you're used to hearing my voice on the world bringing you interviews from around the globe and you hear me reporting environment and climate news i'm carolyn beeler and i'm marco werman we're now with you hosting the world together more global journalism with a fresh new sound listen to the world on your local public radio station and wherever you find your podcasts When I started as editor-in-chief at Quanta magazine a couple of years ago, one of the people I was most excited to collaborate with was the physics editor at the time, Natalie Wolchover. Natalie had been at Quanta as a writer and editor since almost the very beginning of the publication. She was responsible for hundreds of stories, and her landmark feature on the James Webb Space Telescope helped the magazine win a Pulitzer Prize for explanatory reporting. Now Natalie has transitioned to being Qantas' first columnist while she's putting the finishing touches on her first book, and she'll be writing monthly essays for us under the name Qualia that will dig into some of the biggest questions in the universe. The first of those essays has just dropped on the site, and it looks at particle physics and whether the field is dead or dying or just really, really hard. Welcome to the Quantum Podcast, where we explore the frontiers of fundamental science and math. I'm Samir Patel, Editor-in-Chief of Quantum Magazine. Particle physics is all about the fundamentals, literally, forces and particles that make up the energy and matter in the universe. There's some theory, but it's also the place in physics where scientists get to take tiny, tiny particles, accelerate them to absurd speeds, and smash them together just to see what happens. But since the famed discovery of the Higgs boson in 2012, this is the special particle that gives all the other particles mass, the field hasn't exactly produced any new headlines. A kind of state of the union for particle physics was the subject of Natalie's first essay, and she's here with us today to talk about it. Welcome to the show, Natalie. It's exciting to finally have you on. Oh, great to be here, Samir. We start every conversation the same way. What's the big idea we're going to be exploring today? The big idea here is that particle physics really is stuck and potentially stuck forever. Okay. Before we get into that, this piece that you wrote for us about particle physics, this is the first in a new series of essays that we're calling Qualia, which is a term for the subjective experience of the world that you helped us conceive and develop. So tell me a little bit about what your thought process is going into writing an essay, which is a bit of a departure for Quanta. Yeah, so in recent years, a lot of journalism has been taking the form of newsletters, essays, first-person explorations. And that seems to be really appealing to people because in this era of information being so readily at our fingertips, I think people are really looking for perspective and individuals who have perspective on things and have curiosity and insight. I wanted to do some of that kind of writing at Quanta, and it seemed like that was an area that Quanta can move into, is presenting these perspectives on these big, important topics. So why did you want to write about particle physics for the first one of these essays? You know, I started here in 2012, and that was the year of the discovery of the Higgs boson. So it was a super exciting discovery. The Large Hadron Collider had turned on, then it pretty quickly delivered this particle that people had been talking about and looking for for literally decades. That was big news, but within the field, there was a crisis going on, and people knew that what had happened at the Large Hadron Collider was actually pretty bad for particle physics, that they had not discovered anything new beyond the Higgs boson, And really the purpose of the machine had been to get past just the particles we knew or expected to exist and find the new particles that could lead the way to a more complete theory. So that was like at the very beginning of my career as a science journalist. And at that time, people were predicting particle physics is going to die. We've gone to the end of the road of all that we can know. And here on out, that's it. When we talk about a field dying, is it because it was so ultimately successful or because it was going down completely the wrong path? It's kind of a combination. In some ways, particle physics is dying because it was so successful. Over the course of the 20th century, we were discovering more and more particles by building bigger and bigger colliders. and, you know, you smash particles together at higher energies, and then they produce heavier particles as the decay products. And so gradually doing that more and more energetically, we discovered more and more particles and eventually saw the pattern that was being mapped out and then figured out this theory called the Standard Model of Particle Physics that connects this set of 25 particles together in this neat way. And so we discovered that theory in 1975. and some of the particles in it hadn't been actually detected yet. And so then the next few decades were detecting those final particles of the Standard Model, the last to be discovered, which was the Higgs boson. That theory, the Standard Model, was so successful at describing the basic building blocks of the universe that it's just hard to get past it. So the Standard Model does not answer all the questions that we have about the universe. But the Large Hadron Collider couldn't find new pieces of the puzzle that would solve these big questions. So it's a case of such a successful theory that it's then hard to supersede it, even though we know that there must be a more complete theory because of all the outstanding questions about the laws of nature. Just so we're in the same place, the standard model is a set of equations that describes how matter and energy behave at the very smallest scales. And it's great. Everything that the standard