2–2Physics before 1920 2–2 1920年以前的物理学
It is a little difficult to begin at once withthe present view, so we shall first see how things looked in about 1920 andthen take a few things out of that picture. Before 1920, our world picture wassomething like this: The “stage” on which the universe goes is the three-dimensionalspace of geometry, as described by Euclid, and things change in a mediumcalled time. The elements on the stage are particles, for examplethe atoms, which have some properties. First, the property of inertia:if a particle is moving it keeps on going in the same direction unless forcesact upon it. The second element, then, is forces, which were then thoughtto be of two varieties: First, an enormously complicated, detailed kind of interactionforce which held the various atoms in different combinations in a complicatedway, which determined whether salt would dissolve faster or slower when we raisethe temperature. The other force that was known was a long-range interaction—a smoothand quiet attraction—which varied inversely as the square of the distance, andwas called gravitation. This law was known and was very simple. Whythings remain in motion when they are moving, or why there is a law ofgravitation was, of course, not known.
从现在这个观点，立即开始，稍微有点困难，所以，我们先看看，在1920年前后，事情是怎么回事，然后，从那幅图像里，拿出几个事情来。在1920年之前，我们关于世界的图像大致如此：宇宙运行的“舞台”，是一个三维的地理空间，正如欧几里德{Euclid}所描述，而事物的变化，是在一个被称为时间的媒介中进行的，舞台上的元素，就是粒子{particles}，例如原子，粒子有若干属性{properties}。首先，惯性{inertia}的属性，如果一个粒子在运动，那么，它就一直沿着一个方向运动，直到有力作用于它。因此，就有了第二个元素，力，在那个时候，它被认为有两个品种：第一种力，巨复杂，从细节上看，又是相互作用的，它以一种复杂的方式，把不同的原子，以不同的组合方法，抓在一起；这种方式，决定了为什么当我们提高温度的时候，盐在水中溶解的快还是慢。另外一个力，就是我们知道的长距离的交互作用，一种平稳而安静的吸引力，与距离的平方成反比，被称为万有引力。这条规律，众所周知，且非常简单。当事物运动的时候，为什么会保持运动状态，或者，为什么会有一条万有引力定律？当然，是不知道的。

A description of nature is what we are concernedwith here. From this point of view, then, a gas, and indeed all matter,is a myriad of moving particles. Thus many of the things we saw while standing atthe seashore can immediately be connected. First the pressure: this comes fromthe collisions of the atoms with the walls or whatever; the drift of the atoms,if they are all moving in one direction on the average, is wind; the randominternal motions are the heat. There are waves of excess density, wheretoo many particles have collected, and so as they rush off they push up pilesof particles farther out, and so on. This wave of excess density is sound.It is a tremendous achievement to be able to understand so much. Some of thesethings were described in the previous chapter.
对自然的描述，是我们这里所关心的一个问题。从这个观点出发，气体，事实上所有的物质，都是极大数量的移动着的粒子。这样，我们站在海边能看到的所有事物，都立即被联系了起来。首先是压力，它来自原子对墙壁之类的碰撞；原子的漂流，如果它们平均是在一个方向上移动，就是风；随机的内部运动，就是热。还有过剩密度的波浪，这样，当它们冲击的时候，就在更远的地方，把粒子堆起来。这个过剩密度的波浪，就是声音。能理解这么多，已然是巨大的成就了。其中的一些事情，我们上一章都曾讲过。

What kinds of particles are there?There were considered to be 92 at that time: 92 different kinds of atoms were ultimately discovered. They had differentnames associated with their chemical properties.
都有哪些种类的粒子呢？那时，总共有92种，即有92种不同的原子，最终被发现了。它们有不同的名字，而名字，是与它们的化学属性相关联的。

The next part of the problem was, what arethe short-range forces? Why does carbon attract one oxygen or perhaps twooxygens, but not three oxygens? What is the machinery of interaction betweenatoms? Is it gravitation? The answer is no. Gravity is entirely too weak. But imaginea force analogous to gravity, varying inversely with the square of the distance,but enormously more powerful and having one difference. In gravity everythingattracts everything else, but now imagine that there are two kinds of “things,”and that this new force (which is the electrical force, of course) has theproperty that likes repel but unlikes attract. The “thing” thatcarries this strong interaction is called charge.
