"I Thought It Would Fail!" Francis Halzen: Winner of the 2026 Nobel Prize In Physics [Reupload from 2022]

The physicist who turned a cubic kilometer of Antarctic ice into a telescope says the most exciting moment of his career was not the discovery. It was the first atmospheric neutrino. Before that, he was deep in debt to NSF and his own university with no neutrino to show for it. Francis Halzen is principal investigator of the IceCube Neutrino Observatory at the South Pole and Hilldale and Gregory Breit Distinguished Professor of Physics at the University of Wisconsin-Madison. We cover: why ice under the South Pole is clearer than anything a lab can make, the 2,600 TeV event that dwarfs the LHC, why IceCube sees more energy in cosmic neutrinos than in gamma rays, how neutrinos crossing the universe test quantum gravity, and the quark he refused to believe in. Physics is a miserable career unless you are obsessed by it. Recorded in 2022, before IceCube detected neutrinos from our own galaxy. Learn from Nobel Prize winners, and you could win a meteorite: Please join my mailing list here 👉 briankeating.com/x Chapters 00:00 Physics is a miserable career, unless 02:54 A textbook written before the W was found 06:11 Breaking into Lemaître's computer at night 10:57 Do scientists owe the public anything? 13:55 Deep in debt with zero neutrinos 19:40 The persuasion nobody teaches scientists 20:15 Why it could only be the South Pole 23:20 Learn physics by doing, not by courses 26:00 How to turn Antarctic ice into a telescope 31:30 2,600 TeV: far beyond the LHC 35:00 More energy in neutrinos than gamma rays 40:00 Tracing ghost particles to NGC 1068 46:00 Testing quantum gravity with neutrinos 1:01:00 Ten times the ice for the same price 1:07:08 What he would leave his descendants 1:11:19 What his generation should be proud of 1:12:51 The quark he refused to believe in 1:17:09 Imagination can trump intelligence 📺 Watch my most popular videos: Neil Turok Believes Physics Is In Crisis Nobel Prizewinner Frank Wilczek Stephen Wolfram vs. Eric Weinstein Sir Roger Penrose: Nobel Prize in Physics, Black Holes and More Noam Chomsky: Consciousness, Elon Musk, and More Sabine Hossenfelder Avi Loeb: UFOs and UAPs Neil deGrasse Tyson Follow me to ask questions of my guests: 🏄‍♂️ Twitter: @DrBrianKeating 📝 Mailing list: briankeating.com/mailing_list ✍️ Detailed blog posts: briankeating.com/blog 🎙️ Listen on audio-only platforms: briankeating.com/podcast A production of imagination.ucsd.edu Executive Producer: Brian Keating Producer P. G. A: Stuart Volkow Editing: Lucas Scheiblich Learn more about your ad choices. Visit megaphone.fm/adchoices

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Speaker 00

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• 0:46Speaker 04

  Being a physicist, from all

• 0:51Speaker 04

  objective point of views, is a miserable career. Yes. And I don't have to state the reasons. The only reason it's worth doing is you just enjoy it, is you're obsessed by it. You love what you're doing. And so if you do it as a job, it's going to be very, very disappointing, I think. So don't underestimate yourself. Until I went on this crazy adventure of Amanda and Ice Cube. I always live with the insecurity that I didn't belong to the circles I moved in, which I think must be true for almost every graduate student. Just get over that.

• 1:36Speaker 05

  Any sufficiently advanced technology is indistinguishable from magic.

• 1:42Brian Keating?

  Well, it's not every day you get to talk to a hero of physics, of modern physics, someone whose roots go back quite a ways, someone who's been a leader in the field of astrophysics, of particle physics, who's an educator and a communicator of science, but also who was actually, I think today's guest is my first ever guest, who is a professor of mine, although I took his class as an adjunct student while I was at the University of Wisconsin. And it is one of my personal heroes. This is Francis Halzen, who is a Belgian particle physicist, although he's been in America probably more than half his life.

• 2:25Brian Keating?

  He's the Hildale and Gregory Bright distinguished professor at the University of Wisconsin-Madison. He's a director of the Institute for Elementary Particle Physics, and he's the principal investigator of the Ice Cube Neutrino Observatory, which has operated at the South Pole, Antarctica since 2010. Before that, there was Amanda. Francis, it's a certain treat to be here, for me to host you here, rather, and I just hope you won't share the grade that I got in your class. Please don't tell my audience, I don't want to.

• 2:56Speaker 04

  I don't think my bureaucracy, my administration is so good that I would be able to produce it.