model has ever predicted, including the existence of the Higgs boson itself, has come true. In some ways, it's ironclad. But, and this is the big but, right, there are things that it doesn't address. You mentioned one in the piece. I know gravity is a big problem here. Explain the outstanding problem that particle physics didn get to What the core of that problem Mm Even though the standard model explains all the matter that we see we know that dark matter exists and that actually makes up six-sevenths of the matter in the universe. And there is no dark matter particle in the standard model. So that's a big one right there. And we know dark matter exists because of the gross behavior of matter and gravity out in the universe that we observe. There has to be something there. Yes. I mean, okay, caveat that we might somehow have the complete wrong end of the stick in terms of what's going on. But there is very good evidence for dark matter. A number of different lines of evidence that all point to there being this very heavy particle that's just wafting around in galaxies, holding them together, throwing its weight around in the universe. So we know that the Sander model isn't the full story just because of that. There's a number of other technical clues about the equations that tell you where you might look for dark matter and what it is that might be missing here that you could look for in a particle collider. The big question that has really driven research on the theory side in particle physics for decades is this puzzle called the hierarchy problem. And this is a puzzle about basically this huge hierarchy between the scales of the standard model particles. So basically the size of atoms and this other scale of quantum gravity, which is basically like where gravity becomes really strong. And so it's a very high energy scale and it's associated with a very tiny length scale. You can think of it as like the scale of the substructure of space time, something where quantum gravity becomes important. So these two scales of atoms and quantum gravity are 17 orders of magnitude apart. The atoms are much, much larger than the scale at which quantum gravity becomes relevant. And this is a problem because of the way quantum equations work. That basically the Higgs boson should talk to whatever new physics is happening at that small scale and should be dragged towards that small scale. So it's very hard in the equations to get these very far apart mass energy scales. That's an unstable situation. And a solution was suggested in the 80s that everyone thought was a brilliant idea. Basically, people liked it so much that it became almost accepted consensus theory even before it was proven. It's an idea called supersymmetry in general, but this specific version is low-energy supersymmetry. This idea that there are a whole second set of particles that are the superpartners of the known particles. So this new symmetry in nature, this mirroring of the particles, a whole new set. that was supposed to exist just above the mass scale of the Higgs boson. So you would have these heavy particles that were just around the corner. And if you can add those heavy particles in the equations, then you balance things out in a way where you can get this massive discrepancy between the Higgs mass and the Planck scale. Planck scale is the absolute smallest scale. Yeah. Like where the forces we know of kind of converge with the force of gravity and they all become like of equal strength. A little complicated, but trust me that if you have these heavy particles, then suddenly the hierarchy problem is solved. So everyone was like, great, we'll build the Large Hadron Collider. We'll find not only the Higgs boson, but also this whole second set of particles. And then we'll be well on our way to a more complete understanding. And that's not what happened. Yeah. And they were even looking for them in the predecessors of the LHC. So starting in the 80s, they've been looking for these particles for a long time. And every time they didn't find them with a new collider, they had to revise the models to say, okay, they're a little bit heavier than that. Okay, they're a little bit heavier than that. The Large Hadron Collider was kind of a final test because now that they haven't been found, if they're so heavy that the Large Hadron Collider can't make them, then they're now too heavy to possibly solve the hierarchy problem. They're too out of balance with the known particles. So it doesn't work anymore. So yeah, when the Large Hadron Collider was being built, there was the Higgs as a sort of discovery guarantee. Like, you definitely find this. But there was the more kind of compelling reason to build it was really to find these supersymmetry particles. And there were also other ideas about the hierarchy problem that solve it in other ways that also involve new physics just around the corner. And those were also disproven. So as a result of that, physicists are just at a loss as to what's going on with the hierarchy problem, what's going on with dark matter, plus a bunch of other mysteries. It's interesting if folks who remember back to 2012 when Large Hadron Collider was turned on, it was the discovery of the Higgs boson was science news. It was genuinely a celebrated piece of science news. Maybe you recall from this moment, because that's literally when you started reporting on physics. I don't recall there being a lot of conversation was like, wow, this is really like a negative outcome because we're not seeing things that we really hope we would see. They smashed the protons together. They saw 25 particles, which is exactly what they expected to see, and literally nothing else, which means that standard model is beautiful. It's exactly what we want, but it does not fix the rest of the problems in our theoretical conception of the universe. When I did a story about this in the fall of 2012, it was really a situation where particle physicists were quietly panicking, but you did not see a lot of news stories about that