这个问题的第二部分就是：什么是短距离的力？为什么碳只吸引一个或两个氧？而不是三个氧？原子之间相互作用的机制是什么？是万有引力吗？答案是否。重力完全太弱。但是，想象有一种力，它与重力可以类比，与距离的平方成反比，然而，却更强有力，并且，有一个区别。在重力中，每个事物的之间相互吸引，但是，现在想象有两类事物，这个新的力（它当然是电子力），具有一种属性，更像排斥，而不是像吸引。此带有这种强相互作用的“事物”，被称为电荷。

Then what do we have? Suppose that we havetwo unlikes that attract each other, a plus and a minus, and that they stick veryclose together. Suppose we have another charge some distance away. Would it feelany attraction? It would feel practically none, because if the first twoare equal in size, the attraction for the one and the repulsion for the other balanceout. Therefore there is very little force at any appreciable distance. On theother hand, if we get very close with the extra charge, attractionarises, because the repulsion of likes and attraction of unlikes will tend to bringunlikes closer together and push likes farther apart. Then the repulsion willbe less than the attraction. This is the reason why the atoms, which areconstituted out of plus and minus electric charges, feel very little force whenthey are separated by appreciable distance (aside from gravity). When they comeclose together, they can “see inside” each other and rearrange their charges, withthe result that they have a very strong interaction. The ultimate basis of aninteraction between the atoms is electrical. Since this force is so enormous,all the plusses and all minuses will normally come together in as intimate a combinationas they can. All things, even ourselves, are made of fine-grained, enormously stronglyinteracting plus and minus parts, all neatly balanced out. Once in a while, by accident,we may rub off a few minuses or a few plusses (usually it is easier to rub offminuses), and in those circumstances we find the force of electricity unbalanced,and we can then see the effects of these electrical attractions.
那么，我们有什么呢？假设我们有两个异性电荷，互相吸引，一个正一个负，并且非常紧密地粘在一起。假设我们在不远的距离之内，有另外一个电荷。它能感到吸引力吗？它将感觉不到，因为，如果前两个电荷大小相等的话，那么，对一个的吸引力，将与对另一个的排斥力，相互抵消。因此呢，在任何可见的距离内，将只有非常小的力。另一方面，如果我们能够非常接近另外一个电荷的话，那么，吸引就会产生，因为同性间的排斥和异性间的吸引，将倾向于把异性带的更近，而把同性推的更远。因此，排斥将比吸引弱。这就是为什么当原子被分开的时候，只能感觉到非常小的力（重力除外）；而原子，则是由正电荷与负电荷组成的。当它们走得更近的时候，它们相互之间可以“看到对方的内部”，从而重新安排它们的电荷，结果就是，它们有一个非常强的相互作用。原子间相互作用的终极基础，就是电力。由于此力，非常巨大，所有的正电荷和负电荷，通常最后都会形成一种尽可能亲密的组合。所有的事物，甚至包括我们自己，都是由精密的、巨大的、强相互作用的正负电部分所组成，且都精妙的平衡了。有时，由于偶然的原因，我们会擦掉一些负电或正电（通常负的更容易擦掉），在此情况下，我们就会发现，电不平衡了，然后，你就会看到那些电子吸引的作用了。

To give an idea of how much stronger electricityis than gravitation, consider two grains of sand, a millimeter across, thirtymeters apart. If the force between them were not balanced, if everything attractedeverything else instead of likes repelling, so that there were no cancellation,how much force would there be? There would be a force of three million tonsbetween the two! You see, there is very, very little excess or deficitof the number of negative or positive charges necessary to produce appreciable electricaleffects. This is, of course, the reason why you cannot see the difference betweenan electrically charged or uncharged thing—so few particles are involved thatthey hardly make a difference in the weight or size of an object.
