内容来源：https://www.quantamagazine.org/is-there-anything-left-in-the-dream-of-cold-fusion-20261102/

内容总结：

围绕“冷聚变”是否还有研究价值的问题，科学界近年出现了一轮低调而持续的重新审视。曾因1989年两位化学家宣称在桌面实验中实现氢核聚变而引发全球轰动，但随后多国实验室无法复现，相关实验被撤回，个别案例还牵涉数据造假，使这一领域长期背负污名。如今，部分哲学家和投资人主张，不应因当年的学术丑闻而一并否定相关研究方向。剑桥大学哲学家休·普莱斯认为，科学界对冷聚变的态度过于轻率，并援引其参与撰写的论文指出，即便主结论不成立，这类研究也可能带来有价值的科学发现。风险投资家马特·特雷维西克则通过谷歌支持的项目系统梳理相关文献，2019年在《自然》发表论文，虽未发现异常核反应，但称该项目“为一个领域摘掉了污名”，并产出28篇关于氢化金属等课题的学术论文。

报道指出，真正引起物理学家持续兴趣的并非1989年那场争议本身，而是“μ子催化聚变”这一更早提出、确实存在的物理过程。其原理是用质量更大的μ子等带负电粒子替换原子中的电子，使原子尺寸大幅缩小，从而在室温下促成核聚变。相关研究还涉及μ子氢、反质子氢、Kaonic原子等“奇异原子”，为检验量子电动力学、测量质子半径、探测中子皮结构以及寻找超出标准模型的新物理提供了极端精密实验平台。欧洲核子研究中心、日本质子加速器研究设施和美国国家标准与技术研究院等机构均有相关实验推进。日本中部大学物理学家冈田信二团队2026年春季首次直接测量了μ子氢分子发出的X射线，并称即便μ子催化聚变无法实现能量净增益，其反应产物仍可用于医用同位素制备或核废料处理。

文章认为，判断一项科学研究是否值得支持，不应只看其是否兑现“取之不尽的廉价能源”之类宏大承诺，而应看其研究纲领本身是否具有科学价值。1989年的冷聚变宣称未能通过这一检验，而μ子催化聚变及奇异原子研究则因其对基础物理和交叉学科的广泛意义而值得继续推进。受访科学家表示，驱动他们的是好奇心和惊奇感，而非名利预期。

中文翻译：

冷聚变的梦想还剩下什么？

引言

冷聚变：这个话题我已经有一阵子没想过了。它在2026年春天重新回到了我的视野中。我当时写了一篇关于科学家往往倾向于规避风险的文章，剑桥大学三一学院的哲学家休·普莱斯在Bluesky上回应了我，引用了他最近与人合著的一篇关于人们对冷聚变态度的论文。他认为科学家不仅对冷聚变过于不屑一顾，而且对他们“对冷聚变过于不屑一顾”这一说法也过于不屑一顾。仿佛为了证明他的观点，一家期刊刚刚拒绝了他的论文。我一直很欣赏普莱斯关于时间本质和因果关系的著作，所以我产生了兴趣。

1989年冷聚变争议爆发时，我正在远离尘嚣背包旅行，已经走了六个月。（那时候你可以这么做。）等我赶上新闻时，事情已经结束了。那年三月，两位化学家召开新闻发布会，宣布了一个简单的桌面实验，其释放的能量太多，不可能是单纯的化学反应。他们说这必然是核反应：氢原子核聚变形成氦。它承诺带来无限清洁、廉价的能源。物理学家们震惊了。这种事情按理说不可能在如此普通的条件下发生。政客们宣称我们所有的能源困境都将终结。但随后全球各地的实验室试图复现这个实验，却无法做到，于是一场声势浩大的围剿随之而来。整件事只持续了几个月。由于没有实时经历这一事件，加上我天生是个逆向思维者，我起初同情那些勇敢的独行侠科学家。但后来我读到了他们的新手错误、他们对一张关键图表的篡改，以及他们对质疑者发出诉讼威胁的做法。最初佐证结果的实验被撤回了，其中一例还伴有迹象表明有人故意掺入了虚假的聚变产物。

