A Brief History of Time, published in 1988, was a landmark volume in science writing and in world-wide acclaim and popularity, with more than 9 million copies in print globally. The original edition was on the cutting edge of what was then known about the origins and nature of the universe. But the ensuing years have seen extraordinary advances in the technology of observing both the micro- and the macrocosmic world--observations that have confirmed many of Hawking's theoretical predictions in the first edition of his book.
Now a decade later, this edition updates the chapters throughout to document those advances, and also includes an entirely new chapter on Wormholes and Time Travel and a new introduction. It make vividly clear why A Brief History of Time has transformed our view of the universe.
编辑推荐
Stephen Hawking, one of the most brilliant theoretical physicists in history, wrote the modern classic A Brief History of Time to help nonscientists understand the questions being asked by scientists today: Where did the universe come from? How and why did it begin? Will it come to an end, and if so, how? Hawking attempts to reveal these questions (and where we're looking for answers) using a minimum of technical jargon. Among the topics gracefully covered are gravity, black holes, the Big Bang, the nature of time, and physicists' search for a grand unifying theory. This is deep science; these concepts are so vast (or so tiny) as to cause vertigo while reading, and one can't help but marvel at Hawking's ability to synthesize this difficult subject for people not used to thinking about things like alternate dimensions. The journey is certainly worth taking, for, as Hawking says, the reward of understanding the universe may be a glimpse of "the mind of God." --Therese Littleton名人推荐
走近霍金
宇宙论是一门既古老又年轻的学科。作为宇宙里高等生物的人类不会满足于自身的生存和种族的绵延，还一代代不懈地探索着存在和生命的意义。但是，人类理念的进化是极其缓慢和艰苦的。从亚里士多德——托勒密的地心说到哥白尼——伽利略的日心说的演化就花了2000年的时间。令人吃惊的是，尽管人们知道世间的一切都在运动，只是到了20世纪20年代因哈勃发现了红移定律后，宇宙演化的观念才进入人类的意识。人们甚至从来没有想到过宇宙还会演化。牛顿的万有引力定律表明，宇宙的物质在引力作用下不可能处于稳定的状态。即使在爱因斯坦的广义相对论中，情况也好不到哪儿去，为了得到一个稳定的宇宙模型，他曾将宇宙常数引进理论中。他们都希望在自己的理论中找到稳定的宇宙模型。可见，宇宙演化的观念并不是产生于这些天才的头脑之中。
