A Brief History of Time

斯蒂芬·威廉·霍金（Stephen William Hawking），1942年1月8日出生于英國牛津，英國劍橋大學應用數學與理論物理學系教授，是繼牛頓和愛因斯坦之后最杰出的物理學家之一，被世人譽為“宇宙之王”。著名的黑洞輻射理論就是由霍金提出的，但對于很多人來說，霍金最引人注目之處在于他是一個身患頑疾的人。他除了頭腦活動如常之外，只能斜躺在輪椅上動動手指，這使得他的人生和作品都充滿了傳奇色彩。《時間簡史》（A Brief History of Time）是他出版于1988年的一部科普作品，主要向人們介紹了什么是宇宙論以及宇宙論最新的發展情況，包括宇宙圖像、空間和時間、基本粒子、黑洞等內容。該書目前已成為全球科學著作的里程碑。

The eventual goal of science is to provide a single theory that describes the whole universe. However， the approach most scientists actually follow is to separate the problem into two parts. First there are the laws that tell us how the universe changes with time. （If we know what the universe is like at any one time， these physical laws tell us how it will look at any later time.） Second， there is the question of the initial state of the universe. Some people feel that science should be concerned with only the first part； they regard the question of the initial situation as a matter for metaphysics2） or religion. They would say that God， being omnipotent3）， could have started the universe off any way he wanted. That may be so， but in that case he also could have made it develop in a completely arbitrary4） way. Yet it appears that he chose to make it evolve in a very regular way according to certain laws. It therefore seems equally reasonable to suppose that there are also laws governing the initial state.

It turns out to be very difficult to devise a theory to describe the universe all in one go. Instead， we break the problem up into bits and invent a number of partial theories. Each of these partial theories describes and predicts a certain limited class of observations， neglecting the effects of other quantities， or representing them by simple sets of numbers. It may be that this approach is completely wrong. If everything in the universe depends on everything else in a fundamental way， it might be impossible to get close to a full solution by investigating parts of the problem in isolation. Nevertheless， it is certainly the way that we have made progress in the past. The classic example again is the Newtonian theory of gravity， which tells us that the gravitational force between two bodies depends only on one number associated with each body， its mass， but is otherwise independent of what the bodies are made of. Thus one does not need to have a theory of the structure and constitution of the sun and the planets in order to calculate their orbits.

Today， scientists describe the universe in terms of two basic partial theories—the general theory of relativity5） and quantum mechanics6）. They are the great intellectual achievements of the first half of this century. The general theory of relativity describes the force of gravity and the large-scale structure of the universe， that is， the structure on scales from only a few miles to as large as a million million million million （1 with twenty-four zeros after it） miles， the size of the observable universe. Quantum mechanics， on the other hand， deals with phenomena on extremely small scales， such as a millionth of a millionth of an inch. Unfortunately， however， these two theories are known to be inconsistent with each other—they cannot both be correct. One of the major endeavors in physics today， and the major theme of this book， is the search for a new theory that will incorporate them both—a quantum theory of gravity. We do not yet have such a theory， and we may still be a long way from having one， but we do already know many of the properties that it must have. And we shall see， in later chapters， that we already know a fair amount about the predictions a quantum theory of gravity must make.

Now， if you believe that the universe is not arbitrary， but is governed by definite laws， you ultimately have to combine the partial theories into a complete unified theory that will describe everything in the universe. But there is a fundamental paradox in the search for such a complete unified theory. The ideas about scientific theories outlined above assume we are rational beings who are free to observe the universe as we want and to draw logical deductions from what we see.

In such a scheme it is reasonable to suppose that we might progress ever closer toward the laws that govern our universe. Yet if there really is a complete unified theory， it would also presumably determine our actions. And so the theory itself would determine the outcome of our search for it！ And why should it determine that we come to the right conclusions from the evidence？ Might it not equally well determine that we draw the wrong conclusion？ Or no conclusion at all？

The only answer that I can give to this problem is based on Darwin’s principle of natural selection. The idea is that in any population of self-reproducing organisms， there will be variations in the genetic material and upbringing that different individuals have. These differences will mean that some individuals are better able than others to draw the right conclusions about the world around them and to act accordingly. These individuals will be more likely to survive and reproduce and so their pattern of behavior and thought will come to dominate. It has certainly been true in the past that what we call intelligence and scientific discovery have conveyed a survival advantage. It is not so clear that this is still the case： Our scientific discoveries may well destroy us all， and even if they don’t， a complete unified theory may not make much difference to our chances of survival. However， provided the universe has evolved in a regular way， we might expect that the reasoning abilities that natural selection has given us would be valid also in our search for a complete unified theory， and so would not lead us to the wrong conclusions.