尽管冷聚变是一个病态案例，但聚变总体上是梦想的坟墓。我是在它唤起的梦想中长大的。无论聚变发生在室温下——就像冷聚变事件中 supposedly 发生的那样——还是发生在太阳核心的温度下——就像常规热核反应堆（和炸弹）那样——聚变都不需要露天开采（和处置）铀，也不需要护送油轮穿过霍尔木兹海峡。理想情况下，你所需要的只是一点海水。出于着迷，我曾根据《Make》杂志上的一篇文章在地下室里造了一个“聚变器”。聚变器是真实存在的，是唯一合法的桌面聚变技术。在聚变器中，高压产生炽热的等离子体，将原子核撞击在一起。我的装置没有实现聚变，但经过改进它本可以做到，尽管产生的功率微乎其微。我喜欢向客人展示它发出的紫色辉光等离子体，但我对聚变了解得越多，幻灭感就越强烈。几年后，一家私营聚变公司的朋友带我参观了一个真正的实验性聚变反应堆。它复杂且昂贵。廉价？算了吧。它产生强烈的致命中子辐射。清洁？算了吧。而且它需要氚燃料，氚在自然界中不存在，必须人工制造。只需一点海水？算了吧。

那么，像普莱斯这样一位善良的哲学家是怎么卷入这种事情的呢？通过Zoom，他解释说他的兴趣可以追溯到2011年，当时他和其他知名人士正在酝酿成立生存风险研究中心的想法。这个研究小组为核冬天、工程化生物武器、大规模火山喷发和人工智能接管而忧心忡忡——早在这种担忧成为时尚之前，它就已经敲响了警钟。普莱斯告诉我，他看到了末日情景与冷聚变之间的相似之处。它们可能看起来不太可能发生，研究它们是孤独的甚至边缘的活动，但后果是巨大的，所以我们应该给予它们比严格说来似乎应得的更多的重视。

我完全支持开放心态，但普莱斯的论点让我感到不安。肯定有成千上万的其他异常现象，它们为真的可能性与冷聚变相当，而且如果为真，同样能改变世界。为什么偏偏聚焦于这一个？我们之所以还在谈论冷聚变，唯一的原因是1989年我们被欺骗了。最初的谎言制造了一种心理锚定效应，使我们考虑了一个否则不会考虑的可能性。这就好比我说我在后院看到了大脚怪，然后承认我没有，但人们还是开始在附近每年举办隐生动物学会议。一个骗局竟然能催生出一整套学术研究计划，这让我感到震惊。这与反疫苗运动有什么不同？后者同样始于后来被证明是伪造的数据，而在真相大白后本应就此收场。

但既然已经掉进了这个兔子洞，我想不如继续走下去。普莱斯建议我和马特·特里维西克谈谈。

特里维西克是帕洛阿尔托风险投资公司Leitmotif的联合创始人。我通常不和风险投资人交谈，但我很快发现他的思路与普莱斯一致。特里维西克想要开启聚变时代，并支持一系列可能实现这一目标的技术。在我们的对话中，他还表现出一种非常硅谷式的习惯，总是直呼我的名字。

十年前，特里维西克在谷歌工作时组织了一个重新评估冷聚变的项目，最终在2019年发表了一篇《自然》论文。它没有发现任何意外的核反应或其他异常现象，但这并不是唯一的目标。特里维西克说，1989年的那场灾难给某些研究课题蒙上了阴影，而这些课题或许不应该被如此轻易地否定。例如，冷聚变研究者曾在实验中使用钯元素，钯具有像海绵一样吸收氢的奇妙能力，这种能力并不会因为与一场科学野鹅追逐有关联而减损其奇妙之处。特里维西克试图解除这一禁忌，他说该项目最终产出了28篇关于氢化金属和其他现象的学术论文。“乔治，”他说，“我们为一个领域去污名化了。”

于是我翻阅了那篇《自然》论文的参考文献，查找了一些我以前可能不会多加思考的课题。其中最吸引我的是μ子催化聚变。我认出这才是“冷聚变”一词的原始含义，在1989年的研究将其挪用之前。当我深入了解它的含义时，我发现物理学内部有一个活跃的研究计划，它创造出奇异种类的原子和分子，有时是为了尝试将它们聚变在一起，但更广泛地说，是为了寻找新的基本自然规律。

由于仍然对冷聚变的可疑名声保持警惕，我联系了我信任的物理学家以了解更多。其中一位是罗马附近意大利国家核物理研究所的卡特琳娜·库尔恰努。三年前我曾拜访过她，观看她测试量子力学基础的实验。她温和地提醒我，她当时也跟我讲过奇异原子。我想我当时太专注于她的其他工作，以至于没有跟进。“这是一个值得发现的全新世界，”她说。“有时我把它们叫做‘转基因原子’，但我不再这么叫了，因为，你知道的。”