• 3:03Brian Keating?

  Well, it was one of my favorite classes of all time. Not to mention the fact that back then it was rare that professors wrote the textbook that was used for the class. I think I had that only with Leon Cooper at Brown, with one of his quantum mechanics books. But to take this course on particle physics with you, and it was such a treat. And I thought we'd start there, Francis. We always start, we have on, you know, we just had on Martin Rees, Lord Martin Rees, last week. And he spoke about his book. And we always do a scenario called judging books by their covers, where we look at the cover of your book and we judge it, and how did you come up with the name? And hopefully entice, you know, a tenfold increase in book sales instantaneously.

• 3:48Brian Keating?

  So the book we're talking about is called Quarks and Leptons. It was a wonderful, wonderful book that I had there. We'll show it on the screen. It's written with your co-author, Alan Martin. Well, I don't recall much about him, but certainly taking it from you was quite a treat. So Francis, can you help us judge quarks and leptons by its cover? How'd you come up with the title, the subtitle, and the cover illustration?

• 4:15Speaker 04

  The title was actually, first of all, I must say, this was a long time ago. And that's the amazing thing about the book, right? People don't realize now that this book was written a long time ago, and that the W, the Z, the top quark, none of these things, the Higgs, none of these things had been discovered. You know, like the whole book is kind of prediction of the standard model. And in fact, the book was in print when the W was discovered at CERN, the weak intermediate boson.

• 4:58Brian Keating?

  Wow.

• 4:59Speaker 04

  And so the editor called me and said, you can still change things, you know? I've read the newspaper. And I said, there's nothing to change. And he was kind of worried that he had been part of some huge gamble.

• 5:18Speaker 04

  So, but the title is kind of embarrassing because although I think it was really, the books were really written in parallel. Okun, famous Russian theorist, wrote the book Leptons and Quarks that came out around the same time. So it's not that original.

• 5:44Brian Keating?

  And the illustration that you have on the cover, what does that represent there?

• 5:48Speaker 04

  I, I, the only thing I remember is that I actually made it. And it remembers, you know, jets were something rather new then. You know, quark glue on jets, the concept. And so I know that it represents like a jet made in deep in elastic scattering or something like that. It's amazing that I cannot remember.

• 6:17Brian Keating?

  No, I think that rings true. And actually, we have had on past guests Frank Wilczek many times. And he cites that, the discovery of jets at least, not by, you know, Ice Cube or anything personally, but he cites that as the kind of signature achievement of his career and of work that particle physics as a community has led to. And I wonder, you know, if we could pivot from this wonderful book, which I learned a great deal from, and I still make reference from when I have the task of teaching to young people as well, as well as your style. So I want to first take a step back. It is rumored that you knew Le Maitre, the famous Belgian Catholic priest, the progenitor in some sense of the Big Bang. Is that true, Francis?

• 7:02Speaker 04

  I barely knew him. He, he died when I was doing my undergraduate thesis. And so I could tell Le Maitre stories for a long time. But I'll only tell you two, because of course, every interaction I had with him is now legendary. But I'll only tell you two. He had a computer. He built himself to solve Friedman's equations. And it was a big room with vacuum tubes. And that computer, I mean, it was state of the art at the time, was only used during the day.

• 7:47Speaker 04

  And we actually, we mean, another graduate student and I, Rem Ogasman's, we would actually break into the room and use the computer at night. And we used it to calculate Feynman diagrams. Veltman had just discovered the methods to calculate Feynman diagrams by computer. And so I think we may have been the first people to do this after Veltman discovered it. The other story is that when I

• 8:26Speaker 04

  I was an undergraduate, Le Maitre would arrive in a limousine at the physics building. And, you know, he was an important person, and he couldn't walk anymore, barely walk. And we put him on a chair and then carried him to his office on the second floor. And it's only later that someone else who was part of the institute told me that that was actually Le Maitre. I had never made the association.

• 8:58Brian Keating?

  Wow.

• 8:58Speaker 04

  He was not very visible, he was retired. And, you know, he came in very rarely.

• 9:07Speaker 04

  And by the way, he was not famous, right? As you can imagine, he was famous for being a cardinal and for his role, like maybe role in Vatican two, but I don't think so actually.

• 9:22Brian Keating?

  Yeah.

• 9:23Speaker 04

  So he was, I mean, you know, the status of cosmology at that time, right? So it was just at the time he died, as you know, when the microwave background was discovered.

• 9:38Brian Keating?