可以公平地说，哈勃的观测标志着现代宇宙论的诞生。哈勃发现，从星系光谱的红移可以推断，越远的星系以越快的速度离开我们而去，这表明整个宇宙处于膨胀的状态。从时间上倒溯到过去，估计在100亿到2O0亿年前曾经发生过一桩开天辟地的大事件，即宇宙从一个极其紧致极热的状态中大爆炸而产生。伽莫夫在1948年发表的一篇关于热大爆炸模型的文章中作出了一个惊人的预言，早期大爆炸的辐射仍残存在我们周围，不过由于宇宙膨胀引起的红移，其绝对温度只余下几度左右。在这种温度下，辐射是处于微波的波段。然而，在1965年彭齐亚斯和威尔逊观测到宇宙微波背景辐射之前，人们并不认真对待此预言。
一般认为，爱因斯坦的广义相对论是用于描述宇宙演化的正确的理论。在经典广义相对论的框架里，霍金和彭罗斯证明了，在很一般的条件下，时空一定存在奇点，最著名的奇点即是黑洞里的奇点以及宇宙大爆炸处的奇点。在奇点处，所有定律以及可预见性都失效。奇点可以看成空间时间的边缘或边界。只有给定了奇点处的边界条件，才能由爱因斯坦方程得到宇宙的演化。由于边界条件只能由宇宙外的造物主所给定，所以宇宙的命运就操纵在造物主的手中。这就是从牛顿时代起一直困扰人类智慧的第一推动问题
如果时空没有边界，则就不必劳驾上帝进行第一推动了。这只有在量子引力论中才能做到。霍金认为宇宙的量子态是处于一种基态，可把时空看成一个有限无界的四维面，正如地球的表面一样，只不过多了两维而已。宇宙中的所有结构都可归结于量子力学的不确定性原理所允许的最小起伏。从一些简单的模型计算可得出和天文观测相一致的推论，如星系、恒星等等的成团结构，大尺度的各向同性和均匀性，时空的平性，即空间基本上是平坦的，并因此才使得星系乃至生命的发展成为可能，还有时间的方向箭头等等。霍金的量子宇宙论的意义在于它真正使宇宙论成为一门成熟的科学。它是一个自足的理论，即在原则上，单凭科学定律我们便可以将宇宙中的一切都预言出来。
本书作者是当代最重要的广义相对论家和宇宙论家。20世纪70年代他和彭罗斯一道证明了著名的奇性定理，为此他们共同获得了1988年的沃尔夫物理奖。他还证明了黑洞的面积定理，即随着时间的增加黑洞的面积不减。这很自然使人将黑洞的面积和热力学的嫡联系在一起。1973年，他考虑黑洞附近的量子效应，发现黑洞会像黑体一样发出辐射。其辐射的温度和黑洞质量成反比，这样黑洞就会因为辐射而慢慢变小，而温度却越变越高，它以最后一刻的爆炸而告终。黑洞辐射的发现具有极其基本的意义，它将引力、量子力学和统计力学统一在一起。
1974年以后，他的研究转向量子引力论。虽然人们还没有得到一个成功的理论，但它的一些特征已被发现。例如，时空在普郎克尺度（10-33厘米）下不是平坦的，而是处于一种泡沫的状态。在量子引力中不存在纯态，因果性受到破坏，因此使不可知性从经典统计物理、量子统计物理提高到了量子引力的第三个层次。
1980年以后，他的兴趣转向量子宇宙论。
本书的副标题是从大爆炸到黑洞。霍金认为他一生的贡献是，在经典物理的框架里，证明了黑洞和大爆炸奇点的不可避免性，黑洞越变越大；但在量子物理的框架里，他又指出，黑洞国辐射而越变越小，大爆炸的奇点不但被量子效应所抹平，而且整个宇宙正是起始于此。
理论物理学的细节在未来的20年中还会有变化，但就观念而言，现在已经相当完备了。
霍金的生平是非常富有传奇性的。在科学成就上，他是有史以来最杰出的科学家之一，他的贡献是在他20年之久被卢伽雷病禁铜在轮椅上的情况下做出的，这真正是空前的。因为他的贡献对于人类的观念有深远的影响，所以媒介早已有许多关于他如何与全身瘫痪作搏斗的描述。尽管如此，译者之一于1979年第一回见到他时的情景至今还历历在目。那是第一次参力。剑桥霍金广义相对论小组的讨论班时，门打开后，忽然脑后响起一种非常微弱的电器的声音，回头一看，只见一个骨瘦如柴的人斜躺在电动轮椅上，他自己驱动着电开关。译者尽量保持礼貌而不显出过分吃惊，但是他对首次见到他的人对其残废程度的吃惊早已习惯。他要用很大努力才能举起头来。在失声之前，只能用非常微弱的变形的语言交谈，这种语言只有在陪他工作、生活几个月后才能通晓。他不能写字，看书必须依赖于一种翻书页的机器，读文献时必须让人将每一页摊平在一张大办公桌上，然后他驱动轮椅如蚕吃桑叶般地逐页阅读。人们不得不对人类中居然有以这般坚强意志追求终极真理的灵魂从内心产生深深的敬意。每天他必须驱动轮椅从他的家——剑桥西路5号，经过美丽的剑河、古老的国王学院驶到银街的应用数学和理论物理系的办公室。该系为了他的轮椅行走便利特地修了一段斜坡。
在富有学术传统的剑桥大学，他目前担任着也许是有史以来最为崇高的教授职务，那是牛顿和狄拉克担任过的卢卡斯数学教授。
本书译者之一曾受教于霍金达4年之久，并在他的指导下完成了博士论文。从他对译者私事的帮助可以体会到，他是一位富有人情味的人。此书即是受霍金之托而译成中文，以供占人类五分之一的人口了解他的学说。
许明贤 吴忠超^我们从何而来？宇宙为何是这样的？ / 霍金