构建μ子催化聚变的核心思想很简单。普通原子由一个带正电的原子核和围绕其运行的带负电的电子组成。但没有理由说它们必须是电子。其他带负电的粒子同样可以胜任。在粒子物理学的标准模型中，电子有一个叫做μ子的兄弟可以替代它。物理学家还替换过其他家族的粒子，比如K介子、π介子和Ξ重子。他们甚至创造过物质和反物质的杂化物，其中含有质子的原子核被带负电的反质子环绕。简而言之，你可以有普通氢、μ子氢、K介子氢、反质子氢，等等。

“这就像一张新的元素周期表，”科罗拉多州博尔德市美国国家标准与技术研究院的实验物理学家丹尼尔·斯韦茨说，他建造超精密探测器来测量这些奇异原子发出的辐射。“你几乎是在第三维度上把它构建出来。”

这些奇异原子的主要区别在于电子替代物要重得多。μ子的质量是电子的207倍；反质子是1，800倍。根据量子力学，每个物体最终都具有波的性质，质量越大，波长越短。因此，μ子原子比普通原子小多达207倍（取决于化学同位素）；反质子原子小多达1，800倍。当物理学家想要传达原子的尺度时，他们经常把原子核比作一颗弹珠，把整个原子比作弹珠周围的一个足球场。然而，对于反质子原子来说，原子不是一个足球场，而只是一个足球。

“整个系统坍缩了，”巴黎卡斯特勒-布罗塞尔实验室的物理学家南希·保罗说。她正在探索使用更重的带负电粒子来进一步缩小原子。“这在物理学中太罕见了，尤其是当今，你能遇到一个什么都没做过的领域。”

原子缩小会增强其内部的电场。根据库仑定律——它是牛顿万有引力定律的电学对应物——电场强度与距离的平方成反比。那么，对于K介子原子或反质子原子，电场强度会增大一百万倍。这为现代物理学的核心支柱——量子电动力学（QED），即电磁学在量子层面如何运作——提供了一次压力测试。“这是你在实验室中能创造的最强库仑场，用来探测QED，”保罗说。

事实上，它突破了所谓的施温格极限——量子效应失控、真空变得不稳定的阈值。粒子开始从虚无中自发地涌现出来。“你正在用更强的场煮沸真空，”她说。物理学家在20世纪30年代就预言了这种粒子沸腾现象，但至今尚未直接观测到，不过他们利用奇异原子已经辨识出一种密切相关的现象。2026年春天，库尔恰努和她的同事利用处于施温格极限以上电场中的K介子氟做到了这一点。

缩小的原子也为基本物理学的其他方面打开了一扇窗。μ子、K介子或其他电子替代物如此紧密地围绕原子核运行，以至于它们对原子核的内部结构变得敏感。2019年质子半径的测量就是这样完成的。像一颗微型行星一样，原子核可以是分层的，具有外壳或中子“皮层”。“你拥有一个真正美妙的显微镜，可以看到这些中子皮层处发生的情况，”保罗说。缩小的原子可能让研究人员捕捉到全新的物理学，比如对牛顿引力的偏离或标准模型之外粒子的存在。“我们正在极端精度极限下探究未知物理学，”库尔恰努说。“它与极端高能是互补的。”

甚至创造这些原子就颠覆了粒子物理学的直觉。欧洲核子研究中心（CERN）的旗舰仪器大型强子对撞机将粒子加速到接近光速，以引发那些高能相互作用。保罗的团队则依赖一台不太知名的机器——反质子减速器，它将粒子减速到爬行速度，使它们能够渗入原子而不是将其轰碎。在某些方面，这是更困难的工作。“加速比减速容易，”CERN的实验物理学家拉尔斯·约根森说，他帮助开发了这台减速器。

他花了一个小时带我了解这个过程的各个阶段。系统产生反质子并逐步释放它们的能量。有些阶段作用于整团粒子来减慢它们，而另一些阶段则在团块内部起作用以防止其扩散。一种技术是向腔室中注入电子，电子像许多冰块一样冷却反质子。磁场和极端真空——极端到没有任何压力计能测量——确保反质子不会过早遇到普通质子，否则两者都会湮灭。2021年，CERN开始运行超低能量反质子环（ELENA）来进行最终制动。创造和减速其他电子替代物如μ子则更容易，因为它们不存在湮灭的难题。

