内容来源：https://www.quantamagazine.org/is-particle-physics-dead-dying-or-just-hard-20260126/

内容总结：

粒子物理学：陷入沉寂还是蓄势待发？

2012年，欧洲大型强子对撞机（LHC）成功发现希格斯玻色子，为粒子物理学的“标准模型”补上了最后一块拼图。然而，这场胜利却伴随着深刻的失落：科学家们投入巨资建造LHC，不仅为了验证标准模型，更期待发现超越该模型的新物理现象，例如暗物质粒子或解释宇宙物质-反物质不对称性的线索。但除了已知的25种基本粒子，实验数据中再无其他发现。

这一“新物理”的缺失引发了领域内的危机。有物理学家悲观预言，缺乏实验指引的粒子物理学将逐渐萎缩，人才流失不可避免。十多年过去，LHC仍在运行，并借助人工智能提升了数据分析精度，能够更敏锐地探测粒子碰撞的细微特征。尽管如此，所有测量结果至今仍与标准模型的预测高度吻合。

面对困境，全球物理学界正规划下一代对撞机以寻求突破。欧洲核子研究中心（CERN）提议建造周长91公里的“未来环形对撞机”（FCC），旨在以更高能量和精度探索新物理的间接证据。美国则考虑建造新型“μ子对撞机”，利用更重的μ子实现既洁净又高能的碰撞，但需攻克μ子寿命极短的技术挑战。中国则转向建设造价较低的“超级陶粲装置”，专注于在特定能量区域寻找标准模型以外的粒子转化现象。

然而，这些耗资数百亿、历时数十年的计划均无“发现保证”，引发不少争议。部分学者认为，在缺乏明确理论指引的情况下，巨额投入风险过高。与此同时，领域内的人才流失现象显著，许多优秀青年研究者转向人工智能等领域。

尽管如此，坚守者依然存在。他们认为，粒子物理学并非“已死”，而是进入了“艰难探索期”。理论方面，专注于粒子相互作用几何结构的“振幅学”研究正在兴起，或能借助人工智能找到新突破方向。实验方面，对暗物质候选粒子“轴子”或放射性衰变异常等小众方向的探索也在持续。

正如一位物理学家所言：“过去125年里，发现接踵而至的幸运时代已暂告段落。”粒子物理学的未来，取决于人类是否有足够的耐心与智慧，在漫漫长夜中捕捉下一个微光。

中文翻译：

粒子物理学是垂死、消亡，还是仅仅举步维艰？

引言

2012年7月，欧洲大型强子对撞机的物理学家们凯旋般宣布发现了希格斯玻色子——这个亚原子世界寻觅已久的基石。其他基本粒子通过与希格斯玻色子相互作用获得质量，从而减速到足以聚合成原子，继而凝结构成万物。

几个月后，我受聘成为初创科学杂志《量子》的首位专职记者。恰逢物理学界风云渐起之时，我开始了对物理学领域的报道。

这场风云变幻并非关乎希格斯粒子——当它在大型强子对撞机中现形时，其存在已几无悬念。希格斯粒子是粒子物理学标准模型的最后一块拼图，这套诞生于1970年代的方程组统领着25种已知基本粒子及其相互作用。

更引人注目的是数据中未曾显现的迹象。

物理学家耗资数十亿欧元建造这座27公里长的超级对撞机，不仅为了验证标准模型，更期待通过发现更完备自然理论的构成要素来超越它。例如，标准模型未包含可能构成暗物质的粒子，无法解释宇宙中物质为何压倒反物质，也不能阐明大爆炸的起源。此外，希格斯玻色子的质量（它设定了原子的物理尺度）与量子引力相关的高得多的质能尺度（即普朗克尺度）之间存在难以解释的巨大鸿沟。物理尺度间的这道深渊——原子远大于普朗克尺度——显得不稳定且不自然。1981年，伟大理论家爱德华·威滕曾提出解决这一"层级问题"的方案：只要存在仅比希格斯玻色子略重的额外基本粒子，平衡便能恢复。大型强子对撞机的碰撞能量本应足以催生这些粒子。

