Biggest Mysteries in Physics: Antimatter, Dark Energy & ToE - Don Lincoln | Lex Fridman Podcast #497

频道: Lex Fridman
视频: https://www.youtube.com/watch?v=1M3Vdl6DRkU
原文语言: en
统计: 共 295 轮 · Lex 124 · Don 171

[0:00] Lex

The following is a conversation with Don Lincoln, a particle physicist at Firmeny Lab, who has spent decades working at the frontier of high energy physics. This was a mind-blowing and inspiring conversation. Don turned out to be one of my favorite people to talk to about physics. truly a unique mind with that Richard Fineman ability of taking very complicated ideas and explaining them simply without losing any of the essential brilliant insights at the core of those ideas. This is the Lex Freedman podcast. To support it, please check out our sponsors in the description where you can also find ways to contact me, ask questions, give feedback, and so on. And now dear friends, here's Don Lincoln. In describing the search for theory of everything in physics, you describe the history of physics can be told effectively as a kind of history of unifications. There's this centuries long quest to show that these distinct phenomena are actually linked by some unified underlying principles. uh even starting with Newton that you can think of the effort of physics as one as trying to unify the laws of nature. So I was wondering if we could talk through the history of unification that lens of physics. There are of course lots of different ways to do physics, but the the way that I would say that particle physicists, cosmologists do is they are trying to to really find basically the underlying principles that govern the laws of of nature. If we go back say to the I don't know 1650s or so, uh you're the most brilliant person around and you've noticed two things. One you've noticed is that when you trip, you fall. That is the nature of gravity that that we all experience daytoday. But then there's sort of astronomy where you look out at the heavens and you see the stars march across the sky. You see the planets move through the stars and there that seems to have absolutely nothing to do with what happens when you drop your sandwich and and the dog grabs it from you. So

以下是我与 Don Lincoln 的一段对话。他是 Fermilab 的一位粒子物理学家，几十年来一直工作在高能物理的最前沿。这是一场令人脑洞大开、深受启发的对话。Don 后来成了我最喜欢与之谈论物理的人之一——他确实是个独一无二的头脑，拥有 Richard Feynman 式的本领：能把极其复杂的观念讲得简单明了，却又不丢失其核心中那些精彩的本质洞见。这里是 Lex Fridman 播客。如果你愿意支持本节目，请查看简介里的赞助商信息，那里也有联系我的方式，你可以提问、给反馈等等。现在，亲爱的朋友们，有请 Don Lincoln。在描述物理学对万有理论(Theory of Everything, ToE)的探寻时，你说，物理学的历史在很大程度上可以讲成一部「统一」的历史。几个世纪以来，人们一直在追求一件事：证明那些看似各自独立的现象，其实都被某些统一的底层原理联系在一起。甚至从 Newton 开始，你就可以把物理学的努力理解为一个目标——试图统一自然的规律。所以我在想，我们能不能就从「统一」这个视角，来梳理一下物理学的历史。

[2:21] Don

yeah,

好啊。

[2:21] Don

the brilliant thing was when Newton looked at that and he thought about maybe the moon is falling but it's missing the earth. So what we had is that in maybe 1650 you had what we might call the laws of celestial gravity, the gravity that governs the heavens and terrestrial gravity, the gravity that is here on Earth. Now we don't think of that that way anymore. We think of it as just gravity. But at that time that wasn't at all obvious. And in fact, if you look in the books, Newton's theory is Newton's law of universal gravity. The universal is there. And the reason is is because he realized these two things that seem to have nothing to do with one another were indeed one and the same. I mean, this is absolutely brilliant. I mean, Newton is arguably one of the most brilliant humans I of which I'm ever aware. But at any rate, it is the first sort of easily to describe unification of physics that you can state in a way that sort of makes sense to to modern humans. I mean, you can go back farther than that where people are talking about chemistry, the nature of atoms. You go back to Democrus who was wrong about very many things, but the idea that there was a smallest particulate form of matter is right. So, it's kind of funny. You talk, you read the chemistry books and they say that the idea of atoms goes back to Democrus and you know he his idea was that like um there was a smallest atom of oil which was smooth and it was smooth of course because well oil is smooth. There was a smallest atom of vinegar because vinegar is tart and it pricks your tongue so therefore atoms were little sharp pointy things. Um and so he was wrong about a lot but he was right about the idea that there was a small particle and and we now know a very we have a very different concept than he did. So you can go back farther than that but getting to unification there are more examples. For instance if you go back to say 1830 or so scientists were trying to understand electricity for instance and there was a lot going on. people really understood things. But at the time you would have two phenomena that are familiar to us now. One is a magnet which you know at the time mostly magnets were were simply little pieces of iron that had been magnetized and they could stick to steel. And then you had electricity which was at the time they were generating little sparks that they could play and and have fun with or more broadly a uh a lightning bolt blazing across the sky. And so when you think about this, that lightning bolt and that little magnet seemed to be really unrelated.

做物理当然有很多种方式，但我会说，粒子物理学家和宇宙学家的做法是：他们真正想找到的，是支配自然规律的那些底层原理。我们不妨回到大约 1650 年前后。假设你是当时最聪明的人，你注意到了两件事。一件是：你绊倒了，就会摔下去——这就是重力(gravity)的本性，我们每天都在体验。可另一边还有天文学：你抬头望向天空，看见群星划过夜空，看见行星在恒星间穿行，而这一切似乎跟你掉了三明治、狗跑过来叼走它毫无关系。于是，Newton 的过人之处就在于：他看着这两件事，想到——也许月亮其实一直在「下落」，只不过它一直「错过」了地球。所以在 1650 年左右，我们可以说有两套规律：一套是天体重力，支配天上的重力；另一套是地面重力，地球上的重力。如今我们不再这么区分，我们只把它看成一回事——重力。但在当时这一点完全不是显而易见的。事实上，你翻书会看到，Newton 的理论叫「万有引力定律(law of universal gravitation)」——「万有(universal)」这个词就在那里。原因正是他意识到：这两件看似毫不相干的事，其实是同一回事。这绝对是天才之举。Newton 大概是我所知的最聪明的人类之一。但无论如何，这是物理学中第一次「容易表述」、又能讲得让现代人听懂的统一。当然你还可以追溯得更早，比如人们谈论化学、谈论原子的本性。回到 Democritus，他在很多事情上都错了，但「物质存在一种最小的微粒形式」这个想法是对的。说来有趣，你读化学书，会看到原子的概念可以上溯到 Democritus。他的想法是：比如油有一种最小的「原子」，是光滑的——光滑当然是因为油本身就滑；醋也有一种最小的「原子」，因为醋是酸的、会刺激你的舌头，所以醋的原子是带尖角的小东西。他在很多细节上都错了，但「存在一种小颗粒」这个核心想法是对的，只不过我们今天对它的理解和他大不相同。所以你能追溯得更早，但说到统一，还有更多例子。比如回到大约 1830 年，科学家们在试图理解电，当时进展很多，人们也确实搞懂了一些东西。但那时你面对的是两种我们今天都很熟悉的现象。一个是磁铁——当时大多数磁铁不过是被磁化过的小铁片，能吸在钢上。另一个是电——当时人们能造出小火花来玩闹取乐，或者更宏大一点，就是划过天空的闪电。所以你想想，那道闪电和那块小磁铁，看起来真是毫不相干。

[5:02] Lex

Mhm.

嗯。

[5:02] Don

Um but over the 1800s, a number of scientists were exploring little aspects of it. What happens when you run electricity through a wire? It seems to make a magnetic field. You know, they was a whole bunch of experiments and there were a lot of names. But in about the 1860s or so, James Clark Maxwell took all of those ideas that had been percolating around for the previous 50 years and wrote his laws of electromagnetism. And they're really fascinating. If you look at the laws of electromagnetism, they are they're differential equations or integral equations. But basically what they say is on one side you have a bunch of terms that have electricity in them and then you have equals on the other side a magnetism thing. So forgetting all of the mathematical symbols you have electricity side equals a magnetism side. Electricity equals magnetism. And that is a staggering concept. The fact that these two things a lightning bolt and the magnet that holds your kids art to the refrigerator are one and the same. And this was another case where electricity and magnetism became unified into electromagnetism. So now we have two examples. One, gravity being unified, terrestrial and celestial gravity, and then electricity and magnetism. So I I'll tell you about some more in a moment. But one thing that's kind of important because the goal is of course to to unify everything that if if I could do what I want to do, I would have some unified theory that would explain all the behavior of all energy, matter, space and time, which is a grand goal.

但在整个 1800 年代，一批科学家在逐点探索它的各个侧面。比如，电流通过一根导线会发生什么？它似乎会产生磁场。当时做了一大堆实验，也涌现了很多名字。但大约到了 1860 年代，James Clerk Maxwell 把过去 50 年里酝酿的所有这些想法汇总起来，写下了他的电磁学定律(laws of electromagnetism)。这些定律真的非常迷人。如果你去看电磁学定律，它们是微分方程或积分方程。但本质上它们说的是：等号一边是一堆含有「电」的项，另一边等于一个「磁」的东西。所以抛开所有数学符号，你得到的是：电的一边等于磁的一边——电等于磁。这是一个令人震撼的概念。一道闪电，和那块把你孩子的画贴在冰箱上的磁铁，竟然是同一回事。这又是一个例子：电与磁被统一成了电磁(electromagnetism)。所以现在我们有了两个例子。第一，重力被统一了——地面重力和天体重力；第二，电与磁。等会儿我还会讲几个例子。但有一点挺重要：因为最终目标当然是把一切都统一起来。如果我能做到我想做的事，我就会有某种统一理论，能解释所有能量、物质、空间和时间的全部行为——这是一个宏伟的目标。

[6:39] Lex

And and we should say that maybe one of the goals of science more broadly outside of physics even is to construct uh models that can generalize the world. So if you look at Darwinian evolution that was a very beautiful theory that captures another layer of reality of like how this particular thing that we see here on earth happens right

我们或许也该说，即便在物理学之外，更广义的科学的目标之一，也是构建能够把世界一般化(generalize)的模型。比如达尔文进化论，那是一个非常美的理论，它捕捉到了现实的另一个层次——比如我们在地球上看到的这种特定现象是如何发生的，对吧。

[7:07] Lex

so when we talk about theory of everything in physics that's capturing a different layer of abstraction about the functioning of the universe

所以当我们谈论物理学里的万有理论时，它捕捉的是关于宇宙运作的另一个抽象层次。

[7:16] Don

right the whole Darwinian evolution the fact that our genetics has significant overlap with genetics of a banana is is pretty staggering is astonishing that that works. So that is amazing. Um but for at least the class of of scientists that I am what we think of is well sure biology is interesting and all but when you get right down to it it's it's it's caused whatever happens in biology is caused by the movement of molecules. And then you say, "Well, that's great and all, but molecules, they do what they do because they're made of atoms."

对。整个达尔文进化论——我们的基因竟然和香蕉的基因有相当大的重叠——这件事相当惊人，简直令人震惊，它居然成立。所以那确实很了不起。但至少对于我这一类科学家来说，我们的想法是：生物学当然有意思，可归根到底，生物学里发生的一切，都是由分子的运动造成的。然后你会说，那很好，可分子之所以这样表现，是因为它们由原子构成。

[7:53] Don

And then the next step is, well, you know, atoms, that's great, but atoms work the way they do because of the nucleus and the electrons. And then the nucleus is protons and neutrons. And so there are those of us, myself included, who want to dig down at to the very very bottom and find out what is the smallest building block of nature from which all of these other far more complex and interesting and abstract things are, but what is at the very very bottom? And also that's great, but if you know um what the smallest building blocks are, that doesn't tell you the story. That's like having a whole bunch of Legos but not knowing how to put them together. You also need to know how they interact, how they work. And so that's what we study forces. So there are the various subatomic forces of which we're familiar. And um for instance, electricity and magnetism are components of electromagnetism which then governs the behavior of things like this is amazing. Electric electromagnetism explains of course electricity magnetism but it explains how light works. It explains how much of chemistry works. So electromagnetism 1860 or 70 uh the wonderful thing about that is if you take Maxwell's equations and you apply a little bit of calculus it's very easy to see that the laws of electricity and the laws of magnetism combined together make what's called a wave equation which that's shows that these electric and magnetic fields oscillate. they they vary. And if you have a something that's varied, that's a wave. And the wave then moves. And if you do the math, you find out that the speed at which these waves move is the speed of light. And so people said, "Wow, the speed of light comes out of those equations." And that had to be, I think, very persuasive. And of course, electromagnetism also plays a really significant role in chemistry because after all, atoms are held together by electromagnetic forces. There's more to how atoms work. There is all the quantum mechanic stuff. But if you did not have electromagnetism or if electromagnetism was very different, then atoms would be very different. So it plays a very big role in in holding us together. So it it's a a staggering advance in science to have a good behavior on that. And of course being able to to tame electromagnetism is why people can hear you when you do your podcast because through the miracles of the internet just or just electricity running the computers. I mean, this is a case, if I can get on a small soap box, where people back then said, "Well, why are you messing around with magnets and sparks and who cares?" Well, that very fundamental digging into the laws of nature has spin-offs. And it has spin-offs. One of the big spin-offs is our entire technological society. without being able to govern electricity, we'd still be farmers and shoemakers in cities, but we certainly would not have everything that we do. So, off my soap box, but it's really a lovely thing to show how this this digging into deep fundamental, not understood, mysterious things can 100 or 200 years later transform the world. And the type of science I do now, people often ask, well, what good is knowing about how the inside of atoms work, how the inside of quarks work. And I don't know the answer to that. Um, but just being a little more pragmatic, if I go back, say, hundred years, where people were trying to understand how the protons and neutrons inside atoms held together, how they split, how they they how you could combine them and so forth. This has led to nuclear power. Now, whatever you think about nuclear power and some people like it and some people don't, but it is powerful. It will generate uh energy for humanity and and it may be that is the path that that we take as we move away from digging fossil fuels out of the ground. Humanity is going to need power no matter what. Nobody is going to go back to the way things were in the 1700s. And one enormous source of energy that is there for us to take if we so choose is the modification of the nucleus of atoms seem to have absolutely nothing to do with anything. And yet it provides humanity with an opportunity which of course requires that we think carefully of how we do that and and if we want to but it gives us something that we didn't have before. Yeah, it's very clear that nuclear fusion and nuclear fision will unlock huge amount of energy that's required for a civilization to flourish. But that's almost like near-term.

再下一步是：原子也很好，可原子之所以这样运作，是因为有原子核和电子。再往下，原子核又是质子和中子。所以我们当中有些人——包括我自己——想一路往下挖，挖到最最底层，去搞清楚：自然界最小的building block(基本单元)是什么？所有那些更复杂、更有趣、更抽象的东西都由它构成，那么最底层到底是什么？而且这还不够：就算你知道了最小的基本单元是什么，也讲不出完整的故事。那就像你有一大堆乐高积木，却不知道怎么把它们拼起来。你还得知道它们如何相互作用、如何运作。这就是我们研究「力(force)」的原因。我们熟悉各种亚原子力。比如，电和磁是电磁的组成部分，而电磁支配着许多东西的行为——这太神奇了。电磁当然能解释电和磁，但它还能解释光是如何工作的，能解释大量化学现象。所以 1860 或 1870 年的电磁学，妙就妙在：如果你拿 Maxwell 方程组，稍微用一点微积分，就很容易看出，电的定律和磁的定律结合起来，会构成一个所谓的波动方程(wave equation)，它表明这些电场和磁场在振荡、在变化。而如果有东西在变化，那就是一种波。波会传播。如果你把数学算出来，会发现这些波传播的速度正是光速。于是人们说：哇，光速竟然从这些方程里冒出来了。我想这一点当时一定非常有说服力。当然，电磁在化学里也扮演极其重要的角色，毕竟原子是靠电磁力维系在一起的。原子的运作当然还不止于此，还有一大堆量子力学的东西。但如果没有电磁，或者电磁的性质大不一样，原子就会大不相同。所以它在「把我们维系在一起」这件事上扮演了非常重要的角色。能在这上面取得正确的认识，是科学上一个惊人的进步。当然，正是因为人类能够驾驭电磁，别人才能在你录播客时听到你的声音——通过互联网的奇迹，或者只是靠电力驱动计算机。我想说——请允许我站上一个小小的讲台——当年有人会说：你瞎折腾磁铁和火花干嘛，谁在乎啊？可恰恰是这种对自然规律最基础的深挖，会带来衍生成果，而且不止一项。其中一项巨大的衍生成果，就是我们整个技术社会。如果不能驾驭电力，我们今天还会是城里的农民和鞋匠，绝不会拥有我们如今拥有的一切。好，我走下讲台了。但这真是一件美妙的事，它展示了：对那些深层的、基础的、尚未被理解的神秘事物的深挖，可能在一两百年后彻底改变世界。至于我现在做的这类科学，人们常问：搞懂原子内部如何运作、夸克(quark)内部如何运作，到底有什么用？这个问题我答不上来。但务实一点说，如果我回到大约一百年前，那时人们在试图理解原子里的质子和中子如何结合、如何分裂、如何把它们合并起来，等等。这些研究最终带来了核能。无论你怎么看核能——有人喜欢，有人不喜欢——它都很强大。它能为人类发电，而且随着我们逐步摆脱从地下挖化石燃料，这可能正是我们要走的路。无论如何人类都将需要能源。没有人会回到 18 世纪那样的生活方式。而对原子核的改造，正是一个摆在我们面前、只要我们愿意就能取用的巨大能源——原子核看似与任何事都毫不相干，却给了人类一个机遇。当然，这要求我们慎重地思考该怎么做、要不要做，但它给了我们一种过去没有的东西。是啊，很清楚，核聚变(nuclear fusion)和核裂变(nuclear fission)将释放出巨量能源，而一个文明要繁荣昌盛正需要这些能源。但那几乎算是近期的事。

[12:50] Don

Mhm.

嗯。

[12:52] Lex

Longer term, you can think about things like we'll talk about dark energy crisis and antimatter. Maybe if you figure out some of the mysteries around antimatter, that too would lead to energy sources, how to produce energy, that too might lead to counterintuitive propulsion systems

从更长远看，你可以想想这样一些事——我们后面会谈到暗能量(dark energy)危机和反物质(antimatter)。也许如果你解开了反物质相关的某些谜团，那也会带来新的能源，带来产生能量的方法，甚至可能带来反直觉的推进系统(propulsion systems)。

[13:16] Lex

for us humans to travel through through the universe. Now, right now it seems farfetched, too expensive, too complicated, too difficult. But breakthroughs in the fundamentals theoretical physics might lead us to unlock some incredible energy sources, incredible technologies that uh will uh allow humans to explore the universe. And of course, we should also mention that as always with technology, it's a double-edged sword. It will most likely lead to the development of more dangerous weapons or other sources of harm. And then we uh as a civilization kind of have to walk that uh line and hope we figure out how to do more good than bad with the technologies we built.

让我们人类得以穿越宇宙旅行。当然，眼下这看起来还很遥远、太昂贵、太复杂、太困难。但基础理论物理上的突破，也许能让我们解锁某些不可思议的能源、不可思议的技术，让人类得以探索宇宙。当然，我们也该提一句：和所有技术一样，这是一把双刃剑。它很可能会催生更危险的武器，或带来其他危害。然后我们作为一个文明，就得在那条线上小心行走，希望我们能想清楚——如何用我们造出的技术做更多的好事、更少的坏事。

[13:59] Don

Right? But but we have to really remember while people worry about nuclear weapons which are admittedly very dangerous and even nuclear power which has waste that has to be dealt with. What science is doing is working out finding power that nature has presented to us. This is not new. Fire is like that too. Fire can burn down your house or it can cook your steak. Power is like that. And that's just something that we have to understand as humanity. And that's why this needs to be a you know when we talk about science it has to be a broad conversation by all of society because what scientists can do is figure out how the world works. Society has to figure out how we wish to apply that or not apply that.

对。但我们真得记住：人们担心核武器——它们确实非常危险——甚至担心核电站(它产生的废料必须妥善处理)。可科学在做的，其实是把自然早已呈现给我们的力量摸索出来、找出来。这并不新鲜。火也是这样。火能烧掉你的房子，也能煎熟你的牛排。力量就是这样的东西。这是人类必须理解的一点。这也是为什么，当我们谈论科学时，它必须是一场由全社会参与的广泛对话——因为科学家能做的，是搞清楚世界如何运作；而社会得决定，我们希望如何运用、或不运用这些知识。

[14:49] Lex

Also solving the mysteries and the puzzles of the universe in itself is effing awesome.

还有，光是去解开宇宙的谜团和谜题，这件事本身就他妈的超级酷。

[14:56] Don

It is. It is. So, I mean that that's the thing that makes us human in part is looking at a thing and saying, "How does this work?" And then together, uh, a bunch of apes get together like poke the thing, kind of shake the thing,

确实如此，确实如此。我的意思是，这正是让我们之所以为人的一部分：看着一样东西，问「这玩意儿是怎么运作的？」然后一群猿类聚到一起，去戳它、去摇它，

[15:11] Don

and then over time you have rockets going out into space, you build roads and bridges, you build the internet. Anyway, so we talked about Newton, we talked about Maxwell. That takes us in the 20th century in terms of unification. There's a guy named Einstein on whom you wrote a book who did quite a lot of progress on the effort of unification.

随着时间推移，你就有了飞向太空的火箭，你修起了公路和桥梁，你建起了互联网。总之，我们聊了 Newton，聊了 Maxwell。说到统一，这把我们带到了 20 世纪。有一位你为之写过一本书的人，叫 Einstein，他在统一这件事上做出了相当多的进展。

[15:33] Don

Sure. So Einstein, he's a pretty amazing guy. In 1905, he had his miracle year where he wrote multiple papers. The one that most people know about is special relativity where he showed something that makes no sense to anybody who's not really dug into it very hard. And that is that two people experience time differently. Time, you know, is a fascinating thing. We don't really understand what time is, which is weird. You think that that'd be something we'd understand very well, but we really don't. We know a lot about it, but really understanding it, not so much. But, um, Newton thought that time was just universal for everyone. So my time, your time, some person's time on Mars or on Alpha Centator, everybody experienced time the same. What Einstein showed was that that wasn't the case. That different people moving at different speeds with respect to one another experience time differently, which is absolutely a mindblowing concept. Now, most people think that Einstein then said, well, he invented spaceime that that space and time are the same thing. and he was behind that. But that actual insight came from one of his teachers, a guy by the name of Minowski, who looked at Einstein's equations. Mowski was a little bit more mathematically inclined than Einstein. And he saw that if you look at the equations, you have basically one person's space and time equals some numbers times this person's space and time. And so that's kind of a a staggering thing. So, so that is where Einstein and Manowski really did this unbelievable concept that that space and time are actually pretty much the same thing that runs a foul of our understanding of how the world works because time just moves. It's continuous. We we know what it is at a visceral level and an experiential level. We might not understand it at a formal level, but we know what time is. It's what keeps makes today today and not yesterday or tomorrow. Space is a little different. You can walk somewhere, you can walk back, you can move around. You have more freedom to move in space than you have to move in time. You can always move forward in time. It's just moving backwards. It turns out to be a little more difficult. But yeah, Einstein's understanding that that is the case, it caused everybody to think about the world very very differently. And that was in 1908 when Minkowski really laid it out in the strict spaceime.

当然。说到 Einstein，他是个相当了不起的人。1905 年是他的「奇迹年」，他写出了好几篇论文。其中大多数人都知道的那篇是狭义相对论(special relativity)。他证明了一件事，对任何没真正深钻进去的人来说都讲不通：那就是两个人会以不同的方式体验时间。时间，是个迷人的东西。我们其实并不真正理解时间是什么，这很奇怪。你会以为这该是我们理解得很透彻的东西，可我们真的没有。我们对它知道很多，但要说真正理解它，谈不上。Newton 认为时间对所有人都是普适的。所以我的时间、你的时间、火星上或半人马座 α(Alpha Centauri)上某个人的时间，每个人体验到的时间都一样。而 Einstein 证明的是，情况并非如此：彼此以不同速度运动的不同的人，体验到的时间是不同的——这绝对是个令人脑洞大开的概念。如今大多数人以为，是 Einstein 接着说，他发明了「时空(spacetime)」、说空间和时间是同一种东西，是他提出来的。但真正的这一洞见来自他的一位老师，名叫 Minkowski。Minkowski 看了 Einstein 的方程。他在数学上比 Einstein 更有倾向、更擅长。他看出，如果你看那些方程，本质上是：一个人的空间和时间，等于某些数乘以另一个人的空间和时间。这是件相当震撼的事。所以正是在这里，Einstein 和 Minkowski 提出了这个不可思议的概念——空间和时间其实差不多是同一种东西。这与我们对世界运作方式的理解相抵触，因为时间就只是在流逝，它是连续的。我们在直觉层面、在体验层面都知道它是什么。我们或许在形式层面理解不了它，但我们知道时间是什么。是它让今天成为今天，而不是昨天或明天。空间则有点不同。你可以走到某处，也可以走回来，可以四处移动。你在空间里移动的自由度，比在时间里移动的要大。你在时间里只能往前走，往回走嘛，结果证明要难一点。但没错，Einstein 认识到事情确实如此，这让所有人都开始用非常非常不同的方式去思考世界。而真正把它严格地以「时空」形式铺陈出来的，是 1908 年的 Minkowski。

[18:14] Lex

Uh and that also led to the work on special relativity led to the speed limit, the speed of light.

而且这项工作——狭义相对论的研究——也引出了那个速度上限，即光速。

[18:21] Don

Well, it was a premise. He had two premises. One was that the laws of nature are the same for everybody. So if you're moving at some speed or if I'm moving at some speed, I can say I'm not moving and saying you're moving at some speed. That's not controversial. That is what we call Galilean relativity. It's from hundreds of years ago. But what Einstein said that was controversial was that everybody measures that the speed of light is the same irrespective of how we're moving with respect to each other. You'll measure the speed of light to be a number. I'll measure the speed of light to a number. And that's very very different from what Newton would have said or Galile or any of the old guys. And it was taking those two things together that caused all of the weirdnesses of special relativity. Now you could then very easily say, well that second premise that everybody measures the speed of light to the same is just dumb and that you know you could test that. So that's where testing relativity comes in and Einstein's equations which include those two assumptions it predicts the behavior of everything perfectly well. Now we've actually measured uh done experiments where we can say that the speed of light is the same for everybody. That's not how that's been in the beginning. It was really that assumption leads to predictions. The predictions are true. So the assumption is true. Now there is a for for those people for your viewers who want to say well how do you measure that the speed of light is the same for everyone the particle physicists do this and the way you do this is the following there are some subatomic particles that when they decay they emit light that's their decay product and so you collide two things together so you know when the particle was created then you have surround your collision point by a detector and you measure how long it takes for light to get to your detector and by God it's the speed of light which it should be. However, sometimes in these collisions some of these subatomic particles you make are coming out at very high speed. They might be coming out at 95 or 97 or very large fraction of the speed of light and then they decay into photons. And so you measure how long it takes for the photon to get to your detector and it says it's light travels at the speed of light. Now if it were that if Einstein's conjecture was incorrect, you'd have a particle coming out at near the speed of light. It would be decaying into a particle traveling at the speed of light. Then that particle should have traveled at say two times the speed of light or something like that. So it should have taken half as much time to get to the detector. But it doesn't. So this is a hard serious measurement that shows that something you know we we can measure the speed at which light comes out of this stationary created particle and it's the speed of light then we can measure what the speed is of it coming out of something that's moving and it's still the speed of light. So that is an actual measurement but that is not something that was possible in Einstein's day but it is now. Just to take a small tangent. Uh how weird is it in the full ranking of weirdness that is physics? How weird is it that there's that speed limit of this speed of light?

嗯，那其实是一个前提。他有两个前提。一个是：自然规律对所有人都一样。所以如果你在以某个速度运动，或者我在以某个速度运动，我可以说我没动、是你在以某个速度运动。这并不有争议，这就是我们所说的伽利略相对性(Galilean relativity)，几百年前就有了。但 Einstein 说的那件有争议的事是：无论我们彼此如何运动，每个人测出来的光速都一样。你测光速会得到一个数，我测光速会得到一个数，而且这两个数相同。这与 Newton、Galileo 或任何老前辈会说的都非常不同。正是把这两件事放在一起，导致了狭义相对论里那些所有的怪异现象。这时你很容易就会说：第二个前提——所有人测出的光速都相同——简直是胡扯，而且你是可以去检验的。所以这就引出了对相对论的检验。Einstein 的方程包含了这两个假设，它对一切的行为都预测得完美无缺。如今我们确实做过实验，可以说光速对所有人都一样。但一开始并不是这么来的，真正的逻辑是：那个假设导出预言，预言为真，所以假设为真。现在，对那些想问「你到底怎么测出光速对所有人都一样」的观众来说，粒子物理学家就在做这件事，做法如下：有些亚原子粒子衰变时会发出光，那是它们的衰变产物。于是你让两样东西对撞，这样你就知道粒子是何时产生的；然后你在碰撞点周围布满探测器，测量光到达探测器需要多长时间——天哪，它就是光速，本该如此。然而，在这些碰撞里，有些你制造出来的亚原子粒子是以很高的速度飞出来的，可能是以光速的 95% 或 97%、或很大一个比例飞出来，然后它们衰变成光子。于是你测量光子到达探测器需要多久，结果显示光以光速传播。如果 Einstein 的猜想是错的，你会有一个以接近光速飞出的粒子，它衰变成一个以光速行进的粒子，那么这个粒子本应以比如说两倍光速之类的速度行进，于是它到达探测器所花的时间应当只有一半。可它并没有。所以这是一项严谨而困难的测量，它表明：我们既能测出从一个静止产生的粒子里射出的光的速度——是光速；也能测出从一个运动的东西里射出的光的速度——仍然是光速。所以这是一个实打实的测量，只不过在 Einstein 那个年代做不到，而现在可以了。稍微岔开一点：在物理学这整套「怪异程度」的排行榜里，「存在光速这样一个速度上限」这件事到底有多怪？

[21:53] Don

Well, I have to tell you, when I first encountered this, it's pretty freaking weird. It's like pegs the weird meter. But as you become more familiar with it, as you become more more comfortable with the idea, the thing to remember is the speed of light. It's the speed of light through spaceime. Once you embrace that, that makes a whole ton of sense. It all of a sudden makes everything fall much more into place. I think that there is an ultimate speed isn't that shocking. It just simply says that it's a property of space in the same way that there is you know space can can transmit a certain strength electric field. like trans it can support a certain things whatever space is and we don't know what space is but whatever it is it has the capability of of transmitting these things at that one speed through space or time and everything else comes from our insisting that we keep space and time different that's that's how I view it and at least for me that once I accepted that it all became very comfortable

嗯，我得跟你说，我第一次遇到这件事时，它真的怪得要命，简直把「怪异计」的指针打爆。但当你越来越熟悉它，越来越习惯这个想法，要记住的关键是：那是光在时空中的速度。一旦你接受了这一点，它就变得非常说得通，一下子一切都各就各位了。我觉得，「存在一个终极速度」这件事其实没那么令人震惊。它无非是说，这是空间的一种属性——就好比空间能传递某种强度的电场，能支撑某些东西。不管空间到底是什么——我们并不知道空间是什么——但无论它是什么，它都具备这样的能力：以那唯一一个速度，在空间或时间中传递这些东西；而其余一切，都来自我们坚持要把空间和时间区分开来。至少对我而言，这就是我看待它的方式。一旦我接受了这一点，一切就都变得很自然了。

[23:06] Lex

so The nature of my question actually here that will apply over and over

所以，我这个问题的本意——它会反复适用——

[23:11] Lex

is trying to empathize, trying to put ourselves in the shoes of the people before space and time are unified into spaceime

是去共情、去设身处地体会那些生活在「空间和时间被统一成时空」之前的人，

[23:19] Lex

and and really experience and think through how difficult of a leap is that

真切地去体验、去想清楚：那是一次多么艰难的飞跃。

[23:24] Don

huge.