电力比万有引力，究竟有多强？要对这事有点概念，可以考虑两粒沙子，一个毫米左右，30米距离。如果它们之间的力，没有被平衡，如果事物之间是相互吸引，而不是同性排斥，以至于没有抵消，那么，那里会有多大的力呢？两粒沙子之间，将有300万吨力！你明白了吧，要产生可见的电子效果，需要一定数量正电荷或负电荷，且这个数量的上下浮动，是非常非常小的。当然，这就是为什么你看不到：一个事物究竟是充电了还是未充电之间的区别，--这是因为，卷入这件事的粒子太少，以至于，对对象的重量或尺寸，没什么影响。

With this picture the atoms were easier to understand.They were thought to have a “nucleus” at the center, which is positively electricallycharged and very massive, and the nucleus is surrounded by a certain number of“electrons” which are very light and negatively charged. Now we go a little aheadin our story to remark that in the nucleus itself there were found two kinds ofparticles, protons and neutrons, almost of the same weight and very heavy. The protonsare electrically charged and the neutrons are neutral. If we have an atom with sixprotons inside its nucleus, and this is surrounded by six electrons (the negativeparticles in the ordinary world of matter are all electrons, and these are verylight compared with the protons and neutrons which make nuclei), this would beatom number six in the chemical table, and it is called carbon. Atom numbereight is called oxygen, etc., because the chemical properties depend upon theelectrons on the outside, and in fact only upon how many electronsthere are. So the chemical properties of a substance depend only on anumber, the number of electrons. (The whole list of elements of the chemists reallycould have been called 1 , 2 , 3 , 4 , 5 , etc. Instead of saying “carbon,” we could say “element six,” meaningsix electrons, but of course, when the elements were first discovered, it wasnot known that they could be numbered that way, and secondly, it would makeeverything look rather complicated. It is better to have names and symbols forthese things, rather than to call everything by number.)
用这个图，理解原子，更容易些。它们被认为在中心有一个“核”，这个核带正电，质量很大，原子核被一定数量的“电子”包围着，电子很轻，带负电。现在我们要提前说明一点，在原子核中，已经找到了两类粒子，质子和中子，两者重量，几乎相同，且都很重。质子带电，而中子是中性的。如果一个原子，在其核中，有六个质子，且被六个电子所环绕（在通常的物质世界中，负的粒子全是电子，与构成原子核的质子和中子相比，它们很轻），那么，它就是化学周期表中的第六个原子，被称为碳。第八个原子被称为氧，等等，因为化学的属性，依赖于外围的电子，事实上，只依赖于有多少个电子。于是，一个事物的化学属性，就依赖于一个数目，电子的数目。（化学家的全部元素列表，确实可以称为1，2，3，4，5等等。我们可以说“碳”，也可以说“第六个元素”，意思是有六个电子，但当然的是，在元素最初被发现时，并不知道，它们可以这样编号，其次，这样将会让所有的事情，变得非常复杂。对于这些东西，用名字和符号，比用数字更好。

More was discovered about the electricalforce. The natural interpretation of electrical interaction is that two objectssimply attract each other: plus against minus. However, this was discovered to bean inadequate idea to represent it. A more adequate representation of thesituation is to say that the existence of the positive charge, in some sense,distorts, or creates a “condition” in space, so that when we put the negative chargein, it feels a force. This potentiality for producing a force is called an electricfield. When we put an electron in an electric field, we say it is “pulled.”We then have two rules: (a) charges make a field, and (b) charges infields have forces on them and move. The reason for this will become clear whenwe discuss the following phenomena: If we were to charge a body, say a comb, electrically,and then place a charged piece of paper at a distance and move the comb backand forth, the paper will respond by always pointing to the comb. If we shakeit faster, it will be discovered that the paper is a little behind, there isa delay in the action. (At the first stage, when we move the comb ratherslowly, we find a complication which is magnetism. Magnetic influences haveto do with charges in relative motion, so magnetic forces and electricforces can really be attributed to one field, as two different aspects of exactlythe same thing. A changing electric field cannot exist without magnetism.) If wemove the charged paper farther out, the delay is greater. Then an interestingthing is observed. Although the forces between two charged objects should go inverselyas the square of the distance, it is found, when we shake a charge, thatthe influence extends very much farther out than we would guess at firstsight. That is, the effect falls off more slowly than the inverse square.