然而当质子沿隧道双向疾驰并迎头相撞，将碎片喷溅到周围探测器中时，观测到的却只有标准模型的25种粒子。再无其他迹象显现。

"新物理"（超越已知范围的粒子或作用力）的缺席引发了一场危机。"这当然令人失望，"粒子物理学家米哈伊尔·希夫曼在2012年秋对我说，"我们不是神祇，亦非先知。在缺乏实验数据指引的情况下，如何推测自然界的奥秘？"

一旦关于层级问题的标准推理被证明错误，便无人知晓新物理可能现身何处。它很可能超出实验探测范围。粒子物理学家亚当·法尔科夫斯基当时预言，若无法探索更重粒子，该领域将经历缓慢衰亡："粒子物理学职位将稳步减少，粒子物理学家将自然消亡。"

这场危机及其余波为我的报道提供了多年素材，但果然不出所料，粒子物理学相关新闻的出现频率逐渐降低。我与消息来源失去了联系。十三年后的今天，在《量子》杂志新专栏"质觉"的开篇中，我试图审视现状：粒子物理学是否如法尔科夫斯基预言般走向消亡？新物理还能被发现吗？粒子物理学家的未来何在？人工智能会提供助力吗？在探索宇宙众多未解之谜的道路上，还留存多少希望？

有些粒子物理学家表现得仿佛危机从未存在。大型强子对撞机仍在运行且将持续至少十年，其运营者正重燃热情。

过去几年间，对撞机通过运用人工智能改善了数据处理。模式识别器能筛选质子碰撞产生的碎片，其分类碰撞事件的精度超越人工算法。这帮助物理学家更精确测量"散射振幅"——即不同粒子相互作用发生的概率。例如，人工智能系统能更精准判定碰撞后产生顶夸克与底夸克的数量差异。任何偏离标准模型预测的统计异常，都可能意味着未知基本粒子的参与。

像希格斯玻色子这般重量的新粒子不会如此隐晦——它们早该在数据图上显现为显著凸起。但正如哈佛大学粒子物理学家马特·斯特拉斯勒向我解释的，较轻新粒子的踪迹仍可能潜藏于数据的"隐蔽山谷"中。"那里存在大量未勘探领域，"他说。例如可能存在一种不稳定暗物质粒子，通过偶尔出现并立即衰变成过量μ子-反μ子对来留下印记。探测到这种异常将间接指向不稳定粒子的存在。"那些认为所有新物理都存在于高能领域的人——他们现在非常失望，"斯特拉斯勒说，"我持不同观点。自然界有很多机会在低能领域提供线索。"

然而迄今为止，尚未探测到此类新物理的间接证据。大型强子对撞机的统计数据越精确，就越符合标准模型。欧洲核子研究中心粒子物理学家米开朗基罗·曼加诺表示，如今对撞机如同探索标准模型预测的工具，他认为这种探索具有价值，因为并非所有方程推论都易于计算。曼加诺说超越标准模型的新物理探索仍在继续，但"没有获得积极成果并不意味着我们陷入僵局、走向消亡或浪费时间。"

这些问题如此根本，既然我们拥有研究工具，当然值得精确测定每个振幅、探查每个隐蔽山谷。但对新物理的探索者而言，游戏是否止步于此？

学界渴望更大突破。欧洲核子研究中心物理学家计划建造未来环形对撞机，通过在法瑞边境地下修建91公里隧道将大型强子对撞机周长扩展两倍，以探测更高能量并寻找更精微信号。这台未来环形对撞机最初将碰撞电子——与质子不同，电子本身是无内部结构的基本粒子。其洁净碰撞将实现更精确的散射振幅测量，使对撞机对新物理的间接迹象具有超强敏感性。本世纪末，这台巨型对撞机将升级至能像现有大型强子对撞机那样碰撞质子。质子碰撞虽更混沌，但在未来环形对撞机中能达到空前能量——约比当前大型强子对撞机最高能量强七倍——因此仍有渺茫机会揭示超出大型强子对撞机探测范围的重粒子。（理论上，粒子质量可能高达大型强子对撞机能直接产生质量的一百万亿倍，故无理由期待它们在下一阶段出现。）

