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首版内容介绍了宇宙本性最前沿的知识。微观和宏观世界观测技术领域方面10年来的进展证明了霍金教授的许多理论预言。他为了把观测的新知识介绍给读者,重写了前言,全面更新了原版的内容,并新增了一章有关虫洞和时间旅行的激动人心的课题。 内容简介
#1 NEW YORK TIMES BESTSELLER
A landmark volume in science writing by one of the great minds of our time, Stephen Hawking’s book explores such profound questions as: How did the universe begin—and what made its start possible? Does time always flow forward? Is the universe unending—or are there boundaries? Are there other dimensions in space? What will happen when it all ends?
Told in language we all can understand, A Brief History of Time plunges into the exotic realms of black holes and quarks, of antimatter and “arrows of time,” of the big bang and a bigger God—where the possibilities are wondrous and unexpected. With exciting images and profound imagination, Stephen Hawking brings us closer to the ultimate secrets at the very heart of creation.
本书是“推动丛书”辑的一种。 时间有初始吗?它又将在何地终结呢?宇宙是无限的还是有限的? 霍金教授遨游到外层空间奇异领域,对遥远星系、黑洞、夸克、大统一理论、“带味”粒子和“自旋”粒子、反物质、“时间箭头”等进行了深入探讨--其出乎意外的含义引起了人们的极大兴趣。他揭示了当日益膨胀的宇宙崩溃时,时间倒溯引起人们不安的可能性,那时宇宙分裂成11维空间,一种“没有边界”的宇宙理论可能取代大爆炸理论和上帝,上帝--也许曾是造万物时主要推动者,也会因这些新发现而日渐范围变窄。
《时间简史》对我们这些喜用言语表达甚于方程式表达的读者而言是一本里程碑式的佳书。她出于一个对人类思想有杰出贡献者之手,这是一本对知识无限追求之作,是对时空本质之谜不懈探讨之作。 作者简介
Stephen Hawking is Lucasian Professor of Mathematics at the University of Cambridge; his other books for the general reader include A Briefer History of Time, Black Holes and Baby Universes and The Universe in a Nutshell.
史蒂芬·霍金(Stephen W.Hawking),1942年出生于伽利略逝世的三百周年纪念日。他现任剑桥大学卢卡斯数学教授(一度曾为牛顿所任),并广被尊崇为继爱因斯坦以来杰出的理论物理学家。 精彩书评
“[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
“This book marries a child’s wonder to a genius’s intellect. We journey into Hawking’s universe while marvelling at his mind.”— The Sunday Times (London)
“Masterful.”— The Wall Street Journal
“Charming and lucid . . . [A book of] sunny brilliance.”— The New Yorker
“Lively and provocative . . . Mr. Hawking clearly possesses a natural teacher’s gifts—easy, 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 前言/序言
Chapter One
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 400,000 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 due to...
