave in the first place.In the long run, it will lay the foundation for the whole of modern physics.Regardless, it's the first sign that the world is about to change. But the epoch-making event - the dawn of a new age - did not take place until 1905.At that time, the German physics journal "Physical Yearbook" published a series of papers, the author is a young Swiss staff.He didn't go to university, didn't use a laboratory, and usually only ran the small library of the National Patent Office in Bern.He is a third-level technical examiner at the Patent Office. (He applied to be promoted to second-level examiner, but was rejected.) His name was Albert Einstein.In that fateful year, he submitted five papers to the Annals of Physics, three of which, in the words of CP Snow, "arguably the greatest works in the history of physics" -- one using The quantum theory just proposed by Ranke examines the photoelectric effect, one treats the situation of suspended small particles (now called Brownian motion), and one outlines special relativity. The first, which explained the properties of light (and made many things possible, including television), won the author a Nobel Prize.The second provides evidence that atoms do exist -- a fact that, surprisingly, has been somewhat disputed in the past.The third book completely changed the world. Einstein was born in Ulm in southern Germany in 1879 but grew up in Munich.His early life hardly speaks to the big man he will become in the future.It is well known that he did not learn to speak until he was three years old. His father's electrical business went bankrupt and the family moved to Milan in the 1890s, but Albert, now a teenager, went to Switzerland to continue his studies - although he failed the university entrance exams at first. In 1896, he renounced his German citizenship to avoid being drafted into the army and enrolled in a four-year course at the Federal University of Technology in Zurich, designed to train secondary school teachers.He is a bright but unobtrusive student. After graduating from school in 1900, he began submitting papers to the Annals of Physics within a few months.His first paper, on (among so much to write about) the physics of fluids in straws, was published in the same issue as Planck's quantum theory.From 1902 to 1904 he wrote a series of papers on statistical mechanics, only to find that the prolific J. Willard Gibbs had quietly published the same work in Connecticut in 1901: Statistical Fundamentals of Mechanics". Albert once fell in love with a classmate, a Hungarian girl named Minerva Marici. In 1901 they had a child without marriage, a daughter.They were very cautious and gave their children to others.Einstein never met his own children.Two years later, he and Maric were married.During this time, Einstein accepted a position at the Swiss Patent Office, where he remained for the next seven years.He loved the job: it was challenging and kept his mind busy without distracting him from physics.It was against this background that he created the special theory of relativity in 1905. "On the Electrodynamics of Moving Bodies" is one of the best scientific papers ever published, both in its presentation and in its content.It has no footnotes, no citations, very little mathematics, no mention of any work that influenced or preceded this paper, just a acknowledgment of one's help.He was a colleague at the patent office named Michel Besso. CP Snow wrote that Einstein seemed to "come to his conclusions entirely from his own thoughts, alone, without the advice of others. To a large extent, that was the case". His famous equation E=mc2 does not appear in this paper, but appears in a short supplement a few months later.As you may recall from school, E in the equation is energy, m is mass, and c2 is the speed of light squared. In the simplest terms, this equation means: mass and energy are equivalent.They are two forms of the same thing: energy is released mass; mass is energy waiting to be released.Since c2 (the speed of light squared) is a huge number, this equation means that every object contains an enormous amount—really an enormous amount—of energy. 