There is a prequel to The Da Vinci Code. It's called Angels and Demons, and in it, terrorists steal an eighth of a gram of antimatter from CERN to blow up the Vatican. The plot device is real physics dressed in pulp: when antimatter and matter meet, they annihilate, turning nearly 100% of their combined mass into pure energy. E = mc², all the way down. It is the most violent process physics allows.

《达·芬奇密码》有部前传，叫《天使与魔鬼》。情节是这样的：恐怖分子从 CERN 偷出八分之一克反物质，准备拿它炸掉梵蒂冈。这个桥段是把硬物理裹了一层通俗小说的皮——反物质遇上物质会湮灭，几乎 100% 的质量直接变成能量。E = mc²，一路到底。这是物理允许的最暴烈的过程。

That part of the novel is correct. Almost everything else is fiction.

小说里这一段，是对的。其他几乎全是虚构。

CERN does make antimatter. It costs more than anything else in the universe — at least a billion dollars per gram, and that number is missing zeros. The factory occupies a building south of the Large Hadron Collider where protons are accelerated to 99.93% the speed of light and smashed into a target the size of a pencil eraser. Twenty million anti-protons spray out every minute.

CERN 确实在造反物质。这是宇宙里最贵的东西——每克至少十亿美元，而且这个数字还少了好几个零。工厂在大型强子对撞机南边的一栋楼里：质子被加速到光速的 99.93%，狠狠撞上一块橡皮大小的靶子，每分钟喷出两千万个反质子。

CERN makes them not to weaponize antimatter — the amounts are eight orders of magnitude below anything dangerous — but to test whether antimatter behaves identically to ordinary matter. Any difference at all, however small, would crack open the deepest unsolved problem in physics.

CERN 造反物质不是为了做武器——他们手里的量比"危险"门槛还低八个数量级——而是为了一件别的事：测一测反物质的行为，跟普通物质到底是不是完全一样。哪怕只有极其微小的差别，都能撬开物理学里最深的那道未解之谜。

The antimatter factory is the single most precise instrument humans have built to look for that something.

CERN 的反物质工厂，是人类造过最精密的一台仪器，专门用来找这"什么东西"。

The story doesn't start at CERN. It starts at a desk in Cambridge, where a young theoretical physicist named Paul Dirac was trying to do something nobody had: write an equation for the electron that obeyed both special relativity and quantum mechanics at once.

故事的起点并不在 CERN，而在剑桥的一张书桌前。一位叫保罗·狄拉克的年轻理论物理学家想干一件没人干成过的事：给电子写一个同时遵守狭义相对论和量子力学的方程。

The equation worked — better than anyone expected. But it had two solutions. One described an electron with energy E = mc², the kind of electron everyone already knew. The other described an electron with energy E = −mc². A negative-energy electron. Nothing in nature was supposed to look like that.

这个方程奏效了——而且效果远超所有人预期。问题是，它给出了两个解。一个对应的是大家已经熟得不能再熟的电子，能量为 E = mc²；另一个则是 E = −mc²，"负能量电子"。可自然界里，根本不该有这种东西。

Dirac refused to throw the second solution out. In 1928 he proposed something radical: the negative-energy solution wasn't a mistake. It was a prediction — of an entirely new particle, identical in mass to the electron but carrying the opposite electric charge. An anti-electron.

狄拉克不肯把第二个解扔掉。1928 年他放出一个相当大胆的解释：那不是错，那是预测——预测了一种当时还不存在于物理学的全新粒子，质量和电子一样，电荷却相反。一个反电子。

Four years later, on August 2, 1932, a young Caltech physicist named Carl Anderson photographed a strange track in his cosmic-ray cloud chamber: a particle with the mass of an electron and a positive charge. He called it a positron. Dirac's math, written before anyone knew what to look for, had described a particle nobody had ever seen — and the universe produced one on cue.

四年后，1932 年 8 月 2 日，加州理工的年轻物理学家卡尔·安德森，在自己的宇宙射线云室里拍到了一条奇怪的径迹：一个质量等同于电子、电荷却为正的粒子。他给它起名"正电子"。狄拉克在没人知道该找什么的时候，凭着方程把这种粒子描述了出来——宇宙就这么按时把它递了上来。

Over the following decades, physicists built on Dirac's equation to construct quantum field theory — the framework that says every electron in the universe is identical not because of any cosmic accident, but because all electrons are excitations of a single underlying field that fills all of space. The field can carry any number of these excitations; each one is identical to every other; and the mathematics that describes the field requires that mirror-image excitations also exist. Same mass, opposite charge.

