弦理论二.docx

1、弦理论二(2）弦理论So hold the mystery of the dark energy in the back of your mind，as I now go on to tell you three key things about string theory.先把暗能量的谜团放在脑后，我继续讲有关弦理论的三个关键的事情。First off, what is it?第一个是什么呢？Well its an approach to realize Einsteins dream of a unified theory of physics, a single overarching

2、framework that would be able to describe all the forces at work in the universe.那是实践爱因斯坦的物理统一理论的梦想的一种途径，一个总体框架能够描述宇宙所有的力量在起作用。And the central idea of string theory is quite straightforward.而弦理论的中心思想非常简单。It says that if you examine any piece of matter ever more finely，at first youll find molecules an

3、d then youll find atoms and subatomic particles.它说，如果你非常细致地检查任何一样物质, 起初你会发现分子，然后你会发现原子和亚原子离子。But the theory says that if you could probe smaller, much smaller than we can with existing technology, youd find something else inside these particles - a little tiny vibrating filament of energy, a little

4、tiny vibrating string.但这个理论说，如果你能够探测到更小的，比我们现有技术能做到的更小，你会在这些粒子里找到别的东西 - 一个小小的能量震动纤维，一个小小的震动弦。And just like the strings on a violin, they can vibrate in different patterns producing different musical notes.就像小提琴上的弦一样，它们通过不同的震动来产生不同的音符。These little fundamental strings, when they vibrate in different p

5、atterns, they produce different kinds of particles - so electrons, quarks, neutrinos, photons, all other particles would be united into a single framework, as they would all arise from vibrating strings.这些小小的基本的弦，当他们以不同的模式震动时，它们产生不同种类的粒子 - 所以，电子、夸克、中微子、光子、所有的粒子会合并成一个单一的框架，它们会通过震动的弦而出现。Its a compelli

6、ng picture, a kind of cosmic symphony, where all the richness that we see in the world around us emerges from the music, that these little, tiny strings can play.那是个令人信服的场面，一种宇宙交响乐，我们看到的从周围世界的音乐而展现的丰富，这些小小的弦也能演奏出。But theres cost to this elegant unification, because years of research have shown that

7、the math of string theory doesnt quite work.但这种优雅的统一是有代价的，因为多年的研究表明弦理论的数学也不是行得通的。It has internal inconsistencies, unless we allow for something wholly unfamiliar extra dimensions of space.它内部不一致，除非我们考虑完全陌生的事, 即额外维度空间。That is, we all know about the usual three dimensions of space.我们都知道通常的三维空间。And you

8、 can think about those as height, width and depth.你可以用高度，宽度和深度来考虑。But string theory says that, on fantastically small scales, there are additional dimensions crumpled to a tiny size so small that we have not detected them.但弦理论认为，在极其小的尺度下，在这么小的尺寸下还有附加的维度，因为太小， 我们还探测不出。But even though the dimensions a

9、re hidden, they would have an impact on things that we can observe, because the shape of the extra dimensions constrains how the strings can vibrate.但即使这些维度是隐藏的，它们对一些东西的影响我们能够观察到，因为额外维度的形状限制着弦的震动。And in string theory, vibration determines everything.在弦理论中，振动决定一切。So particle masses, the strengths of

10、forces, and most importantly, the amount of dark energy would be determined by the shape of the extra dimensions.所以粒子的质量，力量的强度，最重要的，暗能量的总量会取决于额外维度的形状。So if we knew the shape of the extra dimensions, we should be able to calculate these features, calculate the amount of dark energy.如果我们了解额外维度的形状，我们就能

11、计算出这些特征，计算出暗能量的总量。The challenge is we dont know the shape of the extra dimensions.目前的挑战是我们不知道额外维度的形状。All we have is a list of candidate shapes allowed by the math.我们有的是通过数学算出的一些候选形状。Now when these ideas were first developed, there were only five different candidate shapes, so you can imagine analyzi

12、ng them one-by-one to determine if any yield the physical features we observe.当这些想法首次推出的时候，只有5个候补形状，你可以想象到一个一个分析他们来决定哪一个符合我们观察的物理特征。But over time the list grew, as researchers found other candidate shapes.可是随着时间的迁移，研究人员发现了更多的候选形状。From five, the number grew into the hundreds and then the thousands -

13、a large，but still manageable, collection to analyze, since after all, graduate students need something to do.从起初的5个到几百个，最后几千个 - 数目很多但还管得过来，去分析这些工作，就交给刚毕业的学生了。But then the list continued to grow into the millions and the billions until today.但是这个数目单继续增加到了几百万，到今天的数十亿了。The list of candidate shapes has

14、soared to about 10 to 500.候选形状的清单也飙升到了10至500个。So, what to do?那，怎么办呢？Well some researchers lost heart, concluding that was so many candidate shapes for the extra dimensions, each giving rise to different physical features, string theory would never make definitive, testable predictions.有些研究人员失去信心，结论是

15、额外维度有这么多的候选形状，每一个都有不同的物理特征，弦理论永远不会做出确定的，可检验的预测。But others turned this issue on its head, taking us to the possibility of a multiverse.但是从另一个角度考虑，把我们带到多元宇宙的可能性。Heres the idea.想法是这样的。Maybe each of these shapes is on an equal footing with every other.也许这些形状之间是相互平等的。Each is as real as every other, in th