目前未来环形对撞机的命运尚未可知，成员国正式批准与资金承诺需待2028年后。

与此同时，美国粒子物理学家正通过建造全新类型装置——μ子对撞机来补充欧洲战略。μ子与电子同属基本粒子，但质量是电子的200倍，因此其碰撞兼具洁净性与高能量（虽未达到大型强子对撞机碰撞能量）。这种新型装置的优势与挑战在于需要重大技术创新（随之带来衍生潜力），因为μ子极不稳定，必须在产生后微秒级时间内完成加速与碰撞。

技术验证及对撞机建造将耗时约三十年，这还需联邦资金支持。"我们必须找到在100亿至200亿美元间实现的方法，"加州理工学院物理学教授玛丽亚·斯皮罗普卢表示，她也是2025年6月发布的支持μ子对撞机项目国家报告委员会联合主席。未来数年，能源部将权衡是否资助该提案而非其他竞争性科学项目。其不利因素在于缺乏大型强子对撞机曾拥有的"发现保证"——如希格斯玻色子那般确凿目标。

不过，数理物理学家彼得·沃伊特在博客中沉思："或许在这个由万亿富豪科技巨头掌控的新世界秩序里，资金将不成问题。"

据悉中国超级对撞机的讨论已无果而终。中国转而决定推进"超级陶粲装置"——这项低能粒子散射实验仅需数亿美元而非上百亿美元投资。该装置将产生大量τ粒子和粲夸克，部分用于研究τ粒子是否会转变为μ子或电子。标准模型虽未预测这种转换，但某些理论扩展中确实存在这种现象。

好吧，我们不妨验证。我们渴求新物理，而这个代价尚可承受。但本质上，很难判断哪些黑暗中的探索值得尝试。

曾在2012年敲响粒子物理学丧钟的亚当·法尔科夫斯基，过去以其博客"共振"的犀利评论闻名。但这位巴黎粒子物理学家自2022年起再未更新。他表示部分原因是身陷育儿事务，部分则是无甚可述。

视频通话中，法尔科夫斯基告诉我："我对未来对撞机持强烈怀疑态度。我很难对此感到兴奋。"他注意到欧洲核子研究中心未来环形对撞机计划背后的推动力，但个人担忧其巨额成本、漫长周期，以及"完全没有迹象表明下一台对撞机探测范围内存在新物理"。

法尔科夫斯基已转向散射振幅的理论研究，这个不断发展的领域聚焦于粒子相互作用统计背后的几何模式，这些模式可能指向对量子世界更真实的认知。该领域试图用不同数学语言重构粒子物理学方程，期望这种语言能延伸至量子引力。"理解物理理论结构的探索充满活力，"法尔科夫斯基说，"希望借助机器学习，未来几年能取得快速进展。我认为这里正在发生最美好的事情。"

但被称为"振幅学"的领域毕竟抽象——它并非粒子碰撞实验。法尔科夫斯基坦言他认为实验粒子物理学正在消亡。他目睹才华横溢的博士后转向其他研究领域或从事数据科学工作。"我不确定他们还能像过去那样吸纳顶尖人才，"他说，"因为回报前景太过遥远。若想当下改变世界，你会选择人工智能；你会从事与粒子物理学不同的领域。"

这种人才流失似乎已成现实。我曾与人工智能公司Anthropic（聊天机器人Claude的创造者）联合创始人贾里德·卡普兰交谈。上次交流时他还是物理学家。2000年代在哈佛读研期间，他与著名理论家尼马·阿尔卡尼-哈米德共同开创了当今被积极追求的振幅研究新方向。但卡普兰于2019年离开该领域。"我转向人工智能研究是因为……人工智能的发展速度可能超过科学史上几乎所有领域，"他说。人工智能将成为"我们时代最重要的事件，或许是科学史上最重要的事件之一。因此我显然应该投身于此。"