接下来的几十年里，物理学家在狄拉克方程基础上搭起了量子场论。这套框架的意思是：宇宙里每一个电子之所以彼此完全一样，不是因为某种宇宙巧合，而是因为它们都是同一个填满整个空间的"场"被激发出来的产物。这个场能承载任意多个这样的激发，每一个都和其他完全相同；描述这个场的数学，又强制要求"镜像激发"也存在——质量相同，电荷相反。

Antimatter, in other words, is not optional. It is built into the structure of reality.

换句话说：反物质不是可选项，它写在现实的底层结构里。

Which is why it was such a problem when the universe didn't seem to have any.

所以，当宇宙看起来"几乎没有反物质"时，问题就大了。

In the first three seconds after the Big Bang, the universe was hot enough that pairs of photons spontaneously converted their energy into matter–antimatter pairs. As space expanded, it cooled, the photons lost energy, and pair production stopped. Every particle was supposed to find its antiparticle and annihilate. The universe was supposed to be photons all the way down.

大爆炸最初的三秒钟，宇宙热到一对光子能把能量直接转成"物质 + 反物质"一对粒子。空间膨胀、温度下降、光子能量越来越小，这种"对生"过程也就停了。按剧本，每一个粒子都该和它的反粒子相遇、湮灭——宇宙里就该只剩下光子。

It isn't.

但它没这么走。

When astronomers count the photons in the cosmic microwave background — the thin radiation bath left over from those first seconds — they find about 10⁸⁹ of them. When they count the matter particles in the observable universe today — every proton in every star, every neutron in every iron core — they find about 10⁸⁰.

天文学家数过宇宙微波背景里的光子（那是大爆炸最初几秒留下的微弱辐射），大约 10⁸⁹ 个。再数今天可观测宇宙里的物质粒子——每颗恒星里的每个质子、每颗铁核里的每个中子——大约 10⁸⁰ 个。

That ratio is not a rounding error. For every billion matter particles that existed in the early universe, a billion antiparticles annihilated with them perfectly. Then one matter particle didn't find its partner. Across the entire observable cosmos, that one-in-a-billion remainder is everything.

这个比例不是凑整的误差。早期宇宙里每十亿个物质粒子，都精确地有十亿个反粒子和它们成对湮灭——然后多出一个物质粒子没找到伙伴。在整个可观测宇宙的尺度上，这十亿分之一的"漏网之物"就是今天的一切。

So the laws of physics that govern matter and antimatter are almost identical — but not quite. And "not quite" is the strangest possible answer. If they were truly different, there would be different rules for the two kinds. If they were truly the same, there would be no asymmetry. What physics actually describes is two sets of rules that match to a billionth of a part — and disagree just enough to leave us behind.

所以，支配物质和反物质的物理定律几乎一模一样——但不完全一样。"几乎"才是最古怪的答案。如果两种粒子彻底不同，那就该有两套独立的规律；如果完全相同，那就根本没有不对称。可物理学描述出来的，是两套对到十亿分之一精度都还几乎重合的规律——只在一点点细缝里不重合，恰好把"我们"留了下来。

Where does the disagreement hide? In four symmetry-breaking milestones — each one a crack in the mirror.

那一点点不重合，藏在哪里？四次对称性破缺，每次都是那面镜子上的一道裂缝。

CERN is best known for the Large Hadron Collider — a 27-kilometer underground ring where protons reach 99.9999% the speed of light. At the southern edge of the LHC sits a smaller, older ring: the proton synchrotron. Its protons are merely accelerated to 99.93% c. Some of that beam is fed out of the ring and into a different building entirely.

CERN 最出名的是大型强子对撞机：27 公里的地下环，质子被加速到 99.9999% 光速。LHC 南端，还藏着一个更小、更老的环——质子同步加速器（PS）。它的质子"只"加速到 99.93% 光速。其中一束被引出环外，送进另一栋建筑。

Inside that building is an iridium rod. Three millimeters in diameter, fifty-five millimeters long, embedded in graphite, then in a titanium alloy. Iridium is the second-densest element on Earth — chosen because its nuclei are packed tightly enough to make a proton collision likely.