到那时，将这些粒子插入原子就很容易了。原子在涉及电子方面出奇地笨拙。它们很容易因各种原因失去电子，而奇异原子的形成正是利用了这种倾向，新颖之处在于失去的电子被一个入射粒子所取代。如果原子原本处于最低可能的能量状态，新来者立即定义了一组新的能级，就像一架突然降下的消防逃生梯。原子穿过新建立的能级下落。在此过程中，它 eject 所有剩余的电子并发射一系列X射线。

原子最终会再次稳定下来，但不会持续太久。在反质子原子中，反质子达到如此紧密的轨道，以至于它触及原子核并湮灭。在其他类型的奇异原子中，电子替代物会迅速衰变。μ子仅持续2微秒，其他种类更加短暂。但在这些被截短的生命周期中，奇异原子甚至可以形成短寿命的分子。

我从日本中部大学的物理学家冈田信二那里听说了它们。2026年春天，他的团队使用斯韦茨的探测器和日本质子加速器研究综合体测量了μ子氢分子的结构，其中氢以氘同位素的形式存在——这是首次直接测量此类分子发射的X射线。当它们被轰入由两个普通氢原子组成的分子时，μ子原子将自己植入这些分子中并同化了其中一个氢。这创造了冈田所说的“套娃分子”——一个嵌入在更大的普通分子内部的奇异分子。

这就回到了最初让我开始探索的想法：μ子催化聚变。在其他实验中，当奇异分子达到其最终构型时，它如此紧凑，以至于两个氢几乎瞬间聚变。这个过程在室温下发生，所以在这个意义上它是“冷”的，但在其他方面它与1989年的实验非常不同——尤其是因为它确实发生了。μ子通常被弹出，使它能够创造一个新的奇异原子并重新开始循环；因此，μ子充当催化剂，一个核聚变的媒人。如果它能重复这个把戏300次或更多，这个过程产生的能量将超过其消耗的能量。大多数物理学家怀疑它能否达到300次，但冈田说他和他的团队并不完全排除这种可能性。尽管如此，聚变反应释放的粒子可以被收集用于合成医用同位素或处理裂变反应堆的核废料。“即使达不到能量收支平衡，μ子催化聚变也可能有用，”冈田说。

这很重要，因为尽管物理学家在20世纪50年代首次观测到μ子催化聚变，但很少有人研究它，认为它不过是一种好奇现象。如果它不能产生能量，又有什么用处呢？近年来的主要进展不是μ子回收方面的突破，而是认识到我们根本不需要这样的突破。

我认为这对评估科学进展有一个普遍的教训。成为头条新闻的东西——丰富的能源！人类得救了！——并不是你应该关注的。相反，要问：这个研究计划会有趣吗，即使主要主张未能实现？它是对单一结果的全有或全无的赌博，还是通往更广阔科学领域的大门？

1989年向世界展示的冷聚变没有通过这个测试。那两位化学家从未阐明为什么他们的实验即使没有预示能源救赎也可能有趣。这个任务落在了30年后的特里维西克身上，当时他的项目表明，冷聚变类型的实验如果按照其自身的价值来追求，可以揭示迷人的材料特性。

μ子催化聚变通过了测试，因为奇异原子和分子丰富了我们对宇宙的认识，即使它们从未产生一瓦特的电力。与我交谈的科学家们显然不是被任何名利期望所驱动，而是被好奇心和惊奇感所驱动。“这不令人惊叹吗？”冈田告诉我。“原子物理学、分子物理学和核物理学在一个单一的反应循环中汇聚在一起。正是这种相互作用让我着迷。”