巨大无比。

[23:25] Don

The reason I I sort of say that is we are now in the modern day in the 21st century and of course we're going to have to make leaps like that in our future. Mh.

我之所以这么说，是因为我们如今身处现代、身处 21 世纪，而将来我们当然也得做出类似的飞跃。嗯。

[23:36] Lex

So what are the unifications we're not seeing in front of our eyes? So for example, there's so many examples through through your work, through your lectures of um uh Paul Durak taking antimatter seriously.

那么，有哪些统一就在我们眼前、我们却没看见？比如，在你的工作里、你的讲座里有那么多例子——比如 Paul Dirac 认真对待反物质。

[23:50] Don

Mhm.

嗯。

[23:51] Lex

Looking at what the math shows and saying, I really think this thing exists,

他看着数学所揭示的东西，然后说：我真的认为这个东西存在。

[23:57] Don

right?

对。

[23:57] Lex

I mean, it just sounds insane.

我是说，这听起来简直疯了。

[23:59] Don

It does.

确实如此。

[24:00] Lex

And so I think this is a good warm-up. The space-time unification is a good warm-up as we march through the 20th century because it gets uh in my view at least weirder and weirder even with Einstein himself.

所以我觉得这是个很好的热身。当我们沿着二十世纪的脉络往下走时，时空的统一是个不错的起点，因为在我看来，接下来的东西会变得越来越离奇——哪怕在Einstein本人身上也是如此。

[24:13] Don

Well, let me give you an even more basic example. Sodium and chloride. Sodium is an explosive metal. You put it in water and and it's kind of neat. You put it in water and it just it doesn't quite explode, but it gets hot and it pops around. Chlorine, it's a gas. It's going to kill you. So these two things are deadly. They're awful. And yet when you mix them, you put it on your food at night. Salt, right? And so this is a case where where this whole a unification and b this deeper understanding in this case of chemistry of how two things that that are dangerous can be brought together and turned into something not only innocuous but necessary for human life. And so this is not unusual that what what you're describing. I mean when you think about it, forget about everything else. Just the fact that you know we tell little kids little kids that the world is made of atoms. Now that's crazy. Most people have never seen atoms and yet nobody really doubts it anymore. And I think it's just a a case of of familiarity and then the culture slowly accepts it and it's then it's real even without the evidence. In fact, one of the courses you described there, um, how we know what we know. I think that's a valid question. How do we know there are atoms? And, and of course, there are ways we do. And by the way, on that front, I would love to go through how we know the building blocks in the universe as we march towards quirks. That in the course that you mentioned is one of the most fascinating things of this philosophy of atoms being around for a very long time. Then you concretize and you actually can prove or have strong observations that indicate that there is atoms and then there is a nucleus, there is electrons, there is photons, there is quarks and I mean it gets weirder and weirder and now we're facing the mystery. Is there building blocks even smaller than that? But anyway, Einstein turns out didn't just do special relativity. By the way, I I really think he deserves three Nobel prizes. He got it for photoelectric effect. The fact that he didn't get it for general relativity is a crime against humanity. I don't understand. Obviously should have gotten it for general relativity and and special relativity. I mean I think special relativity is separate for general relativity in ter as far as Nobel prizes go. Uh so general relativity is another unification.

我给你举个更基础的例子吧：钠和氯。钠是一种会爆炸的金属，把它扔进水里挺有意思——倒不至于真的炸开，但会发热、四处乱蹦。氯则是一种气体，能要你的命。这两样东西都是致命的、可怕的。可一旦把它们混在一起，你晚上就把它撒在食物上了——盐，对吧？所以这个例子既体现了统一，也体现了一种更深层的理解，在这里是化学层面的理解：两种危险的东西怎么会结合成不仅无害、甚至是人类生命所必需的东西。所以你描述的那种现象其实并不罕见。你想想看，别的都先不说，单单是这件事——我们告诉小孩子，世界是由原子构成的。这其实很疯狂。大多数人从没见过原子，可如今没人会去真正怀疑它了。我觉得这就是一个熟悉化的过程：文化慢慢接受了它，于是它就成了真实的，哪怕你手头并没有证据。其实你描述的那门课里有一句话——我们是怎么知道我们所知道的东西的。我觉得这是个站得住脚的问题。我们怎么知道有原子？当然，我们确实有办法知道。顺带一提，在这方面，我很想沿着通往夸克(quark)的路线，梳理一下我们是怎么认识宇宙基本组成单元的。你提到的那门课里，最迷人的内容之一就是这种关于原子的理念——它存在了很久很久，然后你把它具象化，真正能够证明、或者拿到强有力的观测证据，表明确实存在原子，然后是原子核，是电子，是光子，是夸克——它变得越来越离奇，而现在我们正面对着新的谜团：是否存在比这些还要小的基本组成单元？不过总之，事实证明Einstein做的并不只是狭义相对论。说句题外话，我真心觉得他应该拿三个诺贝尔奖。他凭光电效应拿了一个。他没能凭广义相对论拿奖，简直是反人类的罪行，我实在想不通。他显然应该凭广义相对论拿奖，也应该凭狭义相对论拿奖——就诺贝尔奖而言，我觉得狭义相对论和广义相对论是两码事，是分开的。而广义相对论又是一次统一。

[26:42] Don

Yes, that's right. What Einstein realized was that if you were in a rocket ship and the rocket ship was a very quiet rocket ship and it was accelerating, it would feel like you're experiencing gravity. And so, as as you say, it's one of his happiest moments when he realized that acceleration and gravity feel very much the same. What I'm impressed by is that idea, which is already a pretty neat idea, somehow led him to take his space-time idea, take this acceleration gravity idea and realize that he could describe gravity as the bending of spacetime. Spacetime being constant like east, west, north, south, that's already hard enough. But now he's saying, well, you know, take your your map and crinkle it and bend it and so forth and that's gravity. That is a staggering mind-blowing idea.

是的，没错。Einstein意识到的是：假如你身处一艘飞船里，这艘飞船非常安静，而它正在加速，那种感觉就跟你正在经历引力一模一样。所以正如你说的，当他意识到加速和引力感觉如此相似时，那是他最快乐的时刻之一。让我印象最深的是，这个想法本身已经相当精妙了，可它居然引导他把时空的概念、把加速与引力等效的概念结合起来，进而意识到他可以把引力描述成时空的弯曲。时空是恒定的，就像东西南北那样——光是这一点就已经够难理解了。可现在他却说：拿起你的地图，把它揉皱、把它弯折，诸如此类，而这就是引力。这是一个令人瞠目结舌、震撼人心的想法。

[27:40] Lex

I guess I wonder if you can comment on what do you think is the idea generation process that leads to that. So it probably in Einstein case has to start with what if gravity is itself space-time geometry. You you have to have a thought like that, right?

我很好奇，你能不能聊聊，在你看来，催生出这种想法的灵感生成过程是怎样的。所以在Einstein这个例子里，起点大概必须是这样一个念头：万一引力本身就是时空的几何呢？你必须先有一个这样的念头，对吧？

[27:59] Don

Yes, I think so. There's a lot about science. There's of course knowing what went before. There is knowing the mathematics that allows you to figure out the implications of your theory. There is the discipline to argue with yourself and other people because most ideas are wrong. But then there's what you just described that intuitive spark and that is something that is very very difficult to to create. There's a reason that we venerate these people is because it is an unusual feature and most people only have that aha moment once in their lifetime if they have it at all. Mhm.

对，我想是这样的。科学里有很多东西。当然，要知道前人做过什么；要懂得那些数学，好让你能推算出自己理论的种种推论；还要有那种自律，去和自己、和别人辩论，因为大多数想法都是错的。但除此之外，就是你刚才描述的那种直觉的火花，而这恰恰是极其极其难以创造出来的东西。我们之所以崇敬这些人，是有原因的——因为这是一种非同寻常的特质，大多数人一辈子哪怕真有过那种顿悟的时刻，也只会有那么一次。嗯。

[28:40] Don

And then there's a tricky business because I'm sure you do and I get a lot of letters from from creative thinkers who don't have all of the the history and the mathematical discipline and the the self, you know, self-critique that's necessary. Um, and so they come up with these ideas and often it's easy to see where they just don't play out. Um so in order to be that person who changes the way we see the world, ideas themselves are not enough. These these creative ideas that's not enough. You need it with the discipline and the critique. And it's that amalgam of those things that you know make you a genius that that history remembers.

接下来就有个棘手的问题了。我相信你也一样——我收到很多富有创造力的思考者寄来的信，他们并不具备全部的历史积累、数学训练，以及必要的那种自我批判。于是他们想出这些点子，而往往很容易就能看出它们在哪里根本行不通。所以，要想成为那个改变我们看待世界方式的人，光有想法是不够的，光有这些天马行空的创意是不够的。你还需要把它和自律、和批判结合起来。正是这几样东西的融合，才造就了那种会被历史铭记的天才。

[29:26] Lex

But it's hard to know in in a field of people you might uh be tempted to call crazy, there could be geniuses there. And it's hard to know which is which. We should mention that Einstein himself couldn't see the genius in quantum mechanics initially. Couldn't see the the correctness, I should say. So he could see the the insanity of gravity bending spacetime, but quantum mechanics was too weird for Einstein.

但很难判断——在一群你或许会忍不住称之为疯子的人里，可能就藏着天才，而你很难分辨谁是谁。我们得提一句，Einstein本人起初也没能看出量子力学里的天才之处。或者更准确地说，他没能看出它的正确性。所以他能看出引力弯曲时空有多么疯狂，可量子力学对他来说还是太古怪了。

[29:57] Don

In all fairness, it's weird for me, too. But um

说句公道话，量子力学对我来说也很古怪。不过呢——

[30:01] Don

but the thing is even while that is true and Einstein maybe spent the last few years of his life trying to to blend um electricity and magnetism, gravity in a a single thing and he was unsuccessful but he still was a very very valuable critic of quantum mechanics. It's not that he didn't understand it because he did understand it. He thought about the implications and all this quantum entanglement business. Well, not all of it, but he was responsible for saying, well, if you're right, then this. And of course, then people went out and found out that that Einstein's implication of quantum mechanics was real. And so they could say, see, quantum mechanics is real. So, you know, he was thinking deeply about it. And he was doing exactly that thing I said. There's that spark idea, but there's that critique idea. And if you're able to critique an idea, you might kill it. And that is it's always depressing when I have this brilliant idea and it gets killed, but it's better to be killed than to keep it around and waste time on it. Um, and so he was in that case not generating the the aha, but he was saying is, "All right, let's take your aha. Let's see it's right. What does it mean? It means this." that allows people to go test it. And so he was contributing very crucially to that other part of scientific advancement, which is not just the aha moment, but the beat it to death, test it, critique it, and make sure it's real. And it's only after all of that has been done that you really are sure you're right. And that's why science is such a a powerful tool. It is that that combative just downright kind of jerky critique that most people don't like. They don't like people saying your ideas, you know, might be wrong. But that is it is crucial. It is crucial part of the scientific process.

不过问题在于，即便如此——Einstein晚年或许花了好几年时间，试图把电、磁、引力糅合进一个统一的框架里，但没有成功——他依然是量子力学一位极其宝贵的批评者。并不是他不理解它，因为他确实理解。他思考过它的种种推论，思考过所有这些量子纠缠的事情。嗯，倒也不是全部，但他正是那个站出来说的人：好，假如你是对的，那么就会有这样的结果。当然，后来人们真的去做了实验，发现Einstein从量子力学推导出的那个推论是真实的。于是他们就能说：瞧，量子力学是真的。所以你看，他在对它做深入的思考。他做的恰恰就是我刚才说的那件事——有那个火花式的想法，但也有那个批判式的想法。如果你有能力去批判一个想法，你可能会把它扼杀掉。而每当我想出一个绝妙的点子、它却被扼杀时，总是让人沮丧，但被扼杀也好过留着它、白白浪费时间。所以在那个例子里，他贡献的不是那声“啊哈”，而是说：好，我们就拿你那声“啊哈”，看看它对不对，它意味着什么，它意味着这样。这就让人们得以去检验它。所以他在科学进步的另一个环节上做出了极其关键的贡献——不只是顿悟的那一刻，还有把它往死里推敲、检验它、批判它、确保它是真的。只有把这一切都做完之后，你才能真正确信自己是对的。这就是为什么科学是如此强大的工具。正是那种好斗的、坦白说有点讨人厌的批判——大多数人都不喜欢，他们不喜欢别人说“你的想法可能是错的”——但它至关重要，是科学过程中至关重要的一环。

[32:04] Lex

Plus, there's that quote on the other side of it that I've heard you mention which is uh you know, I believe your idea is crazy, but is it crazy enough? Was that

另外还有一句话，是从另一个角度说的，我听你提起过——大意是：我相信你的想法很疯狂，但它够不够疯狂？是这句吗——

[32:17] Don

Yes. Yes. We all agree that your idea is crazy, but is it crazy enough?

对，对。我们都同意你的想法很疯狂，可它够不够疯狂呢？

[32:20] Lex

And there is some degree of taking those leaps uh of crazy, but it has to be backed with rigor,

所以确实需要有那么一点纵身一跃、跳进疯狂的勇气，但它必须有严谨作为支撑——

[32:27] Don

right?

没错。

[32:28] Lex

And the unifications continue that as we uh take steps towards the standard model, which is such an incredible part of of physics in the 20th century. So, can you describe that unification?

而这种统一一直在延续，伴随着我们一步步走向标准模型(Standard Model)——它是二十世纪物理学中极其了不起的一部分。那么，你能描述一下那次统一吗？

[32:39] Don

So, you know, we're sort of jumping forward here now to the 1930s or thereabout. And at by that time people had realized that there are four distinct forces that do not seem to be connected. One is gravity, two is electromagnetism, and those are things people are relatively familiar with. But there are two other forces that only have any real importance inside the nucleus of atoms, which is why most people have no experience with them. One is the strong nuclear force which holds the nucleus of the atoms together and the other one is what we call the weak nuclear force which is responsible for some types of of radioactivity. And since most people don't play around with nuclei and most people don't play around with radioactivity, they don't know what that is. But um by the 30s scientists had done enough experiments, done enough theorizing to to say that there were these four forces and that was already a triumph. I mean we in our goal for a theory of everything we'd like to think that there is one force which is what we're talking about the unification. Maybe these four forces are are just different ways of looking at a single underlying force. But in the 30s that's where we were. there were the four forces. So we move ahead and in the late 50s and early 60s some people were thinking that maybe the weak nuclear force and electromagnetism actually were the same. So they were working on trying to bring together these two forces to show that they're connected. And it came true. They were able to show that electricity and magnetism were actually two different facets of a single force that we now call the electroeak force. Mhm.

好的。现在我们要往前跳一跳，跳到大约二十世纪三十年代。到那时，人们已经意识到存在四种各不相同、看上去彼此毫无关联的力。一种是引力，二是电磁力，这两种是人们相对熟悉的。但还有另外两种力，它们只在原子核内部才真正具有重要性，这也是为什么大多数人对它们毫无体验。一种是强核力(strong nuclear force)，它把原子核束缚在一起；另一种是我们所说的弱核力(weak nuclear force)，它要为某些类型的放射性现象负责。由于大多数人既不会摆弄原子核，也不会摆弄放射性物质，他们并不知道那是什么。但到了三十年代，科学家已经做了足够多的实验、足够多的理论推演，得以断言确实存在这四种力——这本身就已经是一大成就了。要知道，在追寻万有理论(Theory of Everything)的目标中，我们更愿意相信存在唯一的一种力，这就是我们所说的统一：也许这四种力只是观察同一个底层之力的不同角度而已。但在三十年代，我们就停在那里——存在四种力。我们继续往前走，到了五十年代末、六十年代初，有些人开始猜想，也许弱核力和电磁力其实是同一种力。于是他们着手尝试把这两种力合到一起，证明它们是相互关联的。结果成真了。他们成功证明了电与磁其实是同一种力的两个不同侧面，而我们现在把这种力称为电弱力(electroweak force)。嗯。

[34:37] Don

Now, the story that you're told in in articles about this about what you people have called the Higs Bzon or the God particle, the story is very very simplified because in 1964 the um there were three groups with six individuals who came up with important papers talking about what's called the Higsfield. I'll get to back get to what that is in a minute. But the Higsfield is important. But it wasn't until 1967, so 3 years later, that Steven Weinberg and and some others actually unified electromagnetism and the weak force. Sheldon Glashau, Abdul Salam and Steven Weyberg successfully unified electromagnetism and the weak nuclear force that uh showing that high energies uh these two forces were merged into a single electroeak force,

现在，文章里讲给你听的、关于人们所称的希格斯玻色子(Higgs boson)或者“上帝粒子”的那个故事，其实被大大简化了。因为在1964年，有三个研究组、共六位个人，发表了几篇重要论文，谈到了所谓的希格斯场(Higgs field)。我等会儿再说它到底是什么。希格斯场很重要。但直到1967年，也就是三年之后，Steven Weinberg和另外几个人才真正把电磁力和弱力统一了起来。Sheldon Glashow、Abdus Salam和Steven Weinberg成功地把电磁力和弱核力统一了，证明在高能下这两种力会融合成一个单一的电弱力。

[35:34] Don

right? And that was in ' 67. All right. Um everybody talks about this thing happening in ' 64, but it it really wasn't. It happened over quite a few years actually. But all right. So now let's what you said is true. So um uh Weinberg, Glacial and Salam showed that electromagnetism in the weak force at high energies were the same. There was a problem however and the problem is that electromagnetism has an infinite range. Um and we know that because we can see stars that are millions of light years away. I mean that shows you that the range of that force is essentially infinite.

对吧？那是在1967年。好。大家都说这件事发生在1964年，但其实并非如此，它实际上是在好几年间陆续发生的。但没关系。所以现在——你说的是对的。Weinberg、Glashow和Salam证明了，在高能下电磁力和弱力是同一回事。不过有个问题，问题在于电磁力的作用范围是无限的。我们之所以知道这一点，是因为我们能看到几百万光年之外的恒星——这就向你表明，这种力的作用范围基本上是无限的。

[36:15] Don

The weak force however um basically becomes non-existent on distances much smaller than the size of a proton.

然而弱力呢，在比一个质子还小得多的距离上，基本上就消失得无影无踪了。

[36:24] Lex

Mhm.

嗯。

[36:25] Don

So that you know to say oh they're the same and yet one can reach across the universe and one can't reach out of an atom. Well that's just dumb. I mean the obvious thought here is well we just proved that that whole idea is stupid so throw it away ridiculous. And that is where these ideas from 1964 came in and saved the day. So how can it be true that the electroeak force is real and electromagnetism and the weak force act so differently? The way that could happen is if these forces were transmitted by a particle moving from one subatomic particle to the other. In the case of electromagnetism, it's the photon. In the case of the weak force, we call them now the W and Z particles. So the idea is that that Higgs and his colleagues came up with is saying all right electroeak force is real. The way we make it so that there is now an electromagnetic force and a weak force is the force carrying particle of electromagnetism has no mass. The force carrying particle of the weak force has a mass. And so what was done is a field was postulated that there was this additional field that was kind of distinct from this electroeak field and we call it the Higs field. And the Higs field permeates all of space. And and here's the kicker, some particles interact with a field and some particles don't interact with a field. The ones that interact with the field get mass and the ones that don't interact with the field don't have mass. And so that's the idea is that the Higs field gives the weak force particles mass. However, the photon laughs at the Higs field, doesn't see it, and it has no mass. And I should say here, going to perplexity, the big picture view, the Higs field is a quantum field that fills all of space and gives many elementary particles. Just as you're saying their mass through their interaction with it, the Higs Bzon is the particle associated with ripples or excitations of this field. In modern particle physics, every type of particle corresponds to a field that exists everywhere. The Higs field is one such scalar field, meaning at each point in space, it has a single numerical value rather than a direction. The Higs field differs from most other fields because even in empty space, empty in quotes by the way, empty space, it's uh average value is not zero. This nonzero vacuum value is what enable it to endow particles with mass.

所以说，你嘴上说它们是同一回事，可一个能横跨整个宇宙，另一个连一个原子都伸不出去——这听上去就很蠢。我是说，这里显而易见的念头是：我们刚刚不就证明了整个想法很愚蠢吗，那就把它扔掉吧，太荒唐了。而正是在这个节骨眼上，那些来自1964年的想法登场，挽救了局面。那么，电弱力是真的、而电磁力和弱力的表现又如此不同，这怎么可能同时成立呢？要让这成立，办法在于：这些力是由某种粒子从一个亚原子粒子传递到另一个亚原子粒子来传递的。对电磁力来说，这种粒子是光子(photon)；对弱力来说，我们现在把它们叫做W粒子和Z粒子。所以希格斯和他的同事们想出的点子是：好，电弱力是真的。我们要让它如今表现为一种电磁力和一种弱力，办法就是——电磁力的传力粒子没有质量，而弱力的传力粒子有质量。于是人们做的，是假设存在一个场，存在这样一个额外的场，它跟电弱场是有区别的，我们把它叫做希格斯场。希格斯场弥漫于整个空间。而关键来了：有些粒子会与这个场相互作用，有些则不会。那些与场相互作用的粒子就获得了质量，那些不与场相互作用的粒子就没有质量。所以这就是那个想法：希格斯场赋予了弱力粒子质量。然而光子对希格斯场嗤之以鼻，根本看不见它，于是它就没有质量。我得在这里说一句——去查一下perplexity，从大局来看：希格斯场是一个弥漫于整个空间的量子场，正如你所说，它通过粒子与它的相互作用，赋予了许多基本粒子质量；希格斯玻色子则是与这个场的涟漪或激发相对应的粒子。在现代粒子物理学里，每一种粒子都对应一个无处不在的场。希格斯场就是这样一个标量场(scalar field)，意思是在空间的每一点上，它只有一个数值，而没有方向。希格斯场与大多数其他场不同，因为即便在空无一物的空间里——顺便说一句，这里的“空无一物”是要打引号的——在空旷的空间中，它的平均值也不为零。正是这个非零的真空值，使它能够赋予粒子质量。

[39:31] Don

Right? So let's talk about something a little more familiar just to to try and hang some some intuition on those words. All right? So right in front of us there is a gravitational field. Now, you can't see it, but right there. Right there. Check it out.

对吧？那我们来聊点更熟悉的东西，好给这些字眼挂上一点直觉。好吧？就在我们正前方，存在着一个引力场。你看不见它，但它就在那儿。就在那儿。来感受一下。

[39:46] Lex

Yep.

嗯。

[39:46] Don

If I were to take something, a pen or whatever, and put it there, it feels a force and a falls.

如果我拿起某样东西，一支笔之类的，把它放在那儿，它就会受到一个力，然后掉下去。

[39:53] Lex

Mhm.

嗯。

[39:53] Don

Very insightful. I know. So, we have the gravity field and we have the pen that has a mass. And the mass and the gravity field interact and it drops. Now, if we had another

非常有洞见。我知道。所以呢，我们有引力场，还有这支带质量的笔。质量和引力场相互作用，于是笔就掉了下来。那么，如果我们再拿一个——

[40:07] Lex

I have uh object for you demonstration purposes,

我这儿有个东西，给你做演示用——

[40:11] Don

performance art. Here we go. This is great.

行为艺术。来吧。太棒了。

[40:13] Don

This thing has mass and we drop it. How remarkable. It falls. But when we step back and think about what really happens, it's the mass of this thing and the interaction with this invisible field we see here. That's what gives this weight.

这东西有质量，我们把它松手。多么了不起啊——它掉下去了。但当我们退一步、思考真正发生了什么，其实是这东西的质量，与我们这里看到的这个看不见的场之间的相互作用，正是这种作用赋予了它重量。

[40:30] Don

Now, I have this particle here that you can't see, but it's there. It has no mass and I leave it there. Well, since it has no mass, it doesn't feel gravity. It's still floating there. And that is really all the Higs field is. Some particles have effectively what you could call the Higs charge that interacts and sees the field and other particles don't. And that is really what what what you read just basically means. Now it's kind of neat because in the ordinary day there is a Higs field right there and the Higs field is not zero just like gravity is not zero and things will get mass but at super high energies the Higs field the strength of the Higs field goes to zero so whether things have mass whether they have a Higs charge or not they have no char or they have the Higs charge Higs field zero they don't interact it has no mass so that's kind of what uh Weineberg and Salam Glass show said is at very high energies, the Higs field is zero. Since the Higs field is zero, the weak force particles don't feel mass and therefore they can travel at the speed of light just like the photon does and everything's happy.

现在，我这儿有一个粒子，你看不见它，但它就在那儿。它没有质量，我把它放在那里。既然它没有质量，它就感受不到引力，于是它依旧悬浮在那儿。而这其实就是希格斯场的全部含义了。有些粒子，姑且说带有一种可以称为“希格斯荷”的东西，它会相互作用、会“看见”这个场；另一些粒子则不会。这其实就是你刚才读到的那段话的基本意思。妙的是，在日常情况下，那里就有一个希格斯场，而这个希格斯场不为零，就像引力不为零一样，于是物体就会获得质量；但在超高能下，希格斯场——希格斯场的强度——会趋于零，那么无论物体是否带有质量、是否带有希格斯荷，只要希格斯场为零，它们就不再相互作用，也就没有质量。所以Weinberg、Salam和Glashow说的大致就是：在极高的能量下，希格斯场为零。既然希格斯场为零，弱力粒子就感受不到质量，于是它们就能像光子一样以光速运动，皆大欢喜。

[41:44] Lex

Mhm.

嗯。

[41:45] Don

It is when the universe cooled down after the big bang. It was very hot, very high energy. Nothing had mass. the universe cooled and at a certain temperature what happened is the Higs field turned on and at the moment it turned on it gave mass to the weak force particles did not give mass to the photons. So that's what we call electroeak symmetry breaking. So, it's a mouthful, but all it says is there was a moment in time early in the history of the universe at 10 the -12 seconds after the big bang, the Higs field turned on and particles got mass. So, that's the whole idea. So, this is another really neat thing. So, the electroeak symmetry theory doesn't need Higs because that only really applies at very very high energies. But in order to make it work at low energies, you need to fix the theory. And you need to fix the theory by effectively putting a band-aid on the theory. Higs theory is just a band-aid on top of electroeek symmetry theory. And that is the band-aid that fixes it because it gives mass to particles at low energy. Well, how does then Higs this band-aid the field and uh the Higs Bzon come into play on the experimental front on the evidence? Okay.

事情是这样的：大爆炸之后，宇宙逐渐冷却下来。一开始它非常炽热、能量极高，所有粒子都没有质量。随着宇宙冷却，到达某个温度时，希格斯场(Higgs field)被"打开"了。它一开启，就赋予了弱核力相关粒子质量，但没有赋予光子质量。这就是我们所说的电弱对称性破缺(electroweak symmetry breaking)。这个词听起来很拗口，但它说的不过是：在宇宙历史的极早期，也就是大爆炸后约10⁻¹²秒那一刻，希格斯场开启了，粒子由此获得了质量。整个概念就是如此。这里还有一个非常妙的地方：电弱对称性理论本身并不需要希格斯，因为那套理论只在极高能量下才真正成立。但要让它在低能量下也能自洽，你就得修补这个理论——说白了，就是给它打个补丁。希格斯理论就是贴在电弱对称性理论之上的一块"创可贴"，正是这块补丁修好了它，因为它在低能量下给了粒子质量。那么问题来了，希格斯这块"补丁"——这个场，还有希格斯玻色子(Higgs boson)——在实验层面、在证据层面，是怎么登场的呢？好的。

[43:07] Lex

Discovery front. So, what is this uh Higs Bzon?

在发现的层面上说。那么这个希格斯玻色子到底是什么？

[43:10] Don

Okay. Excellent.

好。问得太好了。

[43:11] Don

So, we have never seen the Higsfield. Higsfield is a hypothetical theoretical thing.

我们从来没有"看见"过希格斯场。希格斯场是一个理论上假设出来的东西。

[43:17] Don

But that is true of of most of our fields. We've never seen the electromagnetic field. We've never seen the gravity field. We've seen the effect of the field. And so all of these theories are now what we call quantum field theories. And that the whole idea of quantum fields if you have a quantum field, but that field can vibrate like a drum head. And so it doesn't vibrate just exactly like a drum head, but it vibrates locally. So you can have specific localized vibrations. And those specific localized vibrations are the particles. In the electromagnetic field, the vibration is the photon. In the Higs field, the vibration is the Higs Bzon. And so what we can do is not see the field, but we can actually excite the field, make it vibrate and detect the vibrations. So the Higs Bzon idea was predicted in ' 64. It became useful in ' 67. And then scientists started looking for it. So in the early 2000s, people were starting to think that we had built part particle accelerators more powerful or powerful enough to actually to be able to create these vibrations and detect them. So the accelerator that was working at the time was a large particle accelerator outside Chicago at Firmeny Lab called the Tevatron.

但这一点对我们绝大多数的"场"都成立。我们从没见过电磁场，也从没见过引力场，我们看到的只是场所产生的效应。如今所有这些理论都属于我们所说的量子场论(quantum field theory)。量子场的核心思想是：如果你有一个量子场，那么这个场可以像鼓面一样振动。它不是整张鼓面一起完全均匀地振动，而是局部地振动，也就是说会出现一些特定的、局域化的振动，而这些特定的局域振动就是粒子。在电磁场里，这种振动就是光子；在希格斯场里，这种振动就是希格斯玻色子。所以我们能做的，不是去看那个场，而是去激发那个场、让它振动起来，然后探测这些振动。希格斯玻色子的概念在1964年被预言，到1967年开始变得有实际用处，之后科学家们就开始寻找它了。到了2000年代初，人们开始觉得，我们造出的粒子加速器已经足够强大，强到真的有可能制造出这些振动并探测到它们。当时正在运行的那台加速器，是芝加哥郊外Fermilab的一台大型粒子加速器，名叫Tevatron。

[44:44] Don

And we were colliding protons and antimatter protons at near the speed of light at very high energy. And that was the accelerator at which the top quark was discovered in '95. But we had upgraded our apparatus. We had 10 times the number of collisions per second. We had slightly more energy and we were banging the protons and the antimatter protons together hoping that we would actually find the Higs bzon.