那栋楼里，立着一根铱棒。直径 3 毫米、长 55 毫米，外面裹着石墨，再外一层是钛合金。铱是地球上密度第二大的元素——选它，是因为它的原子核排列得够紧密，质子撞上去的概率才够高。

When a proton arrives at 99.93% c carrying 26 GeV of energy, it doesn't bounce off the iridium nucleus. It penetrates it and slams directly into one of the protons or neutrons inside. What happens next is invisible by any normal sense of time. The colliding proton's three quarks — bound by gluons acting like rubber bands — are stretched, broken, and re-forged. Where there were three quarks, there are now showers of quark–antiquark pairs. Most of them stay bound and fly off as ordinary matter. Occasionally, three antiquarks find each other and form an anti-proton.

一个 99.93% 光速、带着 26 GeV 能量的质子撞上来，它不会弹开——它会直接穿进铱原子核，砸到核里面的某个质子或中子上。接下来发生的事，按普通时间感根本"看不见"。被撞进去的质子由三个夸克组成，被像橡皮筋一样的胶子绑着；这下橡皮筋被拉断、夸克被打散、又被重新粘合。三个夸克的位置，现在涌出一阵"夸克–反夸克对"的喷射。多数对子整对飞走，变成普通物质；偶尔，三个反夸克会凑齐，组合成一个反质子。

Total elapsed time from collision to anti-proton: 10⁻²³ seconds. A hundred billion-trillionths of one second.

从撞击到反质子诞生，全部时间不到 10⁻²³ 秒——也就是一秒的千亿亿亿分之一。

Every proton that hits the target produces trillions of these collisions. From the spray of debris — protons, anti-protons, neutrons, photons, all moving at 96% the speed of light — a magnetic filter pulls out only the anti-protons and steers them into the next ring: the Anti-proton Decelerator. There, electric fields slow them from 96% c to 10% c. Then a second ring called ELENA, installed in the mid-2010s, slows them further still — to 1.5% c, a leisurely 16.2 million kilometers per hour.

每一个打到靶上的质子，都会引发数以万亿计的这种碰撞。撞出来的"喷射物"——质子、反质子、中子、光子，全都以 96% 光速朝外射——会经过一个磁场筛选器：只把反质子留下来，引进下一个环——反质子减速器。在这里，电场把它们从 96% 光速减到 10% 光速。再下一个环叫 ELENA，2010 年代中期建成，把速度进一步压到 1.5% 光速——也就是悠悠的 1620 万公里每小时。

That is what "making antimatter" looks like. The factory's output: tens of millions of anti-protons every couple of minutes. The price tag, by the on-site physicist's reckoning, is somewhere north of a hundred trillion dollars per gram. A billion is "missing zeros."

所谓"造反物质"，差不多就是这么个流程。工厂的产量：每两分钟几千万个反质子。按现场物理学家自己估的价：每克得在百万亿美元这个量级——所以"十亿一克"，是真的"少了零"。

There's a reason the factory feels like a fortress. To make positrons (anti-electrons) for one of the experiments, technicians fire a 99.9% c electron beam at a tungsten target and harvest the gamma-ray-induced positrons that fall out — through a beam so radioactive the building wraps it in 1.2 meters of concrete and iron, weighing 1,400 tons.

这工厂之所以像座要塞，也是有原因的。为了给某个实验造正电子（也就是反电子），技术员要把一束 99.9% 光速的电子束打在钨靶上，然后收集由此产生的伽马射线诱发出的正电子——这束电子辐射强到必须用 1.2 米厚的混凝土加铁、合计 1,400 吨的护墙包起来。

Antimatter, the substance that annihilates on contact, is not even the most dangerous thing in the building. The matter beam that makes it is.

"沾上就湮灭"的反物质，居然不是这栋楼里最危险的东西。最危险的，是制造它的那束普通物质。

Producing 20 million anti-protons a minute is impressive. Keeping any of them is harder.

每分钟造两千万个反质子，听上去够厉害。难的是怎么留住哪怕一个。

The first anti-hydrogen atoms were made at CERN in 1995. They lasted only 40 billionths of a second before annihilating against the walls of their detector. In 40 nanoseconds you cannot measure anything useful about an atom — and yet the entire reason for making anti-atoms is to compare them, atom-for-atom, against ordinary hydrogen. To find the difference physicists know must be there.

CERN 在 1995 年第一次造出了反氢原子，它们撞到探测器壁上湮灭，从产生到消失只有 四百亿分之一秒。40 纳秒里你测不到关于这个原子的任何有用信息——而造反原子的全部意义，恰恰就是把它们和普通氢一颗一颗地比对，去找物理学家"明知道一定存在"的那点差别。

So for thirty years, CERN has been obsessing over a single question: how do you store antimatter in a world full of matter?