我没有为《时间简史》的初版写前言。卡尔·沙冈写了一个前言。取而代之，我写了简短的《感谢》，人们建议我感谢每一个人。有些支持过我的基金会不高兴；由于我提到它们而收到大量申请。
我以为没有一个人，包括我的出版人，我的代理人甚至我自己能预料到，这本书会卖得这么好。它荣登伦敦《星期日时报》畅销书榜达237周之久，这比任何其他书都长（圣经和莎士比亚的书当然不算在内）。它被翻译成四十多种语言，并且在全世界每750名先生、女士以及儿童中都有一本。正如微软的纳珍·米尔伏德（我的前博士后）评论的：我关于物理的著作比玛当娜关于性的书还更畅销。
《时间简史》的成功，说明人们对重大问题具有广泛的兴趣。那就是：我们从何而来咛宙为何是这样的？
我想趁此机会增订本书，并把从它初版（1988年4月愚人节）以来新的理论和观测结果包括进去。我增加了虫洞和时间旅行的崭新的一章。爱因斯坦的广义相对论似乎为我们提供创生和维持虫洞的可能性，那是连接时空中不同区域的细管。如是，我们也许可以利用它们在星系之间看良行或者在时间中旅行到过去。当然，我们从未邂逅来自未来的人（也许我们曾经有过）。对此，我将给出一种可能的解释。
我还描述了近年在寻求“对偶性”或表现不同的物理理论之间的对应方面的进展。这些对应强烈地表明，存在一种完整的统一的物理理论。但是它们也暗示，也许不可能用一个单独的基本表式将这个理论描述出来。相反地，在不同的情形下，我们必须使用基本理论的不同的影像。这和描绘地球表面很相似，人们不能用一张单独的地图，在不同区域必须用不同的地图来代表。这就变革了我们科学定律的统一观。但是它并没有改变最重要的观点：宇宙是由一族可被我们发现并理解的合理的定律所制约。
在观测方面，迄今最重要的发展是由COBE（宇宙背景探险者卫星）和合作者测量的宇宙微波背景起伏。这些起伏是宇宙创生以及在它光滑均匀的早期阶段中微小的初始无规性的指纹。这些无规性后来成长为星系、恒星以及在我们周围看到的所有结构。起伏的形式和无边界宇宙设想的预言相吻合。无边界设想是讲，在虚时间方向宇宙没有边界或者边缘。为了区分这个设想以及对背景中起伏其他可能的解释，还需要进一步的观测。然而，我们在几年之内就应能知道，我们是否生活在一个完全自足的无始无终的宇宙之中。
史蒂芬·霍金
1996年5月，于剑桥 媒体推荐
[Hawking] can explain the complexities of cosmological physics with an engaging combination of clarity and wit. . . . His is a brain of extraordinary power.The New York Review of Books
Lively and provocative . . . Mr. Hawking clearly possesses a natural teachers giftseasy, good-natured humor and an ability to illustrate highly complex propositions with analogies plucked from daily life.The New York Times
Even as he sits helpless in his wheelchair, his mind seems to soar ever more brilliantly across the vastness of space and time to unlock the secrets of the universe.Time
This book marries a childs wonder to a geniuss intellect. We journey into Hawkings universe while marvelling at his mind.The Sunday Times (London)
A masterful summary of what physicists now think the world is made of and how it got that way.The Wall Street Journal
Charming and lucid . . . [A book of] sunny brilliance.The New Yorker作者简介
Stephen Hawking is Lucasian Professor of Mathematics at the University of Cambridge; his other books for the general reader include the essay collection Black Holes and Baby Universes and The Universe in a Nutshell.