我们在那里让质子和反质子以接近光速、极高的能量对撞。正是用这台加速器，我们在1995年发现了顶夸克(top quark)。后来我们对设备做了升级：每秒的对撞次数提高到了原来的10倍，能量也略有提升，我们让质子和反质子相互轰击，期望真的能找到希格斯玻色子。

[45:09] Lex

Can you actually back up a little bit and look at the bigger picture? So, Firmy Lab has this legendary accelerator that there's also a personal story with you connected to it because I mean there's a million questions uh I want to ask you and we'll ask you about some aspects of that. So, this idea of an accelerator, the design and the physics of an accelerator, how is that productive for understanding and discovering uh different aspects of particle physics?

你能不能稍微往回退一点，从更宏观的角度讲讲？Fermilab有这台传奇般的加速器，而你和它之间还有一段私人渊源。我有无数个问题想问你，关于这些方方面面我们都会聊到。那么，加速器这个概念——它的设计、它背后的物理学——究竟是怎样帮助我们去理解和发现粒子物理的各种面貌的？

[45:37] Don

Well, I'm so glad you asked. I mean, this is fascinating. All right, everybody has heard Einstein's equation E= MC². Nobody knows what it means. Maybe they heard that energy equals mass and mass equals energy. I don't know, you know, but they've heard the equation, the most famous equation in all of science. But buried inside that equation is a really thoroughly fascinating concept that energy and matter are equivalent. And you can in fact convert movement energy into mass. And so this is something that we've known for a long time. This was predicted back in basically 1928. So a long time ago, actually almost 100 years ago. And it is not in the slightest bit controversial. We can do this all the time. So the simplest thing is to take two particles that have no no structure. So you know the closest thing you can have to BB's that are just true mathematical BB's. If you smash those two things together, it's coming in with a huge amount of energy from one direction, a huge amount of energy from the other direction, the directions cancel. So the net momentum, the net energy of this has no motion. So you have these two things coming in with a you know exactly balanced energy and if they collide they could stop. Well that energy has to go somewhere and that energy can literally create mass create particles. Now there are special rules about what happens if you have two things coming together and it creates a particle. It has to create an antimatter particle to balance it. That's just kind of the rules of the laws of nature. Why is that the case? Well, we have some ideas, but in many respects the answer is because those are the laws of the universe and that's the things that we try to understand. But this is absolutely true. So what what particle accelerators do among other things is simply transform energy into particles. And so basically any uh particle that doesn't exist in nature we can make in this way. You can make the antimatter electron by taking two particles, smashing them together. The energy sits there and it will make an electron and an antimatter electron and it just does. And we know that the antimatter electron was discovered in 1932. This is all pretty easy. The antimatter proton was discovered in 1955 at the Berkeley Bevatron. And so this is just what you do. You can convert energy into a matter antimatter particle. Now the converse goes true and that's something we might talk about. You can take matter and antimatter and bring it together and it'll make energy. It's the uh the process can go both ways. Energy can make matter and antimatter. Matter and antimatter can make energy. And this is just true. We do it all the time. There's no question that this is the case. We should also mention that uh this is the reason why Firmeny Lab had a nice stash of antimatter particles. So as as a side effect, you can also collect antimatter in this kind of way.

你能问这个我太高兴了，这实在太迷人了。好，每个人都听说过爱因斯坦(Einstein)的方程E=mc²，但没人真正懂它是什么意思。也许他们听说过"能量等于质量、质量等于能量"，我也说不准，但反正这个方程他们都听过——全科学界最有名的方程。可这个方程里藏着一个极其迷人的概念：能量和物质是等价的，而且你确实可以把运动的能量转化成质量。这件事我们早就知道了，最早大约在1928年就被预言了，所以是很久以前的事，差不多快100年了。而且这一点丝毫没有争议，我们随时都能做到。最简单的例子，是拿两个没有内部结构的粒子——你可以把它们想象成最接近"小钢珠"的东西，纯数学意义上的小钢珠。如果你把这两样东西对撞，一个从一个方向带着巨大的能量冲过来，另一个从相反方向也带着巨大的能量冲过来，两个方向相互抵消。所以总动量、总的净能量是没有运动的。于是你有这样两个东西，带着精确平衡的能量迎面相撞，撞上之后它们可能就停下来了。可那些能量总得有去处，而这些能量真的可以凭空创造出质量、创造出粒子。不过这里有些特殊规则：如果两样东西相撞产生了一个粒子，它必须同时产生一个反物质粒子来"配平"。这就是自然法则的规矩。为什么会这样？我们有一些想法，但在很多方面，答案其实就是：因为这就是宇宙的法则，而这恰恰是我们试图去理解的东西。但这件事是千真万确的。所以粒子加速器的功能之一，简单说就是把能量转化为粒子。基本上，任何自然界中不存在的粒子，我们都可以用这种方式造出来。你可以造出反物质电子(反电子)：拿两个粒子撞在一起，能量停在那里，它就会生成一个电子和一个反电子，自然而然就发生了。反电子早在1932年就被发现了，这一切都相当容易。反质子则是在1955年于伯克利的Bevatron加速器上被发现的。所以这就是常规操作：你可以把能量转化为一对正反物质粒子。反过来也成立，这一点我们或许之后会聊到——你可以把物质和反物质放到一起，它们就会生成能量。这个过程是双向的：能量能产生物质和反物质，物质和反物质也能产生能量。这是千真万确的，我们一直在这么做，这一点毫无疑问。我们还应该提一句，这也正是为什么Fermilab当年攒下了一批不错的反物质粒子库存——作为副产品，你也可以用这种方式收集反物质。

[48:56] Lex

You can produce antimatter, but it's an extremely costly

你可以制造反物质，但代价极其高昂——

[49:00] Don

well very very costly. Um in order at the Firmeny Lab machine, we would have to smash 100,000 protons into something to make one antimatter proton. So I mean it it took some work. Is there some extremely precise recipe of uh of being able to produce particular kinds of particles and all this kind of stuff when you smash two things together? Is there like how can you control accurately which kind of particles you're trying to produce? If you want to make antimatter electrons, you smash together energy at a certain it's just easier with electrons because the electrons to the best of our knowledge have nothing inside them. So they're simple. They have a certain mass and that's that. So if you smash particles together with the right energy, you can make them very very easily because you can it's like a old style radio back in the day where you had to dial it in. you could get right on the station and you could hear the the signal and if you were off a little it didn't work. The problem for things like protons and so forth is they're not pointlike particles. They're kind of like garbage cans full of stuff and so it's very difficult to make antimatter protons. Now you can get more of them by increasing the um energy at which you collide two particles together. If you're at below a certain energy, the and you collide, say you collide two protons together at kind of low energy, you just don't have enough energy to make an anti-roton

对，非常非常昂贵。在Fermilab那台机器上，我们差不多要把10万个质子撞向靶子，才能造出一个反质子。所以这真的得下不少功夫。（Lex：）那么，当你把两样东西撞在一起时，有没有一套极其精确的"配方"，能让你制造出某种特定种类的粒子之类的？比如说，你怎么能准确控制自己想造出哪一类粒子？（Don：）如果你想造反电子，就在某个特定能量下把能量撞到一起——用电子会更容易些，因为据我们所知电子内部什么都没有，所以它很简单：有一个确定的质量，仅此而已。所以只要你用合适的能量去撞，就能非常非常容易地造出它们。这就像过去那种老式收音机，你得慢慢拧旋钮调台：调到正好对准电台，就能听到清晰的信号；要是偏一点点，就不行了。质子之类东西的麻烦在于，它们不是点状粒子，更像是一只装满了各种杂物的垃圾桶，所以造反质子就难得多。不过，你可以通过提高两粒子对撞的能量来获得更多反质子。如果能量低于某个阈值，比方说你让两个质子在较低的能量下相撞，那能量根本不够造出一个反质子，

[50:33] Don

and so it doesn't happen. You get to a certain energy and you can just barely make them. The more energy you collide them together, the more you make. So that is just sort of how it works. More is better. And then uh with with CERN if you compare maybe CERN and Firmayab going to perplexity here CERN's accelerator the large hydron collider LHC is the world's highest energy proton collider while Firmayab's current and plant accelerators focus on intense proton beams for neutrino physics rather than pushing the absolute energy frontier. Absolute energy frontier meaning highest possible energy smashing of protons together.

于是它就不会发生。到达某个能量时，你才勉强能造出一些。对撞的能量越高，造出来的就越多。事情大体就是这么运作的：越多越好。然后，说到CERN——如果你拿CERN和Fermilab做个比较，这里去查一下Perplexity——CERN的加速器，也就是大型强子对撞机(Large Hadron Collider, LHC)，是世界上能量最高的质子对撞机；而Fermilab目前在用的及规划中的加速器，重点放在用强质子束做中微子(neutrino)物理，而不是去冲击能量的绝对前沿。所谓能量的绝对前沿，意思就是用尽可能高的能量去对撞质子。

[51:16] Don

Correct. So one we were talking about like accumulating antimatter. Yes. All right. And so um there that is typically making anti-roton as opposed to making all particles in general. So let's focus on the anti-roton side to begin with. All right.

没错。所以，我们刚才在聊的其中一件事是"积攒反物质"。对。那么，这通常指的是制造反质子，而不是泛泛地制造所有粒子。所以我们先聚焦在反质子这一块。好。

[51:33] Don

So formula doesn't make anti-rotons anymore. We stopped making them in 2011 and it's because we shut our big accelerator down to concentrate on a different facet of particle physics. However, at the time we would smash um protons with a an energy of 120 GEV and in that we would make anti-roton. So that's a ton of energy. It's true that the CERN accelerator, the big accelerator, is now much higher energy than the Firmenab accelerator was. No problem. But that's not how they make anti-roton. The all of these big beam uh big laboratories, it's not one accelerator. At Firmay Lab, there were five distinct accelerators and it was basically like shifting an old standard car cuz you couldn't just go zero to super speed in one accelerator. you had to go from one to another getting higher and higher. Well, at CERN, they use one of the basically their second gear in their very big accelerator complex to make antimatter protons. And their accelerator is only 26 GEV compared to the 120 GV at Firmeny Lab. Firmay Lab's not operating, but when it was operating, it operated at an energy of about four times higher than what CERN is doing now. And why is that? Well, it's because what CERN needs to do is to not make as many anti-rotons as Firmay Lab did. They are doing a very different current experimental program. They're doing a fascinating experimental program including trying to figure out does anti-gravity fall up or down, which is kind of neat and we sort of know the answer to that different that's separate. But anyways, so getting back to the anti-roton business.

所以Fermilab现在已经不造反质子了。我们在2011年停止了制造，原因是我们关停了那台大加速器，转而集中精力研究粒子物理的另一个侧面。不过在当年，我们会用120 GeV的能量去撞质子，并在这个过程中造出反质子。所以那是相当大的能量。确实，CERN那台大加速器现在的能量比当年Fermilab的加速器高得多，这没问题。但他们造反质子用的并不是那台机器。所有这些大型束流实验室都不是只有一台加速器。在Fermilab，一共有五台不同的加速器，整个过程基本上就像开一辆老式手动挡汽车在换挡——因为你没法用一台加速器就从零直接飙到超高速，必须一台接一台、能量逐级提高。而在CERN，他们是用其庞大加速器群里相当于"二挡"的那一台来制造反质子的。他们那台加速器的能量只有26 GeV，相比之下Fermilab当年是120 GeV。Fermilab现在不运行了，但当它运行时，能量大约是CERN现在的四倍。这是为什么呢？因为CERN要做的，是不必造出像Fermilab那么多的反质子。他们当前的实验项目方向很不一样，是一套非常引人入胜的实验项目，其中包括试图搞清楚反物质在引力下是"向上掉"还是"向下掉"——这相当有意思，而我们大致已经知道答案了，不过那是另一回事，跟这里说的是两码事。总之，言归正传，回到反质子的话题。

[53:20] Lex

Yeah.

嗯。

[53:21] Don

Well, Firmay Lab doesn't do it now. It was top dog. It's not anymore. Um, the only really big anti-roton accelerator creator is a small accelerator at CERN. Okay, so that's the anti-roton thing. And if we get back to antimatter, we could talk about that because that is way cool.

Fermilab现在不做这件事了。它曾经是行业老大，但现在不是了。如今唯一一台真正大规模制造反质子的加速器，是CERN的一台小型加速器。好，反质子的事就说到这。如果我们回到反物质这个话题，倒是可以好好聊聊，因为那实在太酷了。

[53:36] Lex

Yeah. So,

嗯。那么，

[53:38] Don

now the other side of your thing about making high energergy unknown particles, bigger is better. And it is true that the LHC is a very high energy machine. It is about seven times more powerful in terms of energy per collision. It is also about a hundred times more collisions per second than the Firmeny lab machine. So it is true that the LHC can make bigger heavier uh particles that the old firm lab the Tevatron ever couldn't and that is true. So if you want to look at high energy stuff, yeah, you go to CERN now. Which is why many of my colleagues including myself once we had measured all of the sort of frontier measurements we thought we could make with the Firmeny Lab accelerator, we saw this bigger, more powerful machine with seven times the energy and 100 times more collisions per second. We said, "Heck yeah, let's go work on that." And to give you a sense of scale, the top quark, which is the heaviest particle ever discovered, discovered at Firmeny Lab in 1995. There were two discovery papers and the one on which I was a co-author. We had worked for a good chunk of between 6 months and a year of collecting collisions and there were a lot of collisions and our paper had 38 top quirk candidates. 38. And we knew that half of them were crap because when you make a detector like that, there's what you call background. So you have the background and the good stuff. And we know it was about 50/50. So we had maybe 19 top quarks after working for between 6 months and a year of collecting data. But now at the LHC, we make a top quark every second. And that's what higher energy and more collisions per second will do for you. That extra energy, you're above threshold. You make a ton of them. And when you compare the 1995 Firm Firmab accelerator to the current CERN accelerator, it's probably a thousand times of collisions per second. So it went from painstaking, pulling teeth to, yeah, now top quarks are a background. We try to get rid of them. There's just too many of them. They get in the way of searching for the stuff we really want to search. They are like so 30 years ago. By the way, is there something to be said about the the kind of sort of signal processing here? How you remove the noise, how you remove the background, how you determine which particle is which. There's probably some like incredible nuance there

现在说你提到的另一面——制造高能量的、未知的粒子，这方面是"越大越好"。确实，LHC是一台能量极高的机器，就每次对撞的能量而言，它大约比Fermilab那台强七倍；而且它每秒的对撞次数也大约是Fermilab那台机器的一百倍。所以确实如此：LHC能造出更大、更重的粒子，那是当年Fermilab的Tevatron永远造不出来的，这是事实。所以如果你想研究高能量的东西，没错，现在就得去CERN。这也正是为什么我的许多同事——包括我自己——一旦我们用Fermilab的加速器把所有自认为能做的前沿测量都做完之后，眼看着这台更大、更强、能量七倍、每秒对撞次数百倍的机器，我们就说："那当然，咱们去那儿干吧！"给你一个量级感：顶夸克是人类发现过的最重的粒子，1995年在Fermilab被发现。当时有两篇发现论文，我是其中一篇的合著者。我们花了大约半年到一年的时间收集对撞数据，对撞次数非常多，可我们那篇论文里只有38个顶夸克候选事件，38个。而且我们知道其中有一半是"垃圾"，因为当你建造这样一台探测器时，会有所谓的本底(background)。所以你有本底，也有真正有用的信号，而我们知道大概是各占一半。所以辛辛苦苦干了半年到一年收集数据，最后大概只得到19个顶夸克。可如今在LHC，我们每秒钟就能造出一个顶夸克。这就是更高能量、更高对撞频率能为你带来的东西：能量上了台阶，越过了产生阈值，你就能造出一大堆。要是把1995年的Fermilab加速器和现在CERN的加速器比一比，每秒对撞次数差不多差了一千倍。所以从当年那种像"拔牙"一样费劲的状态，变成了如今顶夸克反倒成了本底——我们还得想办法把它们去掉，因为它们实在太多了，碍事，妨碍我们去搜寻真正想找的东西。它们已经是"30年前"的老古董了。顺便问一句，关于这里的信号处理，是不是有很多门道值得一说？比如你怎么去除噪声、去除本底，怎么判定某个粒子是哪一种粒子。这里头大概有一些极其精妙的讲究，

[56:12] Lex

even outside of the scope of this conversation.

甚至已经超出了这次对话的范畴。

[56:14] Don

So, let me just throw some numbers out. All right. So, at the CERN accelerator when it's operating, the collisions occur at a prodigious rate. We get about a billion with a B collisions per second. Now each one of those Yeah. Yeah. That's what I said. Wow. Now it turns out some of them are happening at the same time. So there's about of order 40 million moments in time per second where you would take a shot and inside that moment there might be 20 collisions.

那我就抛几个数字出来吧。好，CERN的加速器运行时，对撞发生的速率高得惊人：我们每秒大约有十亿次对撞——是billion，十亿。而这其中每一次……（Lex：）对，对。（Don：）我说的就是这个。哇。（Don：）不过实际情况是，有些对撞是同时发生的。所以每秒大约有4000万个时间点，在每一个时间点上你都会"拍下一张快照"，而在那一瞬间里可能有20次对撞。

[56:46] Don

So that's why where we get to the billion.

所以这就是十亿这个数字的来历。

[56:48] Lex

Yeah. But can you individually pinpoint the collisions

嗯。但你能不能把每一次对撞单独地精确定位出来？

[56:51] Don

sort of to a to a degree. So the beams are, you know, the when people think of beams, they think of like laser beams, but that's not really what particle beams look like. Particle beams look like little tiny sticks of spaghetti, except they're much thinner. They're not as fat as a stick of spaghetti, and they're at the LHC. Different accelerators are different. They're about this long. And so you have one of them going one way full of protons and another one going the other way full of protons. And they pass through each other. And as they pass through of each other, you should think of this as like a swarm of bees. And this is like a swarm of bees. And mostly the bees pass through each other and don't do anything. But every so often some of the bees hit nose on and stripes and and and wings and everything everywhere.

在一定程度上可以。事情是这样的：说到"束流"，人们一想到束流，就会联想到激光束，但粒子束其实根本不是那个样子。粒子束看起来像一根根细小的意大利面条，只不过比那细得多，没有意大利面那么粗。在LHC里，不同的加速器情况各不相同，它们大约有这么长。所以你有一束朝一个方向走、装满了质子，另一束朝相反方向走、也装满了质子，两束相互穿过对方。当它们彼此穿过时，你可以把它想象成一群蜜蜂——这就像两群蜜蜂相互穿过。大多数蜜蜂彼此穿过去什么事都没有，但时不时地，会有几只蜜蜂正面撞上，撞得鼻子、翅膀、条纹满天飞，到处都是。

[57:38] Lex

That's awesome.

太棒了。

[57:39] Don

And so as they collide through each other, you know, one collisions here and one's here and one's here and you can't tell too much side to side because the beams are really small. They're sort of the thickness of a human hair. But you can see along the direction and there, you know, this is about the right size. And so we have detectors around them and we can actually see, oh, particles came from here and particles came from here. And that's amazing. All right. So at any one crossing, there's maybe 20 collisions. Now, most collisions are absolutely boring. They're boring because they are they they exemplify physics that we know a great deal about already. We've tested it for for decades. We know all about it. We don't care. I mean, it's kind of blas that we can say, "Oh, yeah, yeah, we're making a billion partic subatomic particles every second, but who cares?" Because, you know, but that's just the way of, you know, frontier scientists. So, what you need is you need to pick out the cool ones, the weird ones, the ones that nobody's seen before. And so what happens is uh these things these beams uh collide and we surround the collision point within the enormous detector. There are two absolutely ginormous detectors at the LHC. One of them called CMS which is the one I'm on and the other one is called Atlas

当它们相互穿过、发生对撞时，这里一次对撞、那里一次、另一处又一次。你在左右横向上分辨不出太多，因为束流非常细，差不多只有一根头发丝那么粗。但沿着束流方向你是能分辨的，这个尺度大致是合适的。所以我们在它们周围布置了探测器，就真的能看出来：哦，这些粒子是从这里飞出来的，那些粒子是从那里飞出来的。这太了不起了。好，那么在任何一次束流交叉中，大约有20次对撞。而绝大多数对撞其实无聊透顶。它们无聊，是因为它们体现的都是我们早已了解得一清二楚的物理——我们已经检验了几十年，对它们了如指掌，我们根本不在乎。说起来甚至有点漫不经心："哦对对，我们每秒造出十亿个亚原子粒子，可那又怎样？"因为，你懂的，前沿科学家就是这种心态。所以你真正要做的，是从中挑出那些酷的、古怪的、谁都没见过的事件。具体过程是这样：这些束流相撞，我们用一台巨大的探测器把对撞点整个包围起来。LHC上有两台绝对庞大无比的探测器，一台叫CMS，就是我参与的那台；另一台叫ATLAS——

[59:04] Don

which is the other one and we don't speak of because well no they're both really amazing.

就是另外那台，我们一般避而不谈——好吧，其实不是，它俩都真的非常了不起。

[59:09] Lex

Okay. It's good to know that there's friendly competition even inside that's awesome.

好。很高兴知道，即便在内部也存在着友好的竞争，这太棒了。

[59:13] Don

I mean the fact is they are both amazing absolutely amazing detectors

我是说，事实上它们两台都很了不起，绝对了不起的探测器——

[59:17] Don

but CMS is just a little cooler than

不过CMS就是比那台稍微酷那么一点点。

[59:19] Don

Oh yeah. Yeah. I mean you know in in in particle physics we really absolutely want our competitors to do extremely well just not quite as well as we do.

哦对，对。你懂的，在粒子物理这行，我们是真心希望自己的竞争对手表现得极其出色——只是别比我们做得更好就行。

[59:29] Lex

Got it. All right. So these two giant detectors

明白了。好的。那么这两台巨型探测器——

[59:32] Don

right. So but one of them our detector the CMS detector it's the small one. It is 70 ft long, 50 ft high, 50 ft wide. It's 5 stories tall. It weighs 14,000 tons.

对。其中一台是我们的探测器，CMS 探测器，它是比较小的那台。它长 70 英尺、高 50 英尺、宽 50 英尺，有 5 层楼那么高，重达 14,000 吨。

[59:44] Lex

Small

这还算小？

[59:45] Don

small. Atlas experiment is 150 ft long, 80 ft across. It weighs only 7,000 tons. Just piece of cake.

算小的。ATLAS 实验装置长 150 英尺、横向 80 英尺，重量才 7,000 吨。小菜一碟。

[59:52] Don

You could take the Atlas detector and you could put four of them on a soccer or football field and it would fill the field up with just enough room on the sidelines for the cheerleaders and the water boy and the coaches and stuff. That's how big they are. So these are absolutely ginormous detectors and basically they're cameras and what they can do is they can take pictures 40 million times per second. Now all the data comes streaming off that detector and we can't record it all. It would just fill up all of our tapes and it would be full of all these boring things we don't care about. So what we do is as the beams pass through one another, we teach our detectors to say we only want one where there are certain configurations that might be interesting like there's gobs of energy in the detector or there's a gob of energy on one side and nothing on the other side or there's four gobs of energy or whatever. These are called triggers. And so these what we have is fast electronics that take the 40 million possible pictures per second and it says you know about a 100,000 of those are really cool. We should think about them. And then it passes not all of the 40 million but those 100,000 to the next level which are commercial processors that have uh basically our final uh analysis code but optimized to run very very quickly. And what they do is they do a really quick and dirty analysis to say to to further refine what's good and what's not. And that that computer form then accepts about a thousand collisions per second and we record those for further analysis. So that's what's really happening of the 50 million possible collisions per second the fast electronics and then the computers pick the thousand and then we pass those through analysis software and hand them to the graduate students and they pick through them looking and finding the handful that are the next Nobel Prize. So that's how that works and that that is truly astonishing. I'm hats off to the accelerator builders, the detector builders, the the the people who make the software work, the people who make the not not gigabytes, not terabytes, but pabytes of data flow around the world seamlessly. It's really amazing. I'm very grateful.

你可以把 ATLAS 探测器拿来,在一个足球场上摆四台,正好把整个场地填满,边线上还剩一点地方给啦啦队、打杂的水童、教练之类的人站。它们就有这么大。所以这些探测器绝对是庞然大物,本质上它们就是相机,能做的事情是每秒拍摄 4000 万次。问题是,所有数据都从探测器上滚滚而来,我们根本没法全部记录下来。那会把我们所有的磁带塞满,而且里面全是我们不在乎的无聊东西。所以我们的做法是:当两束粒子相互对穿时,我们训练探测器只挑出那些可能有意思的特定构型——比如探测器里出现了大量能量,或者一侧有一大团能量而另一侧什么都没有,或者出现了四团能量等等。这些叫做触发器(trigger)。我们有一套快速电子学系统,从每秒 4000 万张可能的图像中筛选,它会说:这其中大约有 10 万张真的很酷,值得我们考虑。然后它不是把 4000 万张、而是把这 10 万张传给下一级——也就是商用处理器,上面跑的基本上是我们最终的分析代码,但经过优化能够极快地运行。它们会做一次又快又糙的分析,进一步区分哪些有价值、哪些没有。这套计算机集群随后接收每秒约 1000 次对撞事件,我们把这些记录下来留待进一步分析。这就是真实发生的过程:在每秒 5000 万次可能的对撞中,先由快速电子学、再由计算机挑出那 1000 次,然后我们让它们通过分析软件,交到研究生手里,由他们逐一筛查,从中找出极少数有望摘取下一个诺贝尔奖的事件。这就是它的运作方式,这真是令人惊叹。我向加速器的建造者、探测器的建造者、让软件运转起来的人,以及让数据——不是吉字节、不是太字节、而是拍字节(petabytes)的数据——在全球无缝流动的人致以敬意。这真的很了不起,我满怀感激。

[1:02:12] Lex

Uh so take me to uh July 4th, 2012, the discovery of Higs Bzon. So this is really fun because the people searching for the Higs, it's a it's a community and the entire community knew that the LHC was coming online. So even though many of us had been working on the Firmenab accelerators, a lot of us were transitioning to the CERN uh accelerator. So we were in the very funny business of wearing our Firmenab detector people hats trying desperately to find the Higs Bzon at Firmeny Lab

带我回到 2012 年 7 月 4 日,希格斯玻色子(Higgs boson)被发现的那一天吧。这真的很有意思,因为寻找希格斯的这群人是一个共同体,整个共同体都知道 LHC 即将投入运行。所以,尽管我们很多人当时还在 Fermilab 的加速器上工作,但很多人也正在向 CERN 的加速器过渡。于是我们处在一个很滑稽的处境里:一边戴着 Fermilab 探测器人员的帽子,在 Fermilab 拼命想找到希格斯玻色子——

[1:02:52] Don

while simultaneously wearing our CERN hats knowing that CERN was going to be able to find it if existed. And so you know we were a little neurotic kind of wanted you know our old stuff to work and and there was an awful lot of people on both experiments. Did you um have a sense that one of the two places would be able to find the Higs? First, did you think the Higs Bzon existed? And second, did you think that these accelerators have the chance to find them?

——一边又戴着我们的 CERN 帽子,心里清楚如果希格斯存在,CERN 是能找到它的。所以你知道,我们当时有点神经质,既希望我们自己原来那套装置能成功,而且两个实验上都有非常多的人。你当时是否有种预感,这两个地方之一能够找到希格斯?第一,你当时认为希格斯玻色子存在吗?第二,你认为这些加速器有机会找到它吗?

[1:03:22] Don

So, I was cognizant of the fact that the Higs Bzon might not exist, but there was a lot of evidence pointing in the direction that it might be. I knew that both experiments, the Firmeny Lab accelerator and the CERN accelerator would either find or rule out the Higs if it existed.

我心里很清楚希格斯玻色子有可能并不存在,但有大量证据指向它可能存在的方向。我知道这两个实验——Fermilab 的加速器和 CERN 的加速器——如果希格斯存在,要么能找到它,要么能把它排除掉。

[1:03:42] Lex

Rule out?

排除掉?

[1:03:43] Don

Well, that's a possibility. I mean, maybe the Higs theory was wrong.

对,这也是一种可能。我是说,也许希格斯理论本身是错的。

[1:03:46] Lex

Yeah.

嗯。

[1:03:46] Don

Right. Until you until you know it's there, it might be wrong. It's like dark matter. People talk about dark matter. It might not be real.

对。在你确认它存在之前,它都有可能是错的。这就像暗物质(dark matter)一样,人们谈论暗物质,但它也可能并不真实存在。

[1:03:52] Don

I mean, I it probably is, but it might not be.

我是说,它大概率是存在的,但也可能不存在。

[1:03:55] Lex

So, you knew at these energy levels, you would be a you should be able to find the Hig boson.

所以你知道在这些能量水平下,你应该能够找到希格斯玻色子。

[1:03:59] Don

Yes. So that's the nice thing about this kind of physics because there was a theory that theory made predictions. Now there were parameters in the theory we didn't know if the mass was this we'd get this thing. If the mass was this we get this thing. But we could do the the calculation for every conceivable Higs mass. And so then we could search look well let's say the Higs mass is 100 in some units. Did we see it there? No. then it's not 100. Well, let's look at 103. Is it there? No. So, we could do that. Both accelerators could either find it or definitively rule out the predictions of simple Higs theory. 100% guaranteed.

是的。这正是这类物理学的妙处所在,因为已经有了一套理论,这套理论会做出预言。当然,理论里还有些参数我们并不知道:如果质量是这个值,我们会得到这种结果;如果质量是那个值,我们会得到那种结果。但我们能够针对每一个可能的希格斯质量做计算。于是我们就可以搜索:假设希格斯质量在某种单位下是 100,我们在那里看到它了吗?没有,那它就不是 100。那我们再看 103,在那儿吗?没有。我们可以这样一步步排查。两台加速器要么能找到它,要么能确凿地排除简单希格斯理论的预言——百分之百有把握。

[1:04:45] Don

However, the CERN accelerator had 10 times the collisions per second and three and a half times the energy. So remember when I said it with the top quirks it was like 6 months for 19 versus one a second. There's no question the writing is on the wall. The h the the LHC was going to have an easier time of it if it was real.

