你好，量子世界！/ Hello, Quantum World!

你蹲在小区的水泥地上跳房子的时候，是不是总得按顺序踩 1、2、3 的格子？要是你跳过 2 直接踩 3，玩伴肯定会喊你“犯规”啦！/ When you’re playing hopscotch on the concrete ground of your neighborhood, don’t you always have to step on the squares numbered 1, 2, 3 in order? If you skip 2 and jump straight to 3, your friends will definitely shout “Foul!”

上次你拆掉那个会唱《孤勇者》的机器人玩具，是不是从里面掉出来好多 tiny 小螺丝、小弹簧？还有个会发光的小灯珠，你盯着它看了好久，想知道它为什么会亮，可它小到你想用指甲抠都抠不动。/ Last time you took apart that robot toy that sings *The Brave One*, didn’t a bunch of tiny screws and springs fall out? There was also a little glowing lamp bead. You stared at it for a long time, wondering why it glows, but it was so tiny that you couldn’t pick it out even with your nails.

你有没有过拆到一半，突然发现某个 tiny 小零件不见了，翻遍整个沙发缝都找不到的经历？/ Have you ever taken a toy apart halfway, only to find a tiny part missing, and searched every crack of the sofa but couldn’t find it?

其实你找不到的那个小零件，说不定就躲进了微观世界——那个所有 tiny 到我们肉眼看不见的东西住的地方：小到细菌、小到细胞、小到原子、小到电子，都在这里面。/ Actually, that missing tiny part might have hidden in the microscopic world—the place where all things too tiny for our naked eyes to see live: bacteria, cells, atoms, electrons, they’re all in there.

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我们平时生活的世界叫宏观世界，所有我们能看见、摸到的东西——桌子、皮球、小狗、跳房子的格子——都是宏观世界的东西。宏观世界里的规则特别“讲道理”：你站在操场上扔一个皮球，用力的大小、角度都知道，物理老师就能算出皮球飞多高、飞多远、最后落在什么地方。/ The world we live in every day is called the macroscopic world. All the things we can see and touch—tables, bouncy balls, puppies, hopscotch squares—are all part of the macroscopic world. The rules here are very “reasonable”: if you throw a bouncy ball on the playground, and you know how hard you threw it and at what angle, your physics teacher can calculate how high it will fly, how far it will go, and where it will land in the end.

可微观世界就不一样啦！那里的规则“调皮”得很，就像一群总爱玩捉迷藏的小朋友，根本不按常理出牌。/ But the microscopic world is totally different! The rules there are very “naughty”, just like a group of kids who always love playing hide-and-seek, they never follow the common sense.

你扔出去的皮球，轨迹是确定的，你闭着眼都能知道它往哪飞，可要是你扔的不是皮球，而是一个 tiny 小电子，那可就完全乱套了：你越是想盯着它看它飞哪儿，它就越是跟你躲猫猫，一会儿出现在这儿，一会儿出现在那儿，你根本算不准它下一秒会在哪！/ The trajectory of the bouncy ball you throw is certain, you know where it flies even with your eyes closed. But if you’re not throwing a bouncy ball, but a tiny electron, then it’s totally chaotic: the more you try to stare at it to see where it flies, the more it plays hide-and-seek with you, appearing here for a second, there the next, you can never calculate where it will be in the next second!

这种 tiny 到不能再分的“微观小碎片”，就是量子。/ These tiny, indivisible “microscopic fragments” are called quanta (singular: quantum).

【📚 小术语卡 1】 量子 / Quantum：微观世界里最小的能量/物质单元，就像你玩乐高积木的最小块，掰成两半就不再是原来的积木块啦。你每次跳房子只能踩一个格子，不能同时踩两个，就像量子是一份一份的，你没法拿半份量子，就像没法踩半个格子一样。 *Quantum: The smallest unit of energy/matter in the microscopic world, just like the smallest Lego brick you play with. If you break it in half, it’s no longer the original Lego brick. Just like you can only step on one hopscotch square at a time, you can’t step on two at once, quanta come in indivisible chunks, you can’t have half a quantum, just like you can’t step on half a square.*

是不是觉得有点奇怪？我们平时见的东西不都能切吗？巧克力能掰成两半，苹果能切成块，为什么量子就不能切？/ Isn’t that a little weird? We can cut everything we see every day, right? Chocolate can be broken in half, apples can be cut into pieces, why can’t quanta be cut?

其实啊，宏观世界的东西是由超级多的微观粒子组成的：你手里的那个皮球，里面有差不多 $10^{23}$ 个原子，每个原子里面又有好多好多的电子、质子、中子。这么多微观粒子加在一起，“调皮”的地方就互相抵消啦，整体就表现出了我们看到的“讲道理”的宏观规则。/ Actually, macroscopic things are made of super many microscopic particles: the bouncy ball in your hand has about $10^{23}$ atoms, and each atom has lots of electrons, protons and neutrons inside. When so many microscopic particles are added together, their “naughty” parts cancel each other out, and the whole thing shows the “reasonable” macroscopic rules we see.

就像你们班的小朋友一起做游戏：单个小朋友可能调皮乱跑，但是全班一起排队的时候，就特别有秩序，你根本看不出哪个小朋友刚才还在乱跑。/ It’s like the kids in your class playing a game together: a single kid might be naughty and run around, but when the whole class lines up, it’s very orderly, you can’t tell which kid was running around just now.