  That's right. And one of the things that's always impressed me about him and many others is that he was an advocate that the Pope, uh, was it Gregory? I forget who it was in Vatican. But they, they, uh, attempted, the Vatican attempted to, uh, utilize the, you know, predictions of the big bang, at least as a motivation for Genesis. And I, I was actually just in Galileo's, uh, house in, in Florence, Archetti, Italy. And of course, you know, he was refuted by the, the Catholic Church and repudiated his own ideas under penalty of death, basically. But, um, did you ever get the sense, or was there anything in the Belgian physics community, perhaps that, uh, what, that, that, you know, spoke of what

• 10:19Brian Keating?

  was his true, you know, um, emotional investment in the big bang? Did he have one or was he able to detach being a scientist from being a theologian?

• 10:29Speaker 04

  Yeah, I cannot tell. I was not, you know, he, I never got any class. He basically was at the end of his life. And so we had really no interactions scientifically with him. But the fact that he, uh, he denied that the big bang had any connections to creation. That's, I think, well documented.

• 10:52Brian Keating?

  Mm hmm. Yeah.

• 10:53Speaker 04

  You read his bio, there are a couple of biographies of his, which I've read, of course, and, uh, uh, they, they clearly document that he, he didn't see, he didn't make any connection to religion.

• 11:07Brian Keating?

  Mm hmm. And when we were getting ready to start recording today, um, I wanted to kind of get your, you know, take on the obligations of a scientist in terms of what he or she should do, quote unquote, should do. Uh, and I think, you know, La Matter certainly took that role seriously, but, but, you know, he had so many hats that he was wearing, you know, pontifical hats, maybe, and science hats. But, um, but what's your philosophy? We'll, we'll come to more kind of big picture questions later, um, after we review Ice Cube and your career. But, um, what is your view of, of what the obligation, if any, that a scientist has to

• 11:48Brian Keating?

  explain things to the public? And then do they have to kind of be careful how they explain things? Because maybe the public doesn't understand what they're doing.

• 11:58Speaker 04

  Well, I think I, uh,

• 12:02Speaker 04

  from this point of view, I am a very practical person. I don't think I'm on a mission of anything. And on the other hand, uh, I think that, uh, even we are supported, uh, by the public to do our science, we owe some return to them. And, you know, I have never turned an invitation, you know, to talk about my work to anyone, to at any level, any student of any age, I always react positively to an invitation to discuss my work. And, and

• 12:42Speaker 04

  that's, I think, an obligation we have. Uh, beyond that, uh, I think it's very dangerous to, you know, our expertise is science and it's actually even within science, it's a very limited expertise. And I think it's, uh, to the advantages of scientists that they stick to their expertise. And that's certainly something I always do.

• 13:10Brian Keating?

  Yeah, I always say that, you know, the, the problem that we as scientists deal with is that sometimes we become political scientists and

• 13:17Speaker 04

  Yeah, exactly.

• 13:18Brian Keating?

  delve into politics. Uh,

• 13:21Speaker 04

  No, that's not a good idea. And it also, it hurts science, right? Because it then science begin to look like something that it shouldn't be, and it's not.

• 13:33Brian Keating?

  Right. And there's a danger in what we call audience capture, that you have to, um, only do what your audience wants you to do. So on this channel, a lot of times people want me to only have people that won the Nobel Prize, or only talk about aliens, or only talk about dark matter. And I have to be very careful because I get a lot of attention from the videos, uh, that are popular, but that isn't necessarily the totality of what I think a scientist should be interested in. So anyway, I think you're absolutely right. And I want to ask you, um, you know, first, if we can go back, uh, to maybe a moment in your career that was a little bit, you know, maybe perilous. I remember being in Madison, as you know, from 97 till, uh, Peter Timby, my, my wonderful advisor, who's been

• 14:17Brian Keating?

  a guest on the channel. So you're my second guest from the University of Wisconsin Madison, the great Badgers, uh, cheese state, Dairyland state. Um, so, uh, I had nothing but fond memories of being there. Uh, when I had Peter on, we were kind of, you know, speculating on, on the, the notion as a scientist to deal with uncertainty. And I remember you building, you preparing to build and, and starting to build up Amanda. And it wasn't just the technology, it wasn't just the theory, it wasn't just the science, it was the people. It was the team that you built, which is, you know, which is unrivaled. And it seems to me you've been working on this for so long. Was there ever a time that you had doubts in yourself, that the funding would come about, that you might not succeed as you've

• 15:02Brian Keating?

  done so spectacularly well, uh, with Ice Cube? Did you ever have a moment of panic, uh, that you just were so terrified that project might not move forward?