不过,CERN 的加速器每秒对撞次数是我们的 10 倍,能量是我们的 3.5 倍。所以还记得我说过顶夸克(top quark)的事吗——找 19 个事件大概要花 6 个月,而对方差不多每秒一个。毫无疑问,大势所趋已经写在墙上了:如果希格斯是真的,LHC 找起来会轻松得多。

[1:05:09] Don

However, so but you know I'm a Firmay Lab scientist and we wanted Firmen Lab you know come on we want Firm Lab to win not you know. So we were busting our butt and we had done what I said. We had ruled out this region. And we had certain R mass ranges. We knew it wasn't there. And we finally said if there was a Higs Bzon, if it existed, which we didn't know at the time, its mass was somewhere between, if I recall, between like 120 and 145. All right, we'd ruled out all the other stuff. And so, wearing our our CERN hat, we said, "Okay, we're going to find that." But we were really, really, really trying to do it. Now, if we had had another 2 years or maybe 3 years of running the Fermy accelerator, Fermy Lab would have discovered or ruled out or in this case turning out discovered the Higs boson because it's a real thing. We would have found it without a question, but we didn't have enough data in July of 2012. We needed a couple more years. Unfortunately, in 2008, or fortunately, the LHC had turned on. It broke. They had to fix it. Turned on again in 2010. It ran poorly in 2011. In 2012, they pushed up their sleeves and said, "Let's do this." And it turned on. And so, you know, there was this the Firmy Lab knew if it didn't have it now, it wasn't it was too late. Anyways, come 2012 rolls around and um like two days before uh the announcement at CERN was July 4th. So two days before that, Firmayab made a measurement and said we can rule out certain regions but certain regions we can't rule out but what we know and this is important. If the Higs Bzon exists, it must be in this region for which we are not capable yet of ruling out. So that's where we were 2 days before the LHC said we got it. That was uh July 4th, 2012. So detecting the Higs Bzon confirmed the existence of the Higs field, the mechanism through which fundamental particles like electrons and quarks acquire mass in the standard model. Correct? Although let's be very specific of what we did then we found a particle consistent with the existence of the Higs boson. There were alternative theories at the time that predicted not one but multiple Higs bosons. So there's a theory called super symmetry which said that there was not one but five Higs bosons. The standard original 1964 Higs theory says there were one. And so all we really knew at the time was we found a theory. We did not necessarily confirm that Higs was right. We found data that said that it looked like Higs was right. But until we ran for longer, we were unable to rule out other alternative theories. So that's the the deal. Now in the fullness of time, it is after all uh what 14 years now later, we have been able to basically rule out some of those other things. And by now we have validated a things. We found the mass of the particle. We know the spin of the Higs Bzon. It has a spin of zero. We have discovered Hig Bzon decays. It preferentially decays into the heaviest particles. It can through energy conservation can't decay into top quarks. It's too light to decay into top quarks, but it can decay into bottom quirs. It can decay into W and Z particles. Can decay into a weird way into photons. And we have looked for all of the hypothesized decays of the original Higs theory. And we have validated that it decays in those ways at the rates that theory predicted. And so now in the fullness of time, I'm pretty comfortable saying Peter Higgs and Robert Brout and Franco and his colleagues, they were right back in the 60s. But we weren't sure on July 4th. All we knew is we found a particle consistent. But the thing is with these discoveries, they're often just barely discoveries. it takes a while to go and do the more complex detailed measurements and that's what we've done.

不过呢,你知道我是 Fermilab 的科学家,我们当然希望 Fermilab——拜托,我们想让 Fermilab 赢,而不是别人。所以我们拼了命地干,做了我前面说的那些事:我们已经排除了某个区域,在某些质量范围里我们确知它不在那里。最后我们说,如果存在一个希格斯玻色子——当时我们还不知道它是否存在——它的质量,如果我没记错的话,应该在 120 到 145 之间。好,我们已经把其它范围都排除掉了。于是戴着我们的 CERN 帽子,我们说:好,我们要把它找出来。我们真的真的非常非常努力地想做到。其实,如果当时我们能再让 Fermilab 加速器运行个两年、也许三年,Fermilab 本会发现或排除——在这个例子里是会发现——希格斯玻色子,因为它确实存在。我们毫无疑问会找到它,只是到 2012 年 7 月时我们的数据还不够,还需要再积累几年。不巧的是,2008 年——或者说幸运的是——LHC 开机了。它出了故障,他们不得不修;2010 年再次开机;2011 年运行得不太理想;到了 2012 年,他们撸起袖子说:我们就把这事干成。然后它就运转起来了。所以你知道,Fermilab 心里清楚,如果现在还拿不到结果,那就太晚了。总之,到了 2012 年,大约在 CERN 宣布前两天——CERN 是 7 月 4 日宣布的——也就是那之前两天,Fermilab 做了一次测量,说我们能排除某些区域,但有些区域我们无法排除,而我们所知道的、也是关键的一点是:如果希格斯玻色子存在,它必定落在这个我们尚无能力排除的区域里。这就是 LHC 宣布找到它前两天我们所处的状态。那是 2012 年 7 月 4 日。

那么,探测到希格斯玻色子,就确认了希格斯场(Higgs field)的存在,而正是通过这个机制,电子、夸克(quark)等基本粒子才在标准模型(Standard Model)中获得了质量,对吗?——不过我们得说得非常精确:我们当时所做的,是找到了一个与希格斯玻色子的存在相符的粒子。那时还有一些替代理论,预言的不是一个、而是多个希格斯玻色子。有一种叫超对称(supersymmetry)的理论就说,希格斯玻色子不是一个,而是五个。而 1964 年最初的标准希格斯理论说只有一个。所以当时我们真正知道的,只是我们找到了一种理论——我们并不一定确认了希格斯是对的,我们找到的数据看上去说明希格斯是对的。但在运行更长时间之前,我们没法排除其它替代理论。情况就是这样。如今随着时间的推移——毕竟那都是 14 年前的事了——我们已经基本能够排除其中一些其它的可能性。到现在我们已经验证了很多东西:我们测出了这个粒子的质量,知道了希格斯玻色子的自旋,它的自旋为零;我们发现了希格斯玻色子的衰变,它优先衰变成最重的粒子。出于能量守恒,它无法衰变成顶夸克——它太轻了,衰变不出顶夸克——但它可以衰变成底夸克(bottom quark),可以衰变成 W 和 Z 粒子,还能以一种古怪的方式衰变成光子。我们寻找了最初希格斯理论预言的所有衰变模式,并验证了它确实以那些方式、以理论所预言的速率发生衰变。所以现在,随着时间的沉淀,我可以相当有把握地说:Peter Higgs、Robert Brout、François Englert 和他们的同事,他们在上世纪 60 年代就是对的。但在 7 月 4 日那天我们并不确定,我们只知道找到了一个相符的粒子。问题在于,这类发现往往只是勉强算得上发现,要做更复杂、更细致的测量需要相当长的时间,而这正是我们一直在做的事。

[1:09:40] Lex

So at the time I remember being called referred to as the god particle.

我记得当时它被称作"上帝粒子"(god particle)。

[1:09:46] Lex

Uh you also uh had a minor in theology. So throwing that all together. So calling it the god particle is speaking to the importance the potential importance of discovering this particle. Do you think uh that is in some degree justified like if we look at the big impact of it on the the history of physics? How important was it to find and show that the the the Higs fields is real?

你还辅修过神学,把这些放到一起来看——把它叫做上帝粒子,是在强调发现这个粒子的重要性、潜在的重要性。你觉得这在某种程度上是说得通的吗?比如说,如果我们看它对物理学史的重大影响——找到并证明希格斯场是真实存在的,这件事到底有多重要?

[1:10:14] Don

Well, I don't think it is as important as for instance some of Einstein's stuff. I mean it was it's an important prediction like the prediction of quirks was very important and interesting in validating this. The Higs was kind of like um validating that quirks existed. it it's an important stepping stone and I I do not wish to to denigrate it in any way but there's ones that change the way we thought about the world like Einstein did it wasn't that sort of thing and there is a funny story so the reason they call it the God particles this book by Leon Letterman and um and if you read his book he uh he says well you know we we call it the god particle but but we should call it the godamn particle because it's been causing us so much trouble trying to find it.

嗯,我不认为它有比如爱因斯坦(Einstein)某些成果那么重要。我是说,它是一个重要的预言,就像对夸克的预言一样非常重要、有意思,而验证这一点也很重要。希格斯有点像是验证夸克确实存在那一类——它是一块重要的垫脚石,我丝毫不想贬低它,但它不属于那种改变我们看待世界方式的发现,不像爱因斯坦做的那种。这里还有个有趣的故事:之所以叫它上帝粒子,是因为 Leon Lederman 写的一本书。如果你读他的书,他说:你知道,我们管它叫上帝粒子,但其实该叫它"该死的粒子"(goddamn particle),因为为了找到它,它给我们惹了太多麻烦。

[1:11:03] Don

And Leon ran Firmy Lab. So, and he wrote a a forward for one of my books. And you know, I talked to him. He's he was a really funny guy.

Leon 当过 Fermilab 的主任。他还给我的一本书写过序。我跟他聊过,他是个非常风趣的人。

[1:11:10] Don

And the real truth was the book was called The God Particle because his publisher thought it would sell more copies.

而真相是,这本书之所以叫《上帝粒子》(The God Particle),是因为他的出版商觉得这个书名能多卖几本。

[1:11:18] Don

But but you know, then that got into the mindset of the reporters and so forth and we called it the God Particle. Leon never really thought of it as anything to do with a religious or even I mean he was an incredible jokester. the goddamn particle.

但是你知道,这个说法后来钻进了记者们的脑子里,于是大家就管它叫上帝粒子。Leon 从来没真把它当成跟宗教有什么关系的东西,甚至——我是说,他是个特别爱开玩笑的人——他想的是"该死的粒子"。

[1:11:30] Lex

It is a really important part of our model of the universe. It is that there's this field that it gives mass to some particles and not others. That's

它在我们对宇宙的模型里确实是非常重要的一部分,就是说存在这样一种场,它赋予某些粒子质量、而不赋予另一些粒子质量。这——

[1:11:38] Don

right. It it's a huge thing but it was part of the standard model. The standard model had known forces. It had known particles. It had all that. The the Higs Bzon the one thing that is true is it was the last unvalidated piece of the standard model. The standard model does not answer all questions which is why we have unanswered questions in physics. But it was a punctuation point end of about 50 years of discovery and searching where we finally were able to say the standard model while while incomplete, it's mostly right as far as it goes. Quick 10-second thank you to our sponsors. Check them out in the description. It really is the best way to support this podcast. Go to lexreman.com/sponsors. And now, dear friends, back to my conversation with Don Lincoln. We did a whirlwind tour of the history of physics and took a little tangent on this incredible discovery of the Higs boson. Uh, but we didn't go all the way yet. There's this dream of the grand unified theory, the gut that uh is a step towards the toe theory of everything. So can we talk about the gut first? So what what's what's entailed in the gut? So the gut is short for grand unified theory. We talked about that there were four known subatomic forces. the um electromagnetic force, gravity, the strong force and the weak force and electroeak symmetry unification merged the weak force and electromagnetism into the electroeak force. So what gut hopes to do is to merge the electroeak force and the strong force into one grand unified force. Now that leaves gravity outside because gravity is seemingly fundamentally significantly different. Then subsequently it is hoped that a higher energy we will be able to blend the theory of everything together with all of the known subatomic forces the strong weak and electromagnetic forces and then gravity but so as you say gut is sort of a a way station along the way that's the goal and uh at this point I would have to say that I do not see a fast progress in the immediate future. I think we're a ways away from that at this point.

没错。它是件大事,但它是标准模型的一部分。标准模型已经有了已知的各种力,有了已知的各种粒子,有了那一切。关于希格斯玻色子,有一点是确凿的:它是标准模型中最后一块尚未被验证的拼图。标准模型并不能回答所有问题,这也正是物理学中至今仍有未解之谜的原因。但它是大约 50 年发现与探索历程的一个句点,到这时我们终于能够说:标准模型虽然并不完整,但就其适用范围而言,大体上是正确的。

用十秒钟快速感谢一下我们的赞助商,在视频简介里可以了解他们,这真的是支持本播客的最好方式。请访问 lexfridman.com/sponsors。现在,亲爱的朋友们,让我们回到与 Don Lincoln 的对话。

我们做了一次物理学史的旋风式速览,还顺带聊了聊希格斯玻色子这个了不起的发现这条岔路。不过我们还没把整条路走完。有一个大统一理论(grand unified theory)的梦想——也就是 GUT,它是迈向 ToE(万有理论,Theory of Everything)的一步。那我们能先谈谈 GUT 吗?GUT 究竟包含哪些内容?——GUT 是 grand unified theory 的缩写。我们说过有四种已知的亚原子力:电磁力、引力、强力和弱力,而电弱对称统一(electroweak unification)已经把弱力和电磁力合并成了电弱力。GUT 想做的,是把电弱力和强力合并成一种大统一力。这样一来引力就被排除在外了,因为引力看上去在本质上有着显著的不同。再往后,人们希望在更高的能量下,能够把万有理论拼合起来,把所有已知的亚原子力——强力、弱力、电磁力——再加上引力统统融为一体。所以正如你所说,GUT 算是这条路上的一个中途站。这就是目标。而到这个阶段,我不得不说,我看不到近期会有快速的进展。我觉得我们现在离那个目标还相当遥远。

[1:14:02] Lex

You mean on the gravity front?

你是指引力这一块吗?

[1:14:04] Don

Maybe we'll come up with something really cool. We certainly had some ideas back in the early 80s that we tested and they didn't pan out.

也许我们会想出某个特别酷的东西。我们在 80 年代初确实有过一些想法,也做了检验,但都没成功。

[1:14:12] Lex

Uh speaking of which, string theory is the thing you're referring to.

说到这个,你指的是弦理论(string theory)吧。

[1:14:16] Lex

Uh so string theory posits that particles are tiny vibrating strings and by tiny we mean extremely tiny at the scale of a plank length. Uh then there's there's other leading candidates like loop quantum gravity. Uh maybe there's some alternate theories in the works. So can you uh linger on that a little bit more? Do you think a theory of everything exists? So I hold personally that there are rules that govern matter and energy space time and they probably are rules that I don't know. There are probably phenomena I'm not aware of. But I do believe that something there are is a rule that governs reality. And so in that sense once we understand the rules that govern reality, the fundamental rules that would be a theory of everything. You know there are things that are unknowable like for instance inside black holes we don't know what's inside there but that doesn't mean that there's not something inside there. So there's a distinction between what we can know and truth. So I I do believe that there are the rules and I do believe that with sufficient time, technology, effort, we will be able to figure this all out. Now, this isn't a thing in my lifetime. It's not a thing in my grandchildren's lifetime or even their grandchildren's lifetime.

弦理论认为粒子是微小的振动的弦,而所谓微小,我们指的是极其微小,达到普朗克长度(Planck length)的尺度。此外还有其它一些有力的候选理论,比如圈量子引力(loop quantum gravity),也许还有些尚在酝酿的替代理论。那你能不能就这个话题再多停留一会儿?你认为万有理论存在吗?——我个人坚信存在着支配物质、能量、时空的规则,它们大概是一些我并不知道的规则。大概也存在一些我尚未意识到的现象。但我确实相信,存在某种支配现实的规则。从这个意义上说,一旦我们理解了支配现实的规则、那些最根本的规则,那就是一个万有理论了。你知道,有些东西是不可知的,比如黑洞内部,我们不知道里面是什么,但这并不意味着里面没有东西。所以"我们能知道什么"和"真相是什么"之间是有区别的。我确实相信存在这些规则,也确实相信,只要有足够的时间、技术和努力,我们终将能把这一切都弄明白。当然,这不是我有生之年能见到的事,也不是我孙辈有生之年、甚至他们孙辈有生之年能见到的事。

[1:15:38] Lex

Whoa, whoa, whoa. That's a pretty strong statement, right? That's a pretty strong statement saying we're

哇,等等、等等、等等。这话说得相当重啊,对吧?这是个相当强的论断,你是说我们——

[1:15:44] Don

we're 50 to 100 years out from finding a theory of of everything. It took 200 years to go from unifying gravity to unifying electromagnetism. It took a hundred years to go from unifying electromagnetism to unifying the electroeak force. Now you could say, well, gee, that's went from 200 to 100. So it's getting faster, but it's also getting harder because the unification scale is of order 10 the 15, which we can do the math. That's a quadrillion times higher than the highest energy accelerator we can build today.

我们距离找到万有理论(Theory of Everything)还有 50 到 100 年。从统一引力到统一电磁力，花了 200 年；从统一电磁力到统一电弱力(electroweak force)，花了 100 年。你可能会说：哦，从 200 缩短到 100，速度在加快。但难度也在加大，因为统一所发生的能量尺度大约是 10 的 15 次方——这个我们可以算一下——比我们今天能建造的最高能量加速器还要高一千万亿倍(a quadrillion)。

[1:16:19] Don

And it was one thing to, you know, we are reaching diminishing returns. We get something like a factor of seven increase in particle accelerator energy every 20 years. And so we have to get to a quadrillion times. Now, you know, if you really did believe uh a factor of seven every 20 years, then that's we're talking like 500 years, but you know, this is like Mo's law that it doesn't continue forever. We're not going to every seven year. I mean, every 20 years get another factor of seven. So, yes, I I think it's a very long time. That's my prediction. Um, you know, some people are far more optimistic and we can talk about that. We should also actually mention that I guess your intuition behind that is not just the part where you come up with a theory that's beautiful and seems to be internally consistent, but you have to have a theory that's making falsifiable testable predictions.

而且，我们正在逼近收益递减的阶段。粒子加速器的能量大约每 20 年才能提升 7 倍。可我们需要提升一千万亿倍。如果你真的相信每 20 年提升 7 倍，那算下来要花 500 年——不过这就像摩尔定律一样，不可能永远持续。我们不可能每 20 年都再翻 7 倍。所以，是的，我认为还要很长很长时间，这是我的预测。当然，有些人乐观得多，这个我们可以聊。其实还得提一句，我猜你这个直觉背后的依据，不只是说你要提出一个漂亮、看起来自洽的理论，你还得提出一个能做出可证伪、可检验预测的理论。

[1:17:19] Lex

Correct? And you have to have a a feasible engineering construction a methodology for creating an experiment that tests that prediction. So I think a lot of your this is 50 100 200 years from now. Intuition is maybe about the second part of that which is like you need to have an experiment. Yeah. Yes. Yes. But you know let's say I mean you alluded to super strings. I haven't answered that question. And I'll table that for a moment. Super strings is a fascinating idea. I don't believe it. Um but I love it. I hope it's true. And there's a real, you know, apherism and it says you should absolutely never believe what you think. So even if you think Superstrings is true, you shouldn't believe it because it hasn't been tested.

对吧？而且你还得有一套可行的工程构建方法，能造出一个实验来检验那个预测。所以我觉得，你说的这个 50 年、100 年、200 年的直觉，可能更多是关于后半部分——也就是你必须得有个实验。是的，对，对。不过，你看，你之前提到了超弦(superstrings)。我还没回答那个问题，先把它放一放。超弦是个迷人的想法，我不相信它，但我喜欢它，我希望它是真的。有句很妙的格言说：你绝对永远不该相信你自己所想的。所以即便你认为超弦是对的，你也不该相信它，因为它还没经过检验。

[1:18:06] Don

Now let's say super string is correct. I mean hypothesis it's correct. 100% correct. I don't know it's correct. So I don't care. I mean, you know, it could be correct, but I don't, you know, until it's validated, it's just a wild ass guess, you know. So, I we have to have a way of validating it. So, yes, the the the empirical side of it is important. I mean, you could wake up tomorrow and have the theory that is the perfect theory, but if I can't prove it, I don't care. If we were to think, this is going back to the great courses on the evidence for modern physics,

好，那我们假设超弦是对的。假设它百分之百正确。我不知道它对不对，所以我并不在意。我是说，它可能是对的，但在它被验证之前，它就只是个瞎猜而已。所以我们必须有办法去验证它。所以，是的，它的经验(empirical)一面非常重要。你可能明天一觉醒来就想出了那个完美的理论，但如果我没法证明它，我就不在乎。如果我们回到我在 Great Courses 里讲过的「现代物理学的证据」这个话题——

[1:18:45] Lex

we're talking about energy levels and tiny particles to the degree where the kind of prediction we would be making is not accelerator type predictions. So, it's probably going to be impossible to build an accelerator that detects something like a string. So you have to make predictions about macrocale behaviors.

我们谈的是能量层级和微小粒子，到了这种程度，我们要做的那种预测，就不再是加速器那一类的预测了。所以，要造一台能探测到像弦这样东西的加速器，大概是不可能的。于是你只能去对宏观(macroscale)行为做出预测。

[1:19:13] Lex

That's another alternative.

这是另一种替代方案。

[1:19:15] Lex

It's a different kind of prediction.

这是一种不同类型的预测。

[1:19:17] Don

Sure.

当然。

[1:19:18] Lex

Do we even have intuitions about what kind of predictions they would be? So one one of course one of the lines of intuitions has to do with black holes where in the singularity the physics of black holes combine certain elements of general relativity and quantum mechanics. So there

我们对它们会是什么样的预测，哪怕有点直觉吗？当然，其中一条直觉的线索跟黑洞有关——在奇点处，黑洞的物理学把广义相对论(general relativity)和量子力学(quantum mechanics)的某些要素结合在了一起。所以——

[1:19:34] Lex

you could see some kind of predictions you can make.

你或许能看出这里能做出某种预测。

[1:19:38] Don

Uh but you can't really mess with a black hole. It's not like you can create a black hole in the lab.

可是你又没法真去摆弄一个黑洞，你又不能在实验室里造一个黑洞出来。

[1:19:43] Don

And the energies that you were talking about, the sizes we're talking about are inside a black hole, which you can intrinsically never see.

而你说的那些能量、那些尺度，都是在黑洞内部的，那是你从根本上永远看不到的地方。

[1:19:50] Lex

Yeah.

对。

[1:19:51] Don

So you know, you can only see the outside of a black hole, not the inside of a black hole. So what you said, you did say something that was incredibly important and incredibly correct and probably won't happen, but that's still good. Okay. So we have two choices when you talk about super strings. Either super strings are correct and they're making predictions up at the plank energy scale at which point we have to somehow build facilities that can generate plank plank energies. That's possibility one. Possibility too is this theory which is currently only applicable at plank energy scales. Someone figures out a way to take those equations and solve them in a way that say predicts the mass of the electron.

所以你只能看到黑洞的外面，看不到里面。你刚才说的那句话其实极其重要、极其正确，而且大概实现不了——但那仍然是好事。好，那当我们谈超弦时，我们有两种选择。要么超弦是对的，而它做出的预测处在普朗克能标(Planck energy scale)上——那样的话我们就得想办法建出能产生普朗克能量的设施。这是第一种可能。第二种可能是：这个目前只在普朗克能标下适用的理论，有人想出一种办法，把那些方程拿来，用某种方式求解，比如能预测出电子的质量。

[1:20:37] Lex

Mhm.

嗯。

[1:20:38] Don

Right. And that is a tricky business. Um, I am not a string theorist, so I can't tell you that that's likely, but I can tell you that they've been working on it since the 80s, and they haven't gotten very far. Furthermore, if I uh I think it's fair to characterize that string theory is still a a vague idea, and that's unfair. But let me tell you why I say that. Because what they have are approximate solutions to approximate equations. And that is already saying that we're a ways away from really getting a handle on that. So yes, if there could be some bright young ladder lass out there, someone listening to this podcast right now who figures out a way to take super string theory and solve them in tractable ways that makes predictions from the scale at which they currently apply down to measurable scale today. And if that happens, well, then I might retract my my question or my my concept. There's a reason why I think that probably isn't true. That's probably not valid. So, let let me I I love this. All right, so let's back up. I'm going to pitch. I wrote this book for Oxford, Einstein's Unfinished Dream. And Einstein's unfinished dream was to come up with a theory of everything. It was unfinished because, well, it's unfinished. And so the the second part the tagline of that book is practical progress towards a theory of everything with the emphasis on practical. Because when you read books about theories of everything, when you see podcasts, when you listen to YouTube videos or whatever, they are often written by theorists. And theorists are they're big idea people. They're very very smart. But but there's a pragmatism that is often missing in the sense that they say well super strings look you know have these little vibrating things and wouldn't it be cool and you know but you got to get to the do you know it. So let's pretend super string theory or something like it is correct. The energy scale at which um that should occur is of order um 10 to the 15 times higher 10 to the 19 Gev. We can currently do things at 10 the 4th GEV give or take. So that is 10 the 15 that's a quadrillion times higher energy. So what we are doing now is we are looking at the world with our very best measurements and we are trying to project out a quadrillion times higher and figure out a theory that explains everything. Now I I have this I have a couple of analogies but I like this. Suppose that you were some, you know, Joe oustralopythecus 2 million years ago or something in Africa wandering around somewhere in Kenya.

对。而这是一件很棘手的事。我不是弦论学家，所以我没法告诉你这有多大可能，但我可以告诉你，他们从上世纪 80 年代就一直在做这件事，至今进展甚微。再者，我觉得这么说是公平的：弦论(string theory)至今仍是个模糊的想法——这话有点不厚道，但让我说说为什么我这么讲。因为他们手里有的，是「对近似方程的近似解」。光这一点就说明，我们离真正掌握它还差得很远。所以是的，可能有某个聪明的年轻人——也许就是此刻正在听这个播客的某个人——想出了办法，把超弦理论用可处理(tractable)的方式求解，让它能从目前适用的尺度一直预测到今天可测量的尺度。如果真发生了，那好，我或许会收回我的疑问、收回我的看法。但我之所以认为这大概不会成真、大概站不住脚，是有原因的。我特别喜欢这个话题。好，我们退一步。我来推荐一下——我给牛津(Oxford)写了一本书，叫《爱因斯坦未竟的梦》(Einstein's Unfinished Dream)。爱因斯坦未竟的梦就是想出一套万有理论。它未竟，是因为，嗯，它确实还没完成。这本书的副标题(tagline)是「迈向万有理论的务实进展」，重点在「务实」二字。因为当你读那些讲万有理论的书、看那些播客、看 YouTube 视频时，它们往往是理论家写的。理论家是搞大想法的人，非常非常聪明，但他们身上常常缺少一种务实精神——他们会说，超弦嘛，你看，有这些小小振动的东西，要是真的那多酷啊。可你得真正落到实处，你怎么知道它是真的呢？所以我们假装超弦理论（或类似的东西）是对的，它应该出现的能量尺度大约是高出 10 的 15 次方倍，也就是 10 的 19 次方 GeV。而我们现在大约能做到 10 的 4 次方 GeV 上下。所以那是 10 的 15 次方倍，也就是高出一千万亿倍的能量。我们现在所做的，就是用我们最好的测量手段去看这个世界，然后试图外推到高一千万亿倍的地方，去琢磨出一个能解释一切的理论。我有几个类比，不过我喜欢这个：假设你是 200 万年前非洲的某个「南方古猿乔」(Joe Australopithecus)之类的家伙，在肯尼亚某处晃悠。

[1:23:29] Lex

Mhm.

嗯。

[1:23:30] Don

All right. You're about a meter in size. So you can walk a meter meter scale is like your scale.

好。你身高大约一米。所以你能走一米——米这个尺度就是你的尺度。

[1:23:36] Lex

Mhm.

嗯。

[1:23:36] Don

You can walk 10 meters in every direction. That's 30 ft. No problem. You can work 100 meters, 300 feet. You can work a thousand meters, that's half a mile. You can work 10,000 meters, that's 60 miles. 100,000 meters is 10 to the 5th. And that that's unlikely. But the distance that we need to go from what we can see to the plank scale, it's not 10 to the 5th, it's 10 to the 15th. So that means in my analogy, think about this guy who's walking around Africa. Now, if he walks, you know, 100 ft or something, it looks a lot like what it is now. He can make a prediction about what he sees, and when he goes to that new place, it's probably going to be okay. But if he starts walking 500 miles east, well, he walking around the center of Africa has no concept of, for instance, the Indian Ocean, he would never predict sperm whales or Kraken. He would never predict what it's like the bottom of the ocean is going north. He's he's in Africa. He would never ever have a clue about the Alps or Antarctica. Going even smaller distances, going a mile up, things wouldn't be very different. But if he goes 10 miles up, he wouldn't breathe and he'd freeze. If he goes 100 miles up, he would die. If he goes two miles down, he would roast. The point being is we are like that oropycus. We have a realm that we can study and we can even predict to some validity what would happen if we go some distance away. But the farther away we go, the less and less our local prediction really represents the reality of those more distant times. And so basically his theory about the the world would be totally bogus. So even if he had the best theory, his theory would not have anticipated the elps. It would not have anticipated penguins,

你能朝各个方向走 10 米，也就是 30 英尺，没问题。你能走 100 米，300 英尺。你能走 1000 米，那是半英里。你能走 10000 米，那是 6 英里。10 万米就是 10 的 5 次方——这就有点不太可能了。可我们要从能看到的尺度走到普朗克尺度，需要的不是 10 的 5 次方，而是 10 的 15 次方。所以在我这个类比里，想想这个在非洲到处走的家伙：如果他走个 100 英尺左右，看到的跟现在差不多，他能对眼前的景象做出预测，等他到了那个新地方，结果大概也没错。但要是他开始向东走 500 英里，那么——在非洲中部转悠的他，根本不知道印度洋是什么，他永远不会预测到抹香鲸或北海巨妖(Kraken)，永远不会预测到海底是什么样的；往北走，他在非洲，永远不会对阿尔卑斯山(Alps)或南极洲有半点概念。往更小的距离上走也一样：往上走一英里，情况不会差太多；可往上走 10 英里，他就没法呼吸、会被冻僵；往上走 100 英里，他就死了；往下走两英里，他会被烤焦。要点在于：我们就像那个南方古猿。我们有一片可以研究的领域，甚至能在一定的有效性内预测「走开一段距离会发生什么」。但我们走得越远，我们这套本地预测就越发无法代表那些更遥远之处的真实情况。所以基本上，他关于这个世界的理论会完全是胡扯。即便他有最好的理论，他的理论也不会预见到阿尔卑斯山，不会预见到企鹅，

[1:25:33] Lex

right? Flamingos not there, you know,

对吧？那儿没有火烈鸟，你懂的，

[1:25:36] Don

and that is just the case. So now that's what we're doing. We are taking something and we have reason to understand what we know and we can predict a factor of 10 or 100. But I think it is the absolute the pinnacle of arrogance to think that what we can do given the understanding that we have from what we've measured now and predict it out a quadrillion times higher than we can see now. So my opinion and this is partly because I'm an experimentalist. The correct way to make progress, practical progress towards a theory of everything, is to look around at the things that we don't have answers to right now. For instance, are there something smaller than quarks? I don't know. Is dark matter real? I don't know. If it's real, what is it? I don't know. Is dark energy real? Yes, probably. But I don't know. What is the nature of space and time? I don't know. But these are questions we can explore. And I would expect, and this is my prediction, that all right, we're going to figure things out at a factor of 10 or 100 times better than we can do now. And we might be able to do that in my kids' lifetime or something like that. But in order for us to predict a quadrillion times higher, I'm pretty sure super string theory is wrong. Not because people aren't smart, but because something new is going to happen. I mean, if you were talking about chemistry, you would have never predicted nuclear physics. And that's a small increase in energy, right? The idea that there is something in the nucleus of atoms that causes the sun to burn. There's a reason why people didn't believe, you know, they they calculated how old the sun should be and it should only be 10 million years old because otherwise it would burn out. Well, that's clearly wrong. And it's wrong because of nuclear physics. That is why I feel fairly confident to say while someone could think well super string might be right or something and maybe it's right and I hope it's right. It would be awesome if it's right but what are the odds when you making something with that tiny lever arm predicting it out a quadrillion away and say oh yeah we got it right. What are the odds? And my answer is you got to be kidding me. Now I could be wrong and I admit that I could be wrong but that's why I I think the real issue is not the brilliance of humanity. It's the stuff we haven't found. We don't know. I mean the simple one and I'm say simple and it's not but what is dark matter.