aspect of the LHC results. And I just came across an essay that was posted online by a particle physicist basically saying, we need to give up on supersymmetry. It's not there. This is the end of the road. And conveying a lot of emotion about this. So that's what clued me into this bigger story here. And so I reported on it the failure to find supersymmetry, the failure to find anything beyond the standard model at the Large Hadron Collider. And that article was pretty controversial when it came out. People were mad that we were saying that supersymmetry had failed. I quoted someone saying that particle physics was now going to die out, jobs would disappear, this was the end. And people got really upset about that. There was not a lot of reporting at that time, but over the next few years, that narrative became more clear to everyone. We're talking even 10 or more years ago, people were concerned about the fate of particle physics If you go to the border between France and Switzerland CERN is still there The Large Handron Collider is still operating It going to operate for a while You revisited this question now this much time on Obviously, there's been no new particle found. What did you find out in the course of looking into this question afresh a dozen years on? It was interesting to me. A couple of particle physicists I spoke to didn't seem to recognize that there's a problem even now. The Large Hadron Collider is still running. It will be running for another decade. People there are still excited about what they're doing. They've, in the past couple of years, really integrated AI into their data handling in a way that has allowed them to get more out of their data, more precision in understanding the outcome of a collision. Is there any prospect that increased precision would lead to a revolution in thought? It's a good question because, you know, if they did do this and then figure out, oh, wow, when we look more carefully, this one decay channel is really different than what the standard model would predict. There's way more, you know, muons and antimuons than we thought we should see. So there's a chance for anomalies. There is. That would indicate something deeper. And I think, you know, if they find that, that's great. But the problem is that as the precision increases, they're not finding anything like that. It's a standard model all the way down. Yes. So that's one thing that's going on. There's also, you know, at the same time, ParticleVis is campaigning for a bigger collider. Just as that Large Hadron Collider followed the Tevatron, and then there was LEP at CERN before the Tevatron, and then the collider before that. The idea when the Large Hadron Collider was built was that there'll be another one after that that will be even bigger, that we'll discover more particles, that this would all keep going. And there are still particle physicists campaigning for the Next Generation Collider. In fact, there's a campaign in Europe to build a 91-kilometer-around proton collider. That's how much bigger than the LHC? Yeah, the Large Hadron Collider is 27 kilometers around. So yeah, three times bigger. And that would reach energies seven times higher than the Large Hadron Collider. And that could show evidence of heavier particles, supersymmetry. Do we not know? You know, there's no longer any reason to think there are particles right around the corner that the Large Hadron Collider just missed, but that another collider would find. So that's a real problem for this campaign. How do you sell all the governments of Europe on funding your next machine? Hundreds of billions of dollars without even knowing that you're going to get one significant particle physics headline out of it. Yeah. Physicists know that these questions are fundamental, that this is our chance to take one more step. And so to them, that feels totally worth doing. To government funders who are being asked for money left and right by all kinds of scientists, I don't know that that's going to be funded. And then in the U.S., there's a campaign to build a muon collider, which should be a totally new kind of collider. It would not even reach the energy of the Large Hadron Collider, but because it would collide muons instead of protons, muons are elementary particles, so they don't have any substructure like protons do. So their collisions are really clean. And so you can measure the pattern of what comes out even more precisely and cleanly. Another precision play. Yeah. The problem there is that muons decay really quickly, so you have to develop a whole new technology for producing them and colliding them within moments. So there's an idea that just the mere technological innovation there would make the project worth doing, even if the likelihood of a discovery is even lower than with the project in Europe. You know, it's important, of course, physics as a field trains a lot of technical people that then go into other areas of research. So if we can keep this going by creating a new kind of collider, that might be just good for the country, for the world to do that. We'll see if the Department of Energy is convinced by that and just by the desire to try our best to make a discovery if we can. Do you feel like, on the basis of your experience as a physics writer and reporter and editor, that there's a promising direction here? If we're going to find new physics that resolves these longstanding problems, where do you think it's going to be found? I don't have any kind of brilliant answer to that. There's a lot of different experiments going on. There's searches for dark matter particles. There's precision tabletop experiments measuring fundamental constants better and better. there's all these different small-scale experiments going on, any of which could surprise everyone by making a discovery. There's little shots in the dark happening all over the place. And it's very possible that someone will find something and it would change everything. I mean, I would have to say that to me, the more interesting work is