16、e sense，that there are many universes, each with a different shape, for the extra dimensions.每一个都是真实的，就是说，有很多的宇宙，每个对额外维度都有不同的形状。And this radical proposal has a profound impact on this mystery: the amount of dark energy revealed by the Nobel Prize-winning results.这种激进的建议对这个谜团有着深刻的影响：诺贝尔得奖结果揭示了暗能量的总量。

17、Because you see, if there are other universes, and if those universes each have, say, a different shape for the extra dimensions, then the physical features of each universe will be different, and in particular, the amount of dark energy in each universe will be different.因为你看, 如果有很多的其他宇宙，而这些宇宙每个都有不

18、同的额外维度形状，那么每个宇宙的物理特征将会不同，特别是每个宇宙的暗能量将会不同。Which means that the mystery, of explaining the amount of dark energy weve now measured would take on a wholly different character。也就意味着，我们现在测量到的暗能量总量的解释将会是一个完全不同的角色。In this context, the laws of physics cant explain one number for the dark energy，because ther

19、e isnt just one number, there are many numbers.在这种背景下，物理定律不能解释能量的一个数，因为不只是一个数，有很多数。Which means, we have been asking the wrong question.也意味着，我们一直问错了问题。Its that the right question to ask is, why do we humans find ourselves in a universe with a particular amount of dark energy weve measured, instead of

20、 any of the other possibilities that are out there?应该问正确问题是，为什么我们人类在一个宇宙中测量一种特定量的暗能量，而不是在另外的其他外围宇宙呢？And thats a question on which we can make headway.我们在这个问题上能取得进展。Because those universes that have much more dark energy than ours, whenever matter tries to clump into galaxies, the repulsive push of t

21、he dark energy is so strong, that is blows the clump apart and galaxies donfrom.因为那些宇宙有着比我们更多的暗能量，当物质要聚成星系时，暗能量的排斥力太强，把物质快吹散了，星系就无法形成。And in those universes that have much less dark energy, well tehy collapse back on themselves so quickly, that, again, galaxies dont form.在那些较少暗物质存在的宇宙中，它们非常快的崩塌回来，也形

22、成不来星系。And without galaxies, there are no stars, no planets, and no chance for our form of life to exist in those other universes.没有星系，就没有星星，没有行星，所以在别的宇宙中没有像我们这样的生命存在。So we find ourselves in a universe with the particular amount of dark energy weve measured, simply because our universe has conditions

23、 hospitable to our form of life.我们发现我们自己存在于一个我们简单测量的有一个特别数量的暗能量的宇宙中，只因为我们的宇宙有适合的条件供我们生命的存在。And that would be that.就是那个。Mystery solved, multiverse found.谜题破界了，多元宇宙被发现了。Now some find this explanation unsatisfying.有些人对这个解释不满意。were used to physics giving us definitive explanations for the features we ob

24、serve.我们习惯于物理学给我们观察的特征的明确解释。But the point is, if the feature youre observing can and does take on a wide variety of different values across the wider landscape of reality, then thinking one explanation for a particular value is simply misguided.但问题是，如果你观察的特征能够并且确实承担现实中的不同价值，那么对于一种特定值用一种解释就会很容易误导人。An

25、 early example comes from the great astronomer Johannes Kepler, who was obsessed with understanding a different number - why the Sun is 93 million miles away from the Earth.一个早期的例子来自于伟大的天文学家约翰. 开普勒，他很着迷于研究不同的数字 - 为什么太阳离地球9千3百万英里。And he worked for decades trying to explain this number, but he never s

26、ucceeded, and we know why.他花了几十年的时间试图解释这个数字，但没有成功，我们知道为什么。Kepler was asking the wrong question.开普勒问错了问题。We now know that there are many planets at a wide variety of different distances from their host stars.现在我们知道有许多行星距离它们的宿主恒星有不同的距离。So hoping that the laws of physics will explain one particular num

27、ber, 93 million miles, well that is simply wrongheaded.单单希望物理定律能解释一个特殊的数据，9千3百万，是执迷不悟。Instead the right question to ask is, why do we humans find ourselves on a planet at this particular distance, instead of any of the other possibilities?正确的问题应该是，为什么我们人类发现我们在一个行星上的距离是特定的，而不是别的可能呢？And again，thats a

28、question we can answer.同样，这个问题我们能回答。Those planets which are much closer to a star like the Sun would be so hot, that our form of life wouldnt exist.那些行星更接近于一颗星就像太阳一样热，以至像我们这样的生命无法存在。And those planets that are much farther away from the star, well theyre so cold, that, again , our form of life would

29、not take hold.而那些离这个星太远的行星，因为太冷，同样也没法有我们这样的生命。So we find ourselves on a planet at this particular distance simply because it yields conditions vital to our form of life.所以，我们发现我们在这棵行星的特定距离只是因为它的条件符合我们生命的存在。And when it comes to planets and their distances, this clearly is the right kind of reasoning.

30、讲到行星和它们的距离是，这显然是合理的推理。The point is, when it comes to universes and the dark energy that they contain, it may also be the right kind of reasoning.关键是，讲到宇宙和他们所含的暗能量时，它也可能是合适的推理。One key difference, of course, is we know that there are other planets out there, but so far Ive only speculated on the possibility that there might be other universes.一个重要的区别是，我们知道外边还有很多别的行星，但到目前为止，我只是推测可能会有其他的宇宙。So to pull it all together, we need a mechanism that can actually generate other universes.把这些结合起来，我们需要一个机制，实际上可以生成其他宇宙。And that takes me to my final part, part three.这样我就来到最后一部分，第三部分。Cosmic explosion宇宙爆炸