事情就是这样。那么现在，我们正在做的就是这件事。我们拿着某样东西，我们有理由理解我们已知的部分，我们能往外预测 10 倍或 100 倍。但我认为，凭着我们从现有测量中得到的理解，就以为我们能往外预测到比现在能看到的高一千万亿倍的地方——这是傲慢的极致。所以我的看法是——这部分也是因为我是个实验物理学家——迈向万有理论、取得务实进展的正确方式，是去环顾那些我们眼下还没有答案的问题。比如说，有没有比夸克(quark)更小的东西？我不知道。暗物质(dark matter)是真实存在的吗？我不知道。如果它真存在，它是什么？我不知道。暗能量(dark energy)是真的吗？是，很可能是，但我不知道。空间和时间的本质是什么？我不知道。但这些都是我们能去探索的问题。我预期——这是我的预测——我们会把现在能做的事情再搞清楚到好上 10 倍或 100 倍的程度，而且我们也许在我孩子这辈子内就能做到。但要让我们预测到高一千万亿倍的地方，我相当确信超弦理论是错的。不是因为人不够聪明，而是因为会有全新的东西冒出来。打个比方，如果你只懂化学，你绝不会预测到核物理(nuclear physics)。而那只是能量上的一点小幅提升而已。原子核里有某种东西让太阳燃烧——这个想法当年人们不信是有原因的：他们算过太阳应该有多老，算出来只有 1000 万年，否则它就该烧光了。可这显然错了，错就错在核物理。正因如此，我才相当有把握地说：虽然有人可以觉得超弦也许是对的，也许它真是对的，我也希望它是对的，要真是对的那就太棒了——可你用那么短的「杠杆臂」(lever arm)去往外预测一千万亿倍的地方，然后说「对，我们猜对了」，这胜算能有多大？我的回答是：你在逗我吧。当然，我可能错，我也承认我可能错，但这正是为什么我认为真正的关键不在于人类的聪明才智，而在于那些我们还没找到、还不知道的东西。我是说，最简单的那个——我说「简单」其实并不简单——就是：暗物质到底是什么？

[1:28:09] Don

We don't have a bleeping clue. Not a clue. We know a lot of what it isn't but we don't know what it is. And so you know talk about super strings. All right. Well, maybe dark matter fits in superstrings. Or maybe dark matter is governed by a physics that is completely diametrically opposed to the super string concept.

我们他妈的一点头绪都没有，毫无头绪。我们知道很多它「不是」什么，但我们不知道它「是」什么。所以你说超弦——好吧，也许暗物质能塞进超弦里；又或者，暗物质遵循的物理学和超弦概念恰恰是截然相反的。

[1:28:26] Lex

And allow me a bit of a thought experiment here. A brief thought. My intuition says that when you propose a theory of everything, the kind of prediction you want to make involves a kind of leap of conceptual understanding that Einstein did. So for example, you want to come up with something like spacetime and then gravity bends space time.

容我在这里做个小小的思想实验，简短地想一下。我的直觉是，当你提出一个万有理论时，你想做出的那种预测，需要一种概念上的飞跃，就像爱因斯坦做到的那样。比如说，你想提出像「时空」(spacetime)这样的东西，然后说引力会弯曲时空。

[1:28:53] Don

So it's not merely that you have this beautiful mathematical framework, but that framework allows you to rethink how you see reality enough to make a prediction that's about the macro world. I mean to come up with something like spacetime you know there's one idea for instance to say that space and time aren't real they they emerge from from entropy yeah that's a way of a new way of thinking and maybe there's some validity and I want people to think about it but in the end it's just an idea and that's the real key thing and and as you say it has to tie to a macro world you have to validate if you don't validate it's a crazy idea theorists are incredibly creative, smart, wonderfully interesting people. But I don't care. I want a measurement that validates the idea because there are so many I mean if you read the the journals, there are so many theoretical papers with all these nifty ideas that die. you know, uh, one that was recently I liked and and might still be true was, um, that dark matter that, you know, our simple model of dark matter is that there's a subatomic particle out there that's heavy and it's floating around and it's causing gravity. But someone said, well, you know, maybe there's complex dark matter, which means there's a whole dark sector. So, there are dark atoms and they interact with one another. And that is a nifty idea and I love it. And that was all the rage for a while. and we looked at it and it may still be true but the simple ideas have been mostly invalidated because we've tested it and it doesn't work. Same thing there was a talk about um large extra dimensions. The reason that gravity is so much weaker than the other forces was well maybe gravity can sneak into more dimensions than the other forces.

所以关键不只是你有了这套优美的数学框架，而是这套框架让你能重新思考你看待现实的方式，足以做出关于宏观世界的预测。我是说，要想出像「时空」这样的东西——比如说有一种想法认为，空间和时间并不是真实的，它们是从熵(entropy)中涌现出来的。对，那是一种全新的思考方式，也许有几分道理，我希望大家去思考它。但归根结底，它仍然只是个想法，这才是真正的关键。而且正如你所说，它必须和宏观世界挂上钩，你得去验证它。如果你不验证，那就是个疯狂的念头。理论家们极富创造力、很聪明、奇思妙想、风趣迷人，但我不在乎，我要的是一个能验证那个想法的测量。因为有太多——你要是去读那些期刊，会发现有太多理论论文，里头全是各种精巧的想法，最后都「死」了。比如最近有一个我挺喜欢的、可能还成立的：我们对暗物质的简单模型，是说外头有一种又重又飘的亚原子粒子，靠引力发生作用。但有人说，嘿，也许存在「复杂暗物质」，意思是有一整个「暗扇区」(dark sector)，里头有暗原子，它们彼此发生相互作用。这是个精巧的想法，我很喜欢，而且有一阵子风头很盛。我们检验了它，它也许还成立，但那些简单的想法大多已被否证——因为我们测过了，行不通。还有件类似的事，曾有人谈「大额外维度」(large extra dimensions)。引力之所以比其他力弱那么多，是因为——也许引力能溜进比其他力更多的维度里去。

[1:30:47] Lex

It leaks into those dimensions.

它泄漏到那些维度里去了。

[1:30:49] Don

That was a cool idea. I mean but that's the point is you have these lovely cool interesting ideas that constantly die. Mhm.

那是个很酷的想法。可问题就在于，你有这些可爱、很酷、很有意思的想法，它们却接二连三地「死」掉。嗯。

[1:30:57] Don

And so, you know, I I would love for a new nifty idea to be the idea, but I don't know how to pick it out of the the hurricane of wrong ideas.

所以你知道，我特别希望某个新奇精巧的想法就是那个对的想法，但我不知道该怎么把它从一大堆错误想法的飓风里挑出来。

[1:31:08] Don

I mean, that's the real beauty of science. It really is. I mean, the theories kind of get some of the glory sometimes, but the real beauty emerges from the experiment and the demonstration that the theory is is correct.

我是说，这才是科学真正的美妙之处，真的。理论有时候会抢走一些光环，但真正的美妙是从实验、从「证明这个理论是对的」当中涌现出来的。

[1:31:22] Lex

And there are two directions. You're talking a top down. someone comes up with this big idea that's testable. But you also have the other way that science advances and it's not with a theory that is then tested. It's with the huh that's weird. For instance, either in in the 1930s with Fritz Wiki or in the 1970s with Vera Rubin, she did a simple thing. She said, "How fast are galaxies rotating?" Cuz it's an easy thing to calculate. You can literally calculate that with high school physics and you get an answer and then you measure it and it's wrong. And so all that that's the wow. Huh. I don't know what that is. And that led to the hypothesis of of dark matter. Now dark matter is not a theory of everything, but it's a clue. It's a powerful clue. We should pull tug at that thread. Maybe our entire theoretical edifice unravels. Or maybe it doesn't. Maybe it's just a snag and we can fix what we have now. I'm not sure. So that's another option is to simply look at many measurements that are very precise and find ones where the outcome and the prediction with established theory disagree and that is a clue. Before we leave the topic, we got to talk about string theory. In your view, is it basically dead? as I understand uh one of the primary flaws of string theory outside of the testable experiments that we were talking about is uh because it's relies on these unobserved extra dimensions. There was a hope that it uh it uniquely could explain our universe, but it turns out this quote landscape, there's an enormous so-called landscape of possibilities that it'll lead to. And so it renders the theory basically unpredictive because you can describe all kinds of universes and therefore you can just select

而且有两个方向。你说的是自上而下(top-down)：有人提出一个大想法，然后它是可检验的。但科学进步还有另一条路，它不是先有理论再去检验，而是从那一声「咦，这怪了」开始的。比如说，1930 年代的弗里茨·兹维基(Fritz Zwicky)，或者 1970 年代的薇拉·鲁宾(Vera Rubin)，她做了件很简单的事：她问，「星系转得有多快？」因为这很好算，你用高中物理就能算出来，得到一个答案，然后你去测量，结果却对不上。于是那就是那声「哇，咦，我不知道这是什么」，而它引出了暗物质的假说。暗物质本身不是万有理论，但它是一条线索，一条强有力的线索。我们应该顺着这根线头使劲拉。也许我们整座理论大厦会随之解体，也许不会，也许它只是个小钩挂，我们能在现有基础上修补好，我也说不准。所以这是另一个选择：单纯去看大量非常精密的测量，找出那些「结果」和「现有理论的预测」对不上的地方，那就是一条线索。在我们离开这个话题之前，我们得聊聊弦论。在你看来，它是不是基本上已经死了？据我理解，弦论的一个主要缺陷——除了我们刚才说的可检验实验之外——是它依赖这些未被观测到的额外维度。曾经有人希望它能独一无二地解释我们这个宇宙，但结果发现，存在一个所谓的「景观」(landscape)，一个极其庞大的可能性景观，它会导向无数种结果。于是这让该理论基本上失去了预测能力，因为你可以用它描述各种各样的宇宙，因而你只能随便挑一个——

[1:33:16] Don

uh tune it to describe ours. I I agree to a degree,

呃，把它调成能描述我们这个宇宙。我在某种程度上同意，

[1:33:21] Don

but I bring it back to my prior objection. It is absolutely true that super string theory um in its current manifestation aside from the extra dimensions which are at some level small potatoes, it allows for an extremely large number of possible universes. What if we were able to take those predictions and somehow connect it to a physical measurement? Then what we would do is we'd lop off those alternatives. We'd throw them away as saying, well, you know, those are like an equation, you know, x + 5. I can put in any number I want in there. It doesn't matter. But if x + 5 equals 9, then I've ruled out a whole bunch of pe numbers except four. And so this is a case of string theory does allow for many predictions. But if we could rule them out by connection to a measurement, then it would no longer do it. We would modify string theory and we would retain the vibrating string concept, which I really really like. I mean, I really like it. But until we can can validate this, it's it's I we can't. So now you ask is it dead or not? In my opinion, it is very difficult to kill such a theory. I mean really truly kill it cuz kill it means make a prediction and it fails. But what can happen and what is happening is people have been working on it since the 70s. So we're talking of order 50 years. people have been working on it and it has not solved the problem. And so I think what's happening is people are looking at that and saying I do I want to spend my life working in this direction with a very likely possibility that 30 years from now we'll be not much farther along than we are now. It's a lot like back in the 1940s when people started thinking about the meaning of quantum mechanics. And I wanted to do that when I was a kid in in the 70s. But then when I went to grad school, I realized that people very smart people smarter than me had been working on that for most of their lives and made no definitive progress. And so you have to decide as a scientist who wants to answer questions. Do I really want to take on a question that is so hard that it will not be answered in my lifetime? And I think that's what's happening with a lot of super string theory is people are saying it's really neat. It might be right, but I don't want to devote my life to something that I might not see progress forward in my lifetime.

但我还是要回到之前的那个质疑。确实，超弦理论(superstring theory)在它目前的形态下——先不说那些额外维度，那些某种意义上算是小问题——它允许存在数量极其庞大的可能宇宙。如果我们能把这些预言以某种方式与一个物理测量挂钩呢？那样的话，我们就能把那些其他的可能性砍掉。我们会把它们扔掉，就好比说：你看，这就像一个方程 x+5，我可以往里代入任意数字，无所谓。但如果 x+5 等于 9，那我就把一大堆数字都排除掉了，只剩下 4。所以这是个典型情况：弦理论确实允许做出许多预言。但如果我们能通过与测量挂钩把它们排除掉，它就不会再有这个问题了。我们会修正弦理论，同时保留那个我非常非常喜欢的「振动的弦」的概念。我是说，我真的很喜欢它。但在我们能验证它之前，它就是……我们做不到。所以现在你问它死没死？依我看，要杀死这样一个理论非常困难。我是说，真正彻底地杀死它——因为「杀死」意味着它做出一个预言，而预言失败了。但有可能发生、而且正在发生的是：人们从上世纪70年代就开始研究它了，也就是说大概有50年了。人们一直在研究它，但它并没有解决问题。所以我认为现在的情况是，人们看着这一切心想：我真的想把一生投入到这个方向上吗？而且很可能30年后我们还是没比现在前进多少。这很像上世纪40年代，人们开始思考量子力学(quantum mechanics)的意义时的情形。我小时候、在70年代时，也想做这件事。但等我上了研究生院，我意识到那些非常聪明、比我聪明得多的人，已经为此投入了大半辈子，却没取得任何决定性的进展。所以作为一个想要回答问题的科学家，你必须做出抉择：我真的想去啃一个难到此生都无法解答的问题吗？我想超弦理论现在的处境很大程度上就是这样：人们说它真的很妙，它也许是对的，但我不想把一生奉献给一件我有生之年都可能看不到进展的事。

[1:36:08] Lex

What do you think about the alternate theories? Do you think there's anything interesting in those?

那你怎么看那些替代理论呢？你觉得它们里面有什么有意思的东西吗？

[1:36:14] Don

You know, many of those theories are espoused by passionate people. They have fans, people love them, but they don't do what science needs to do, which is make predictions. Now, loop quantum gravity is a little different. That one is better developed. And that one is not a theory of everything. So, we should be make that clear. Loop quantum gravity is not a theory of everything. It is simply a theory of quantum gravity. Period. It does not aspire to include all of the known forces. It simply tries to take gravity which is currently intrinsically it treats space as smooth and continuous. For those of your viewers who are mathematically inclined in Einstein's theory of general relativity, gravity is infinitely divisible. There is no smallest bit. And so essentially the laws of calculus apply.

你知道，那些理论中有不少是由满怀热情的人在倡导的。它们有粉丝，有人爱它们，但它们做不到科学需要做的事，那就是做出预言。不过，圈量子引力(loop quantum gravity)有点不一样。它发展得更成熟一些。而且它不是一个万有理论(Theory of Everything)。所以我们得说清楚这一点：圈量子引力不是万有理论。它只是一个量子引力理论，仅此而已。它并不奢望把所有已知的力都纳入进来。它只是试图处理引力——目前在本质上，它把空间当作光滑、连续的。对于你们当中那些有数学背景的观众来说，在Einstein的广义相对论(general relativity)里，引力是可以无限细分的。不存在最小的一份。所以本质上微积分的规律是适用的。

[1:37:10] Don

Mhm. However, it is possible that at a small enough scale um space is no longer divisible in the same way that you can, you know, take a cup of water out of a swimming pool and then a/4 a cup and so forth, but eventually once you've taken out a single molecule of water, you can no longer take out a smaller thing. So, loop quantum gravity attempts to quantize gravity. So, that's what it does. And so this is unlike string theory which attempts to bring gravity in with the other forces. And in fact the reason the fundamental the one reason why string theory became so um interesting to the theoretical community is string theory was not being developed as a theory of everything. It was being developed as a theory of the strong force. And it was in competition with QCD, which is the currently accepted theory of the strong force. And it turned out the the two groups, the string theory groups and the um QCD groups competed for a while. And string theory basically failed the race and people paid attention to to quantum chromodnamics, QCD. But then somebody noticed in string theory that one of the things it predicted was a zero mass spin 2 particle. And you can prove that any zero mass spin 2 particle is the graviton. And so if you see a theory that has a zero mass spin 2 particle, you are now have a candidate for dragging gravity in. And then oh my gosh, people got terribly excited because now this theory which was um working in the direction of the other quantum forces brought in gravity and now it was a candidate theory for everything. But um but that's not what loop quantum gravity is. Loop quantum gravity is simply trying to understand the nature of space itself which is already a fantastic thing. And you I talk to Ralli every so often. I write about his theory um and I point out some of the issues with the theory but I'm usually about like two months behind as he and his colleagues are developing and so forth because one of the things is originally loop quantum gravity predicted that the speed of light would not be universal. The speed of light would depend on the frequency of the light. So high frequency would travel at one speed and low frequency would travel at a different speed. didn't it had to do with the wavelength of light basically interacting with the structure of space if you know and so that was an issue with loop quantum gravity and so if you look at gammaray bursters which are you know super explosions of astronomical events that are a billion lightyears away or more and they spit out light in all wavelengths and if that loop quantum gravity prediction were correct when you saw a um one of these gammaray bursters you would see the wavelength of one light appearing on Earth at a different time than another wavelength because of the different speeds. And that wasn't the case. They appear at the same time. And so I went on to say, well, let's pretty much kill loop quantum gravity only to get a prickly note from Mr. or Dr. Ralli saying, you know, we've disproved that. We've changed the theory. That's no longer true. And now that that prediction, that old prediction of loop quantum gravity is no longer valid. And so that observation of the the uniformity of the speed of light no longer kills the new loot quantity. It would have killed the old one, but it didn't kill the new one.

嗯。不过，有可能在足够小的尺度上，空间就不再以同样的方式可分了。就好比你可以从游泳池里舀出一杯水，再舀四分之一杯，如此下去，但最终一旦你舀出单个水分子，你就没法再舀出更小的东西了。所以圈量子引力试图把引力量子化。这就是它在做的事。这一点和弦理论不同，弦理论是想把引力和其他的力放到一起。而事实上，弦理论之所以变得让理论物理学界如此感兴趣，有一个根本性的原因是：弦理论起初并不是作为万有理论被开发出来的。它最初是作为描述强力(strong force)的理论被开发的。它当时和QCD在竞争——QCD是目前公认的强力理论。结果是这两派人，弦理论这一派和QCD这一派竞争了一阵子，而弦理论基本上输掉了这场赛跑，大家把注意力转向了量子色动力学，也就是QCD。但后来有人注意到，弦理论预言的东西里有一个是「零质量、自旋为2」的粒子。而你可以证明，任何零质量、自旋为2的粒子就是引力子(graviton)。所以如果你看到一个理论里有一个零质量、自旋为2的粒子，你现在就有了一个能把引力拽进来的候选者。然后哎呀，大家激动坏了，因为这个原本朝着其他量子力方向发展的理论，现在把引力也囊括进来了，于是它就成了万有理论的候选者。但是——但圈量子引力不是这么回事。圈量子引力只是想去理解空间本身的性质，这本身就已经是件了不起的事了。我时不时会和Rovelli聊聊，我写文章介绍他的理论，也指出理论里的一些问题，但我通常会落后他和同事们的进展大概两个月左右。因为有件事是这样的：圈量子引力最初预言光速不是普适的，光速会取决于光的频率。所以高频率的光以一种速度传播，低频率的光以另一种速度传播。这基本上和光的波长与空间结构发生相互作用有关。所以这是圈量子引力的一个问题。于是如果你去看伽马射线暴(gamma-ray burst)——你知道，那是发生在十亿光年甚至更远之外的天文事件中的超级爆发，它们会喷射出各种波长的光——如果圈量子引力那个预言是对的，那么当你看到一个伽马射线暴时，你会看到一个波长的光抵达地球的时刻和另一个波长不同，因为速度不同。但事实并非如此。它们是同时抵达的。所以我就接着说，好吧，那我们基本上可以把圈量子引力枪毙了。结果就收到了Rovelli先生、或者说Rovelli博士一封带刺的便条，说：你知道吗，我们已经驳倒那一点了，我们改了理论，那已经不成立了。现在圈量子引力那个旧的预言已经不再有效了。所以光速一致性的那个观测结果不再能枪毙新版的圈量子引力。它本来能枪毙旧版，但它没能枪毙新版。

[1:40:51] Lex

By the way, that example of uh different uh speeds of light uh based on wavelength, that's a beautiful thing that a theory that's a testable thing.

顺便说一句，你刚才说的那个例子——光速随波长而不同——那是个很美的东西，那是一个理论里可被检验的东西。

[1:41:02] Don

It is.

确实如此。

[1:41:03] Lex

Right. So like those kinds of things and if it in fact did explain a phenomena of that sort that's a good sign for the theory right

对。所以正是这类东西，如果它真的解释了某种这样的现象，那对这个理论来说就是个好兆头，对吧？

[1:41:10] Don

if it correctly predicted. There was another brilliant observation recently. I love it. Um the observation of uh gravity waves.

如果它正确地做出了预言的话。最近还有另一个绝妙的观测，我太喜欢了。呃，就是引力波(gravity waves)的观测。

[1:41:19] Lex

Mhm.

嗯。

[1:41:20] Don

And it was from two neutron stars orbiting and coalescing. And so they made gravitational waves. Fantastic. But they also because they were not black holes, they were neutron stars. They hit and exploded. Gave off a tremendous bright flash of light. And so astronomers saw the flash.

它来自两颗相互绕转并最终并合的中子星(neutron star)。它们产生了引力波，太棒了。但由于它们不是黑洞、而是中子星，它们还撞到了一起并发生爆炸，释放出一道极其明亮的闪光。所以天文学家看到了那道闪光。

[1:41:41] Lex

Mhm.

嗯。

[1:41:42] Don

Gravitational wave astronomers saw the ripples of spaceime. It was 140 million lighty years away, which means light would have traveled 140 million years to get here. And the two incidents, light and gravity, both arrived within 1.7 seconds of one another. And that tells you that gravity travels at the speed of light. That was a brilliant, fantastic measurement. Now we thought gravity traveled at the speed of light, but now we have a measurement. We proved it and damn it, I am impressed. Our universe is so fascinating. Speaking of which, since we brought up antimatter, we have to talk about it. Uh you've talked about in several of your lectures from different angles, including uh the dark energy crisis and including uh empty space and vacuum and so on. So let's look at the empty space angle. So uh you know it turns out the empty space is not empty.

而引力波天文学家看到了时空的涟漪。这个事件发生在1.4亿光年之外，也就是说光要走1.4亿年才能到达这里。而这两个信号——光和引力——抵达的时刻彼此相差不到1.7秒。这告诉你引力是以光速传播的。这是一次绝妙、了不起的测量。我们原本就认为引力是以光速传播的，但现在我们有了实测。我们证明了它，我真是服了，太佩服了。我们的宇宙实在太迷人了。说到这个，既然我们提到了反物质(antimatter)，我们就必须聊聊它。呃，你在好几次讲座里从不同角度谈过它，包括暗能量危机(dark energy crisis)，也包括空无的空间、真空之类的话题。那我们就从「空无的空间」这个角度来看吧。所以，呃，你知道，事实证明空无的空间其实并不空。

[1:42:40] Don

It's true which is kind of bizarre.

是真的，这其实挺离奇的。

[1:42:42] Lex

Can you can you speak about what do we know about what makes up empty space?

你能不能讲讲，关于构成空无空间的东西，我们都知道些什么？

[1:42:47] Don

That's a hard hard question because we don't know what space is. But let's start out

这是个很难很难的问题，因为我们并不知道空间是什么。不过让我们先从

[1:42:52] Don

let's just start out with something simple. We'll assume that space is not quantized. Okay. Now it probably is. I don't know. But you know, we got to start with somewhere. So, let's start out with sort of the space of calculus, the space that you can divide forever. The modern version of quantum mechanics is called quantum field theory. And it postulates that a space exists. Then it postulates that within space there exist fields for every known subatomic particle. So there is a photon field, there's an electron field, there's an up quark field, there's a down quark field, there's a all the fields and those fields can vibrate and when they vibrate those are the subatomic particles. So an electron field vibrating in a characteristic way is an electron. Now, it's also possible for the electron field to vibrate not in the characteristic way, but in a way that's still vibrating, but it's not an exact electron. So, this is what we call virtual particles. Now, virtual particles, there are lots of ways to talk about them, and the way I'm talking about now is the most correct and the most sophisticated way that we can talk about them. I will talk about them briefly in a in a simpler way to help but right now that's the important thing is that there are these fields specific vibrations are the known particles vibrations that are a little different are are these virtual particles they're particles that don't truly exist and so that is what we think space is. There is all of these these these fields. They are all vibrating a little. If you insert the right amount of energy, you can get it to vibrate in the characteristic way and make that subatomic particle. But even when you don't there is um the particles I mean the fields are there and they are vibrating. So those vibrating vibrations are what we called virtual particles. Now your viewers may have heard of virtual particles in other ways in which case it says that space is just empty and what happens is matter and antimatter particles briefly appear for a very short period of time before they coalesce back again and disappear and and reemerge back into the field. And so that these are both correct. So what happens is is that's what quantum field theory says is it says that these ripples are hearing or these particles are appearing and disappearing. And so that just sounds nuts. You look at empty space, you're not seeing anything happening, but they're happening fast enough that they can't be seen. But they do have consequences. And there are two experimental measurements that I can think of that validate that this thing that sounds crazy is really happening. And one is called the casemir effect. So in the casemir effect you take two metal plates that parallel plates and you put them near one another very very close. Now if this is the case if if these virtual particles exist then in between the plates these particles appearing and disappearing and outside the plates the particles are disappear appearing and disappearing. However, because these plates are close to one another, this puts a constraint on the wavelength of the particles that can occur between the two plates because they the particles cannot extend outside the plates. So the short wavelength particles can exist inside the between the plates, but the longer ones cannot. However, outside the plates there is no constraint. So short wavelength and long wavelength particles can exist there. And the net effect is there are more particle virtual particles outside and less particles inside. And therefore you have a net pressure which would then push those two plates together. That is a prediction we've been talking about. And guess what? It happens. Those plates push together. So that is a validation for the existence of these particles in empty space. Now there is another measurement and this changes the magnetic properties of particles like the electron the muon and and so forth and so this was uh discovered in 1948. So if you take old school standard quantum mechanics um you know the spin of an electron you know its charge you can calculate its magnetic moment and it comes out to a number. If you do the measurement, what you find is the measurement disagrees with the quantum mechanics, the 1930s quantum mechanical prediction by 0.1%. And that was measured in 1948. And people went, huh? So this happened at the Shelter Island conference in New York. And on the way home, someone who saw the this measurement thought about it and they invented what we now call quantum electronamics. So old quantum mechanics quantizes matter. The second quantization quantizes both matter and the fields. In this case, quantized the electric fields. And so in this quantized um field, it predicts that surrounding a bare say electron which is spinning and has a has a charge, there is this this bath of particles, virtual particles appearing and disappearing all around it. And the ensemble of all of those particles appearing and disappearing will alter the magnetic properties that you can measure for the subatomic particle. and it changes it by 0.1%. And we have measured this and we have not measured this imprecisely. We have measured the magnetic properties of both the electron and the muon to 12 count them 12 significant figures. And the theory and the data agree number for number for 10 places. And then once you get out to the very end where both the theory and the data have some imprecision, they then disagree. And so maybe there's some interesting stuff going on there. But 10 figures, it's just staggering. So virtual particles refer to matter and antimatter particles coming to life.

我们就先从一个简单的东西开始吧。我们假设空间不是量子化的。好。其实它很可能是量子化的，我也不知道。但你知道，总得从某个地方起步。那我们就从某种「微积分式的空间」开始——那种可以永远细分下去的空间。量子力学的现代版本叫做量子场论(quantum field theory)。它假定空间存在。然后它假定，在空间之中，每一种已知的亚原子粒子都对应一个场。所以有一个光子场，有一个电子场，有一个上夸克(up quark)场，有一个下夸克(down quark)场，有所有这些场，而这些场可以振动，当它们振动时，那些振动就是亚原子粒子。所以一个电子场以某种特征方式振动，那就是一个电子。现在，电子场也可能不是以那种特征方式振动，而是以另一种仍在振动、但并不是一个确切电子的方式振动。这就是我们所说的虚粒子(virtual particles)。关于虚粒子，有很多种谈论方式，而我现在采用的这种说法，是我们能采用的最正确、最精深的说法。我等会儿会用一种更简单的方式简略地讲一下来帮助理解，但眼下重要的是：存在着这些场，特定的振动就是已知的粒子，而稍微有点不同的振动就是这些虚粒子——它们是并不真正存在的粒子。所以这就是我们认为空间的样子：有所有这些场，它们都在轻微地振动。如果你注入恰当数量的能量，你就能让它以特征方式振动，从而造出那个亚原子粒子。但即便你不注入能量，那些粒子——我是说那些场——也都在那里，并且在振动。所以那些振动就是我们所说的虚粒子。现在你的观众可能在别处听过虚粒子的另一种说法，那种说法是：空间就是空的，而发生的事情是物质和反物质粒子短暂地出现一小会儿，然后又重新并合、消失，再回归到场里去。这两种说法都是对的。所以发生的事情就是量子场论所说的：这些涟漪在出现，或者说这些粒子在不断出现又消失。这听起来简直疯了。你看着空无的空间，看不到有任何事情在发生，但它们发生得太快了，根本看不见。可它们确实有后果。我能想到有两个实验测量，验证了这件听起来很疯狂的事是真实发生的。一个叫做卡西米尔效应(Casimir effect)。在卡西米尔效应中，你取两块金属板，两块平行的板，把它们放得彼此非常非常近。如果这些虚粒子确实存在，那么在两板之间，这些粒子在不断出现又消失，在两板之外，粒子也在不断出现又消失。然而，由于这两块板靠得很近，这对能在两板之间出现的粒子的波长施加了一个约束，因为粒子不能延伸到板外。所以短波长的粒子能存在于两板之间，而较长波长的就不行。然而在板外没有这种约束，所以短波长和长波长的粒子都能存在于那里。最终的净效果是：板外的虚粒子更多，板内的更少。于是你就有了一个净压力，这个压力会把两块板推向彼此。这正是我们一直在谈论的那个预言。你猜怎么着？它真的发生了。那两块板被推到了一起。所以这就是空无空间中存在这些粒子的一个验证。现在还有另一个测量，它改变了像电子、缪子(muon)等粒子的磁学性质。这是1948年发现的。如果你用老派的标准量子力学——你知道电子的自旋，知道它的电荷，你就可以算出它的磁矩，会得到一个数字。如果你去做测量，你会发现测量结果和量子力学、和那个1930年代的量子力学预言之间相差了0.1%。这是1948年测出来的。人们当时一愣，啊？这件事发生在纽约的Shelter Island会议上。在回家的路上，一个看到了这个测量结果的人对它思考了一番，然后发明了我们现在所称的量子电动力学(QED)。所以老的量子力学只把物质量子化，而第二次量子化把物质和场都量子化了。在这个例子里，是把电场量子化。在这个量子化的场里，它预言：在一个比如说裸的电子周围——它在自旋、带有电荷——会有这样一层「粒子浴」，虚粒子在它周围不断出现又消失。而所有这些不断出现又消失的粒子的总体，会改变你能为这个亚原子粒子测出的磁学性质，把它改变0.1%。我们已经测量过这个，而且我们测得绝不粗糙。我们已经把电子和缪子两者的磁学性质测到了12位有效数字——数一数，整整12位。理论和数据逐位吻合，前10位完全一致。然后一旦走到最末尾、理论和数据都各自带有一些不精确性的地方，它们才开始不一致。所以也许那里正有一些有意思的事情在发生。但10位有效数字的吻合，简直令人震撼。所以，虚粒子指的就是物质和反物质粒子在不断诞生。

[1:49:37] Lex

Correct.