1 You may think that you are not very strong, but if you are an ordinary adult, your inconspicuous body contains no less than 7×1018 joules of potential—the power of the explosion is equivalent to 30 hydrogen bombs , if you know how to release it, and really want to.Every object contains such energy inside.We're just not very good at letting it out.Even a uranium bomb -- the most powerful thing we've ever built -- releases less than 1% of the energy it could release if we were smarter. Among them, Einstein's theory explains how radioactivity occurs: how a block of uranium emits a steady stream of intense radiant energy without melting like an ice block. (This is possible as long as mass is converted to energy extremely efficiently: E=mc2.) The theory explains why stars can burn for billions of years without running out of fuel. (Ibid.) Einstein used a simple formula to suddenly extend the horizon of geologists and astronomers by billions of years.In particular, the theory shows that the speed of light is constant, the fastest, and nothing can exceed it.So this brings us to the core of the nature of the universe in one fell swoop.Moreover, this theory also solves the problem of light ether, which shows that it does not exist.Einstein's universe doesn't need an ether. Physicists generally do not pay much attention to what the Swiss patent office staff publishes, so Einstein's paper did not attract much attention, despite the informative and useful information it provided.Having just solved some of the most intractable mysteries in the universe, Einstein applied for a position as a university lecturer and was rejected, then applied for a position as a high school teacher and was rejected again.So he went back to his job as a third-level inspector—though, of course, he didn't stop thinking about it.He is far from done. When the poet Paul Valéry once asked Einstein if he carried around a notebook to record his thoughts, Einstein gave him a look of mild but real surprise. "Oh, that's unnecessary," he replied, "I seldom carry a notebook." I needn't point out that if he did have a notebook, it would be very helpful.Einstein's next idea was the greatest idea of ​​all -- indeed the greatest idea, say Booles, Motz, and Weaver in their thoughtful history of atomic science. "As an ingenuity of a brain," they wrote, "it is undoubtedly the highest intellectual achievement of the human race." That rating is certainly high. In 1907, anyway, sometimes that's how it's written in the books, a worker fell off a roof, and Einstein started thinking about gravity.Gosh, like so many moving stories, there seems to be a question of veracity in this one.According to Einstein himself, when he thought about gravity, he was just sitting in a chair. In fact, what Einstein was thinking of was more like starting to find an answer to the problem of gravity.It was clear from the beginning that there was one thing missing from special relativity, and that was gravity.The reason why the special theory of relativity is "narrow" is that what it studies are things that move in an unobstructed state.But what if a thing in motion -- especially light -- encounters an obstacle such as gravity?He pondered the question for the better part of the next decade, culminating in early 1917 in a paper entitled "Cosmological Reflections on the General Theory of Relativity."Of course, the special theory of relativity in 1905 was a profound and important achievement.But, as CP Snow once pointed out, if Einstein didn't think of it, someone else would, probably within five years.This is something waiting to happen.But that general theory of relativity is something else entirely. "Without it," Snow wrote in 1979, "we might still be waiting for that theory today." Einstein, pipe in hand, affable, unrevealable, with tousled hair, was a remarkable figure.Such a figure cannot remain in obscurity forever. In 1919, the war was over, and the world suddenly found him.Almost at the same time, his theory of relativity became famous for being incomprehensible to ordinary people. The New York Times decided to write a story -- for reasons that will never be understood -- and sent one of the paper's golf reporters, Henry Crouch, to do the interview, and it turned out just as David Bodenis As pointed out in his excellent book "E=mc2", does not solve the problem at all. Crouch was so overwhelmed by the interview that he almost got everything wrong.Among the many memorable errors in his reporting was his assertion that Einstein had a publisher who had the guts to publish a book that only a dozen people in the world could understand.Of course, no such book exists, no such publisher exists, and no such small academic community exists, but the perception has taken hold.Before long, the number of people who could figure out relativity was much smaller in people's imagination--it should be noted that the scientific community has not tried to clarify this myth. A reporter asked the British astronomer Arthur Eddington if he was really one of only three people in the world who could understand Einstein's theory of relativity.Eddington thought carefully for a moment, then replied, "I'm wondering who the third person is." Actually, the problem with relativity is not that it involves many differential equations, Lorentz transformations, and other complex mathematics ( While it does involve—even Einstein needed help in some ways), it's that it's not fully intuitive. In essence, the content of the theory of relativity is: space