1.1 微观世界的“小调皮鬼”们 / The Naughty Little Guys in the Microscopic World

你蹲在地上看蚂蚁搬家的时候，是不是觉得蚂蚁就像个巨型的小卡车，扛着比它身体还大的食物往前走？要是你缩小到和蚂蚁一样大，再缩小、再缩小，小到能看见蚂蚁身上的小绒毛的时候，你会发现，连蚂蚁身上的每一个小原子，都像个 tiny 小太阳系：中间的原子核是太阳，围着它转的电子是行星。/ When you squat on the ground watching ants move house, don’t you think ants are like giant little trucks, carrying food bigger than their bodies and walking forward? If you shrink to the size of an ant, then shrink again, and shrink again, until you’re small enough to see the tiny hairs on the ant’s body, you’ll find that every tiny atom on the ant’s body is like a tiny solar system: the nucleus in the middle is the sun, and the electrons spinning around it are the planets.

就是这些围着原子核转的电子，是微观世界最出名的“小调皮鬼”。/ These electrons spinning around the nucleus are the most famous “naughty little guys” in the microscopic world.

在宏观世界里，你扔个皮球，你知道它肯定往你扔的方向飞，不会突然掉头往你脸上砸（除非你力气太小没扔出去）。可电子不一样，它根本没有确定的轨迹，你根本没法说它下一秒一定会在哪，它可能出现在原子核的周围任何地方，甚至可能突然跑到原子外面去，再突然跑回来。/ In the macroscopic world, if you throw a bouncy ball, you know it will definitely fly in the direction you threw it, it won’t suddenly turn around and smash into your face (unless you threw it too weakly and it didn’t go out). But electrons are different, they don’t have a definite trajectory at all, you can never say for sure where it will be in the next second, it might be anywhere around the nucleus, or even suddenly run out of the atom, then run back.

你玩过“拍照片”的小游戏吗？就是你拿个手电筒照在墙上，把手放在手电筒前面，墙上就会出现手的影子。可要是你想给电子“拍照片”，那可就更难了：你得用光去照它，可光的能量是一份一份的，你用一份光去照它，这份光的能量会把电子撞飞，你拍到的就不是它原来的位置了；你要是不用光，又根本看不到它在哪。/ Have you ever played the “shadow puppet” game? You hold a flashlight against the wall, put your hand in front of the flashlight, and your hand’s shadow will appear on the wall. But if you want to “take a photo” of an electron, it’s even harder: you have to use light to shine on it, but light’s energy comes in chunks. If you use one chunk of light to shine on it, the energy of that light will knock the electron flying, and the position you captured is not where it was originally. If you don’t use light, you can’t see where it is at all.

是不是超级像爱玩捉迷藏的小朋友？你越想找它，它越躲着你，你找到的还不是它真正的样子。/ Isn’t that just like a kid who loves playing hide-and-seek? The more you try to find it, the more it hides from you, and what you find is not its real appearance.

这种“你越观测它，它就越不一样”的性质，在量子力学里叫不确定性原理，是微观世界最“调皮”的规则之一。/ This property of “the more you observe it, the more it changes” is called the uncertainty principle in quantum mechanics, one of the naughtiest rules in the microscopic world.

【📚 小术语卡 2】 不确定性原理 / Uncertainty Principle：你没法同时知道一个微观粒子的位置和速度，就像你没法同时抓住两个玩捉迷藏的小朋友，你抓到一个的时候，另一个肯定跑了。 *Uncertainty Principle: You can’t know both the position and the speed of a microscopic particle at the same time, just like you can’t catch two kids playing hide-and-seek at the same time. When you catch one, the other will definitely run away.*

```mermaid graph LR A[宏观世界<br/>Macroscopic World] --> A1[我们能看见摸到的<br/>皮球、桌子、蚂蚁] A --> A2[规则是确定的<br/>扔皮球能算准落点] A --> A3[粒子数量超级多<br/>10^23个原子以上] B[微观世界<br/>Microscopic World] --> B1[我们看不见的<br/>原子、电子、光子] B --> B2[规则是“调皮”的<br/>电子会捉迷藏] B --> B3[单个粒子行为不确定<br/>观测会改变它的状态] ```

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【💡 电子版侧边栏小思考】你有没有想过，如果你缩小到电子那么小，你会不会也有“分身术”，同时出现在两个地方？下一章我们就会告诉你答案哦！

1.2 什么是量子？/ What Is Quantum?

刚才我们说量子是微观世界最小的“小碎片”，那它到底是个什么东西？/ Just now we said quantum is the smallest “fragment” in the microscopic world, so what exactly is it?

你可以把量子理解成微观世界的“最小计量单位”。/ You can think of quantum as the “minimum measurement unit” of the microscopic world.

比如你玩跳房子，格子是画在地上的，最小的一格就是1，你不能有0.5格跳房子，不然就犯规啦。宏观世界里的能量好像是可以随便切的，比如你拿个暖水袋，里面的能量可以多也可以少，随便切多少都行，就像跳房子的格子可以画成0.1格、0.01格一样。/ For example, when you play hopscotch, the squares are drawn on the ground, the smallest square is 1, you can’t jump 0.5 of a square,