在卡普兰看来，对于粒子物理学的未来，当前的忧虑毫无意义。"我认为制定十年规划意义不大，因为如果十年后建造对撞机，那将是人工智能在建造；人类不会参与。我估计两三年内，理论物理学家被人工智能取代的概率约50%。像尼马·阿尔卡尼-哈米德或爱德华·威滕这样的杰出人物，人工智能将能相当自主地生成与他们论文同等水平的成果……因此我不太考虑超过这个时间尺度的规划。"

欧洲核子研究中心理论组博士后卡里·切萨罗蒂对此未来持怀疑态度。她注意到聊天机器人的错误，以及它们如何成为物理学学生过度依赖的拐杖。"人工智能正让人们物理水平下降，"她说，"我们需要的是人类阅读教科书、静坐思考层级问题的新解法。"

发现希格斯玻色子时，切萨罗蒂还是高二学生。她在费米实验室附近长大，这个位于伊利诺伊州的美国国家实验室拥有大型强子对撞机之前世界最高能量的粒子对撞机Tevatron（顶夸克于1995年在此发现）。这种地理亲近性让她明白，成为粒子物理学家是可能的职业选择。后来这果真成了她的事业。"宇宙的基本构成单元是什么——这些是我最渴望答案的问题，"她告诉我，"但人们总说：‘粒子物理学已死。别干这行。’"

这或许是中肯警告；作为冉冉升起的粒子物理学家，切萨罗蒂尚未获得永久职位。她与他人指出，随着教职招聘委员会和研究生转向其他方向，该子领域持续萎缩。"那些宣称无所发现、应当放弃的论调——人们确实听进去了，"她说，"这当然意味着从业者减少，形成自我应验的预言。如果你将所有试图解决这些问题的人才推向更容易产生影响的领域，那无异于自设败局。"

切萨罗蒂呼应了我从他人处听到的观点，这在我看来也正确："粒子物理学未死；它只是艰难。"难以确定该思考什么、寻找什么。但最执着的粒子物理学家仍在持续思考与探索。

"过去125年很轻松，"斯特拉斯勒说，"发现接踵而至。那个幸运的世纪至少在中短期内已经终结。这可能明天改变，也可能下个世纪改变，谁知道呢。"

理论上，新轻量粒子的线索可能出现在大型强子对撞机或其他实验中。斯特拉斯勒对放射性钍-229衰变研究特别兴奋，这可能揭示基本常数的变化。我则略微偏爱寻找"轴子"的实验——这种轻量级暗物质候选粒子能表现出类似光的特性。

理论方面，层级问题的明显解决方案可能自然浮现于散射振幅背后的几何结构中。或者，如果卡普兰所言不虚，人工智能系统或许有天会提出强大新见解，揭示标准模型25种粒子如何融入更宏大的图景——这个可能性在危机初现时我未曾预见。

显然，粒子物理学仍有可能向真理推进。但不存在发现保证。十三年的思考让我认识到，这始终是个令人不安的前景：我们所能搜集的关于自然基本法则与构成单元的所有经验线索，或许已尽在掌握。宇宙或许打算保守其余的秘密。