《時間簡史》是一本有關宇宙學的經典著作。在書中，霍金將高深的理論轉化為通俗的語言，使文章讀起來通俗易懂，所以這部作品也被譽為普通人都能讀懂的宇宙學著作。這部作品著于1987年，據說是霍金為了給女兒籌措學費而寫。作品在1988年一經出版立即成為暢銷書，至今已發行逾1000萬冊，被譯成40多種語言。

雖然《時間簡史》被很多人歸為“科普讀物”，但是其探討主題的深度和廣度遠超“科普”的范疇。書中不僅包含那些令人望而生畏的主題，例如宇宙、黑洞、時間和空間，而且在討論這些主題時霍金也一并探討了傳統科學家極少涉及的方面，包括很多發人深思的哲學和宗教問題，比如宇宙的起源。

在本文節選中，霍金認為科學的終極目的不僅是提供一個能解釋宇宙運行規律的統一理論，而且要解答宇宙起源的問題。這種說法對于從小接受無神論教育的我們來說也許并沒有特別之處，但是對于宇宙起源這個問題，當代科學理論只能解釋宇宙的運行規律，而無法解釋宇宙是如何誕生的，現有科學能給出的解釋（宇宙是永有、固有的）并不比宗教解釋（由上帝創造）高明多少。所以，在基督教思想根深蒂固的西方，包括很多最頂尖的科學家都將宇宙起源的問題歸于宗教或者玄學的范疇，而霍金大膽地涉及這個敏感的話題，可謂勇氣可嘉。

實際上，霍金在書中秉持著較為謙虛、開放的宗教觀，他并沒有全然否定上帝和宇宙間存在關系的可能性，他只是質疑“從無而有”的創造觀。同樣，霍金也并沒有將科學理論看做是一成不變的。對很多人而言，科學是實實在在的東西，是最可靠的真理，但是霍金卻說科學的進展由想象力的跳躍組成。對于科學理論，霍金曾經在一次訪談中這樣說：“我們將永遠不能完全肯定我們是否確實找到了正確的理論，因為理論不能被證明。”所以，在霍金筆下，科學發展史就是不斷否定前代理論的歷史。在書中，霍金呈現給讀者的是開放的科學觀和宗教觀，或許正是這一點使得《時間簡史》與所有的科普讀物都有所不同。

在本段節選中，對于當代科學界最重要的兩個理論——相對論和量子力學，霍金認為它們是兩個互不協調的理論，它們不可能同時正確。物理學家的目標應該是尋找一個能解釋宇宙的統一理論：量子引力論?；艚鹫J為量子引力論是一個自足的理論，即在原則上，單憑科學定律人們便可將宇宙中的一切都預言出來，包括很多被認為屬于人類社會科學范疇的事件。

也正是因為霍金和他的《時間簡史》，量子引力論一直在不斷地發展，并逐漸成為一門成熟的科學，而霍金對解釋宇宙萬物的統一理論的追求也促使他觸及了很多終極的哲學問題。比如，在文中，霍金指出應該有一個終極的統一理論時，也頗幽默地指出：“如果真有一套完整的統一理論，則它將決定我們的行動。這樣一來，理論本身將決定我們對之探索的結果！那么為什么它必須確定我們從證據得到正確的結論？它不也同樣可以確定我們引出錯誤的結論嗎？”這幾句讀起來有點繞，卻表現出霍金跳躍而敏感的哲學思辨思維。本書后半部分，在涉及黑洞和時間等更加高深的概念時，霍金同樣涉及了眾多哲學問題。在探討時間可逆性的物理學理論的同時，霍金還提出了關于時間方向性的更加類似哲學的問題，比如時間的推移總是造成更多的無序——隨著時間推移，杯子會從桌子上落下來摔碎，而你永遠無法讓碎杯子自己回到桌子上并恢復完整。

在這部《時間簡史》中，霍金帶領讀者暢游外層空間，對遙遠星系、黑洞、夸克、“帶味”粒子、“自旋”粒子、“時間箭頭”等進行了深入淺出的介紹，并對宇宙、空間和時間以及相對論等問題做了闡述，使讀者初步了解了相對論以及時間、宇宙的起源等宇宙學的奧妙。更為重要的是，霍金在書中不斷挑戰人們固有的認知，激發人們去思考。這也使得這部作品超越了普通的科學著作。

霍金身有殘疾，但是偉人往往并不需要同情，反而他會同情眾生。歷史上很多杰出的人都曾經飽受煎熬，但在痛苦磨練中他們也感知到普通人感知不到的東西。我們常常只能看到他們表面上的痛苦，卻體味不到他們內心的深奧。《星期日時報》在評論《時間簡史》時，稱其為“童真好奇與天才智慧的結合”，《紐約客》也稱贊其為“迷人而清澈……光輝四射的巨作”。這些評價都毫不為過?；艚鹚岢龅睦碚搼撌悄壳懊枋鲇钪孀詈玫睦碚摯?，當然它并非無懈可擊。就像霍金自己所說的，科學永遠在不斷跳躍發展，而我們的好奇和懷疑就是這種發展的源泉。當我們在閱讀《時間簡史》這部偉大著作時，也應秉持霍金那樣的開放思維，用好奇、懷疑來面對浩瀚的宇宙。

1.英文節選部分選自作品的第一章，主要闡述了科學的目標應是尋找一個能解釋宇宙的統一理論。

2.metaphysics [?met??f?z?ks] n. 形而上學，玄學

3.omnipotent [?m?n?p?t?nt] adj. 全能的，萬能的，無所不能的

4.arbitrary [?ɑ?（r）b?tr?ri] adj. 任意的；隨機的

5.the general theory of relativity：廣義相對論，愛因斯坦于1915年發表的用幾何語言描述的引力理論，它代表了現代物理學中引力理論研究的最高水平。

6.quantum mechanics：量子力學，是研究微觀粒子的運動規律的物理學分支學科。