关于电子力，还发现了更多。对于电子相互作用的自然解释，就是两个对象间简单的相互吸引：一正一负。然而，后来发现，用这个想法来表现此事，并不是很合适。对这个现象的更合适的表现是说，正电荷的存在，在某种意义上，使空间变形、或者在空间中创造了一个“条件”，这样，当我们把一个负电荷放进去的时候呢，它就感觉到了力。这个潜在产生力的东西，被称为“电场”。当我们把一个电子放进电场时，我们说电子“被拉了”。这样，我们就有了两条规则，（a）电荷形成电场；（b）电场中的电荷，受到力的作用而移动。这样说的理由，在我们讨论下面的现象时就清楚了：如果我们给一个物体，比如说梳子，充电，然后，把一张充了电的纸，放在一定距离，然后把这个梳子，在这个纸的旁边，来回移动，那么这个纸，就会对这个移动做出反应，并且总是指向这个梳子。如果我们把梳子，晃得快一点，就会发现，纸的移动，稍微有点慢，在这个运动中，有一个滞后。（在第一阶段，当我们慢慢地移动梳子时，我们发现了一个复杂的状态，它就是磁场。磁力影响，与相对运动中的电荷有关，这样，磁力和电力，确实就可以被归入同一个领域，作为同一个事物的两个不同方面。没有磁场，一个正在改变的电场，是不可能存在的。）如果能把充电纸张移得更远，那么，滞后就会变大。然后，就会观察到一个有趣的事情。虽然两个充电体之间的力，应该与距离的平方成反比，但却发现，当我们摇动一个充电体时，其影响的扩展，比我们一眼看上去时的猜测，要远的多。也就是说，其效果，与平方的反比相比，降低的慢的多。

Here is an analogy: If we are in a pool ofwater and there is a floating cork very close by, we can move it “directly” bypushing the water with another cork. If you looked only at the two corks,all you would see would be that one moved immediately in response to the motionof the other—there is some kind of “interaction” between them. Of course,what we really do is to disturb the water; the water then disturbsthe other cork. We could make up a “law” that if you pushed the water a little bit,an object close by in the water would move. If it were farther away, of course,the second cork would scarcely move, for we move the water locally. On theother hand, if we jiggle the cork a new phenomenon is involved, in which themotion of the water moves the water there, etc., and waves travel away, sothat by jiggling, there is an influence very much farther out, an oscillatoryinfluence, that cannot be understood from the direct interaction. Therefore theidea of direct interaction must be replaced with the existence of the water, orin the electrical case, with what we call the electromagnetic field.
这里是个类比：如果我们在一个水池中，且有一个飘动着的浮木在附近，我们可以通过用另外一个浮木推水，来把前一浮木“直接地”推走。如果你只看这两个浮木，那么你所看到的，只是一个浮木移动，而另一个对此做出反应，直接被移走，两浮木之间，有某种“交互作用”。当然，我们真正做的，是搅动了水，然后水又去搅动了另外一个浮木。我们可以建造一条“规律”，如果你把水推一点，那么附近水中的物体，将会移动。如果第二个浮木离得比较远，当然，它就会移动的很少，因为我们只是在近处移动水。另一方面，如果我们轻摇浮木，一个新的现象就会出现，即水的移动，会移动水，等等，然后，波浪就会扩散开，于是通过轻摇，产生的影响，就会非常远，即振动影响，不可能通过直接的交互影响，来理解它。所以，直接的交互影响这种想法，就应该被水存在的想法来替代，或者，在电子的情况下，被我们称为电磁场的东西来替代。

Table 2–1 The Electromagnetic Spectrum
Frequency in oscillations/sec Name Rough behavior
102 Electrical disturbance Field
5×105 – 106 Radio broadcast Waves
108 FM—TV
1010 Radar
5×1014 – 1015 Light
1018 X-rays Particle
1021 γ -rays, nuclear
1024 γ -rays, “artificial”
1027 γ -rays, in cosmic rays
表2-1 电磁波谱
震荡频率/秒 名称 大致表现
102 电子干扰 场
5×105 – 106 广播 波
108 FM—TV
1010 雷达
5×1014 – 1015 光
1018 X-射线 粒子
1021 γ -射线, 原子核
1024 γ -射线, “人工的”
1027 γ -射线, 在宇宙射线中

2–3Quantum physics 量子物理学
Having described the idea of theelectromagnetic field, and that this field can carry waves, we soon learn thatthese waves actually behave in a strange way which seems very unwavelike. Athigher frequencies they behave much more like particles! It is quantummechanics, discovered just after 1920, which explains this strange behavior.In the years before 1920, the picture of space as a three-dimensional space,and of time as a separate thing, was changed by Einstein, first into a combinationwhich we call space-time, and then still further into a curved space-timeto represent gravitation. So the “stage” is changed into space-time, and gravitationis presumably a modification of space-time. Then it was also found