英文来源：

Is Particle Physics Dead, Dying, or Just Hard?
Introduction
In July 2012, physicists at the Large Hadron Collider (LHC) in Europe triumphantly announced the discovery of the Higgs boson, the long-sought linchpin of the subatomic world. Interacting with Higgs bosons imbues other elementary particles with mass, making them slow down enough to assemble into atoms, which then clump together to make everything else.
A couple of months later, I took a job as the first staff reporter at the nascent science magazine that would become Quanta. Turns out I was starting on the physics beat just as the drama was picking up.
The drama wasn’t about the Higgs particle; by the time it materialized at the LHC there was already little doubt about its existence. The Higgs was the last piece of the Standard Model of particle physics, the 1970s-era set of equations governing the 25 known elementary particles and their interactions.
More striking was what did not emerge from the data.
Physicists had spent billions of euros building the 27-kilometer supercollider not only to confirm the Standard Model but also to supersede it by uncovering components of a more complete theory of nature. The Standard Model doesn’t include particles that could comprise dark matter, for instance. It doesn’t explain why matter dominates over antimatter in the universe, or why the Big Bang happened in the first place. Then there’s the inexplicably enormous disparity between the Higgs boson’s mass (which sets the physical scale of atoms) and the far higher mass-energy scale associated with quantum gravity, known as the Planck scale. The chasm between physical scales — atoms are vastly larger than the Planck scale — seems unstable and unnatural. In 1981, the great theorist Edward Witten thought of a solution for this “hierarchy problem”: Balance would be restored by the existence of additional elementary particles only slightly heavier than the Higgs boson. The LHC’s collisions should have been energetic enough to conjure them.
But when protons raced both ways around the tunnel and crashed head-on, spraying debris into surrounding detectors, only the 25 particles of the Standard Model were observed. Nothing else showed up.
The absence of any “new physics” — particles or forces beyond the known ones — fomented a crisis. “Of course, it is disappointing,” the particle physicist Mikhail Shifman told me that fall of 2012. “We’re not gods. We’re not prophets. In the absence of some guidance from experimental data, how do you guess something about nature?”
Once the standard reasoning about the hierarchy problem had been shown to be wrong, there was no telling where new physics might be found. It could easily lie beyond the reach of experiments. The particle physicist Adam Falkowski predicted to me at the time that, without a way to search for heavier particles, the field would undergo a slow decay: “The number of jobs in particle physics will steadily decrease, and particle physicists will die out naturally.”
The crisis and its fallout made for years of interesting reporting, but sure enough, the frequency of news stories related to particle physics diminished. I fell out of touch with sources. More than 13 years on, in this first column for Qualia, a new series of essays in Quanta Magazine, I’m taking stock. Is particle physics dying, as Falkowski predicted? Can new physics still be found? What’s the future for particle physicists? Will artificial intelligence help? How much hope is left in the search for answers to the many remaining mysteries of the universe?
Some particle physicists act as if there’s no crisis at all. The LHC is still running and will for at least another decade, and its operators are finding new sources of enthusiasm.
In the last couple of years, data handling at the collider has improved with the use of AI. Pattern recognizers can sort through the outgoing debris of proton collisions and classify collision events more accurately than human-made algorithms can. This helps the physicists to more accurately measure the “scattering amplitude,” essentially the probability that different particle interactions will occur. For instance, AI systems can determine more precisely how many top quarks arise in the aftermath of collisions versus the number of bottom quarks. Any statistical deviations from the predictions of the Standard Model could signify the involvement of unknown elementary particles.
Novel particles as hefty as Higgs bosons would not be so subtle; they would have shown up already as pronounced bumps on data plots. But as Matt Strassler, a particle physicist affiliated with Harvard University, explained to me, the traces of lighter novel particles could still lie in so-called hidden valleys in the data. “There’s a huge amount of unexplored territory there,” he said. There might exist, for instance, an unstable type of dark matter particle that leaves its mark by occasionally arising and immediately decaying into an excessive number of muon-antimuon pairs. Detecting such an excess would point indirectly to the unstable particle’s existence. “For people who thought all the new physics is at high energies — they’re very disappointed right now,” Strassler said. “I don’t share that view. There are many opportunities for nature to provide clues at low energies.”