From the Trade Paperback edition.文摘
Chapter 1
OUR PICTURE OF
THE UNIVERSE
A well-known scientist (some say it was Bertrand Russell) once gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: “What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise.” The scientist gave a superior smile before replying, “What is the tortoise standing on?” “You’re very clever, young man, very clever,” said the old lady. “But it’s turtles all the way down!”
Most people would find the picture of our universe as an infinite tower of tortoises rather ridiculous, but why do we think we know better? What do we know about the universe, and how do we know it? Where did the universe come from, and where is it going? Did the universe have a beginning, and if so, what happened before then? What is the nature of time? Will it ever come to an end? Can we go back in time? Recent breakthroughs in physics, made possible in part by fantastic new technologies, suggest answers to some of these longstanding questions. Someday these answers may seem as obvious to us as the earth orbiting the sun–or perhaps as ridiculous as a tower of tortoises. Only time (whatever that may be) will tell.
As long ago as 340 B.C. the Greek philosopher Aristotle, in his book On the Heavens, was able to put forward two good arguments for believing that the earth was a round sphere rather than a flat plate. First, he realized that eclipses of the moon were caused by the earth coming between the sun and the moon. The earth’s shadow on the moon was always round, which would be true only if the earth was spherical. If the earth had been a flat disk, the shadow would have elongated and elliptical, unless the eclipse always occurred at a time when the sun was directly under the center of the disk. Second, the Greeks knew from their travels that the North Star appeared lower in the sky when viewed in the south than it did in more northerly regions. (Since the North Star lies over the North Pole, it appears to be directly above an observer at the North Pole, but to someone looking from the equator, it appears to lie just at the horizon. From the difference in the apparent position of the North Star in Egypt and Greece, Aristotle even quoted an estimate that the distance around the earth was ,000 stadia. It is not known exactly what length a stadium was, but it may have been about 200 yards, which would make Aristotle’s estimate about twice the currently accepted figure. The Greeks even had a third argument that the earth must be round, for why else does one first see the sails of a ship coming over the horizon, and only later see the hull?
Aristotle thought the earth was stationary and that the sun, the moon, the planets, and the stars moved in circular orbits about the earth. He believed this because he felt, for mystical reasons, that the earth was the center of the universe, and that circular motion was the most perfect. This idea was elaborated by Ptolemy in the second century A.D. into a complete cosmological model. The earth stood at the center, surrounded by eight spheres that carried the moon, the sun, the stars, and the five planets known at the time, Mercury, Venus, Mars, Jupiter, and Saturn (Fig 1.1). The planets themselves moved on smaller circles attached to their respective spheres in order to account for their rather complicated observed paths in the sky. The outermost sphere carried the so-called fixed stars, which always stay in the same positions relative to each other but which rotate together across the sky. What lay beyond the last sphere was never made very clear, but it certainly was not part of mankind’s observable universe.
Ptolemy’s model provided a reasonably accurate system for predicting the positions of heavenly bodies in the sky. But in order to predict these positions correctly, Ptolemy had to make an assumption that the moon followed a path that sometimes brought it twice as close to the earth as at other times. And that meant that the moon ought sometimes to appear twice as big as at other times! Ptolemy recognized this flaw, but nevertheless his model was generally, although not universally, accepted. It was adopted by the Christian church as the picture of the universe that was in accordance with Scripture, for it had the great advantage that it left lots of room outside the sphere of fixed stars for heaven and hell.