that therules for the motions of particles were incorrect. The mechanical rules of“inertia” and “forces” are wrong—Newton’s laws are wrong—in theworld of atoms. Instead, it was discovered that things on a small scale behave nothinglike things on a large scale. That is what makes physics difficult—and veryinteresting. It is hard because the way things behave on a small scale is so “unnatural”;we have no direct experience with it. Here things behave like nothing we knowof, so that it is impossible to describe this behavior in any other thananalytic ways. It is difficult, and takes a lot of imagination.
前面我们讲了电磁场的概念，以及这个场可以载波，很快我们就会学到，这些波的实际表现，比较特殊，似乎并不像波。在较高频率时，其表现更像粒子！，这就是量子力学，1920年之后被发现，它解释了这个奇怪的表现。在1920年之前，空间的图像就是三维空间，时间的图像就是一个独立的事物，但这些被爱因斯坦改变了，首先，被变成了空间-时间的组合，然后更进一步，被变成了弯曲的空间-时间，以代表万有引力。于是，这个“舞台”就{从原来的空间时间}变成了空间-时间，而万有引力则被假设为是对空间-时间的一种修改。然后还发现，粒子运动的规则并不正确。在原子世界中，“惯性”和“力”的力学规则是错误的--牛顿定律是错误的。取而代之的，是发现事物在微观世界中的表现，与在宏观世界中的表现，根本不一样。正是这一点，让物理学变得困难、同时也很有趣。之所以很艰难，是因为事物在微观世界的表现，是如此的“不自然”；对此我们没有直接的经验。在微观世界中，事物的表现，与我们所知道的，完全不一样，所以，要描述这种表现，只能用分析的方式，其他方式都不可能。这很困难，且需要大量的想象力。

Quantum mechanics has many aspects. In thefirst place, the idea that a particle has a definite location and a definitespeed is no longer allowed; that is wrong. To give an example of how wrongclassical physics is, there is a rule in quantum mechanics that says that one cannotknow both where something is and how fast it is moving. The uncertainty of themomentum and the uncertainty of the position are complementary, and the productof the two is bounded by a small constant. We can write the law like this: ΔxΔp≥ℏ/2 , but we shall explain it in more detail later. This rule is theexplanation of a very mysterious paradox: if the atoms are made out of plus andminus charges, why don’t the minus charges simply sit on top of the pluscharges (they attract each other) and get so close as to completely cancel themout? Why are atoms so big? Why is the nucleus at the center with theelectrons around it? It was first thought that this was because the nucleus wasso big; but no, the nucleus is very small. An atom has a diameter of about10−8 cm. The nucleus has a diameter of about 10−13 cm. If we had an atom and wished to see the nucleus, we wouldhave to magnify it until the whole atom was the size of a large room, and thenthe nucleus would be a bare speck which you could just about make out with theeye, but very nearly all the weight of the atom is in that infinitesimalnucleus. What keeps the electrons from simply falling in? Thisprinciple: If they were in the nucleus, we would know their position precisely,and the uncertainty principle would then require that they have a very large(but uncertain) momentum, i.e., a very large kinetic energy. With thisenergy they would break away from the nucleus. They make a compromise: theyleave themselves a little room for this uncertainty and then jiggle with acertain amount of minimum motion in accordance with this rule. (Remember thatwhen a crystal is cooled to absolute zero, we said that the atoms do not stopmoving, they still jiggle. Why? If they stopped moving, we would know where theywere and that they had zero motion, and that is against the uncertaintyprinciple. We cannot know where they are and how fast they are moving, so theymust be continually wiggling in there!)