So far, though, no such indirect evidence of new physics has been detected. The more accurate the statistics have become at the LHC, the better they match the Standard Model. Michelangelo Mangano, a particle physicist at CERN, the laboratory that houses the LHC, said the collider today is like a tool for exploring the Standard Model’s predictions, and he considers this exploration worthwhile because not all consequences of the equations are easy to calculate. The search for new physics beyond the Standard Model is ongoing, Mangano said, but “the fact that it’s not giving positive results does not mean we are stuck, dead, or wasting our time.”
These questions are so fundamental that of course it’s worth nailing down every amplitude and checking every hidden valley, since we have the tool for the job. But for hunters of new physics, does the game end there?
The community wants to go bigger. CERN physicists want to build a Future Circular Collider, tripling the circumference of the LHC with a 91-kilometer tunnel beneath the Franco-Swiss border, to both probe higher energies and look for subtler signals. This FCC would initially collide electrons, which, unlike protons, are themselves elementary particles, with no substructure. Their clean collisions would allow more precise measurements of scattering amplitudes, making the FCC ultrasensitive to indirect signs of new physics. By the end of the century, the mega-collider would be upgraded to collide protons, as the LHC does now. Proton collisions are messier, but at the FCC they would achieve unprecedented energies — about seven times higher than the LHC can currently muster — so they have a chance, however slim, of revealing heavy particles beyond the LHC’s reach. (In theory, particle masses could range up to a million billion times greater than what the LHC energy scale can produce directly, so there’s no reason to expect them around the next bend.)
As of now, the FCC’s fate is unknown; formal approval and funding commitments by member countries won’t come before 2028.
Meanwhile, U.S. particle physicists are aiming to complement the European strategy by constructing a brand-new type of machine: a muon collider. Muons are elementary like electrons, but they’re 200 times heavier, so their collisions would be both clean and energetic (albeit not reaching the collision energies of the LHC). Both the selling point and the challenge of this newfangled type of machine is that it will require major technical innovations (with all the spin-off potential that can bring), because muons are highly unstable. They must be accelerated and collided mere microseconds after they’re created.
Demonstrating the technology and then constructing the collider would take roughly 30 years, and that’s with federal funding. “We have to figure out how to do it in between 10 and 20 billion [dollars],” said Maria Spiropulu, a physics professor at the California Institute of Technology and co-chair of the committee behind a national report endorsing a muon collider program that came out in June 2025. Over the coming years, the Department of Energy will weigh whether to fund the proposal rather than competing science projects. What hurts its case is the lack of a “discovery guarantee,” which the LHC had with the Higgs boson.
Then again, as the mathematical physicist Peter Woit mused on his blog, “Perhaps in our new world order where everything is controlled by trillionaire tech bros, the financing won’t be a problem.”
Deliberations about a Chinese supercollider have come to naught, I’m told. Instead, China has decided to pursue a “super-tau-charm facility”: a lower-energy particle scattering experiment that would cost mere hundreds of millions of dollars instead of tens of billions. The facility will produce a lot of tau particles and charm quarks, partly to study whether taus ever shape-shift into muons or electrons. This kind of switching isn’t predicted by the Standard Model, but it does happen in some theoretical extensions of it.
Okay, we might as well check. We’re desperate for new physics, and the price is good. But by definition it’s very difficult to know which shots in the dark are worth taking.
Adam Falkowski, who sounded the death knell for particle physics back in 2012, used to be known for the sharp commentary he supplied on his blog Résonaances. But the Paris-based particle physicist hasn’t posted anything since 2022. He said that’s partly because he’s been tied up with fatherhood and partly because there hasn’t been much to say.
When we caught up on a video call, Falkowski told me, “I am very skeptical about future colliders. For me it’s very difficult to get excited about it.” He sees momentum behind CERN’s FCC campaign, but personally he worries about the huge costs and timescales, and the fact that “there are absolutely no hints that something is there within the reach of the next collider.”
For his part, Falkowski has turned to the theoretical study of scattering amplitudes, a growing research area focused on the geometric patterns underlying particle interaction statistics, patterns that could point toward a truer perspective on the quantum world. The field seeks to reformulate the equations of particle physics in a different mathematical language in hopes that this language might extend to quantum gravity. “There is a very vibrant program in trying to understand the structure of the physical theories,” Falkowski said. “The hope is that with the help of machine learning, that there can be very fast progress in the coming years. I think that’s where the best things have happened.”