A simpler model, however, was proposed in 1514 by a Polish priest, Nicholas Copernicus. (At first, perhaps for fear of being branded a heretic by his church, Copernicus circulated his model anonymously.) His idea was that the sun was stationary at the center and that the earth and the planets moved in circular orbits around the sun. Nearly a century passed before this idea was taken seriously. Then two astronomers–the German, Johannes Kepler, and the Italian, Galileo Galilei–started publicly to support the Copernican theory, despite the fact that the orbits it predicted did not quite match the ones observed. The death blow to the Aristotelian/Ptolemaic theory came in 1609. In that year, Galileo started observing the night sky with a telescope, which had just been invented. When he looked at the planet Jupiter, Galileo found that it was accompanied by several small satellites or moons that orbited around it. This implied that everything did not have to orbit directly around the earth, as Aristotle and Ptolemy had thought. (It was, of course, still possible to believe that the earth was stationary at the center of the universe and that the moons of Jupiter moved on extremely complicated paths around the earth, giving the appearance that they orbited Jupiter. However, Copernicus’s theory was much simpler.) At the same time, Johannes Kepler had modified Copernicus’s theory, suggesting that the planets moved not in circles but in ellipses (an ellipse is an elongated circle). The predictions now finally matched the observations.
As far as Kepler was concerned, elliptical orbits were merely an ad hoc hypothesis, and a rather repugnant one at that, because ellipses were clearly less perfect than circles. Having discovered almost by accident that elliptical orbits fit the observations well, he could not reconcile them with his idea that the planets were made to orbit the sun by magnetic forces. An explanation was provided only much later, in 1687, when Sir Isaac Newton published his Philosophiae Naturalis Principia Mathematica, probably the most important single work ever published in the physical sciences. In it Newton not only put forward a theory of how bodies move in space and time, but he also developed the complicated mathematics needed to analyze those motions. In addition, Newton postulated a law of universal gravitation according to which each body in the universe was attracted toward every other body by a force that was stronger the more massive the bodies and the closer they were to each other. It was this same force that caused objects to fall to the ground. (The story that Newton was inspired by an apple hitting his head is almost certainly apocryphal. All Newton himself ever said was that the idea of gravity came to him as he sat “in a contemplative mood” and “was occasioned by the fall of an apple.”) Newton went on to show that, according to his law, gravity causes the moon to move in an elliptical orbit around the earth and causes the earth and the planets to follow elliptical paths around the sun.
The Copernican model got rid of Ptolemy’s celestial spheres, and with them, the idea that the universe had a natural boundary. Since “fixed stars” did not appear to change their positions apart from a rotation across the sky caused by the earth spinning on its axis, it became natural to suppose that the fixed stars were objects like our sun but very much farther away.
Newton realized that, according to his theory of gravity, the stars should attract each other, so it seemed they could not remain essentially motionless. Would they not all fall together at some point? In a letter in 1691 to Richard Bentley, another leading thinker of his day, Newton argued that his would indeed happen if there were only a finite number of stars distributed over a finite region of space. But he reasoned that if, on the other hand, there were an infinite number of stars, distributed more or less uniformly over infinite space, this would not happen, because there would not be any central point for them to fall to.
This argument is an instance of the pitfalls that you can encounter in talking about infinity. In an infinite universe, every point can be regarded as the center, because every point has an infinite number of stars on each side of it. The correct approach, it was realized only much later, is to consider the finite situation, in which the stars all fall in on each other, and then to ask how things change if one adds more stars roughly uniformly distributed outside this region. According to Newton’s law, the extra stars would make no difference at all to the original ones on average, so the stars would fall in just as fast. We can add as many stars as we like, but they will still always collapse in on themselves. We now know it is impossible to have an infinite static model of the universe in which gravity is always attractive.
It is an interesting reflection on the general climate of thought before the twentieth century that no one had suggested that the universe was expanding or contracting. It was generally accepted that either the universe had existed forever in an unchanging state, or that it had been created at a finite time in the past more or less as we observe it today. In part this may have been d...
| 出版社 | Bantam |
|---|---|
| 作者 | 史蒂芬·霍金 (Stephen Hawking) |