英文来源：

Is There Anything Left in the Dream of Cold Fusion?
Introduction
Cold fusion: Now there’s an idea I hadn’t thought about in a while. It came back onto my radar in spring 2026. I had written an article on how scientists tend to be risk averse, and Huw Price, a philosopher at Trinity College at the University of Cambridge, responded to it on Bluesky, citing a paper he’d recently co-authored on attitudes toward cold fusion. He thinks scientists have been overly dismissive not only of cold fusion, but also of the claim that they have been overly dismissive of cold fusion. As if to prove his point, a journal had just rejected his paper. I’ve long admired Price’s work on the nature of time and causation, so I was intrigued.
When the cold-fusion controversy erupted in 1989, I was in the middle of backpacking off the grid for six months. (You could do that back then.) By the time I caught up on the news, it was over. In March, two chemists had called a press conference to announce a simple tabletop experiment that released too much energy to be a mere chemical reaction. They said it had to be nuclear: hydrogen nuclei fusing to form helium. It promised limitless clean, cheap power. Physicists were stunned. That sort of thing wasn’t supposed to be possible under such pedestrian conditions. Politicians proclaimed the end of all our energy woes. But then labs across the globe tried to replicate the experiment and couldn’t, and an almighty takedown ensued. The whole thing only lasted a few months. Not having experienced the episode in real time, and being a contrarian by nature, I initially sympathized with the plucky maverick scientists. But then I read about their rookie mistakes, their fudging of a crucial graph, and their threats of lawsuits against skeptics. Experiments that initially corroborated the results were retracted, in one case amid indications of deliberate spiking with fake fusion products.
Although cold fusion was a pathological case, fusion in general has been a graveyard of dreams. I grew up on the dream it evoked. Whether it occurs at room temperature, as it was supposed to have done in the cold-fusion episode, or at center-of-the-sun temperatures, as in conventional thermonuclear reactors (and bombs), fusion doesn’t require strip-mining (and disposing of) uranium or escorting oil tankers through the Strait of Hormuz. All you would need, ideally, is a bit of seawater. Fascinated, I once built a “fusor” in my basement based on an article in Make magazine. Fusors are real, the one legitimate tabletop fusion technology. In them, a high voltage creates a hot plasma that smashes nuclei together. My unit didn’t achieve fusion, but with work it could have, although it would have produced negligible power. I loved showing guests its glowing purple plasma, but the more I learned about fusion, the more a sense of disillusionment grew in me. A couple of years later, a friend at a private fusion company gave me a tour of an actual experimental fusion reactor. It was complex and costly. So much for cheap. It produced intense, deadly neutron radiation. So much for clean. And it required tritium fuel, which does not occur naturally and has to be manufactured. So much for just a bit of seawater.
So how did a nice philosopher like Price get mixed up in a business like this? Over Zoom, he explained that his interest dates to 2011, when he and other luminaries were hatching the idea for the Center for the Study of Existential Risk. This research group frets over nuclear winter, engineered bioweapons, massive volcanic eruptions, and artificial intelligence takeover — it rang that alarm bell long before it became fashionable. Price told me he saw parallels between doomsday scenarios and cold fusion. They may seem improbable, and studying them is a lonely or even fringe activity, yet the consequences are huge, so we should give more weight to them than might strictly seem warranted.
I’m all for open-mindedness, but Price’s argument troubled me. There must be a thousand other anomalous phenomena that are as likely to be real as cold fusion and, if they are, to transform the world. Why focus on this one? The only reason we are talking about cold fusion at all is that we were lied to in 1989. The initial mistruth created a kind of psychological anchoring effect, causing us to entertain a possibility that we otherwise wouldn’t have. It is as if I said I saw Bigfoot in my backyard, then confessed I hadn’t, but people started holding annual cryptozoological conferences nearby anyway. I found it jarring that a deception could conjure an entire academic research program. How is this any different from the antivax movement, which also started with data that turned out to be faked and should have just packed up once that became known?
But having started down this rabbit hole, I figured I might as well keep going. Price suggested I talk to Matt Trevithick.
Trevithick is a co-founder of Leitmotif, a venture capital firm in Palo Alto. I don’t normally speak to venture capitalists, but I quickly saw that his approach aligns with Price’s. Trevithick wants to usher in the fusion age and supports a range of technologies that might make it happen. In our conversation, he also had a very Silicon Valley tendency to keep addressing me by name.