and time are not absolute, but relative to both the observer and the observed; the faster a person moves, the more obvious this effect is.We can never accelerate ourselves to the speed of light; the harder we try (and therefore the faster we go) relative to an observer, the more distorted we become. At about the same time, those engaged in the popularization of science tried to make these concepts understandable to the broad masses.The ABCs of Relativity, written by the mathematician and philosopher Russell, was one of the more successful attempts—at least commercially.In this book Russell uses a metaphor that has been used many times before.He asked readers to imagine a 90-meter-long train traveling at 60% the speed of light.To someone standing on the platform watching it pass, the train will appear to be only 70 meters long, and everything on it will be similarly reduced.If we could hear the people in the car talking, their voices would sound muffled and sluggish, like a record played too slowly, and their movements would seem clumsy.Even the car clock would seem to be ticking at only four-fifths of its normal speed. And yet—and that's the problem—the people in the car don't feel transformed.From their point of view, everything in the car seemed normal.Instead, we standing on the platform became strangely smaller and our movements slowed down.You see, it's all about where you are relative to the moving object. In fact, every move you make has this effect.Fly across the United States, and you'll step out of the plane in about a quadrillionth of a second, a little younger than the person leaving the plane behind you.Even when you walk from one end of the room to the other, your own experience of time and space changes slightly.It has been calculated that a baseball thrown at 160 kilometers per hour will gain 0.000 000 000 002 grams of matter on its way to home plate.Therefore, the effect of the theory of relativity is concrete and can be measured.The problem is that the change is so small that we don't notice it.But when it comes to other things in the universe—light, gravity, the universe itself—those are big, big things. So if the concept of relativity seems weird, it's only because we don't experience these kinds of interactions in normal life.Still, having to turn to Bonidance, we all often encounter other kinds of relativity—such as sound.If you're in a park and somebody's playing bad music, you know, if you go further away, the music seems to get softer.Of course, that's not because the music is really lighter, it's just because your position with respect to the music has changed.For something so small or slow that it can't have the same experience -- like a snail -- it might be hard to believe that a single speaker seems to blast music at two volumes to two listeners at the same time. Of the many concepts in "general relativity," the most challenging, and least intuitive, is the notion that time is an integral part of space.We instinctively regard time as eternal, absolute, and unchangeable, and believe that nothing can interfere with its steadfast pace.In fact, Einstein believed that time is mutable and ever-changing.Time even has shape.One part of time combined with three parts of space -- "inextricably intertwined," in Stephen Hawking's words -- to form, uncannily, one "time and space." Usually, space-time is explained like this: Please imagine a flat and flexible object-such as a carpet or a stretched rubber mat-on which is placed a heavy and round object, such as an iron ball.The weight of the iron ball causes the bottom pad below to stretch and sag slightly.This is roughly similar to the effect of a huge object such as the sun (iron ball) on space-time (the bottom cushion): the iron ball makes the bottom cushion stretch, bend, and tilt.Now, if you roll a smaller ball across the mat, it tries to move in a straight line, just like Newton's laws of motion require.However, when it approached the big ball and the sunken part of the bottom pad, it rolled down and was inevitably sucked by the big ball.This is gravity - a product of the curvature of space-time. Any object with mass can create a small pit on the floor of the universe.Thus, as Dennis Overby puts it, the universe is "the ultimate sunken floor".From this point of view, gravity is not so much a thing as a consequence—in the words of physicist Michio Kaku: "Not a force, but a by-product of the curvature of space-time. "Kaku went on to say: "In a sense, there is no gravity; what moves the planets and stars is the deformation of space and time." Of course, the metaphor of a sunken floor can only help us so far, since time is not involved.That being said, our brains can only imagine so much.It is almost impossible to imagine that space and time are woven into a space-time in a ratio of 3:1, like threads are