宇宙的编织:对时间与空间的深度探索 作者:[此处留空,或填写虚构的作者名] 装帧:精装 页数:约 600 页 --- 导言:在寂静的星空中追问存在的本质 自人类第一次仰望夜空,那无垠的黑暗中闪烁的无数光点,便引发了最古老、最深刻的疑问:我们从何处来?宇宙的边界在哪里?时间,这条似乎永恒流淌的河流,究竟是真实的,还是仅仅是我们感知的一种幻象? 本书并非对既有理论的简单罗列,而是一次对宇宙结构、时间本质以及人类认知局限性的深刻哲学与科学之旅。它旨在邀请读者,暂时放下日常琐碎,与我们一同潜入物理学的最前沿,去触摸那些定义了“实在”的深层代码。我们将从最宏大的尺度——可观测宇宙的边缘——开始,逐步深入到最微小的尺度——量子场的振动之中,力图描绘一幅既符合严谨数学逻辑,又充满诗意想象的宇宙全景图。 第一部分:空间几何的重塑——从欧几里得到黎曼 我们对空间的直觉建立在日常生活的三维欧几里得几何之上:平行线永不相交,三角形内角和恒为 180 度。然而,当我们将视野投向星际尺度,或者试图理解引力的本质时,这一直觉便开始瓦解。 本部分将详细探讨非欧几何的诞生与意义。我们不仅会回顾高斯对曲面几何的开创性工作,更会深入解析黎曼几何如何为爱因斯坦的广义相对论提供了必要的数学框架。引力不再被视为一种力,而是时空本身的几何属性——物质和能量弯曲了它所处的时空结构,而我们所感受到的“运动”,本质上是在这个弯曲时空中沿着“测地线”的自然路径。我们将用直观的类比和严格的数学推导相结合的方式,剖析时空度规张量的含义,理解黑洞周围极端弯曲的几何形态,以及光线如何在引力透镜效应中被“扭曲”。 此外,我们还将探讨时空维度本身的可能性。从卡鲁扎-克莱因理论对第五维的初步设想,到现代弦理论中对额外紧致维度的需求,空间的概念正在被不断拓宽,挑战着我们对“方向”的传统理解。 第二部分:时间的箭与宇宙的演化 时间,这个我们最熟悉却最难捉摸的概念,是本书的核心议题之一。我们体验到的时间是单向的——鸡蛋可以碎裂,但无法自行复原。物理学中的“时间之箭”指向何方? 我们将从热力学第二定律(熵增定律)出发,探究宏观世界中时间不可逆性的根源。随后,我们将检视微观物理定律的“时间对称性”,分析为何粒子层面的基本作用力似乎并不区分过去与未来,并讨论这在量子力学中引发的深刻矛盾。 随后,我们将转向宇宙学的宏大叙事。从普朗克时间尺度开始,我们追踪宇宙的膨胀历史。哈勃常数的测量、宇宙微波背景辐射(CMB)的精妙结构,如何共同构建了我们对大爆炸模型的信心?我们不仅会分析标准Lambda-CDM模型的成功之处,更会聚焦于模型中的未解之谜:暴胀理论试图解释的初始奇点问题、暗物质的引力证据、以及暗能量所代表的驱动宇宙加速膨胀的神秘负压。这些现象要求我们超越经典时空观,拥抱一个动态的、不断演化的宇宙剧场。 第三部分:量子的深渊与实在的边界 当我们试图将引力(宏观的几何学)与量子力学(微观的概率论)统一起来时,我们便触及了现代物理学的“圣杯”——量子引力的难题。 本部分将深入探索量子场论(QFT)的基本框架,理解物质粒子如何被视作基本场的激发态。我们将讨论不确定性原理的哲学含义,以及测量行为在构建实在中所扮演的角色。波函数的坍缩、量子纠缠现象——爱因斯坦所称的“幽灵般的超距作用”——如何挑战了我们对定域性(Locality)的认知? 最终,我们将考察当前最有希望统一两大理论的尝试。圈量子引力(LQG)如何尝试将时空本身“量子化”,使其不再是连续的背景,而是由离散的“量子时空原子”构成?而弦理论则提出,所有基本粒子都是一维能量弦的不同振动模式,这一理论对多维空间和超对称性的要求,极大地扩展了我们对可能性宇宙的想象。这些前沿理论的数学结构,揭示了时间与空间在普朗克尺度下可能呈现出的完全不同的、甚至颠覆性的面貌。 结论:人类心智与无限的交汇 本书的旅程从可见的星空延伸到不可见的量子泡沫,最终导向一个核心命题:我们对宇宙的理解,是否受限于我们自身的感知结构?当我们试图用有限的数学工具去描述无限的实在时,我们究竟是在发现宇宙的内在真理,还是仅仅在构建一个最自洽的“故事”? 通过对这些宏大主题的细致梳理,本书旨在为严肃的科学爱好者提供一个全面、深入且具有前瞻性的视角,去思考我们所处的这个宇宙——关于它的起源、它的结构、以及它那令人敬畏的、尚未完全揭示的最终命运。这是一部关于“我们是谁,我们在哪里”的终极探索。