A decade ago, while working at Google, Trevithick organized a project to reevaluate cold fusion, culminating in a Nature paper in 2019. It didn’t find any unexpected nuclear reactions or other anomalies, but that wasn’t the only goal. Trevithick said the 1989 debacle had cast a pall over certain research topics that perhaps shouldn’t be so easily dismissed. For instance, cold fusioneers used the element palladium in their experiments, and it has a wondrous ability to absorb hydrogen like a sponge, an ability that is no less wondrous for its association with a scientific wild goose chase. Trevithick sought to lift this taboo, and he said the project ultimately produced 28 academic papers on hydrogenated metals and other phenomena. “George,” he said. “We destigmatized a field.”
So I went through the references in the Nature paper and looked up topics I might not have given a second thought to before. The one that captivated me was muon-catalyzed fusion. I recognized it as the original meaning of the term “cold fusion” before it was co-opted by the 1989 studies. As I unpacked what it meant, I discovered a lively research program within physics that creates exotic breeds of atoms and molecules, sometimes to try to fuse them together, but more broadly to search for new fundamental laws of nature.
Still wary of the dubious reputation of cold fusion, I reached out to physicists I trusted to learn more. One was Cătălina Curceanu of the Italian National Institute for Nuclear Physics near Rome. I had visited her three years before to see her experiments testing the foundations of quantum mechanics. She gently reminded me that she had told me about exotic atoms back then, too. I guess I was so focused on her other work that I failed to follow up. “It’s a whole world to discover,” she said. “Sometimes I call them ‘genetically modified atoms,’ but I stopped doing that because, you know.”
The core idea that builds to muon-catalyzed fusion is simple. Ordinary atoms consist of a positively charged nucleus orbited by negatively charged electrons. But there’s no reason they have to be electrons. Other negatively charged particles serve just as well. In the Standard Model of particle physics, the electron has a sibling called the muon that can stand in for it. Physicists have also swapped in particles from other families, such as kaons, pions, and Xi baryons. They have even created hybrids of matter and antimatter, in which a nucleus containing protons is orbited by negatively charged antiprotons. In short, you can have regular hydrogen, muonic hydrogen, kaonic hydrogen, antiprotonic hydrogen, and so on.
“That’s like a new periodic table,” said Daniel Swetz, an experimental physicist at the National Institute of Standards and Technology in Boulder, Colorado, who builds ultraprecise detectors to measure radiation emitted by these exotic atoms. “You’re almost building it out in the third dimension.”
The main difference in these exotic atoms is that the electron substitutes are much heavier. A muon is 207 times as massive as an electron; an antiproton, 1,800 times. According to quantum mechanics, every object is ultimately wavelike, and the greater its mass, the shorter its wavelength. Consequently, a muonic atom is as much as 207 times smaller than its vanilla counterpart, depending on the chemical isotope; an antiprotonic atom, as much as 1,800 times smaller. When physicists want to get across the scale of atoms, they often compare the nucleus to a marble and the whole atom to a football stadium around that marble. With antiprotonic atoms, however, the atom is not a football stadium, but just a football.
“The whole system is collapsed down,” said Nancy Paul, a physicist at the Kastler Brossel Laboratory in Paris. She is exploring using even heavier negatively charged particles to shrink atoms still further. “It’s so rare in physics, especially nowadays, where you get something where nothing has been done.”
Shrinking atoms intensifies the electric field within them. According to Coulomb’s law, which is the electric counterpart of Newton’s law of gravity, the electric field strengthens as the inverse square of distance. For a kaonic or antiprotonic atom, then, it scales up a millionfold. That provides a stress test of a central pillar of modern physics, quantum electrodynamics (QED), or how electromagnetism behaves at the quantum level. “It is the strongest Coulomb field that you can create in the lab to probe QED,” Paul said.
In fact, it breaches the so-called Schwinger limit, the threshold at which quantum effects go berserk and empty space becomes unstable. Particles begin to materialize spontaneously out of nothingness. “You’re boiling the vacuum with the stronger field,” she said. Physicists predicted this particle effervescence in the 1930s and have yet to observe it directly, but they have discerned a closely related phenomenon using exotic atoms. In spring 2026, Curceanu and her colleagues did so using kaonic fluorine that was experiencing an electric field above the Schwinger limit.
Shrunken atoms open a window into other aspects of fundamental physics, too. The muons, kaons, or other electron substitutes orbit the atomic nucleus so tightly that they become sensitive to its interior structure. This was how the radius of the proton was measured in 2019. Like a miniature planet, the nucleus can be layered, with an outer crust or “skin” of neutrons. “You have a really beautiful microscope of seeing what’s happening at these neutron skins,” Paul said. Shrunken atoms might allow researchers to pick up on wholly new physics, such as deviations from Newtonian gravity or the existence of particles beyond the Standard Model. “We are looking into unknown physics at the extreme precision limit,” Curceanu said. “It’s complementary to extreme high energy.”