没错。

[1:49:38] Lex

Can we just talk about the the antimatter part of that? So it's starting with Paul Durac, one of the most legendary examples of math leading to physics. So the math suggesting that so something like an antimatter should exist and Paul Direct taking it seriously and then eventually showing that it does exist. So what evidence do we have for antimatter? So antimatter was predicted in 1928. Paul Durac was trying to merge quantum mechanics and relativity because the original Schroinger equation did not was not relativistic and in doing so he basically the equations were complex but in the end it came down to something like equation squar= 1. You take the square root of both sides you get equation equals +1 or minus1. + one was the electron minus one was something you didn't know what it was. Um there was some conversation for a while thought maybe it might be the proton but that didn't seem to work out and so he insisted that his equations were right and that there was an antimatter he didn't call it an antimatter but a positively charged uh sibling of the electron what we now call the posetron the antimatter electron so it was predicted it was discovered in 1932 by Carl Anderson and his student Seth Nettoer they saw saw an antimatter electron and that was pretty cool. So that right there they knew it was real. Antimatter was predicted. It was observed. That's that. In 1956 the antimatter proton was created and that required a large particle accelerator high enough energy um to to to make it and that was done at Berkeley and a year later the antimatter neutron was discovered. So at this point and now jumping ahead to now we can make using uh energy by smashing particles together we can make antimatter protons. We can make antimatter electrons. We have gone so far to make anti-atter helium nuclei. So we have made two anti- protons and two anti- neutrons. Combine them together to make an anti-atter helium nuclei. This has been done, been observed. No question. At CERN, they have gone so far as to make antimatter hydrogen. They take a beam off one of their lower energy accelerators. They make antimatter protons. They collect them. They slow them down. They cool them to almost absolute zero. They take um sodium 22, which makes antimatter electrons. They slow them down. They bring them together. They coalesce them and they make literal antimatter hydrogen atoms with an antimatter proton surrounded by an antimatter electron and they have done incredible measurements. They have agitated the atoms and caused it to emit light. They have looked at the light that comes out of antimatter atoms. And the question is is does the light coming out of antimatter hydrogen atoms have exactly the same spectral characteristics as ordinary hydrogen which we predict that it does and the answer is it does. So the tests have been staggering. We now know a great deal about antimatter hydrogen. recently recently like 2023 I believe it was one of the experiments called alpha at CERN made antimatter hydrogen put it in a bottle and released it and watched which way it would go did it fall up or did it fall down because um while it kind of makes sense maybe to think that maybe antimatter falls up in the same way that we have Kulum's law you've got electric charges and they might attract or repel Well, um, however, there was lots of ample theoretical reasons to believe that antimatter also would fall down. So they did this fantastic measurement and they first they put in hydrogen and they calculated that some if they did this something like 80% of the hydrogen atoms would fall through the bottom of the bottle and 20% would go through the top just because um gravity is very weak and the atoms will escape wherever they do but there will be a bias pulling hydrogen atoms down. So they did the exactly the same thing and what did they find? They find that antimatter falls down. Now they do not have a good enough measurement at this time to say that the gravity that antimatter experiences is 100% that of matter. What they have measured is that antimatter fell down with 75% the strength of regular matter. But there were big uncertainties. There was plus or minus.13 due to the experiment which was good but imperfect and plus or minus.16 due to their um their theoretical model. So it's like 75 plus or minus something like 29 and that means there's a good chance it's between.5 and one which means it's consistent with one. So they are improving their measurements. Well, if I can, I would love to take a bit of a tangent on that topic because I went down a rabbit hole watching some of your v videos on antimatter and I mean Firmmy Lab was the hub for the production of antimatter for quite a while.

我们能单独聊聊其中反物质的那部分吗？这要从Paul Dirac说起，这是数学引领物理学的最具传奇色彩的例子之一。数学暗示着某种类似反物质的东西应该存在，而Paul Dirac认真对待了它，最终证明了它确实存在。那么我们有哪些证据能证明反物质的存在呢？反物质是在1928年被预言的。Paul Dirac当时试图把量子力学和相对论融合起来，因为最初的薛定谔方程(Schrödinger equation)不是、并不是相对论性的。在这个过程中，他基本上——那些方程很复杂，但最终归结为类似「方程的平方等于1」这样的东西。你对两边取平方根，就得到方程等于+1或者-1。+1是电子，-1是某个你当时还不知道是什么的东西。有一阵子有人讨论，觉得也许它可能是质子，但那似乎行不通。于是他坚持认为自己的方程是对的，认为存在一种反物质——他当时没把它叫做反物质，而是叫电子的一个带正电的「同胞」，也就是我们现在所称的正电子(positron)，即反物质电子。所以它被预言了，然后在1932年被Carl Anderson和他的学生Seth Neddermeyer发现，他们看到了一个反物质电子，这相当酷。所以就在那一刻，他们知道它是真实的。反物质被预言了，又被观测到了，就是这样。1956年，反物质质子被制造出来，这需要一台大型粒子加速器、足够高的能量才能造出它，这是在Berkeley完成的。一年后，反物质中子被发现。所以到了这个阶段——现在直接跳到当下——我们可以利用能量、通过把粒子对撞，造出反物质质子，造出反物质电子。我们甚至更进一步造出了反物质氦原子核。我们造出了两个反质子和两个反中子，把它们组合在一起，做成一个反物质氦原子核。这件事已经做成了，已经被观测到了，毫无疑问。在CERN，他们甚至更进一步造出了反物质氢。他们从一台较低能量的加速器引出一束束流，造出反物质质子，把它们收集起来，让它们减速，把它们冷却到几乎绝对零度。他们用钠-22，钠-22会产生反物质电子，他们让这些电子减速，把两者凑到一起，让它们结合，于是造出了货真价实的反物质氢原子——一个反物质质子被一个反物质电子环绕。他们还做了不可思议的测量。他们激发这些原子，让它发光。他们观察从反物质原子里发出来的光。问题是：从反物质氢原子里发出的光，是否拥有和普通氢完全相同的光谱特征？我们预言它会一样，而答案是：确实一样。所以这些检验的成果令人震撼。我们现在对反物质氢已经了解了很多。最近——最近，我想大概是2023年——CERN一个叫ALPHA的实验造出了反物质氢，把它放进一个「瓶子」里然后释放，观察它会往哪个方向走：它是往上掉还是往下掉？因为，呃，虽然某种程度上，认为反物质会往上掉也许是说得通的——就像我们有库仑定律(Coulomb's law)，电荷之间可能相吸或相斥那样——然而，有大量充分的理论依据让人相信反物质也会往下掉。所以他们做了这个绝妙的测量。他们先放进普通氢，并计算出，如果他们这么做，大约80%的氢原子会从瓶底掉出去，20%会从瓶顶逃出去，只因为引力非常微弱，原子会从任意一头跑掉，但会有一个把氢原子往下拽的偏向。然后他们对反物质做了完全相同的事，结果发现了什么？他们发现反物质会往下掉。目前他们的测量精度还不够高，无法断言反物质所受的引力百分之百等同于普通物质。他们测出的是：反物质往下掉时的强度是普通物质的75%。但其中存在很大的不确定度：来自实验本身的误差是正负0.13，这已经不错、但并不完美；来自他们理论模型的误差是正负0.16。所以大概是75%上下浮动约29%左右，这意味着它很有可能落在50%到100%之间，也就是说它和100%是相符的。所以他们正在改进测量。那么如果可以的话，我很想就这个话题稍微岔开一下，因为我看你一些关于反物质的视频时一头扎进了「兔子洞」。我是说，Fermilab曾经在相当长一段时间里是反物质生产的中心。

[1:55:17] Don

It was

确实是。

[1:55:18] Lex

I saw that NASA said that the global estimate for the current rate of production of antimatter is 1 nanog per year. Can you speak to how hard was it to make antimatter? And also you did mention in a video that you know if matter and antimatter meet they produce a lot of energy.

我看到NASA说，目前全球反物质生产速率的估计值是每年1纳克。你能讲讲制造反物质有多难吗？另外你在一个视频里也提到过，你知道，如果物质和反物质相遇，它们会产生大量的能量。

[1:55:38] Lex

I think 20 grams of antimatter is equivalent to a 1 megaton nuclear warhead in terms of explosive energy. Yeah. So all those questions together. So how hard is it to produce antimatter?

我想20克反物质在爆炸能量上相当于一枚100万吨级(1 megaton)的核弹头。是吧。所以把这些问题放在一起：制造反物质到底有多难？

[1:55:52] Don

It's freaking hard. Okay. All right. So here's the deal. So at the time until 2011, Firmay Lab was the most powerful anti-roton production facility on the planet. Every 2.3 seconds, we would smash 10^ the 13 protons into a target and we would get out 10 to the 8th anti-roton. So basically in order to get a single anti-roton we needed to smash 100,000 protons into material. So every 2.3 seconds we would get of order 10 to the 8th antiprotons. And what we would do is we would collect them over the course of 12 hours or so. And we would get in the end we would have to collect them and cool them down and so forth of order 10 the 12th antirotons every 12 to 24 hours. So 10 the 12th sounds like a lot. It really does. That is a trillion. But you need to remember that a gram of antimatter is 10^ the 23 antirotons. So that means over the course of a day we were able to create something like 100 billionth of a gram. And so if we did that for a year then that would be about a nanogram. So about a nanogram a year give or take. That's that's a reasonable estimate. So a nanog one billionth of a gram. So that means at that rate with that facility it would take a billion years running with very little downtime to make a single gram of antimatter. If you combine 1 g of antimatter and 1 g of matter together, the energy release is equivalent to the combined Hiroshima and Nagasaki explosions. So that tells you if you wanted a megat ton, you need about 25 times more. So you would have to run for 25 billion years to get a megat ton of explosive power.

难得要命。好。好的，事情是这样的。直到2011年之前，Fermilab一直是地球上最强大的反质子生产设施。每隔2.3秒，我们会把10的13次方个质子打到一个靶上，然后得到10的8次方个反质子。所以基本上，为了得到一个反质子，我们需要把10万个质子打进材料里。所以每2.3秒，我们大约能得到10的8次方个反质子。我们会做的事是，在大约12小时的时间里把它们收集起来。最终我们必须把它们收集、冷却等等，每12到24小时大约能攒下10的12次方个反质子。10的12次方听起来很多，确实很多，那是一万亿。但你得记住，一克反物质是10的23次方个反质子。所以这意味着，在一天的时间里，我们大约能造出一克的千亿分之一。所以如果我们这样干一年，那大概就是一纳克。也就是大约每年一纳克，上下浮动。这是个合理的估计。所以一纳克，就是十亿分之一克。这意味着以那个速率、用那台设施，要造出区区一克反物质，就得在几乎不停机的情况下运行十亿年。如果你把1克反物质和1克物质合到一起，释放的能量相当于广岛和长崎两次爆炸加起来。所以这告诉你，如果你想要100万吨当量，你还需要大约25倍那么多。所以你得运行250亿年，才能得到100万吨当量的爆炸威力。

[1:58:00] Lex

Let me uh lay it all out because I think it's pretty interesting actually. This is a NASA estimate of how much it cost to produce antimatter. So looking at all the the cost of the accelerator, all everything combined together to do enough for a one megaton antimatter bomb of such a thing would be even possible on the order of 25 grams like we mentioned will cost about based on the NASA estimate

让我把这些都摆出来吧，因为我觉得这其实挺有意思的。这是NASA对生产反物质成本的一个估计。把加速器的所有成本、为造出足够多反物质（哪怕真有可能造出来）所需的一切全部加在一起，要做一枚100万吨级的反物质炸弹——就像我们提到的，大约需要25克——根据NASA的估计，成本大约是

[1:58:28] Lex

uh 1.5 quadrillion. By the way, uh NASA wasn't talking about Obama. It's just me adding NASA was talking about the estimate the cost of 62 to63 trillion per gram of anti-hydrogen actually is what they're referring to. Uh so compared I was looking at estimates the current best estimates how much it takes to produce a 1 megaton nuclear warhead everything combined is about 10 to 50 million in the United States. So you're talking about difference in terms of a weapon with equal power $50 million versus $1.5 quadrillion. To me what's interesting weapons is just one uh indication of this. One other possibility and NASA also writes about this is the use of antimatter and propulsion systems.

呃，1.5千万亿(1.5 quadrillion)美元。顺便说一句，呃，NASA说的不是奥巴马（Obama）——那只是我自己加的玩笑——NASA说的其实是它的估算，是每克反氢的成本为6.2万亿到6.3万亿美元，这才是他们指的数字。呃，相比之下，我看了一些估算，目前对制造一枚100万吨级核弹头的最佳估计，全部加起来，在美国大约是1000万到5000万美元。所以你说的是，同等威力的两种武器之间的差距：5000万美元对1.5千万亿美元。对我来说，有意思的是，武器只是这件事的一个体现。还有另一种可能性，NASA也写到了，那就是把反物质用在推进系统(propulsion system)里。

[1:59:19] Don

Right?

对吧？

[1:59:20] Lex

Uh just like you can use uh nuclear fision and maybe even nuclear fusion down the line in propulsion systems. I saw that one gram can help get us to Alpha Centauri star system. If we can get to 02 times the speed of light in 20 years. Uh meaning it would take us 20 years to get to Alpha Centauri. Is any of this a possible future? The use of antimatter for generation of energy because we should mention that it's extremely compact. It has the obvious downsides that it's extremely costly to produce. who don't know how to do that kind of scale.

呃，就像你可以在推进系统里用核裂变(nuclear fission)、将来甚至也许能用核聚变(nuclear fusion)一样。我看到说一克反物质就能帮我们抵达半人马座阿尔法星(Alpha Centauri)星系——如果我们能在20年里达到0.2倍光速的话。呃，也就是说我们要花20年才能到达半人马座阿尔法星。这一切有没有可能成为现实？把反物质用于产能——因为我们应该提一句，它极其紧凑。它有明显的缺点，就是生产成本极其高昂，而且我们也不知道怎么把它做到那种规模。

[1:59:59] Don

The upside is it's compact. It's

好处是它很紧凑，它

[2:00:01] Lex

very powerful.

非常强大。

[2:00:02] Don

So the short answer is it is not a physics problem. It's an engineering problem. So I have people for that. Okay. Um okay. But no no um the truth is that antimatter if you are able to uh assemble it and store it. Sure. It would be able to take that antimatter, heat up matter and shoot it out the back of a rocket and it would, you know, do what rockets do and it would make us go quick and that would be fine.

所以简短的回答是：这不是一个物理学问题，而是一个工程学问题。所以这事我有人去管（笑）。好。呃，好吧，但不不，呃，事实是，反物质如果你能够把它组装起来并储存住——当然可以，你就能用那些反物质去加热物质，然后从火箭尾部把它喷出去，它就会，你知道，做火箭该做的事，让我们飞得很快，那就太好了。

[2:00:31] Don

And we should mention the thing that you just mentioned is is correct. One of the hugest challenges is the containment.

我们应该提一下，你刚才说的那点是对的。最大的挑战之一就是如何把反物质“关住”、约束住。

[2:00:37] Lex

Oh, because antimatter when it comes in contact with matter

哦，因为反物质一旦和物质接触——

[2:00:42] Don

uh is a is a problem,

对，那就麻烦了，

[2:00:43] Don

right? So if you were unable to uh to contain your trip to Alpha Centuri for even a millionth of a second, boom. And that would not be good.

是吧？所以，假如在你飞往半人马座阿尔法星(Alpha Centauri)的途中，哪怕只有百万分之一秒没能约束住它——砰，炸了。那可不妙。

[2:00:53] Lex

Yeah.

是啊。

[2:00:54] Don

Um you know, it reminds me of the uh the Star Trek where Scotty's saying, "Captain, you know, the antimatter pods are about look, we're losing containment going to blow." And that's exactly what would happen. So the short answer is yes. antimatter as in principle we could make and use as a a source of energy, but there are probably far less expensive sources of energy. Um, you know, it depends on what you need to do. The Voyager probes are still chugging along with plutonium now. They're running out of energy at this point, but we could, you know, presumably do a somewhat better job if we needed to. So, I I like the idea of antimatter, you know, but the reality is the danger, not the obvious danger of weapons, but the danger of if you wanted to be in a ship run by antimatter, if it ever got loose, well, you you would never know it. That would be that.

这让我想起《星际迷航》(Star Trek)里斯科蒂(Scotty)喊的那句话：“舰长，反物质舱要撑不住了，约束场快保不住，要爆了！”实际情况就是这样。所以简短的回答是：可以。原则上我们能制造反物质，也能把它当作能源来用，但很可能还有便宜得多的能源。这要看你想干什么。旅行者号(Voyager)探测器到现在还靠钚在工作，眼下它们的能量快耗尽了，但如果有需要，我们想必能做得更好些。所以反物质这个点子我挺喜欢，可现实是它太危险——不是说造武器那种显而易见的危险，而是说，假如你想坐在一艘靠反物质驱动的飞船里，它一旦失控泄漏，你根本来不及反应，瞬间就完了。

[2:01:51] Lex

The reason I I find this kind of inspiring is antimatter in this space of physics that has a lot of mysteries. There's a lot of exploration to be done. And so this kind of connection to energy means that uh if we have a bunch of breakthroughs on the antimatter side that might lead to a better propulsion system, better energy generation systems

我之所以觉得这事很有启发性，是因为反物质所在的这片物理学领域充满了未解之谜，还有大量探索的空间。而它和能源之间的这种联系意味着：如果我们在反物质方面取得一系列突破，或许就能带来更好的推进系统、更好的能源生产系统——

[2:02:16] Lex

in principle.

原则上是这样。

[2:02:17] Lex

There's some combination of engineering here, but there's some combination of understanding the fundamental physics.

这里头一部分是工程问题，但也有一部分是对基础物理的理解问题。

[2:02:22] Don

I mean, we know how to do this. You know, we we know you take energy, you make antimatter. You have to contain it, you have to store it, you have to do all the hard things. But I I would be shocked if there was some like new addition to the theory that made antimatter production easier.

我是说，我们已经知道怎么做了。你拿能量去造反物质，然后得把它约束住、储存起来，得搞定所有这些难题。但如果说理论上冒出某种新东西，让制造反物质变得更容易，那我会非常震惊。

[2:02:42] Lex

Interesting. So, we know how to produce antimatter with accelerators. You're saying there's not breakthroughs in physics that could lead to different mechanisms for the generation of antimatter.

有意思。所以我们已经知道用加速器(accelerator)来产生反物质。你的意思是，物理学上不会出现某种突破、带来产生反物质的全新机制？

[2:02:54] Don

You have to concentrate energy. That's it. If there's another way to concentrate energy, that would work too.

你必须把能量集中起来，就这么回事。如果有另一种集中能量的办法，那也行得通。

[2:03:00] Don

And our best knowledge of how to concentrate energy is the accelerator.

而就目前所知，我们最拿手的集中能量的方式，就是加速器。

[2:03:04] Don

And remember, we're talking concentrating it into um volumes the size of a proton. I mean, if you concentrated to the size of your thumb, well then, you know, it's really the density that matters, the local density. And so, when you smash two protons together, all of that's occurring in a tiny tiny volume. So, it's the local density of energy that matters. If you had a lot of energy in a thimble or something,

而且记住，我们说的是要把能量集中到一个质子(proton)那么大的体积里。如果你只把它集中到拇指那么大的范围，那其实真正起作用的是密度——是局部密度。所以当你把两个质子撞到一起时，这一切都发生在极其微小的体积内。起决定作用的是能量的局部密度。如果你只是把大量能量装在一个顶针那么大的东西里，

[2:03:29] Don

it's probably not dense enough. You know, it really has to be in close proximity for that to happen. And then when it does it, it's it's okay. So So if there's another way, we know how to do it to to make that that density thing with with accelerators. If someone has a bright idea on how to make highly dense energy then yeah uh making antimatter is a piece of cake but that's the crux concentrated energy.

那密度大概还不够。这事真得在极近的距离内才能发生，一旦发生了，那就成了。所以说，如果有别的办法——我们已经知道怎么用加速器把能量做到那种密度。要是有人想出了制造高密度能量的妙招，那制造反物质就是小菜一碟了。但关键就在这儿：把能量集中起来。

[2:03:59] Lex

Yeah. How to do so in a cost efficient manner not trillions of dollars.

是啊，而且还得以一种成本可控的方式做到，别动辄花上几万亿美元。

[2:04:05] Don

Well yeah.

嗯，是的。

[2:04:05] Lex

So one of the big mysteries with antimatter is the bigger why. Where is the antimatter that should kind of be there? If the whole idea is that anytime you generate matter, you generate the same amount of antimatter. And yet when we look out into the observable universe, it seems like there's not antimatter for the most part there.

所以关于反物质的一大谜团，是那个更深层的“为什么”。本该存在的那些反物质都去哪了？如果整套理论是说，每当你产生物质，就会产生等量的反物质，可当我们望向可观测宇宙时，却几乎看不到反物质的存在。

[2:04:27] Don

So what do we understand about this mystery? What are the possible explanations as to why? So there's this thing called um biogenesis and and as you say so reiterating a little bit what you just said um these are both Einstein things. Einstein says that when you take energy you make matter and antimatter in equal quantities and Einstein says after the big bang there was a lot of energy in the universe which should have made matter and antimatter. We only see matter. Where' the antimatter go? And the answer is we don't know. However, there are some ideas and there's a lot of thinking on it and um in fact for me it's doing an experiment right now with nutrinos trying to to better understand what it was that made the matter and antimatter not be the same. Now, we do have a measurement of how much different it should be. And it's kind of neat. We can do this by counting the number of protons in the universe just looking at galaxies and so forth. And then we can look at the cosmic microwave background which is sort of the aftermath of the big bang. And we can count the number of photons from the cosmic microwave background. And with a little bit of math, what we can do is we can then say that somehow in the early universe, something made a very very tiny asymmetry. So that for every billion billion with a B antimatter particles that existed in the universe, there were a billion and one matter particles. Mhm.

那么关于这个谜团我们究竟了解多少？又有哪些可能的解释？这里涉及一个叫做重子生成(baryogenesis)的东西。正如你刚才说的——稍微重申一下你的话——这两点都和Einstein有关。Einstein说，当你拿能量去造物质时，会等量地产生物质和反物质；Einstein还说，大爆炸(big bang)之后宇宙中有大量能量，这些能量本该造出物质和反物质。可我们只看到了物质。反物质去哪了？答案是：我们不知道。不过，有一些设想，人们也在这上面花了大量心思思考。事实上，对我而言，眼下我正在做一个用中微子(neutrino)的实验，试图更好地理解究竟是什么让物质和反物质没能一样多。现在，我们其实已经测出了二者本该相差多少，这一点挺巧妙的。我们可以通过数宇宙中质子的数量来做到——就是去看各个星系等等。然后我们再去看宇宙微波背景辐射(cosmic microwave background)，它可以说是大爆炸的余波；我们能数出宇宙微波背景辐射里光子(photon)的数量。再做一点数学计算，我们就能得出：在宇宙早期，某种机制造成了一个极其微小的不对称。也就是说，宇宙中每存在十亿乘十亿个反物质粒子（是billion，十亿），就有十亿乘十亿再加一个物质粒子。嗯。

[2:06:09] Don

The billions canled, annihilated, destroyed each other, and that extra one that's left over is us.

那十亿乘十亿对相互抵消、湮灭、彼此摧毁了，而多出来的那一个，就是我们。

[2:06:16] Lex

Mhm.

嗯。

[2:06:17] Don

And so what physics mechanism made that ever so slight asymmetry is not understood. There are some thoughts. One thought is uh that well, it's just how it was when the universe was formed. There was an asymmetry. it was not made by matter and antimatter. Another possibility is um there are various numbers of theories all under the word beriogenesis and berio um coming from word beron which basically means protons and genesis meaning the creation of and we'd say that simply because the protons are the heaviest particles and so biogenesis is just the creation of matter and there are just a number of theories in quantum mechanics that say that matter and antimatter can can oscillate back and forth into one another. And there is a slate slate asymmetry in how that happens. And we know that this is true to a degree. Um we've measured it in the 1960s with a a different form of matter. I mean, you know, not protons, but a a a type of ephemeral matter that only exists in particle accelerators. And so we know that there is a slight difference between matter and antimatter, but it's not enough. If it doesn't explain that, we're not sure. So, at Firmeny Lab, we have this idea which kind of turns things on its head and it it's not beriogenesis, it's leptogenesis. So, lepttons are the electrons. And because Fermy Lab is currently the world's most powerful nutrino accelerator and nutrinos are leptons, there is this idea. Now leptogenesis is incredibly complicated but the idea is that it is possible. We we know that nutrinos actually change their identity. There are three different types of nutrinos like uh I don't know cats and jaguars and tigers. And if you have a beam of just cats if you go along a little while you find there's cats and jaguars and then tigers and then they'll be back to all cats again. And so this oscillation thing is called nutrino oscillation. We've known it's been true since 1998. And what we are studying is we're going to make a beam of nutrinos and another beam of antimatter nutrinos. And we're going to study the oscillation behavior of the two of them. And it is possible, it is unlikely, but it is possible that the two of them will oscillate at slightly different rates.

那么，究竟是什么物理机制造成了这个极其轻微的不对称，目前还没弄明白。有一些想法。一种想法是：呃，这就是宇宙形成时本来的样子，一开始就存在一个不对称，并不是由物质和反物质的相互作用造出来的。另一种可能是——有各种各样的理论都归在“重子生成”(baryogenesis)这个词下面，baryo 来自 baryon（重子）这个词，基本上指的就是质子，genesis 意为“产生、创生”；我们之所以这么叫，单纯是因为质子是最重的粒子，所以重子生成说白了就是物质的创生。量子力学(quantum mechanics)里有一些理论说，物质和反物质可以来回振荡、相互转化，而这个过程中存在一个轻微的不对称。我们知道这在一定程度上是成立的——上世纪60年代我们就用另一种形式的物质测到过它。不是质子，而是一种短命的物质，只存在于粒子加速器里。所以我们知道物质和反物质之间确实有一点点差异，但这点差异还不够。如果它解释不了那个不对称，我们就没把握了。于是在Fermilab，我们有这样一个想法，它可以说把整件事翻了个个儿：不是重子生成，而是轻子生成(leptogenesis)。轻子(lepton)指的就是电子(electron)这一类。由于Fermilab目前是全世界最强大的中微子加速器，而中微子是轻子，于是就有了这个想法。轻子生成的细节极其复杂，但核心思路是：这是有可能的。我们知道中微子实际上会改变自己的身份。中微子有三种，就好比……我也不知道，比方说猫、美洲豹和老虎。如果你有一束全是“猫”的束流，沿着它走一段路，你会发现里面出现了“猫”和“美洲豹”，再走一段又有了“老虎”，然后又全变回“猫”。这种振荡现象就叫中微子振荡(neutrino oscillation)，自1998年起我们就知道它是真实存在的。我们现在要研究的，是制造一束中微子束流，再制造一束反中微子束流，然后比较这两者的振荡行为。有这样一种可能——虽然不太可能，但确实有可能——就是这两者的振荡速率略有不同。

[2:08:54] Don

Mhm. And if the nutrinos oscillate at slightly different rates, then that along with several other highly improbable things can tie together and might explain why there is more matter in the universe. So if I was going to bet the farm, I'll bet that they oscillate at the same rate. But I don't know, and you don't know till you do the measurement. So that's what we're doing. There are some other uh experiments trying to measure it right now. So there's a big race between the Firmeny Lab group and another group in Japan to see who gets there first and make this measurement and we will find out. If it turns out though that there is a difference in this oscillation rate between matter and antimatter, it will be a huge clue in this very very difficult puzzle. I wish I could tell you I knew what the answer is, but but literally nobody knows. I mean, and that's the thing of being a research scientist like me is if you're not confused, you're not doing your job.

嗯。而如果中微子和反中微子的振荡速率确实略有差异，那么这一点连同其他几件高度不可能发生的事联系在一起，或许就能解释为什么宇宙中物质会更多。所以，要是让我押上全部身家来赌，我会赌它们以相同速率振荡。但我并不知道答案，不做实验谁也不会知道。所以这就是我们正在做的事。眼下还有其他一些实验也在试图测量它。Fermilab这个团队和日本的另一个团队之间正在展开一场激烈竞赛，看谁先做到、先测出这个结果，我们终将揭晓。不过，如果最终发现物质和反物质的振荡速率确实存在差异，那将是这道极其棘手的难题里一条重大线索。我真希望我能告诉你答案是什么，可坦白说，没有人知道。这正是当我这样一名研究科学家的真谛所在：如果你没感到困惑，那你就没在好好做你的工作。

[2:09:55] Lex

So, there is this desperate or not desperate, exciting search for this tiny asymmetry.

所以，眼下正有一场对这个微小不对称的——说“绝望”不太对——令人激动的搜寻。

[2:10:01] Don

Yes.

是的。

[2:10:02] Lex

It's so so crazy to think that everything we see around us is a result of this tiny asymmetry that there was this gigantic annihilation of matter and antimatter in the early universe.

想想真是太疯狂了：我们周围所见的一切，竟然都源自这个微小的不对称——源自宇宙早期那场物质与反物质之间巨大的湮灭。

[2:10:16] Lex

And this is just some little accident.

而这一切不过是某个小小的意外。

[2:10:19] Don

Yeah. Yeah. That's crazy.

对，对。简直疯狂。

[2:10:21] Don

It's a happy accident.

这是个美丽的意外。

[2:10:22] Lex

That is just I mean it's totally crazy.

这真是……我是说，简直太疯狂了。

[2:10:25] Don

This is one of the areas of physics where there's a lot of mystery.

这是物理学中充满谜团的领域之一。

[2:10:29] Lex

Mhm.

嗯。

[2:10:31] Lex

Okay. So, uh can we pull at that thread a little further? Let's talk about our intuition of what is uh dark energy as it connects to empty space and everything we've been talking about. Uh what's what's the cleanest definition of dark energy? So dark energy is either energy of space or energy in space. The most common statement is the energy of space. And it is essentially a repulsive form of gravity. And we believe this is real. And the reason we believe this is real is from observation. And this is one of those things where we talked about a while ago where I said that, you know, you can think about things up this theoretical stuff and try to come up with a measurement or you can make measurements and see where they disagree with predictions and lead that in a direction. So back in the late 1990s, some astronomers were looking at the expansion rate of the universe. So the the big bang occurred, the universe is expanding. The universe is full of matter. Matter attracts. So the gravity due to the matter of the universe should slow the expansion of the universe. And the only question was how much? There were three possibilities. The possibilities were there was so much gravitational force that the expansion of the universe would slow and be pulled back together in a big crunch. Number two was that the universe would continue expanding, slowing down, but never really stopping. And then the third possibility was the exact critical case where expansion would slow forever and approach zero only at infinity never quite stopping or reversing. So those were the possibilities. Door number one, two or three. So they did the measurement and what did they found? It was door number four. The universe was not only expanding but the expansion was speeding up. And the only way that could happen given that gravity slows it down is there was a repulsive force. And the name we give to that repulsive force is dark energy. This is something that Einstein postulated early on in his um his development of of general relativity. But then because at the time he knew that his theory predicted that the universe would collapse. Um but he believed the universe was eternal and not unchanging. And so he needed something to counterbalance the uh that uh collapse. And so he invented dark energy. He didn't call it that. Call it the cosmological constant. Um but then a few years later, Edwin Hubble discovered that the universe was indeed expanding. And so since the universe was no longer static, Einstein said no need for cosmological constant, took it back out.