量子力学有很多方面。首先，一个粒子具有确定的位置和确定速度，已经不再成立了；这是错误的。经典物理学是多么错误，这里给个例子，在量子力学中有一条规则，就是，某物的位置和速度，人不可能同时知道。动量的测不准与位置的测不准是互补的，两者的乘积，被一个小的常数所束缚。这条规律可以这样写：ΔxΔp≥ℏ/2，后面我们还会更详细地解释。这条规则是对下面最神秘的悖论的一种解释，该悖论就是：如果原子是由正负电荷组成的，那么，为什么负电荷不简单地坐在正电荷的上面（它们相互吸引），是距离变得很近，以至于完全取消它们？为什么原子会这么大？为什么处于中心的原子核，会有电子围绕？最初的想法，以为这是因为原子核非常大，但不对，原子核其实非常小。原子的直径大约是10 −8 cm。原子核的直径大约是10 −13 cm。如果我们有一个原子，并希望看到它的原子核，那么，我们就必须放大它，直到整个原子，相当于一个大的房间那么大，这时，原子核才是眼睛刚刚能够分辨出的一个小点，但是，原子的全部重量，几乎都在那个无穷小的原子核中。是什么让电子没有直接掉进原子核呢？是这个原理：如果它们在原子核中，那么，我们就可以知道其精确的位置，那么，这个测不准原理就会要求它们有一个非常大的（但不确定的）动量，也就是说，非常大的动能。有了这个能量，它们就会从原子核中逃出。它们做了一个妥协，因为这个测不准原理，它们给它们自己保留了一定的空间，然后，用最小的运动能量来摇动，以与这条规则相一致。（还记得吗，当一个水晶被冷却到绝对0度的时候，我们说过，原子并不是停止运动，它们还要继续摇动，为什么？如果它们停止运动，我们就会知道它们在哪里，及它们不运动了，但这是违背测不准原理的，我们无法知道它们在哪里，和它们运动的速度为何，所以，它们就必须在那里继续摆动！）

Another most interesting change in theideas and philosophy of science brought about by quantum mechanics is this: itis not possible to predict exactly what will happen in any circumstance.For example, it is possible to arrange an atom which is ready to emit light,and we can measure when it has emitted light by picking up a photon particle,which we shall describe shortly. We cannot, however, predict when it isgoing to emit the light or, with several atoms, which one is going to.You may say that this is because there are some internal “wheels” which we havenot looked at closely enough. No, there are no internal wheels; nature,as we understand it today, behaves in such a way that it is fundamentallyimpossible to make a precise prediction of exactly what will happenin a given experiment. This is a horrible thing; in fact, philosophers havesaid before that one of the fundamental requisites of science is that wheneveryou set up the same conditions, the same thing must happen. This is simply nottrue, it is not a fundamental condition of science. The fact is thatthe same thing does not happen, that we can find only an average,statistically, as to what happens. Nevertheless, science has not completelycollapsed. Philosophers, incidentally, say a great deal about what is absolutelynecessary for science, and it is always, so far as one can see, rathernaive, and probably wrong. For example, some philosopher or other said it isfundamental to the scientific effort that if an experiment is performed in,say, Stockholm, and then the same experiment is done in, say, Quito, the sameresults must occur. That is quite false. It is not necessary that sciencedoes that; it may be a fact of experience, but it is not necessary. Forexample, if one of the experiments is to look out at the sky and see the auroraborealis in Stockholm, you do not see it in Quito; that is a differentphenomenon. “But,” you say, “that is something that has to do with the outside;can you close yourself up in a box in Stockholm and pull down the shade and getany difference?” Surely. If we take a pendulum on a universal joint, and pullit out and let go, then the pendulum will swing almost in a plane, but notquite. Slowly the plane keeps changing in Stockholm, but not in Quito. Theblinds are down, too. The fact that this happened does not bring on the destructionof science. What is the fundamental hypothesis of science, thefundamental philosophy? We stated it in the first chapter: the sole test ofthe validity of any idea is experiment. If it turns out that mostexperiments work out the same in Quito as they do in Stockholm, then those“most experiments” will be used to formulate some general law, and thoseexperiments which do not come out the same we will say were a result of theenvironment near Stockholm. We will invent some way to summarize the results ofthe experiment, and we do not have to be told ahead of time what this way willlook like. If we are told that the same experiment will always produce the sameresult, that is all very well, but if when we try it, it does not, thenit does not. We just have to take what we see, and then formulate allthe rest of our ideas in terms of our actual experience.