Even creating these atoms inverts the intuitions of particle physics. CERN’s flagship instrument, the Large Hadron Collider, revs up particles almost to light speed to initiate those high-energy interactions. Paul’s team instead relies on a lesser-known machine called the Antiproton Decelerator that slows particles to a crawl, so that they become able to infiltrate atoms instead of blasting them apart. In some ways, it’s a harder job. “Acceleration is easier than deceleration,” said Lars Jørgensen, an experimentalist at CERN who helped to develop the decelerator.
It took him an hour to walk me through the stages of the process. The system creates antiprotons and gradually bleeds off their energy. Some stages act on entire clumps of particles to slow them down, while others act within a clump to keep it from spreading out. One technique is to flood the chamber with electrons, which cool the antiprotons like so many ice cubes. Magnetic fields and an extreme vacuum — so extreme that no pressure gauge can measure it — ensure that the antiprotons don’t prematurely encounter ordinary protons, which would annihilate both. In 2021, CERN began operating the Extra Low Energy Antiproton ring, or ELENA, to do the final braking. Creating and slowing other electron surrogates such as muons is easier because they don’t pose the annihilation challenge.
At that point, inserting these particles into atoms is easy. Atoms are surprisingly klutzy when it comes to their electrons. They are apt to lose them for all sorts of reasons, and exotic-atom formation exploits this tendency, with the novelty that the lost electron is replaced with an incoming particle. If the atom was originally in its lowest possible energy state, the new arrival immediately defines a new set of energy levels, like a fire-escape ladder that suddenly descends. The atom drops through the newly established energy levels. In the process it ejects all its remaining electrons and emits a series of X-rays.
The atom eventually stabilizes again, but not for long. In an antiprotonic atom, the antiproton reaches such a tight orbit that it touches the nucleus and annihilates. In other types of exotic atoms, the electron substitute quickly decays. Muons last a mere 2 microseconds, and other species are even more fleeting. But during these truncated lifespans, exotic atoms can even form short-lived molecules.
I heard about them from Shinji Okada, a physicist at Chubu University in Japan. In spring 2026, his team used Swetz’s detectors and the Japan Proton Accelerator Research Complex to measure the structure of muonic hydrogen molecules, with the hydrogen taking the form of the isotope deuterium — the first direct measurement of X-rays emitted by such molecules. When they were smashed into molecules consisting of two ordinary hydrogen atoms, the muonic atoms implanted themselves within those molecules and assimilated one of their hydrogens. This created what Okada called a “matryoshka molecule” — an exotic molecule embedded inside a larger ordinary molecule.
And this brings us back to the idea that got me started: muon-catalyzed fusion. In other experiments, when the exotic molecule reaches its final configuration, it is so compact that the two hydrogens fuse almost instantly. This process happens at room temperature, so in that sense it is “cold,” but otherwise it’s very different from the 1989 experiment — not least because it really does happen. The muon is typically ejected, freeing it to create a new exotic atom and restart the cycle; thus, the muon is acting as a catalyst, a nuclear matchmaker. If it could repeat the trick 300 times or more, the process would produce more energy than it consumed. Most physicists doubt it could reach 300, but Okada said he and his team don’t entirely rule it out. Still, the particles released by the fusion reactions could be harvested to synthesize medical isotopes or process nuclear waste from fission reactors. “Even without reaching energy breakeven, muon-catalyzed fusion could be useful,” Okada said.
And that’s important because, although physicists first observed muon-catalyzed fusion in the 1950s, few studied it, deeming it a mere curiosity. What good could it be if it couldn’t generate energy? The main development of recent years has not been a breakthrough on muon recycling but a realization that we don’t need any such breakthrough.
I think that carries a general lesson for evaluating developments in science. What makes headlines — Abundant energy! Humanity saved! — isn’t what you should focus on. Instead, ask: Will this research program be interesting, even if the main claim falls short? Is it an all-or-nothing gamble on a single result, or a portal into a wider area of science?
Cold fusion, as presented to the world in 1989, failed this test. Those two chemists never articulated why their experiment might be interesting even if it didn’t herald energy salvation. That task fell to Trevithick 30 years later, when his project showed that a cold-fusion type of experiment, if pursued on its own merits, could reveal fascinating material properties.
Muon-catalyzed fusion passes the test, because exotic atoms and molecules enrich our view of the universe even if they never produce a watt of electricity. The scientists I spoke to were clearly not driven by any expectation of fame and fortune, but rather by curiosity and wonder. “Isn’t that remarkable?” Okada told me. “Atomic, molecular, and nuclear physics all come together in a single reaction cycle. That interplay is what has captivated me.”