好。那我们能不能顺着这条线再往下挖一点?我们来聊聊对暗能量(dark energy)的直观理解,看看它怎么和空虚的空间、以及我们前面聊的这些东西联系起来。暗能量最清晰的定义是什么呢?——暗能量要么是空间本身的能量,要么是存在于空间中的能量。最常见的说法是,它是空间本身的能量。它本质上是一种排斥性的引力。我们相信这是真实存在的。之所以相信它真实存在,是因为观测。这正是我们前面提到过的那种情况:你可以从理论出发去琢磨这些东西,然后想办法找一个测量来验证;也可以反过来,先做测量,看测量结果在哪里和预测对不上,然后顺着那个方向去追。回到20世纪90年代末,一些天文学家在研究宇宙的膨胀速率。大爆炸发生了,宇宙在膨胀。宇宙里充满了物质。物质会相互吸引。所以宇宙中物质产生的引力应该会让宇宙的膨胀变慢。当时唯一的问题是:变慢多少?有三种可能。第一种是引力大到让宇宙的膨胀减速,最后被拉回来,发生一次大坍缩(big crunch)。第二种是宇宙会持续膨胀、不断减速,但永远不会真正停下来。第三种则是恰好处于临界的那种情况:膨胀永远在减速,在无穷远处趋近于零,但永远不会真正停止或逆转。这就是当时的三种可能。一号门、二号门还是三号门。结果他们做了测量,发现了什么呢?是四号门。宇宙不仅在膨胀,而且膨胀还在加速。既然引力本应让膨胀变慢,那唯一能解释加速的方式就是存在某种排斥力。我们给这种排斥力起的名字就叫暗能量。其实Einstein在他发展广义相对论的早期就提出过类似的东西。当时他知道自己的理论预言宇宙会坍缩,但他相信宇宙是永恒不变的。于是他需要某种东西来抵消那种坍缩的趋势,所以他发明了暗能量——他没这么叫,他管它叫宇宙学常数(cosmological constant)。然而几年后,Edwin Hubble发现宇宙确实在膨胀。既然宇宙不再是静态的,Einstein就说不再需要宇宙学常数了,又把它拿掉了。

[2:13:23] Don

Thought it was a dumb idea that he put it in and was embarrassed. Um, however, in 1998, it became clear that his original idea that there should be some sort of repulsive form of gravity was real and it's put back in the theory.

他觉得当初引入这个东西是个蠢主意,还为此感到难堪。可是到了1998年,人们发现他最初那个想法——应该存在某种排斥性的引力——是真实的,于是这个概念又被放回了理论里。

[2:13:38] Don

And so that's what it is. We are pretty confident at this point that the expansion of the universe is speeding up and the thing driving it is dark energy. Now, what is dark energy? I don't know. Um, as I said, the most common thought is that it is the energy of space itself. But it is at least conceivable that there is a field in space where space exists

所以这就是暗能量的来历。我们现在相当有把握地认为,宇宙的膨胀正在加速,而驱动它的就是暗能量。那暗能量到底是什么?我不知道。就像我说的,最常见的看法是,它是空间本身的能量。但至少在概念上,也可以设想:在空间所在之处存在着某种场,

[2:14:05] Don

and that field is pushing space apart. That's another conceivability that I'm not sure that we have the the instrumentation to distinguish, but that's not what normally people think. People think it is literally a property of space.

是这个场在把空间往外推。这是另一种设想。我不太确定我们现在是否有足够精密的仪器去区分这两种可能,不过大多数人并不这么想。人们倾向于认为暗能量就是空间本身的一种属性。

[2:14:19] Lex

But but there is the what you call the worst prediction in physics which is a

但是,还存在你所说的"物理学中最糟糕的预测",也就是——

[2:14:26] Don

oh yeah that's another one

哦对,那是另一回事。

[2:14:27] Lex

a nice little insight about the complicated nature of dark energy. So the observations as you described say that empty space has a tiny energy density that accelerates expansion of the universe. But quantum field theory's prediction for what vacuum energy should be when coupled with gravity is much larger.

——它能让我们对暗能量的复杂本质有一点很妙的洞察。正如你所描述的,观测结果表明,空虚的空间具有一个极其微小的能量密度,正是它在加速宇宙的膨胀。但量子场论预测的真空能量值——尤其是把它和引力放在一起考虑时——要大得多。

[2:14:51] Don

Mhm.

嗯。

[2:14:52] Lex

Uh so this is what makes for the uh quote you have a video on this worst prediction in physics.

所以这才有了那个说法——你专门拍过一个视频讲它——"物理学中最糟糕的预测"。

[2:14:58] Lex

Can you can you explain this crisis?

你能解释一下这场"危机"吗?

[2:15:00] Don

Well the there's a measurement and you can measure how fast the universe is expanding and from that you get a measurement of dark energy. However, if you then say, well, suppose the dark energy is due to fields in space. So that's quantum field theory. Hey, I know a lot about quantum field theory.

嗯,是这样,有一个测量。你可以测出宇宙膨胀有多快,从中就能得到对暗能量的测量值。但如果你接着说:好吧,假设暗能量来自空间中的场——那就属于量子场论的范畴了。嘿,我对量子场论可懂得不少。

[2:15:21] Don

And so we can take the quantum field theory and we can calculate what the density of energy is due to quantum field theory. And basically what you do is you take within a volume the uh all of the wavelengths, the the longer wavelength, the shorter wavelengths, the shorter shorter and shorter. And you can add them all up. And each wavelength adds a certain amount of energy. And if you add that all up, then you get a number. And that number is the rather embarrassing 10 to the 120 power times that's a one with 120 zeros after it bigger than the measurement of dark energy.

于是我们就可以用量子场论来计算量子场所贡献的能量密度是多少。基本做法是:在一个体积内,把所有的波长都考虑进去——较长的波长、较短的波长、越来越短的波长。你把它们全部加起来,每一种波长都贡献一定的能量。把这些全加在一起,就得到一个数。而这个数大得令人尴尬:它是暗能量测量值的10的120次方倍——也就是1后面跟着120个零。

[2:16:07] Lex

Yeah.

是啊。

[2:16:08] Don

So you go yuck that is not fun at all. And that is because the equation comes to the highest energy or the smallest wavelength particle that you can imagine to the fourth power since anything to the fourth power is a big deal. So that's where you get that awful number. Now if it turns out that there is some new physics that's just about at the energy scale we can measure using our biggest particle accelerators. Remember I told you that that was a factor the maximum energy scale plank scale is 10 the 15 times bigger than what we can measure now. So let's say that we don't have to calculate up to the plank scale because something happens something changes at the energy that we know right now. Well then that means we don't have to integrate to plank scale. We integrate to 10 the 15th less of the plank scale. And this thing is to the 4th power. So 10^ the 15 to the 4th power is 60. So now even if we say you know Don he's brilliant he's going to find something at the LHC tomorrow is going to solve all this problem. Now we've solved it. It's much better. It's only different by 10 to the 60 power which is still pretty bleeding big. So the short answer is there is very clearly something going on, something wrong, very badly wrong in the quantum field theory. You know, we have to have maybe there's another field that balances out the energy that cancels it down. And even that, you know, that that's not so so outrageous. You know, you could imagine that there's another, you know, like we have matter and antimatter. They balance pretty well. Okay, maybe there's something going on. And you could cancel that out. That'd be perfect. But cancelelling something to zero is easy cuz you know plus one and minus one 0 + 2 - 2 0. But we still have dark energy. Dark energy is a little bit. So if it cancels, it doesn't cancel exactly because it left over that little bit of dark energy. So that is its own curiosity. Perfect cancellation pretty easy. Theorists do that, you know, eight times before breakfast. imperfect cancellation much harder.

所以你只能说,呃,这一点都不好玩。之所以会这样,是因为公式里要算到你能想象的最高能量、也就是最短波长的粒子,而且是它的四次方;任何东西取四次方都会变得非常大。这就是那个糟糕数字的来历。现在,假如真有某种新物理刚好出现在我们用最大的粒子加速器所能测量的能量尺度上呢?记得我跟你说过,从那里到普朗克尺度(Planck scale)还差一个因子——最高能量的普朗克尺度比我们现在能测量的还要大10的15次方倍。那么假设我们不必一直算到普朗克尺度,因为在我们目前已知的某个能量处会发生某种变化。那就意味着我们不必积分到普朗克尺度,而只需积分到比普朗克尺度低10的15次方的地方。而这个量是四次方。10的15次方取四次方就是10的60次方。所以现在,就算我们说"你看Don多聪明,他明天就会在LHC上发现点什么,把这个问题全解决了",好,我们解决了,情况好多了——可它仍然差着10的60次方,这还是大得吓人。所以简短的答案是:这里非常明显地存在某种问题,某种错误,而且是量子场论里非常严重的错误。也许存在另一个场,把这部分能量抵消掉、压下去。即便如此,这其实也不算太离谱。你可以设想存在另一个场——就像我们有物质和反物质(antimatter),它们能很好地相互平衡一样。好,也许这里也在发生类似的事,可以把它抵消掉,那就完美了。但是把某个东西抵消到零是很容易的,因为你知道,加一减一等于零,加二减二等于零。可问题是我们仍然有暗能量。暗能量是那么一丁点。所以如果它真的相互抵消,那也不是抵消得干干净净,因为还剩下那么一点点暗能量。这本身就是个谜。完美抵消很简单,理论家在早饭前都能干上八回;但不完美的抵消就难多了。

[2:18:27] Lex

Just to elaborate that a little bit, what do you think solving in quotes solving dark energy would look like?

再稍微展开一点,你觉得所谓"解决"暗能量问题——加引号的"解决"——会是什么样子?

[2:18:33] Don

Well, you could what you would do is you would hypothesize that there existed some other field that had the the the reverse uh effect of existing quantum fields,

嗯,你会这么做:你会假设存在某个别的场,它产生的效应和现有的量子场正好相反,

[2:18:44] Lex

but not to zero.

但不是抵消到零。

[2:18:45] Don

But not to zero. So, but if you had it to go to zero, you know, uh, sure, maybe there's a field that that exists at really high energies that we haven't seen yet. I don't know, but it cancel things out and we're cool.

对,不是到零。不过假如它真的能抵消到零的话——当然了,也许存在某个我们还没见过、只在极高能量下才出现的场,我不知道,但它把东西抵消掉了,那我们就皆大欢喜。

[2:18:58] Lex

How would we then demonstrate the existence of that field?

那我们又该如何证明这个场确实存在呢?

[2:19:00] Don

Uh, well, that would depend on the prediction.

呃,那就要看具体的预测是什么了。

[2:19:03] Lex

How do you even come up with a new field

你究竟是怎么凭空想出一个新的场的?

[2:19:05] Don

like all theorists do? Well, let's add something to my equation and see what happens. I mean, and and that's okay. I mean, I I'm being glib about that, but that is precisely what you do. You say what change? We we have this thing that works quite beautifully except it fails here. What is the addition that we need to make that changes very little in the realm that we measured and yet fixes this hard thing? And so you literally just go da da da. Okay, what do I need plus six or something and as long as it makes no changes where it would hurt our measurements and fixes the big thing, then that is at least a candidate theory. Now, that doesn't mean it's right, but it at least gives you an understanding of what the right answer should look like. M

就像所有理论家做的那样啊。无非是:"让我往方程里加点东西,看看会怎么样。"这是可以的。我是说,我这么讲是有点轻佻,但你做的确实就是这件事。你会问:改什么?我们现在有这么一套理论,运转得相当漂亮,唯独在这里出了问题。那我们需要加进去什么东西,既能在我们已经测量过的范围里几乎不带来任何改变,又能修好这个棘手的地方?于是你真的就一项一项地试:好,我需要加个六还是什么的。只要它在会破坏我们测量结果的地方不带来任何改变,同时又能修好那个大问题,那它至少就是一个候选理论。这并不意味着它一定对,但至少能让你明白,正确答案应该长什么样。

[2:19:59] Don

and so that's the first step is what should the real answer look like or what is a possible real answer and then once you kind of know that then other people can look and say well let me think about a theory that kind of has the required properties to do what we need it to do. So, it's it's a multi-step process, but the first step is how do we tame this problem without coming up with really terrible predictions that we've already ruled out.

所以第一步就是:真正的答案应该是什么样子,或者说一个可能的真答案是什么样子。一旦你大致心里有数了,别人就可以接着看,然后说:好,让我来想一个理论,让它大致具备我们所需要的那些性质,能办成我们想让它办的事。所以这是一个分多步走的过程,但第一步是:我们怎么驯服这个问题,同时又不会引出那些早已被排除掉的、糟糕透顶的预测。

[2:20:31] Don

And and so that's what you do. And and you know that that is literally a a sensible, viable theoretical thing, you know, cuz you have to explore cool ideas. I mean one of the reasons dark energy is super interesting is it kind of gives us a mechanism by which we can talk about the deep future of the universe. I it's making we have observations about the expansion of the universe but it's also giving us the mechanism of that right so we can talk about uh any weirdness any good model we have that that captures some of the weirdness of dark energy

做的就是这件事。而且你要知道,这真的是一件合情合理、行得通的理论工作,因为你必须去探索那些有意思的想法。暗能量之所以超级有趣,原因之一就是它给了我们一种机制,让我们能够谈论宇宙的遥远未来。它让我们——我们有关于宇宙膨胀的观测,但它同时还给了我们这种膨胀背后的机制。所以我们就可以谈论任何古怪之处了:只要我们手里有一个好模型,能抓住暗能量某些古怪的特性,

[2:21:09] Don

might give us insights about how this thing ends how the universe

它就可能让我们洞察到这一切将如何收场,宇宙将如何——

[2:21:14] Lex

about the deep future of the universe right

——关于宇宙的遥远未来,对吧。

[2:21:16] Don

absolutely as it stands right now if dark energy is real and who knows you know if it's a real exact exactly as we've measured it. Then as the um universe gets uh bigger and bigger, dark energy becomes a bigger and bigger component of the energy balance of the universe and it takes over and it drives the continued accelerated expansion of the universe.

完全正确。按现在的情形,如果暗能量是真实的——谁知道呢,它是否真的就完全像我们所测量的那样——那么随着宇宙变得越来越大,暗能量在宇宙能量总账中所占的比重也会越来越大,最终它会占据主导,驱动宇宙持续地加速膨胀。

[2:21:40] Don

And if dark energy gets lower, you know, for some reason that we don't understand, maybe it changes over time, gets smaller, that could change things. If it gets bigger, it could change things. That is one of the big open questions whether it's constant over time or not.

而如果出于某种我们尚不理解的原因,暗能量变弱了——也许它会随时间变化、变得越来越小——那就可能改变结局。如果它变大,同样可能改变结局。它究竟是不是恒定不变、会不会随时间改变,这是当前几个重大的开放性问题之一。

[2:21:53] Don

Right? And there has been a recent measurement that suggests that dark energy is getting smaller. Um however that is a new measurement not confirmed blah blah blah blah blah. Nobody should believe it but it's a hint that maybe it's changing which is kind of cool in itself because the current bias until recently is that dark energy is constant. Now I want to be super careful because it's misleading. People say dark energy is constant. Dark energy is a density.

对吧？最近有一项测量结果暗示暗能量(dark energy)正在变小。不过这是个新结果，还没得到证实，云云。没人应该贸然相信它，但它是一个迹象，说明暗能量也许在变化，这本身就挺酷的，因为直到不久前，主流的看法一直是暗能量是个常数。这里我得格外小心，因为这种说法有误导性。人们说暗能量是常数。暗能量其实是一种密度。

[2:22:24] Lex

Mhm.

嗯。

[2:22:25] Don

Now that think about that. You have a certain density. Let's start with that.

你想想看。你有某个确定的密度，先从这一点说起。

[2:22:30] Don

Then the universe expands. So energy is volume times density. If the universe gets bigger and the density is constant, that means dark energy

然后宇宙开始膨胀。能量等于体积乘以密度。如果宇宙变大，而密度保持不变，那就意味着暗能量

[2:22:40] Don

is increasing. It's not just increasing as a fraction and overwhelming ordinary matter. But ordinary matter as the universe expands its density decreases because it's constant and the volume gets bigger, the density drops. Dark energy until recently is thought to be constant density.

在增加。它不只是作为占比在增加、压过普通物质而已。普通物质随着宇宙膨胀，它的密度会下降，因为物质总量是固定的，而体积变大，密度自然就降低。但暗能量，直到不久前，一直被认为是恒定密度。

[2:23:02] Don

So that's what's implied when you say constant. You say constant density which means it's actually increasing because space is increasing. The size of space is increasing. Interesting. And so that's a a weirdness. And that then ties into the nature of space. Why does that tie into the nature of space? Well, because if dark energy is a field in space, if you increase the volume, you would think the energy density would drop.

所以当你说它是常数时，你真正的意思是恒定密度，而这恰恰意味着它的总量其实在增加，因为空间在增加，空间的尺寸在变大。挺有意思的。这是个怪现象，而它又牵扯到空间本身的性质。为什么会牵扯到空间的性质呢？因为如果暗能量是空间里的一个场，那当你增大体积时，你会以为能量密度应该下降才对。

[2:23:26] Lex

Mhm.

嗯。

[2:23:26] Don

But if space is increasing and space is quantized, and I don't know if it is, then maybe what's happening is space isn't stretching, but like little space particles are appearing as the space You know, there's like bubbles of space appearing and each bubble contains a certain amount of dark energy. And so therefore, that would give you a sense that dark energy is a property of space rather than a field in space. But that's all very handwavy, guessworky stuff. So if you had bet all your money, is dark energy like a real physical what does that even mean thing that exists versus is this just an a renaming of the cosmological constant?

但如果空间在增加，而且空间是量子化的——我不知道它是不是——那么也许情况是这样：空间并不是被拉伸，而是随着空间扩张，一个个小小的“空间粒子”冒了出来。你可以想象成一个个空间的气泡不断出现，每个气泡里都含有一定量的暗能量。这样一来，你就会得到这样一种图景：暗能量是空间的一种属性，而不是存在于空间之中的一个场。不过这全都很含糊，是瞎猜的东西。那么，如果让你押上全部身家——暗能量到底是一种真实存在的物理“东西”（不管这究竟意味着什么），还是仅仅是给宇宙学常数(cosmological constant)换了个名字？

[2:24:13] Don

Unfortunately, I think it's both. I mean,

不巧的是，我觉得两者都是。我是说，

[2:24:16] Don

well, I mean, it is it's describing a reality, but it's also maybe telling us something about space,

嗯，它确实在描述一种现实，但它或许也在告诉我们一些关于空间的东西，

[2:24:24] Don

literally a property of space. Yeah, it's I mean that's kind of what it looks like given that it seems to be constant density. That seems to me now this is not something anybody should believe. Please, nobody believe this. But it seems to me that this is leaning towards the idea that A it's a property of space, B, space is quantized. C as space is expanding little quantum of space are appearing and D each one of those quanta has a certain amount of energy associated with it and that would kind of explain the constant density. Now, please, that's not anybody should, nobody accepts that. This is just nonsense.

也就是说它真真切切是空间的一种属性。是啊，鉴于它看起来是恒定密度，事情看上去就是这个样子。在我看来——再强调一遍，这不是谁该相信的，求各位别信——但在我看来，这倾向于支持这样几点：第一，它是空间的属性；第二，空间是量子化的；第三，随着空间膨胀，一个个空间的量子不断出现；第四，每一个这样的量子都伴随着一定的能量，这就大致解释了恒定密度。再说一遍，拜托，没人应该接受这个说法，谁都不接受，这纯属胡说八道。

[2:25:09] Lex

But a lot of the stuff that you just said is experimentally probably experimentally testable. You can probably construct them

但你刚才说的很多东西，从实验上看大概是可以检验的。你大概可以设计出

[2:25:17] Lex

experiment the bubbles of

实验来验证那些气泡

[2:25:19] Don

Well, finding out the bubbles of space, but those quanta conceivably are planksiz bubbles.

嗯，去找出那些空间气泡，而这些量子可以想象成是普朗克尺度(Planck scale)的气泡。

[2:25:25] Lex

Yeah, the quanta.

对，那些量子。

[2:25:26] Don

Well, they'd be quantum of space. I mean the idea is you know you look at a sand dune and it looks smooth and continuous but you can see individual grains of sand right and so what this is saying is as this dune expands new grains of sand are appearing and each one of them is a quantum of space.

嗯，应该说是空间的量子。这个想法是这样的：你看一座沙丘，它看上去光滑、连续，但你能看到一粒粒单独的沙子，对吧？所以这是在说，当这座沙丘扩张时，新的沙粒不断出现，而每一粒沙就是一个空间的量子。

[2:25:43] Lex

So what kind of experiments can we do in the coming decades or centuries to understand dark energy better? I mean people have been talking about quantum entanglement of gravity. In standard quantum mechanics a particle can be in two places at the same time. All right? So now you have two particles. So this particle can be in two places in the same time. This particle be be two places at the same time. If you put them near one another, well if they're close to each other, there's a certain gravitational force. If they're far apart, they're certain. And if they one is close and one is far, you have another one. You can calculate the effects of gravity having to do with quantum entangled particles being in two places. And people are talking about doing this and trying to see if in doing such a measurement they might be able to definitively determine whether gravity is a quantum phenomena or a continuous phenomena. And that is potentially a measurement that could be done soonish because the technologies of inherent in all of this recent work on quantum mechanics is allowing people to be able to make instrumentation that might be precise enough to do this measurement. Now this will not tell us what quantum gravity is. It will not tell us anything. But it will tell us that gravity is quantized. And just knowing that, well, for one thing, it shuts out a whole realm of of continuous gravity. And the theoretical community will then turn its attention, forget this stuff, and and think over here. Now, that doesn't tell you that space is quantized, but it tells you that gravity is quantized if it bears out. So, and if gravity is quantized, then people will start thinking more about space being quantized.

那么在未来几十年甚至几个世纪里，我们能做哪些实验来更好地理解暗能量呢？我是说，人们一直在谈论引力的量子纠缠。在标准量子力学(quantum mechanics)里，一个粒子可以同时处于两个地方，对吧？那现在你有两个粒子。这个粒子可以同时处于两个地方，那个粒子也可以同时处于两个地方。如果你把它们放到彼此附近——如果它们离得近，就有某个确定的引力；离得远，又是另一个值；一个近一个远，又是另一种情况。你可以计算与这些处于两地的量子纠缠粒子相关的引力效应。人们正在讨论去做这件事，想看看通过这样一次测量，能否一锤定音地确定引力究竟是量子现象还是连续现象。而这是一项有可能在不太远的将来就能完成的测量，因为近年来量子力学这一系列工作所内含的技术，正让人们有能力造出精度足以完成这种测量的仪器。注意，这并不能告诉我们量子引力到底是什么，它什么都不会告诉我们，但它会告诉我们引力是量子化的。而仅仅知道这一点——首先，它就排除掉了一整片连续引力的领域。理论界随即就会把注意力转过来，扔下那一摊东西，转而思考这边。当然，这并不能告诉你空间是量子化的，但如果结论成立，它告诉你引力是量子化的。那么，一旦引力是量子化的，人们就会开始更多地去思考空间是否也是量子化的。

[2:27:42] Lex

I have to ask because you mentioned dark matter is perhaps even more mysterious than dark energy.

我得问一下，因为你提到暗物质(dark matter)也许比暗能量更神秘。

[2:27:47] Don

Okay.

好。

[2:27:48] Lex

Can you can you can you uh build up the intuition why it's more mysterious. What is dark matter?

你能不能帮我们建立起一种直觉，说明为什么它更神秘。暗物质到底是什么？

[2:27:53] Don

Oh gosh. What is dark matter? A, I don't know. B, it's terribly fascinating.

天哪。暗物质是什么？第一，我不知道。第二，它实在太迷人了。

[2:27:59] Lex

Yeah.

是啊。

[2:27:59] Don

All right. So, first thing and the most important thing cuz I'm an experimentalist by God. The first thing is why do we believe there's dark matter? And the reason is that astronomical measurements do not agree with predictions by Newtonian or relativity theory. Galaxies spin too fast. Clusters of galaxies move too quickly. And the distortion of very distant galaxies due to the gravitational field of near galaxies disagrees with the prediction from what we see from the observed matter. So there are three very distinct reasons why we are predicting that that something is wrong in our understanding of either the laws of physics or the matter budget of the universe. The easiest one to talk about is the spinning galaxies. Now this is what I'm saying is not unique to spinning galaxies just easiest to talk about. So, galaxies are observed to spin more quickly than they should if we add up the gravity we see. By all rights, galaxies spinning that fast should blow themselves apart and they don't. So, what can be the answer? Well, you have the force required for a star to orbit to move in a circle and you have the force due to gravity and they're connected by an equal sign and the prediction is wrong. So either the force due to gravity is wrong, the force needed to move in a circle is wrong or the equal sign is wrong. I mean this is really simple. One of those things is wrong. So one possibility is simply that Newton's law of gravity mass time the mass over r 2 time a constant that's just wrong. Another possibility is Newton's F= ma that we are taught in introductory physics is wrong. Both of those are eminently possible over here. Maybe we don't understand gravity or maybe there's more mass than we can see. So these, you know, I mean, it's nice that that you can look at this really simply and come up with a list, you know, cookbook things we can test. And um and so we've done that. We've gone and said, what are the possibilities? Well, the most obvious possibility is that there is more mass than we can see. there's black holes, there's uh um hydrogen gas that we can't see, whatever. There's something out there. So, that was the first thing. So, you go and you look and there's no hydrogen gas because we can see that with radio waves. That's not it. Um in the '9s, we went looking for black holes, rogue planets, things like that. Those exist, but not enough of them. That's not it. And so now we're left with there's some sort of matter that we can't see or we don't understand gravity or we don't understand inertia. Now I personally if you asked me this oh I don't know 25 years ago I would have said the most likely uh answer is that we don't understand inertia or gravity. You know I if 20 years ago 25 years ago that's what I would have said. No problem. However, there have been a couple of observations that um that have caused me to change my thinking and I think that dark matter is more likely. One of them is called the bullet cluster. So, the bullet cluster there are two large clusters of galaxies. In these large clusters of galaxies, well, any galaxy consists of a couple of components. There are the galaxies themselves. There is the hydrogen gas that surrounds the galaxies. And maybe there is dark matter. And if dark matter is real or dark matter is not real, you will get different answers if those two galaxies pass through one another. The galaxies themselves should pass through one another basically not interacting. But the big thing is the gas clouds. So if there's big clouds of gas, as the galaxies pass through one another, the clouds should interact and the gas cloud should stop in the middle and be really really hot. So then you would see if there were no dark matter, you would see a cluster of galaxies, a cluster of galaxies, a big gas cloud in the middle. And because the big gas cloud in the middle is much more massive than the galaxies themselves, you would expect to see distortions that we call dark matter distortions in the middle. If however, dark matter is real, the galaxies pass through one another. The cloud stops. dark matter doesn't interact with the clouds so it passes through. In that case, you would expect to see the distortions where the galaxies are

好吧。那么，第一件事，也是最重要的一件事——因为我可是个实打实的实验物理学家——第一件事是：我们为什么相信存在暗物质？原因是天文观测的结果与牛顿理论或相对论的预言不符。星系自转得太快。星系团运动得太快。还有，远处星系的图像因为近处星系的引力场而发生的扭曲，也与我们根据可见物质所做的预言不符。所以有三个非常独立的理由，让我们推断，我们对物理定律、或者对宇宙物质总账的理解出了问题。最容易讲清楚的是星系自转。我要强调，我接下来说的并不是星系自转独有的，只是它最好讲。所以，我们观测到星系自转的速度比“把我们看得见的引力加起来所应有的速度”要快。按理说，转得那么快的星系应该把自己甩散架才对，可它们并没有。那么答案会是什么呢？你一边有“恒星沿圆周运动所需要的力”，另一边有“引力提供的力”，二者用一个等号连起来，而这个预言是错的。所以要么是引力提供的力算错了，要么是做圆周运动所需的力算错了，要么是那个等号错了。其实非常简单，这三样里必有一样是错的。所以一种可能是：牛顿的万有引力定律——质量乘质量除以 r 的平方再乘一个常数——干脆就是错的。另一种可能是：我们在普通物理课上学的牛顿第二定律 F=ma 是错的。在这边，这两种都完全有可能。也许我们没真正理解引力，又或者存在比我们看得见的更多的质量。所以你看，能这么简单地审视这个问题、列出一张清单、像照菜谱一样逐项去检验，这挺好的。我们也确实这么做了。我们去问：有哪些可能？最显而易见的可能是：存在比我们看得见的更多的质量——有黑洞、有我们看不见的氢气，等等，外面有某种东西。这是第一件要查的。于是你去看，结果没有那么多氢气，因为我们用射电波能看到氢气，不是它。九十年代我们去找黑洞、流浪行星之类的东西，这些确实存在，但数量不够，也不是它。于是我们就剩下这几种可能：存在某种我们看不见的物质，或者我们没理解引力，或者我们没理解惯性。就我个人而言，如果你在——哦，我也说不准——二十五年前问我，我会说最可能的答案是我们没真正理解惯性或引力。要是二十年、二十五年前，我会毫不犹豫地这么说。然而，后来有几项观测让我改变了想法，如今我认为暗物质更有可能是真的。其中一个叫子弹星系团(bullet cluster)。在子弹星系团里，有两个巨大的星系团。任何一个大星系团都由几部分组成：星系本身；环绕星系的氢气；也许还有暗物质。如果暗物质是真实的、或者暗物质不是真实的，那么当这两个星系团相互穿过时，你会得到不同的结果。星系本身相互穿过时基本上不会发生相互作用。但关键在于那些气体云。如果存在大团的气体云，当星系相互穿过时，气体云会发生相互作用，于是气体云会停在中间，并且变得极其炽热。所以，如果没有暗物质，你会看到：一团星系，另一团星系，中间夹着一大团气体云。而由于中间这团大气体云比星系本身重得多，你会预期在中间看到我们称之为“暗物质式扭曲”的引力透镜扭曲。但如果暗物质是真实的，星系相互穿过，气体云停在中间，而暗物质不和气体云发生相互作用，所以它会径直穿过去。在这种情况下，你会预期在星系所在的位置看到那种扭曲——

[2:32:43] Don

and that's what we see. So that is a strong evidence in my mind. The bullet cluster is strong evidence that dark matter is a real thing. And there is another example which is much more recent. Dark bullet cluster was a while ago called the dragonfly galaxies. There's dragonfly 2 and dragonfly 4. These are galaxies that rotate exactly according to Newton's laws. And so the fact that they rotate exactly according to Newton's laws says that whatever is causing galaxies to rotate too fast is not a property of matter. But if you had a galaxy where there was no dark matter, for whatever reason, it got stripped off or something, this is one of those lovely ironies that the existence of a galaxy with no dark matter is very strong evidence that dark matter is real because you can take the dark matter out. So the DF2 and DF4 also suggests to me that dark matter is real. So now while it remains possible that um we need to modify the laws of inertia or we need to modify the laws of gravity those are possible still in my opinion and now this is Dawn's opinion but it's probably the opinion of most of the the scientific community. Dark matter is likely a real thing. Now that's great. I've taken you all the way to dark matter. So now you're going to ask me. You're going to say, "Don, what is dark matter?" I'm going to I don't know. But I know what it isn't. Okay? I know that it is not black holes. I know that it is not rogue planets. I know that we've done the measurements. We've looked across nearly every mass range for compact objects and ruled them out. So if dark matter is real, it can't be made of those. So then you're left with the idea that dark matter is a particle. And that's what we've thought about. The name for the the dark matter particle that we've called for a long time is a wimp for a weekly interacting massive particle. And we have spent the last god 30 years looking for them in the various ways. There are three ways that we might see dark matter. The direct way which says that dark matter exists literally everywhere in this room in our laboratory and the dark matter is passing through the earth like a wind and we put up detectors trying to see those. We have done that and we've seen nothing.