量子力学，给科学的想法和哲学，所带来的另一个有趣的变化就是：在任何情况下，要准确地预测将会发生什么，都是不可能的。例如，安排一个将要发光的原子，是可能的，而且我们可以通过在它发光时，捕捉一个光子来进行测量。然而，我们无法预测它什么时候将会发光，或者，在几个原子的情况下，哪一个将会发光。你可以说，这是因为有一些内部的“轮子”{？}，我们还没有足够近地查看。不，没有内部轮子，按我们今天的理解，自然的表现，是这样的方式：就是在一个给定实验中，要精确地预测，将会发生什么，基本上不可能的。这是一件恐怖的事情，事实上，哲学家以前曾经说过，科学的基础要求之一，就是任何时候，你设定了同样的条件，同样的事情就会发生。这已经不是真的了，它不是科学的一个基础条件了。事实是，同样的事情并不会发生，我们所能做的只是，对于所发生的事情，找出一个平均的、统计上的近似值。尽管如此，科学并没有完全崩溃。顺便说一下，对于科学来说，什么是绝对必然的，关于这点，哲学家说了很多，现在我们可以看到，这很幼稚，甚至大概是错的。例如，有些哲学家或其他人会说，对于科学来说，很基础的一点就是，如果一个实验，是在斯德哥尔摩进行的，然后，又在基多做，那么，同样的结果，就应该出现。这种说法，完全错误。对于科学，这点并非必要；这可能是经验的事实，但并不必要。例如，如果实验之一，是在斯德哥尔摩看天空中的北极光，但在基多，你看不到；这就是一个不同的现象。“但是”你说，“那件事情，与外面有关；你能在斯德哥尔摩，把自己关在一个箱子里，然后拉下遮光物，这样，就能得到任何不同吗？”当然了。如果我们拿一个挂在万向节头上的单摆，推它一下，让它开始摆动，那么，这个单摆将几乎是在一个平面上摆动，不完全是在一个平面。在斯德哥尔摩，这个平面会不断地变化，但在基多不会。百叶窗拉下来的情况，也是这样{?}。如此所发生的事实,并不能破坏科学。科学的基础假设是什么？基础哲学又是什么？我们在第一章曾说过：任何想法的有效性的唯一测试，就是实验。如果在斯德哥尔摩做的大部分实验，在基多都能得到相同结果，那么，这些实验将会被用来形成一些普通规律，而对于那些结果不同的实验，我们将会说，这种结果，与斯摩摩附近的环境有关。我们会发明一些方法，以总结实验的结果，我们无须被预先告知，这些方法长什么样子。如果我们被告知，同样的实践，总是产生同样的结果，这当然非常好，但是，如果当我们试验的时候，并不产生同样的结果，那么，就是这样。我们只需接受我们看到的，然后，依据我们的实际经验，去形成我们想法的所有剩余部分。
{
Stockholm：斯德哥尔摩。
Quito:基多，厄瓜多尔首都，平均海拔2852米 ，距离赤道只有24公里。
}

Thus we have a new view of electromagneticinteraction. We have a new kind of particle to add to the electron, theproton, and the neutron. That new particle is called a photon. The newview of the interaction of electrons and photons that is electromagnetictheory, but with everything quantum-mechanically correct, is called quantumelectrodynamics. This fundamental theory of the interaction of light and matter,or electric field and charges, is our greatest success so far in physics. Inthis one theory we have the basic rules for all ordinary phenomena except forgravitation and nuclear processes. For example, out of quantum electrodynamicscome all known electrical, mechanical, and chemical laws: the laws for thecollision of billiard balls, the motions of wires in magnetic fields, thespecific heat of carbon monoxide, the color of neon signs, the density of salt,and the reactions of hydrogen and oxygen to make water are all consequences ofthis one law. All these details can be worked out if the situation is simpleenough for us to make an approximation, which is almost never, but often we canunderstand more or less what is happening. At the present time no exceptionsare found to the quantum-electrodynamic laws outside the nucleus, and there wedo not know whether there is an exception because we simply do not know what isgoing on in the nucleus.