于是 CERN 整整三十年，一直在咬同一个问题：在一个全是物质的世界里，怎么把反物质装起来？

The answer is a device called the Penning trap — named after the Dutch physicist Frans Penning, whose 1930s ionization-gauge work inspired it. The mechanism is one of the most elegant pieces of engineering in modern physics, and the source of every precision result the antimatter factory has produced.

答案是一种叫做"彭宁阱"的装置——名字来自荷兰物理学家弗朗斯·彭宁，1930 年代他在电离规上的工作启发了它。这是现代物理里最优雅的一种工程结构，也是 CERN 反物质工厂所有精密结果的源头。

Here is how it works.

它的原理是这样的。

The result: anti-protons inside the trap have nothing to annihilate with and nowhere to go. They orbit. They wait. They stay.

结果就是：阱里的反质子，没有可以湮灭的对象，也无处可逃。它们在里面绕圈、等着、留下来。

Three precision measurements followed — each asking the same underlying question: are matter and antimatter truly mirror images, or is there a measurable crack?

三次精密测量接踵而至——每次都在问同一个根本问题：物质和反物质真的是镜中对称吗，还是存在可测量的裂缝？

Trapping antimatter, in other words, is no longer the bottleneck. The bottleneck now is measuring it precisely enough to find the difference physicists know must be there.

换句话说：困住反物质，已经不再是瓶颈。新的瓶颈，是把它测得足够精——精到能看见物理学家"明知道一定在那儿"的那点差别。

So can someone steal an eighth of a gram of antimatter from CERN and blow up the Vatican?

那么——有没有人能从 CERN 偷走八分之一克反物质，把梵蒂冈炸了？

The team ran the simulation — an actual one, with real numbers, on a screen. An eighth of a gram of antimatter, dropped on Vatican City. 22 trillion joules of energy released. A fireball of plasma at 100 million °C. About 36% of the Hiroshima blast in raw yield. St. Peter's Basilica — vaporized.

他们真做了一次模拟——屏幕上真数据。八分之一克反物质，扔在梵蒂冈城上空。22 万亿焦耳能量释放。一团 1 亿 ℃ 的等离子火球。原始当量大约相当于广岛核爆的 36%。圣彼得大教堂——汽化。

That is what an eighth of a gram does, in theory.

这就是八分之一克反物质理论上能干的事。

Now the math the simulation doesn't show. The CERN antimatter factory has been running for about 25 years. In that time, by the on-site physicist's own reckoning, it has produced roughly 10¹¹ anti-protons in total — about one trillionth of a gram. To accumulate one-eighth of a gram, the factory would need to run for longer than the age of the universe.

现在看一下模拟里没有显示的算术。CERN 反物质工厂已经开了大约 25 年。按现场物理学家自己的数：这 25 年里它一共造了大概 10¹¹ 个反质子——加起来大约 一万亿分之一克。想凑出八分之一克，这工厂得不间断运行比宇宙年龄还要久的时间。

If you took every anti-proton it makes in a year and annihilated them all at once, the energy released would be enough to heat one milliliter of water by one degree Celsius.

如果把它一整年生产的反质子全部一次性湮灭掉，释放出的能量大概只够把一毫升水加热一摄氏度。

The novel imagined a substance dangerous enough to level a city. The real factory makes a substance ten orders of magnitude too rare to do anything but answer one of the deepest scientific questions humans have ever posed.

小说想象出来的，是一种能夷平一座城的危险物质。真实的工厂造出来的，则是一种稀有到不可能干别的事——除了回答人类问过的最深刻的科学问题之一——的东西。

And that question — the one Veritasium opened on, the one CERN was built to chase, the one Dirac unknowingly seeded a hundred years ago — remains exactly where it started.

而这个问题——Veritasium 开篇问的那个、CERN 整座工厂为它而建的那个、狄拉克一百年前无意中埋下种子的那个——今天依然停在原地。

Physics has produced ninety-eight years of brilliant partial answers. It has not produced an answer.

物理学给了九十八年漂亮的"半截答案"。它没给出过完整答案。

In the meantime, every reader of this Spark contains trace amounts of radioactive potassium-40 and other isotopes. The average human body emits about 180 positrons per hour. Every banana on every breakfast table makes a positron roughly every 75 minutes.

而在等答案的这段日子里，正在读这篇文章的你，体内多多少少都有点放射性钾-40 之类的同位素。一个普通人体每小时大约会发出 180 个正电子。每顿早餐桌上的每根香蕉，大约每 75 分钟产生一个正电子。