happening on the theory side. A lot of particle physicists who used to maybe spend their time coming up with new models of supersymmetry supersymmetry or new possibilities for how you could extend the standard model. Now what they're doing is thinking harder about these patterns that I was talking about of which particles are coming out of a collision and the probabilities of different results that you get. There's been a lot of interesting work in the past 15 years in a relatively new field called amplitudiology, which really is looking at these patterns and these amplitudes and trying to figure out, okay, what is a completely different mathematical way of understanding these patterns that doesn't even conceive of the problem as particles bashing together and then other particles flying out? It's not thinking about things in terms of particles moving in space and time, but in a whole other mathematical way that's maybe simpler, deeper, more abstract, that could give us a new perspective on particle physics, on the structure of our theories of quantum field theory, and maybe reformulate the whole thing in a way that then makes it obvious why there is this hierarchy of scales, why there is quantum gravity, how that fits into the picture. There have been such amazing discoveries in that area on the theory side that I'm pretty hopeful that that progress will keep happening. You know, it's not new clues. It's a new conceptualization of all the clues, all the data. Yeah, this makes sense to me in a way, because you taking all of this experimental data that you can get to tell the story that you needed to tell So you go back and you look at it statistically you re it you try to find a new mathematical framework that explains it, and then that could point the direction to a new theory, one that's already supported by data inherently. Yeah. So we really have to just try to think our way there by this kind of technique, a re-envisioning, you know, in the style of, say, Einstein being like, okay, space and time are not what we thought. There's this whole other way of looking at it. You know, that is something I could imagine AI helping with if it keeps developing. It's good at pattern recognition, and so it might be able to help develop this new perspective. I spoke to Jared Kaplan. He's one of the co-founders of Anthropic, the AI company, and he comes from a background in particle physics. He actually was one of the people, as a grad student who was sort of instrumental in opening new directions in amplitudes research. And he left the field to go into AI. He told me he really saw that as the place where the most progress could be made in our lifetime, maybe in the history of science. Because it could short-circuit our whole search for a new theory by doing all the things you're talking about with the data and coming with the new mathematical framework for it. Yes, yeah. Like to him, If anyone's going to figure out what we should do next in particle physics or what the answers are that we're not seeing, that's how to understand the standard model together with quantum gravity, that it would be AI. So that's what he's focused on. There's a possibility there. We'll see. I'll confess to a little existential dread with this idea that we've hit a wall in our understanding of reality that we can't push past. And the maybe most promising answer is, oh, let's ask an AI to figure it out for us. There's something a little, I don't know, spiritually scary about that. Yeah, I think it would be totally fair to be skeptical of that. But if it is going to become exponentially more powerful over time, then I think it probably is likely that AI would have some brilliant thoughts about the structure of the underlying unified theory of physics. I'd hope so. We need our geniuses to come up with those ideas. So if AI is our next level genius, or maybe it's just chatbots telling us nonsense and it doesn't get much better than this. It's been a great conversation, Natalie. Before you go, we like to close every episode with a recommendation. So what's exciting your imagination this week? I came across this really interesting essay on Cory Doctorow's blog. He's a writer of fiction and nonfiction. It's called America and National Capitalism. And we're all trying to make sense of this moment in American history and where things are going from here and how we got here. To me, that essay, which talks about Thomas Piketty's theory of capital, basically, spoiler alert, the upward flow of capital, how much that framework explains what's happening now in the United States. It was a very satisfying read for those of us who are scrambling right now to make sense of it all. This has been a pleasure, Natalie. Thanks again for coming on the show. Thank you, too, Samir. Also on Quanta this week, you can read about whether dark matter is made up of tiny microscopic black holes whizzing by, and about how bats and other mammals use an internal compass to navigate their environment. you can imagine that with all of the scientists and folks working in and around the particle collider at cern that there'd be a lot of creativity in the air and you'd be right they work to foster that with an arts residency program we're going to leave you today with another manifestation of that energy a group of physicists composers artists developers created what they called the Large Hadron Collider Sound Project, where they use real and simulated data from the Atlas detector there to create atmospheric soundscapes. This audio is provided by UCL High Energy Physics. So so so Thank you. Please take a moment to rate the show and leave a review. We'd love to hear from you. The executive producer of PRX Productions is Jocelyn Gonzalez. From Quanta Magazine, Simon France and myself provide editorial guidance, with support from Matt Karlstrom, Samuel Velasco, Simone Barr, and Michael Kenyongolo. Our theme music is from APM Music. If you have any questions or comments for us, please email us at quanta at simonsfoundation.org. Thanks for listening. From PRX.