woven into a lattice floor mat.In any case, I think we can all agree that this is indeed a remarkable insight from a young man gazing out the window of the Swiss capital's patent office. Einstein's general theory of relativity offered many insights.Among them, he believes that the cosmic heart is always expanding or contracting.However, Einstein was not a cosmologist, and he accepted the prevailing view that the universe is fixed and eternal. More or less instinctively, he added to his equation what he called the cosmological constant.He uses it as a kind of mathematical pause button, arbitrarily using it to counteract the effects of gravity.The history books of science always forgive Einstein for this mistake, but this is actually a terrible thing in science.He called it "the biggest mistake I've ever made in my life." Coincidentally, around the time Einstein was adding a constant to his theory, an astronomer at Lowell Observatory in Arizona, who was recording readings on the spectrograms of distant stars, noticed that the stars seemed to be moving away. we go away.The astronomer has a galaxy-sounding name: Vesto Slaver (he's actually a native of Indiana).It turns out that the universe is not static.Slifer found that the stars clearly showed signs of a Doppler shift -- the same mechanism that makes the coherent and characteristic "ch-whoosh" sound of passing cars on a racetrack. . 1 This phenomenon also applies to light; in the case of receding galaxies, it is called a redshift (since light receding from us is is moving toward the blue end). Sliever was the first to notice this effect of light and realized that it would be important for future understanding of the motion of the universe.Unfortunately, no one paid much attention to him.You'll recall that Percival Lowell devoted himself to studying canals on Mars here, so Lowell Observatory is a bit of a unique place.By the first decade of the 20th century, it had become in every sense an outpost for the study of astronomy.Slyfer was unaware of Einstein's theory of relativity, and neither was the world, so his discoveries had no effect. The honor went instead to a very pompous mogul named Edwin Harper.Hubble was born in 1889 in a small Missouri town on the edge of the Ozark Plateau, 10 years younger than Einstein; he grew up there and in Wheaton, Illinois, a suburb of Chicago.His father was a successful insurance company manager, so life in the family was always well off.Edwin was also born with a good body.He was a powerful, gifted athlete, charismatic, stylish, and good-looking--in the words of William H. Cropper, "unbecomingly handsome"; in the words of another admirer , "as beautiful as Adonis".In his own words, he often did some righteous things in his life-rescuing people who fell into the water; leading terrified people across the French battlefield and taking them to safety; The world champion boxer fell to the ground, embarrassing them.It's all too good to be true, but it's all true.For all his talent, Hubble was also a stubborn liar. That's unusual, because Hubble's life from an early age was filled with genuine oddities, sometimes downright extraordinary.At one middle school track meet in 1906 alone, he won the pole vault, shot put, discus, hammer throw, standing high jump, approach jump, and was a member of the winning relay team—that is, he won won 7 first places.That same year, he set the Illinois state high jump record. As an academic, he was also very good, and he was admitted to the University of Chicago without any difficulty, studying physics and astronomy (the dean of the department was Albert Michelson, coincidentally).There he was selected as one of Oxford's first Rhodes Scholars. Three years of living in England had clearly gone to his head. When he returned to Wheaton in 1913, wearing a long cloak, smoking a pipe, talking in a queer, eloquent way--not quite English, but somewhat English--he looked Actually keep it for life.He later claimed that he spent most of the 1920s as a lawyer in Kentucky, but in fact he was a high school teacher and basketball coach in New Albany, Indiana, before earning his Ph.D. and spending much time in the Army short time. (He arrived in France a week before the armistice and almost certainly did not hear the angry gunfire.) In 1919, he was already 30 years old.He moved to California and took a position at the Mount Wilson Observatory near Los Angeles.Quite unexpectedly, he quickly became the most outstanding astronomer of the 20th century. It's worth pausing for a moment to consider how little was known about the universe at the time. Astronomers today believe that there are perhaps 140 billion galaxies in the visible universe.That's a huge number, much bigger than you'd think from hearing that.If a galaxy were a jelly bean, those beans could fill a large auditorium -- say, Old Boston Gardens or the Royal Albert Hall. (An astrophysicist named Bruce Gregory actually did the calculations.) In 1919, when Hubble first put his head in the telescope, there was only one known number of galaxies: the Milky Way.Everything else is thought to be either a constituent part of the Milky Way, or a cloud of gas among many in the distant sky.Hubble quickly proved this belief to be extremely wrong. Over the next 10 years, Hubble tackled two of the most fundamental questions about the universe: How long has the universe existed?How big is the universe?In order to answer these two questions, we must first know two things - how far a certain type of galaxy is from us, and how fast they are moving away from us (what is now called the recession speed).Redshift tells us how fast galaxies are receding, but not how far away they are.To do this, you need what's called a "standard candle" -- an accurate measurement of the brightness of a star, which serves as a basis for measuring the brightness of other stars (and thus their relative distances). Hubble's good luck came.Not long ago, a brilliant woman named Henrietta Swan-Levitt figured out a way to find such stars.Leavitt worked at the Harvard University College Observatory as what was then called a calculator.Computers spend their lives studying pictures of the stars and making calculations - hence the name Computers.Computer is just another word for hard work.But, in those days, that was the closest women got to astronomy, at Harvard, or anywhere.The system, while unfair, has an unexpected benefit: it means that half of the brightest minds go to work that few would otherwise, ensuring that women will eventually spot things their male colleagues tend to miss. The fine structure of the universe. A Harvard computer scientist named Anne Jump Cannon took advantage of her familiarity with the stars to develop a system for classifying stars.This system is so useful that it is still used today.Leavitt's contribution was even more profound.She noticed that a class of stars called Cepheids (named after the constellation Cepheid, where the first Cepheids were discovered) pulsated rhythmically -- a sort of "heartbeat" of a star.Cepheid variables are extremely rare, but at least one of them is familiar to most of us.Polaris is a Cepheid variable star. We now know that Cepheids pulsate because -- to use astronomers' jargon -- they have passed through the "main sequence phase" and become red giants.The chemistry of red giants is a bit elusive and beyond the scope of this book (it requires knowing many things, one of which is the properties of single-ionized helium atoms).But, in a nutshell, they produced a rhythmic, incessant flickering on and off as they burned the remaining fuel.Leavitt's genius was that she discovered that by comparing the sizes of Cepheid variables at different angles on the sky, they could calculate their relative positions.They can be referred to as standard candles - a name she also coined and is still widely used today.What you get with this method is only the relative distance, not the absolute distance.但是，即使这样，这也是第一次有人想出了一个计算浩瀚宇宙的实用方法。 （为了合理评价这些深邃的见解，也许值得注意的是，当莱维特和坎农在根据照片上远方星星的模糊影子推定宇宙的基本特性的时候，哈佛大学的天文学家威廉·H.皮克林--他当然能从一流的天文望远镜里想观察多少次就观察多少次--却在建立自己的理论，认为月球上的黑影是由大群大群的、随着季节迁徙的昆虫形成的。） 哈勃把莱维特测量宇宙的标准和维斯托·斯莱弗的红移结合起来，开始以焕然一新的目光有选择地测量空间的点。1923年，他证明，仙女座里一团代号为M31的薄雾状的东西根本不是气云，而是一大堆光华夺目的恒星，其本身就是一个星系，直径有1万光年，离我们至少有90万光年之远。宇宙比任何人想像的还要大--大得多。1924年，哈勃写出了一篇具有划时代意义的论文，题目为《旋涡星云里的造父变星》（"星云"源自拉丁语，意为"云"，哈勃喜欢用这个词来指星系），证明宇宙不仅仅有银河系，还有大量独立的星系--"孤岛宇宙"--其中许多比银河系要大，要远得多。 仅仅这一项发现就足以使哈勃名扬天下，但是，他接着把注意力转向另一个问题，想要计算宇宙到底大了多少，于是有了一个更加令人瞩目的发现。哈勃开始测量远方星系的光谱--斯莱弗已经在亚利桑那州开始做的那项工作。他利用威尔逊山天文台那台新的254厘米天文望远镜，加上一些聪明的推断，到20世纪30年代初已经得出结论：天空中的所有星系（除我们自己的星系以外）都在离我们远去。而且，它们的速率和距离完全成正比：星系距离我们越远，退行速率越快。 这的确是令人吃惊的。宇宙在扩大，速度很快，而且朝着各个方向。你无须有多么丰富的想像力就能从这点往后推测，发现它必定是从哪个中心点出发的。宇宙远不是稳定的，固定的，永恒的，就像大家总是以为的那样，而是有个起点。因此，它或许也有个终点。 正如斯蒂芬·霍金指出的，奇怪的是以前谁也没有想到要解释宇宙。一个静止的宇宙会自行坍缩，这一点牛顿以及之后的每个有头脑的天文学家都应当明白。还有一个问题：要是恒星在一个静止的宇宙里不停燃烧，就会使整个宇宙酷热难当--对于我们这样的生物来说当然是太热了。一个不断膨胀的宇宙一下子把这个问题基本解决了。 哈勃擅长观察，不大擅长动脑子，因此没有充分认识到自己的发现的重大意义。在一定程度上，那是因为他可悲地不知道爱因斯坦的广义相对论。这是很有意思的，因为一方面爱因斯坦和他的理论在这时候已经世界闻名，另一方面，1929年，阿尔伯特·迈克尔逊--这时候已经进入暮年，但仍是世界上最敏锐、最受人尊敬的科学家之一--接受了威尔逊山天文台的一个职位，用他可靠的干涉仪来测量光的速度，至少可以肯定已经向哈勃提到过，爱因斯坦的理论适用于他的发现。 无论如何，哈勃没有抓住机会在理论上有所收获，而是把机会留给了一位名叫乔治·勒梅特的比利时教士学者（他获得过麻省理工学院的博士学位）。勒梅特把实践和理论结合起来，创造了自己的"烟火理论"。该理论认为，宇宙一开始是个几何点，一个"原始的原子"；它突然五彩缤纷地爆发，此后一直向四面八方散开。这种看法极好地预示了现代的大爆炸理论，但要比那种理论早得多。因此，除了在这里三言两语提他一下以外，勒梅特几乎没有取得别的进展。世界还需要几十年时间，还要等彭齐亚斯和威尔逊在新泽西州咝咝作响的天线上无意中发现宇宙背景辐射，大爆炸才会从一种有趣的想法变成一种固定的理论。 无论是哈勃还是爱因斯坦，哪条大新闻里都不会提及多少。然而，尽管当时他们谁也想不到，他们已经作出自己所能作出的贡献。 1936年，哈勃写出了一本广受欢迎的书，名叫《星云王国》。他在这本书里以得意的笔调阐述了自己的重要成就，并终于表明他知道爱因斯坦的理论--反正在某种程度上：在大约200页的篇幅中，他用了4页来谈论这种理论。 1953年，哈勃心脏病发作去世。然而，还有最后一件小小的怪事在等待着他。出于秘而不宣的原因，他的妻子拒绝举行葬礼，而且再也没有说明她怎么处理了他的遗体。半个世纪以后，该世纪最伟大的天文学家的去向仍然无人知道。若要表示纪念，你非得遥望天空，遥望1990年美国发射的、以他的名字命名的哈勃天文望远镜。