而这正是我们观测到的。所以在我看来这是强有力的证据。子弹星系团是暗物质确实存在的有力证据。还有另一个例子，要新近得多。子弹星系团是有些年头的事了，这个新例子叫蜻蜓星系(dragonfly galaxies)，有蜻蜓2号和蜻蜓4号。这些星系的自转完全符合牛顿定律。它们恰好严格按牛顿定律自转这一事实说明：不管是什么东西导致星系自转过快，那东西都不是物质的某种属性。但如果你有一个不含暗物质的星系——不管出于什么原因，它的暗物质被剥离掉了之类的——这里就有一个绝妙的反讽：一个不含暗物质的星系的存在，恰恰是暗物质真实存在的强有力证据，因为你可以把暗物质从里面拿走。所以蜻蜓2号和蜻蜓4号也让我倾向于认为暗物质是真实的。所以，如今虽然“我们需要修改惯性定律”或“我们需要修改引力定律”这两种可能依然存在——在我看来它们仍然有可能——这是 Don 个人的看法，不过这大概也是科学界大多数人的看法：暗物质很可能是真实存在的。好了。我已经把你一路领到暗物质这儿了。所以现在你要问我了，你会说：“Don，暗物质到底是什么？”我会说，我不知道。但我知道它不是什么。好吧？我知道它不是黑洞。我知道它不是流浪行星。我知道我们做过测量，我们几乎在每一个质量区间里都搜寻过这类致密天体，并把它们排除掉了。所以如果暗物质是真实的，它就不可能由那些东西构成。于是你就剩下一个想法：暗物质是某种粒子。这也正是我们一直在思考的。长期以来，我们给暗物质粒子起的名字叫 WIMP，即弱相互作用大质量粒子(weakly interacting massive particle)。过去整整三十年，我们用各种方式去寻找它们。我们可能看到暗物质的方式有三种。一种是直接探测，它的前提是暗物质字面意义上无处不在——就在这个房间里，就在我们实验室里——暗物质像一阵风一样穿过地球，我们架起探测器，试图捕捉到它们。我们做了，结果什么都没看到。

[2:35:06] Lex

So we should say we have done that for nutrinos.

我们应该说明一下，对中微子(neutrino)我们就是这么做的。

[2:35:08] Don

We've done that for many different types of dark matter. We just simply put detectors in labs deep underground and we can see nutrinos in them. It's true. But dark matter would have especially heavy dark matter what these these wimps um they have a different signature and we've seen no evidence of dark matter interaction in these detectors. So nutrinos are also weakly interacting and also have mass they are

我们对许多不同类型的暗物质都试过这套办法。我们只是把探测器放到地下很深的实验室里，而我们在里面确实能看到中微子，这是真的。但暗物质——尤其是重的暗物质，也就是这些 WIMP——会有不同的信号特征，而我们在这些探测器里没看到任何暗物质相互作用的迹象。所以中微子也是弱相互作用的，也有质量，它们是——

[2:35:34] Lex

but not enough ma. So wimps are

但质量不够。所以 WIMP 是——

[2:35:37] Lex

heavy on the um

在质量这方面比较重，

[2:35:38] Don

right? Nutrinos are indeed wimps of a sort. Now we have to be careful what we mean by wimps. They are weakly interacting massive particles but we can calculate and there's just not enough mass in them. It's not it.

对吧？中微子的确算是某种意义上的 WIMP。这里我们得小心“WIMP”这个词的含义。它们是弱相互作用的大质量粒子，但我们可以算出来，它们身上的质量就是不够，所以不是它。

[2:35:50] Don

Got it. So we need another form and we have seen zero evidence of this wind of dark matter through the uh the earth. Another possibility is you look where you think dark matter might be concentrated at the center of galaxies and if dark matter exists and there's antimatter dark matter maybe they annihilate and make photons. And so we look for gamma rays and various other signatures of annihilating dark matter. And there are always constantly announcements of oh we saw it oh we didn't oh you know the problem is that way of looking for dark matter is hard because there are other ways of making for instance gamma rays like neutron stars and stuff and you really need to understand the details of galaxies really really well to believe that and then the final option is what I do where we smash particles together at high ma or high energy we try to make dark matter particles If you make dark matter particles because they don't interact except via gravity, they escape with your detector. So what you're seeing, what you hope to see is an event where you collide particles, a dark matter particle escapes and you don't see it, but the recoil you see on the other side because momentum is conserved. So you see a blob of energy on this side, nothing on the other side. Maybe that's dark matter. And that also happens with nutrinos. So you need to understand everything about nutrinos and calculate how many of those you see and then hope you see more and then that might be dark matter again that hasn't worked. So we've ruled out some dark matter particles but the problem is the range of space of possible mass if dark matter is of a particulate form. The range of viable dark matter ranges from something like the mass of an asteroid to far lighter than an electron and everywhere in between. And we have looked, we've ruled out some little spots in that phase space, but that's a big range.

明白了。所以我们需要另一种形式的暗物质，而对于这股穿过地球的暗物质“风”，我们看到的证据是零。另一种可能是：你去看你认为暗物质可能聚集的地方，比如星系中心；如果暗物质存在，而且存在反物质暗物质，也许它们会湮灭并产生光子。于是我们去寻找伽马射线以及暗物质湮灭的各种其他信号。而总是不断有人宣布：“哦，我们看到了”“哦，我们没看到”，你懂的。问题在于，这种寻找暗物质的方式很难，因为还有其他途径也能产生比如说伽马射线，像中子星之类的东西，你必须把星系的细节理解得非常非常透彻，才敢相信那个信号。最后一种选择就是我所做的：我们让粒子在高质量、或者说高能量下相互对撞，试图制造出暗物质粒子。如果你造出了暗物质粒子，由于它们除了通过引力之外不与任何东西相互作用，它们就会带着能量逃离你的探测器。所以你看到的、你希望看到的，是这样一种事件：你让粒子对撞，一个暗物质粒子逃逸了，你看不见它，但由于动量守恒，你能在另一侧看到反冲。也就是说，你在这一侧看到一团能量，另一侧却什么都没有。也许那就是暗物质。可中微子也会造成同样的现象。所以你必须把关于中微子的一切都搞清楚，算出你预期能看到多少个这样的事件，然后指望你看到的比那个数目更多，那多出来的部分也许才是暗物质——结果，这条路同样没走通。所以我们排除掉了一些暗物质粒子，但问题在于：如果暗物质是粒子形态的，那它可能的质量范围实在太大了。可行的暗物质质量从大约一颗小行星的质量，一直跨越到远比一个电子还轻，中间所有区间都包括在内。我们也搜寻过，在那片相空间里排除掉了一些小小的角落，但那毕竟是个极其巨大的范围。

[2:37:50] Don

Is it really possible to miss a particle the size of an asteroid? the astronomical searches were not sensitive to that level of of dark matter, but you know, then you would expect that there would be some of those in the solar system. And if they're what we think like asteroids or something, then we'd heat them up and we'd eventually see them. But if they're really like truly dark matter doesn't interact with matter, which means they wouldn't absorb energy from the sun, so they'd be really dark. I don't know, maybe they're out there. But the only way we have we searched for them was um a thing called microl lensing. So if a massive object you have a distant star and a massive object pass between that star and your eye that star will momentarily brighten.

真的有可能漏掉一颗小行星那么大的粒子吗?天文观测对那个层级的暗物质(dark matter)其实并不灵敏。不过你想,如果真有这种东西,太阳系里应该也会有一些。要是它们像我们想的那样,类似小行星之类,那我们会把它们加热,最终就能看到它们。但如果它们真是纯粹的暗物质,完全不和普通物质相互作用,也就不会吸收太阳的能量,那它们就会非常暗,根本看不见。我不知道,也许它们就在那儿。我们搜寻它们唯一的办法,是一种叫做微引力透镜(microlensing)的现象。如果一个大质量天体——你有一颗遥远的恒星,一个大质量天体从这颗恒星和你的眼睛之间穿过——那颗星就会瞬间变亮。

[2:38:41] Don

Mhm. And so you just look for these what they call microl lensing events and you count them and you see some and we did see some you know black holes pass in front of stars and and we've seen them but we just haven't seen enough. And for very low mass particles like asteroids they um they just wouldn't make enough brightening effect to see. So there's like a minimum sensitivity of brightening and that about a third the mass of a moon. Our moon is about the sensitivity that we had. So you know that nobody I think really thought that these low mass guys were likely. What they thought was more likely they were just unseen black holes which I thought you know I think is completely reasonable. Then when that got ruled out I thought okay modified gravity or uh

嗯。所以你就去找这些所谓的微引力透镜事件,把它们数出来。我们确实看到了一些,比如黑洞从恒星前面经过,这种我们见过,但数量就是不够多。而对于像小行星那样质量极低的粒子,它们产生的增亮效应太弱,根本看不到。所以增亮存在一个最低灵敏度的门槛,大概在三分之一个月亮质量左右——我们当时的灵敏度差不多就是我们月球的这个量级。所以我觉得其实没人真的认为这些低质量的家伙有多大可能。大家觉得更有可能的,是一些看不见的黑洞,这个我觉得完全合理。可后来这条路也被排除了,我就想,好吧,那要么是修正引力(modified gravity),要么是——

[2:39:32] Don

or inertia. Well, now that you know, bullet cluster and dragonfly seems to ruled that out. So, I'm stuck in my head with dark matter seems to be real and it we don't know what it is

——要么是修正惯性(modified inertia)。可现在你看,子弹星系团(bullet cluster)和蜻蜓星系(dragonfly)的观测似乎又把这些都排除了。所以我脑子里就卡在这个结论上:暗物质看起来是真实存在的,可我们却不知道它到底是什么。

[2:39:43] Don

and it makes up a giant percentage of matter in the universe.

而且它占了宇宙中物质的极大一部分。

[2:39:46] Lex

It is five times more prevalent than ordinary matter.

它的总量是普通物质的五倍。

[2:39:50] Don

This is incredible. It is so fascinating and that's why it's cool. So, if someone out there is, you know, a young person wants to get into this, understanding dark matter is a big deal. I mean, it's five times more prevalent. The problem is is, as I told you, if the mass is ranging from an asteroid to far lighter than an electron, if you get on an experiment that looks at one little range of mass, maybe you weren't the lucky guy that measured the right place, you know, and that's one of the reasons why, as fascinating as I think it is, I'm not doing dark matter experiments, because, you know, if you make an experiment that searches one mass range, it'll be blind to another mass range. So what you need is you need many groups doing all sorts of radically different experiments exploring all sorts of parameter space. And with all that said, until you see it, there still is the possibility that maybe we don't understand gravity or inertia, right? You know, you can't rule that out.

这太不可思议了。它实在太迷人了,而这正是它酷的地方。所以,如果有哪个年轻人想投身这个领域,搞懂暗物质是一件大事——我是说,它的量是普通物质的五倍啊。问题在于,正如我跟你说过的,如果它的质量范围从一颗小行星一直跨到比电子还轻得多,那你要是上了某个只盯着一小段质量区间的实验,也许你就不是那个碰巧测对了地方的幸运儿。这也是为什么——尽管我觉得它无比迷人——我自己并不做暗物质实验:因为你做的实验如果只搜索某一段质量区间,就会对另一段区间完全失明。所以你需要的是许多团队,做各种千差万别的实验,去探索各式各样的参数空间。说了这么多,在你真正看到它之前,仍然存在一种可能:也许是我们没搞懂引力或惯性,对吧?这个你没法排除。

[2:40:51] Lex

If there is dark matter out there, you're hoping it's actually somehow detectable.

如果暗物质真的存在,你是希望它最终能以某种方式被探测到。

[2:40:56] Don

I mean, I don't know what it is. I think it's cool. It's very, very fascinating. That is one thing I really do hope in my lifetime is is understood because I' I'd like to know the answer to that.

我是说,我不知道它是什么,但我觉得它很酷,非常非常迷人。这是我这辈子真心希望能被搞清楚的事情之一,因为我很想知道那个答案。

[2:41:07] Lex

And that that's the thing that you could there legitimately you can see a discovery of.

而且这是那种你确实有可能亲眼见证一项发现的领域。

[2:41:12] Don

You got to get lucky though. I mean you got to look in the right place whatever it is.

不过你得走运才行。我是说,不管它到底是什么,你得朝对的方向去找。

[2:41:16] Don

Just imagine or you have to come up with that really cool theoretical idea that everybody's overlooked which is another possibility. And there are people who are really really religiously hating dark matter largely because we've looked so hard for so many years and the experiments in today's world are a million times more sensitive than when I was a a starting student and they still haven't seen anything and that's why people really hate dark matter. I mean some of them because they think we should have seen it by now but

想象一下,或者你得想出某个所有人都忽略了的、真正绝妙的理论想法——这也是另一种可能。还有一些人简直是带着宗教般的狂热在憎恨暗物质,很大程度上是因为我们这么多年来找得这么辛苦,而如今的实验比我还是个新生时灵敏了上百万倍,结果还是什么都没看到——这正是有些人那么讨厌暗物质的原因。其中一部分人之所以这样,是因为他们觉得我们到现在早该看到它了,可是——

[2:41:46] Lex

you know uh I don't know. I mean, I'm a sucker for direct observation. Not indirect is obviously also really great, but direct. Just imagine pointing your telescope in a certain direction and because of some artifact of cosmology being able to directly detect a giant amount of of a thing that you could say is dark matter.

你知道,呃,我也说不好。我是说,我是直接观测的死忠粉。间接证据显然也非常棒,但我还是偏爱直接的。想象一下,把你的望远镜对准某个方向,因为宇宙学的某种巧合,就能直接探测到一大团你可以确认是暗物质的东西。

[2:42:07] Don

Yeah. You would see it orbit things orbit it or it would eclipse things in front of it or

对。你会看到东西绕着它转,或者它从某些东西前面经过把它们遮住,或者——

[2:42:13] Don

Yeah. like in an obvious way cuz uh some of the stuff you mentioned with DF2 and DF4 those are like brilliant indirect um deductions that there should be something like dark matter but some obvious yeah blocking oluding this kind of thing we did that in the 90s with experiments called macho ogle and some others they looked for a black hole that you just can't see you know black hole you can't see it's perfect it's a perfect candidate for dark matter. And if there's enough of them out there, remember there's five times the number of stars, which means there's a whole lot of freaking black holes out there. We should have seen them and we didn't.

对,就是那种很明显的方式。因为你刚才提到的 DF2 和 DF4 那些东西,是非常精彩的间接推断,推出应该存在某种类似暗物质的东西,但要是有更直观的——对,那种遮挡、掩食之类的现象。我们在九十年代就做过这种事,用了几个叫 MACHO、OGLE 之类的实验,它们寻找那种你根本看不见的黑洞。你知道,黑洞看不见,它简直是暗物质的完美候选者。如果外面真有足够多的黑洞——记住,暗物质的量是恒星的五倍,这意味着外面该有一大堆该死的黑洞——我们本该看到它们,可我们没有。

[2:42:57] Lex

What a grand mystery. We covered so many of them. I could talk to you for a thousand more hours. Don, let me if I can uh ask you about a little bit more of a on the personal side. Um, you have a really inspiring life story. Your folks didn't uh go to college. Can you just tell me about your childhood and where you found the love for physics and science and maybe how you found your journey to to to become a physicist given the the context of where you came from? Well, uh, you know, I grew up a poor kid in the Boondocks. Great parents, but not ones that could guide me terribly academically, but very, uh, very nurturing. You know, my mom would laugh that she could stop helping me math after like sixth or seventh grade, you know. Um, but they were supportive. And there were a couple of things that couple three things I think that folded into it. One is I was a voracious reader as a kid. I loved science fiction. I would read a book a day. It drove my mother nuts cuz she would try to be nice. She'd buy me a book and I'd say thank you and the next day it'd be done. You know, it just drove her completely nuts. But anyways, but science fiction is good for fostering imagination. And so that's precisely what it did. In addition, um, and this is where the more serious science came along, there were lovely science communicators that were popular in the 1970s. Isaac Azimoff, Carl Sean, guy by the name of George Gamma. They wrote books about science aimed at a lay person. I was a kid. I surely couldn't read a a textbook and understand it, but I could read and and you know, get a a hint of what science was. And on top of that, you know, I was, as most scientist, people who became scientists, irrepressibly curious about everything. Um, and I had sort of a quasi philosophical mind. I mean, I was interested in things that questions that have in the past been theological and then philosophical and now are more scientific. Questions about how did the universe come into existence? Um, why is the universe the way it is? Why are the laws of the universe what we see them to be? How will the universe was it created? How will it be destroyed? These are, you know, big questions that have bothered humanity for, well, thousands of years. And so, you know, I did you you said I had uh um you know, philosophy and religion minors in college, and I did because I was curious about that. Um I was hoping that learning that history might help me understand these questions. Um and it was in college where I came to realize that the answers that I were searching for were not to be found in those directions, but I still learned about how those questions have been asked in the past. Um, and so I became a a scientist and the only question was was I going to be uh a cosmologist/astrophysicist or a particle physicist. And when I had to make that decision, it was the mid80s. And at the time, there were a lot fewer cosmology measurements. There was an awful lot of thinking about the universe and not enough measuring. Whereas with uh particle physics, by God, you could do experiments. And so the what attracted me was the ability to actually get an answer and not just mull over what an answer might be. And so I became a particle physicist. Um it was difficult without having you know uh family mentors or anything like that but but you know I managed and that actually is why well I'm here and why I have spent a fair bit of my time writing books and so forth because I figure that there has to be some other kid out there in Iowa, Kansas, Montana somewhere out in some little town without a lot of access to the kinds of thing that people, you know, who have highly educated parents do. And I'm hoping that, you know, some of them will have read some of the things I've written and will find their own path forward because I found it very rewarding over the years. And um, you know, I've been doing this long enough that I'm I'm sure this is true. I've had kids come up to me at the lab and say, "Hey, I'm a summer intern because I saw your video or read your book or you know, whatever." Um, so I know that at least I've made a small impact. I mean, always would like to do more and, you know, I appreciate the uh opportunity that your uh audience affords me um cuz I I think it's important to talk about these things. These are really cool, fascinating questions. They are unanswered and they are just waiting for youngsters to come and spend some time thinking about them because one of your viewers might be one of the people who answer these questions that have stymied very smart people for decades.

多么宏大的谜题啊。我们今天聊了这么多。我能跟你聊上一千个小时。Don,如果可以的话,我想问一些更偏个人的话题。嗯,你的人生故事非常励志。你父母没上过大学。能不能跟我讲讲你的童年,你是在哪里找到对物理和科学的热爱的,以及在你出身的那种背景下,你又是怎么一路走来成为物理学家的?嗯,你知道,我是在穷乡僻壤长大的一个穷孩子。父母很好,但他们没法在学业上给我太多指引,不过非常、非常地呵护我。我妈常笑说,她大概帮我做数学作业到六七年级就帮不上忙了。但他们一直很支持我。我想有几件事——大概三件事吧——共同促成了这一切。第一,我小时候是个如饥似渴的读者,特别爱看科幻小说,能一天看完一本书。这把我妈逼得快疯了,因为她想对我好,会给我买本书,我说声谢谢,第二天就看完了,这彻底把她整懵了。但不管怎样,科幻小说很适合培养想象力,而它确实就起了这个作用。除此之外——这就要说到更正经的科学了——七十年代有一批很棒的科普作家很受欢迎,比如艾萨克·阿西莫夫(Isaac Asimov)、卡尔·萨根(Carl Sagan),还有一位叫乔治·伽莫夫(George Gamow)的。他们写面向普通人的科学书。我那时还是个孩子,肯定读不懂教科书,但我能读这些书,大致领会到科学是什么样子。再加上,你知道,我和大多数后来成为科学家的人一样,对一切都抱有抑制不住的好奇心。而且我多少有种近乎哲学的心性。我是说,我感兴趣的那些问题,过去曾属于神学,后来属于哲学,如今则更多属于科学了:宇宙是怎么诞生的?为什么宇宙是这个样子?为什么我们看到的宇宙定律是这样的?宇宙是怎么被创造出来的?它又将如何毁灭?这些都是困扰人类好几千年的大问题。所以你知道,你刚才说我在大学辅修了哲学和宗教,我确实辅修了,因为我对这些好奇。我当时希望了解这段思想史能帮我理解这些问题。但正是在大学里,我意识到我所追寻的答案并不在那些方向上;不过我仍然学到了过去人们是如何提出这些问题的。于是我成了一名科学家,剩下唯一的问题就是:我到底要做宇宙学家/天体物理学家,还是粒子物理学家。等到我得做这个决定时,已经是八十年代中期了。那会儿宇宙学的测量手段少得多,人们对宇宙有大量的思考,却没有足够的测量。而粒子物理学呢,天哪,你是真能做实验的。所以吸引我的,正是那种能真正得到答案、而不只是反复琢磨答案可能是什么的能力。于是我成了粒子物理学家。没有家里的引路人之类的支持,这条路走得挺难,但你知道,我还是熬过来了。这其实也正是我如今为什么在这里、为什么花了相当一部分时间写书等等的原因:因为我想,在爱荷华、堪萨斯、蒙大拿,在某个小镇上,一定还有别的孩子,接触不到那些父母受过高等教育的人能轻易得到的东西。我希望,他们中有些人能读到我写的东西,从而找到属于自己的前路——因为这些年来,我觉得这件事非常有回报。而且,你知道,我干这行干得够久了,所以我敢肯定这是真的:有孩子在实验室里走到我面前对我说:'嘿,我来做暑期实习,就是因为看了你的视频、读了你的书,或者别的什么。'所以我知道,至少我产生了一点点影响。我是说,我总想做得更多,也很感激你的听众给我的这个机会,因为我觉得谈论这些事很重要。这些都是非常酷、非常迷人的问题,它们悬而未决,正等着年轻人来花些时间思考——因为你的某位观众,说不定就是那个能解答这些把绝顶聪明的人难倒了几十年的问题的人。

[2:48:18] Lex

And we should also say that you're a legit scientist. So we we'll mention Sean Carol who's a legit scientist, legit physicist, but is also a good science communicator. Anyway, I did want to mention, I don't know if this is true, but I I kind of heard you talk about this, that when you first showed up to Firmeny Lab, you were like working crazy hours, working extremely hard,

我们还应该说一句,你是个正儿八经的科学家。我们会提到 Sean Carroll,他也是个正经的科学家、正经的物理学家,同时还是个很好的科普传播者。总之,我想提一件事——我不知道是不是真的,但我好像听你讲过——你刚到 Fermilab 的时候,据说工作起来时间长得吓人,拼命地干。

[2:48:41] Lex

8:00 a.m. to midnight.

从早上八点干到午夜。

[2:48:43] Don

I did.

我确实是这样。

[2:48:44] Lex

Uh, first of all, I love that.

呃,首先,我特别喜欢这一点。

[2:48:47] Lex

Uh, can you speak to what drove you and maybe the value of hard work in those context in your in the early career when you discover a thing you're passionate about? Well, yeah. I mean, obviously being smart, you know, if you're Einstein, then maybe you can slack, I guess. Although even he didn't do that, but I'm not Einstein. But the fact is when I was young and I was unencumbered, no no family, no kids or something. I couldn't imagine anything I wanted to do more. I mean, some people they want to go out to the club, they want to, I don't know, play soccer or something, but I wanted to make measurements and I wanted to understand and and and learn, and that was fantastic. And so, as a graduate student, and this isn't for everybody, but I worked outrageously. I would from Monday through Saturday, I would be at the lab voluntarily because I wanted to be from 8:00 a.m. to midnight. And on Sunday, I would work from 8 until about 5:00. And that's because from 5 to midnight I had to wash clothes and buy groceries and things like that. And I loved it, you know, uh, and I still love it. I can't do that anymore. Um, but but that's simply because I have other obligations, but had I been rich, I would have done the same thing. You know, it's it's something I truly truly loved. And the I mean there is absolutely nothing more fascinating to me than having a hard problem and figuring it out. And that you know that work ethic. Well, there's a couple of things that separate smart people from no kidding scientists cuz all scientists are smart. But the thing that that separates that that that many scientists have is a a drive and a real grit. the um for me and for so many scientists that I know trying to measure something and having it not work just kind of ticks me off and I am not going to let the universe in my lab or whatever beat me. And you know some people they you know if the thing breaks it's like oh man that didn't work and a lot of people well I'm going to go home I'm fed up. No, it would just kind of make me mad and I'd put more effort into it. And you know, not every I mean, okay, I was crazy. I worked long hours, but but I think the people who are really good at this will do maybe not that much. You know, some people have to have a better life than that, but but a lot because it it's just you can't imagine not knowing the answer. Mhm.

呃,你能不能谈谈是什么驱动着你,以及在你刚发现自己热爱的事业、还处在职业生涯早期那段时间里,努力工作的价值在哪里?嗯,是这样。我是说,聪明当然有用——你知道,如果你是 Einstein,那也许还能偷点懒,我猜。不过其实连他都没偷懒。可我不是 Einstein。事实是,我年轻的时候无牵无挂,没有家庭,没有孩子。我想象不出还有什么是我更想做的事。我是说,有些人想去夜店,想去——我也说不好——踢踢足球之类的,可我想做的就是做测量、是去理解、去学习,那感觉棒极了。所以读研究生那会儿——这并不适合每个人——我拼到了离谱的程度。从周一到周六,我都自愿待在实验室,因为我就是想待在那儿,从早上八点干到午夜。周日呢,我从八点工作到大约下午五点。之所以只到五点,是因为五点到午夜我得洗衣服、买杂货之类的。我热爱这一切,你知道,我现在依然热爱。只是我再也没法那样干了。嗯,但那纯粹是因为我有了别的责任要担。要是我那时很有钱,我也会一模一样地那么干。这是我真心真心热爱的东西。我是说,对我来说,世上再没有比手握一个难题、然后把它破解掉更迷人的事了。还有就是那种工作伦理。其实有几样东西把聪明人和货真价实的科学家区分开来——因为所有科学家都聪明,可真正把许多科学家区分出来的,是一股劲头和真正的韧性(grit)。对我、对我认识的那么多科学家来说,想测量某个东西却测不出来,会让我憋着一股火,我绝不会让宇宙、让我实验室里的东西、或者别的什么把我打败。你知道,有些人,东西一坏,就'哎呀,这下不行了',然后很多人就'算了,我回家了,我受够了'。可我不会,那只会让我更来气,然后我会投入更多精力去搞它。而且你知道,不是说每个——好吧,我承认我那是疯了,我工作时间长得离谱。但我觉得,真正擅长这行的人也许不用拼到那个份上。有些人需要过得更有生活气息些,但仍然得投入很多,因为那感觉就是——你没法忍受不知道答案。嗯。

[2:51:30] Don

And that if when when you see that as an older guy, you don't maybe not to that degree, but when you see that kind of drive, that that that intensity of trying to get the answers, you know that person's a winner. And and so if you know some student out there, if it doesn't, you know, bring you joy, as uh what's her name? The Japanese girl says, if it doesn't bring you joy, then it might not be for you. And then you could be a person who reads about it and you know is involved. But if you want to be a real scientist, it it has to be just part of what you are here.

而且,等你上了年纪,也许做不到那个强度了,可当你看到别人身上那种劲头,那种拼命想得到答案的强烈劲儿,你就知道这个人是个赢家。所以,如果你认识某个学生——如果这件事不能给你带来快乐,就像那个谁——那个日本姑娘说的——如果它不能给你带来快乐,那它也许就不适合你。那你可以做一个读读相关读物、参与其中的人。但如果你想成为一个真正的科学家,它就必须成为你之所以是你的一部分。

[2:52:06] Lex

And by the way, it is a hard life, but it is also a very fulfilling one. So working hard towards the thing you love is a really fulfilling way to to be. I think that's true for an artist or something, you know, anybody, a musician, you know, musician, they just keep practicing because it is who they are.

顺便说一句,这是一种艰苦的生活,但也是一种非常充实的生活。所以,朝着你所热爱的事情拼命努力,是一种极其充实的活法。我觉得对艺术家之类的人也是如此,对任何人都一样——比如音乐家,他们之所以不停地练习,是因为那就是他们本身。

[2:52:28] Lex

Well, I'm glad there's people like you at a place I admire like Fermy Lab, uh, one of the many places in the United States, in the world that, uh, is carrying the beacon of great science and great engineering forward. Uh, Don, thank you so much for everything you do, for all the teaching you do uh, online, for all the incredible physics work that you do at Firmay Lab, and uh, thank you so much for talking today.

嗯,我很高兴在 Fermilab 这样一个我敬佩的地方有你这样的人。Fermilab 是美国、乃至全世界众多扛着伟大科学与伟大工程这面旗帜不断向前的机构之一。呃,Don,非常感谢你所做的一切,感谢你在网上做的所有教学工作,感谢你在 Fermilab 做的所有了不起的物理研究,也非常感谢你今天来聊天。

[2:52:59] Don

Thank you for having me.

谢谢你邀请我。

[2:53:01] Lex

Thanks for listening to this conversation with Don Lincoln. To support this podcast, please check out our sponsors in the description where you can also find links to contact me, ask questions, give feedback, and so on. And now, let me leave you with some words from Marie Kuri, a twotime Nobel Prize winner. First in physics, second in chemistry. Nothing in life is to be feared. It is only to be understood. Thank you for listening. I hope to see you next time.

感谢收听这期与 Don Lincoln 的对话。想支持本播客,请查看简介里的赞助商,在那里你也能找到联系我、提问、反馈等的链接。最后,请允许我用 Marie Curie 的一段话作结——她是两届诺贝尔奖得主,第一次是物理学奖,第二次是化学奖。'生活中没有什么值得恐惧,只有需要去理解的东西。'感谢收听,我们下期再见。