这样，对于电磁的交互作用，我们就有了一个新的视图。除了电子、质子和中子外，我们有了一种新粒子：光子。电子与光子的交互作用的新的视图，就是电磁理论，但是，由于其中的每个事物，都符合量子力学，所以，它被称为量子电磁动力学。这个光与物质或者电场与电荷交互作用的基础理论，是迄今为止物理学最伟大的成功。例如，从量子电动力学中，可以得出所有已知的电子、力学和化学的规律：弹子球的碰撞规律，磁场中磁线的运动规律，特殊的一氧化碳的热的规律，霓虹灯的颜色，盐的密度，和氢氧生成水的反应的规律，都是这一条规律的结果。如果情况简单到足以让我们做出一种近似，那么，所有的细节，都可以从中得出；虽然，这种近似，几乎永远也不会发生，但通过它，我们可以或多或少地理解什么正在发生。目前为止，对于量子电动力学的规律来说，在原子核外，还没有发现任何例外，我们也不知道，在那里，是否有例外存在，因为，原子核中究竟发生了什么，我们根本不知道。

In principle, then, quantum electrodynamicsis the theory of all chemistry, and of life, if life is ultimately reduced tochemistry and therefore just to physics because chemistry is already reduced(the part of physics which is involved in chemistry being already known). Furthermore,the same quantum electrodynamics, this great thing, predicts a lot of new things.In the first place, it tells the properties of very high-energy photons, gammarays, etc. It predicted another very remarkable thing: besides the electron,there should be another particle of the same mass, but of opposite charge,called a positron, and these two, coming together, could annihilate eachother with the emission of light or gamma rays. (After all, light and gammarays are all the same, they are just different points on a frequency scale.)The generalization of this, that for each particle there is an antiparticle,turns out to be true. In the case of electrons, the antiparticle has anothername—it is called a positron, but for most other particles, it is calledanti-so-and-so, like antiproton or antineutron. In quantum electrodynamics, twonumbers are put in and most of the other numbers in the world are supposedto come out. The two numbers that are put in are called the mass of the electronand the charge of the electron. Actually, that is not quite true, for we have awhole set of numbers for chemistry which tells how heavy the nuclei are. Thatleads us to the next part.
因此，从道理上讲，量子电动力学，是所有化学的理论，也是所有生命的理论，如果生命最终可归于化学，从而归于物理，因为化学已经被归于物理了（参与化学的那一部分物理，已经知道了）。另外，此同一个电动力学，这个伟大的事物，预测了很多新事物。首先，它告诉了我们非常高的光子和伽马射线的属性，等等。它预测了另外一个非常值得注意的事物：除了电子之外，还有另一个同样质量的粒子，但带有正电荷，被称为正电子，电子和正电子，一起到来，也可以在光或伽马射线发射时，相互湮灭。（光和伽马射线，毕竟是同样的事物，它们只在频率层面上有不同点。）每一个粒子，都有一个反粒子，这个观点的产生，看来是真的。在电子的情况下，反粒子有一个名字，叫正电子，但是，对大多数其他粒子，它被称为反某某子，例如反质子或反中子。在量子电动力学中，两个数字被放进去，而世界上大多数的其他数字，被认为会产生出来。这两个被放进去的数字，被称为电子的质量，和电子的电荷。这并不完全是真的，因为对于化学，我们有一整组数字，告诉我们，原子核有多重。这把我们引向下一部分。