But amplitudeology, as this field is known, is abstract — it’s no atom-smashing experiment. Falkowski said he does think experimental particle physics is dying. He has watched talented postdocs switch to other research areas or take data science jobs. “I’m not sure they are getting the best of the best as they used to,” he said, “because the prospects of returns are so distant. If you want to change the world now, you will do AI; you will do something different from particle physics.”
This brain drain appears to be real. I spoke to Jared Kaplan, co-founder of Anthropic, the company behind the chatbot Claude. He was a physicist the last time we spoke. As a grad student at Harvard in the 2000s, he worked with the renowned theorist Nima Arkani-Hamed to open up the new directions in amplitude research that are being actively pursued today. But Kaplan left the field in 2019. “I started working on AI because it seemed plausible to me that … AI was going to make progress faster than almost any field in science historically,” he said. AI would be “the most important thing to happen while we’re alive, maybe one of the most important things to happen in the history of science. And so it seemed obvious that I should work on it.”
As for the future of particle physics, AI makes worrying about it now rather pointless, in Kaplan’s view. “I think that it’s kind of irrelevant what we plan on a 10-year timescale, because if we’re building a collider in 10 years, AI will be building the collider; humans won’t be building it. I would give like a 50% chance that in two or three years, theoretical physicists will mostly be replaced with AI. Brilliant people like Nima Arkani-Hamed or Ed Witten, AI will be generating papers that are as good as their papers pretty autonomously. … So planning beyond this couple-year timescale isn’t really something I think about very much.”
Cari Cesarotti, a postdoctoral fellow in the theory group at CERN, is skeptical about that future. She notices chatbots’ mistakes, and how they’ve become too much of a crutch for physics students. “AI is making people worse at physics,” she said. “What we need is humans to read textbooks and sit down and think of new solutions to the hierarchy problem.”
Cesarotti was a high school junior when the Higgs boson was discovered. She grew up near Fermilab, the U.S. national lab in Illinois that houses the Tevatron, which was the world’s highest-energy particle collider before the LHC. (The top quark was discovered there in 1995.) This proximity taught her that a particle physicist was a thing you could be. Later, it turned out to be her thing. “What are the fundamental building blocks of the universe — those were the questions that I was most interested in knowing the answer to,” she told me. “But what people said was, ‘Particle physics is dead. Don’t do this.’”
It may have been a fair warning; Cesarotti has yet to land a permanent job as a rising particle physicist. The subfield has continued to shrink, she and others said, as faculty hiring committees and grad students go in other directions. “Definitely all this rhetoric that there was nothing to be found and you should give up on it — people listened,” she said. “And of course that means there are fewer people. It becomes a self-fulfilling prophecy. If you’re pushing all these talented people out of trying to solve these problems into a field that it’s easier to make an impact on, then you’re setting yourself up for failure.”
Cesarotti echoed a sentiment I’d heard from others, which sounds correct to me as well: “Particle physics isn’t dead; it’s just hard.” It’s hard to know what to think about or look for. But the most devoted particle physicists are thinking and looking all the same.
“It was easy for 125 years,” Strassler said. “One thing led to the next. That lucky century has, for now, at least in the medium term, come to an end. That could change tomorrow, or next century, or who knows.”
A hint of a new lightweight particle could, in theory, show up at the LHC, or in some other experiment. Strassler is particularly excited about the study of radioactive thorium-229 decay, which could reveal variations in the fundamental constants. I’m slightly partial to experiments looking for “axions,” dark matter candidates that are so lightweight that they can act a little like light itself.
On the theory side, an obvious solution to the hierarchy problem could drop naturally out of the geometry behind scattering amplitudes. Or, if Kaplan is right, AI systems might someday suggest powerful new ideas for how the 25 particles of the Standard Model fit into a more comprehensive pattern — a possibility I didn’t foresee back when the crisis began.
Clearly, further progress toward the truth remains possible in particle physics. But there’s no discovery guarantee. I’ve had more than 13 years to think about it, and it remains a disturbing prospect: All the empirical clues we can glean about nature’s fundamental laws and building blocks might already be in hand. The universe may plan on keeping the rest of its secrets.