• 15:12Speaker 04

  The whole, the whole story was a story of panic. You, you got the right word. Uh, you know, from the beginning, when, uh, people thought that, uh, this was a very cute idea, but that it wouldn't work. Well, that's what we thought too. So, but it kind of started as a, you know, as a game, it didn't cost that much. We were piggybacking on the, on the South Pole infrastructure that already existed to a large extent. Uh, but then NSF, uh,

• 15:56Speaker 04

  started to fund the project. I actually borrowed a lot of money from the University of Wisconsin.

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• 16:34Speaker 04

  And I was deep in debt to both NSF and the university, and we had never seen a neutrino, not an atmospheric neutrino. And so, and of course, it's because, uh, we really didn't know whether turning ice in a Sharenkov detector was possible. It took us like a decade to figure out what the ice was like. We couldn't put it in a test beam at Fermilab. And so, uh, you know, the most exciting, among all the panic moments, the most exciting moment was not when we discovered cosmic neutrinos, but when we finally observed atmospheric

• 17:17Speaker 04

  neutrinos, because that I felt we have delivered. Now it's up to nature. And even afterwards, I thought, you know, if a scientist, you know, the English like to gamble, right? Scientist wrote an article that gave us six to one to discover, uh, cosmic neutrinos, against, of course. And, uh, I remember not feeling very well when I read this. But then, uh, I, I always thought if we did build something that unusual, we'll do something interesting.

• 17:55Speaker 04

  The big surprise actually is that, uh, we are doing neutrino astronomy and not something totally different. We do different things as well. But the other moment of panic is when we finally got the courage to publish in Science that we had detected cosmic neutrinos. And weeks later, we were declared, uh, breakthrough of the year in 2013. And I must say that, uh, was also a moment of panic. And I remember the press conference and the only thing I thought about is how do we run

• 18:37Speaker 04

  this backwards if this happens not to be true?

• 18:42Brian Keating?

  Right. And that was

• 18:43Speaker 04

  And I lived with that panic for quite a long time. In fact, it's only now that we see sources, right? Since 2017, that, you know, I, I, I sleep better at night.

• 18:58Brian Keating?

  Well, that's a, you know, 30 year journey to

• 19:00Speaker 04

  But this, this was a wild ride, right? This whole story of ups and downs and

• 19:06Brian Keating?

  Yeah. So, um, what was the role of the South Pole in, in this? But could it have been done somewhere else? There, there are alternative approaches, but none even closely related in success to what you've achieved.

• 19:20Speaker 04

  So No, that, that, that was, uh, it's a unique opportunity because you need clear ice. Clear ice exists elsewhere, but you have to build a sophisticated detector in a remote location. And without the South Pole stations, I mean, you, this would not have been possible. Remember, uh, we, we started in a very modest way and nobody would say, oh, there. I, we always wanted to build a kilometer cube detector. Can you imagine someone saying, ah, Halzen wants to build a kilometer cube detector? Let's build a station somewhere above the glacier in Greenland and give him the opportunity.

• 20:05Speaker 04

  It was pure serendipity that these two things came together, the clear ice at the South Pole and, and the station being there. Nobody would have built it for us.

• 20:16Brian Keating?

  No, and it's such a unique location. I've been there twice. Uh, I, I actually prefer going to McMurdo than going to the South Pole, but that's just me. A lot of people love going to the South Pole more than anything. Uh, and the, the results that you've garnered, yeah, it's, it's, it is serendipitous in a way, but it also took a lot of foresight by you and your team to recognize and persuade. I, I think one of the least appreciated aspects of a scientist is his or her ability to persuade. And that includes persuading a undergraduate to work in his or her lab or a funding agency or to get tenure or to get even a professor job is so hard nowadays. But then building a team, so it's, it's not enough to have the right idea.

• 21:00Brian Keating?

  Like the idea is just kind of the table stakes, you know, to use a gambling analogy. Um, so when, when did the, the kind of, um, that, that subsiding of that panic? What has been, I mean, of all the things that Ice Cube does, and we're going to cover it a little bit of technical detail because my audience is the most sophisticated in the known regions of the multiverse that we inhabit. Um, but I want to ask you of, of the technical breakthroughs. Could Ice Cube have been done, you know, 50 years ago? Let's say if there was a, you know, very, very young Francis Halzen as a, as a graduate student, could you have done it 50 years ago? Or were there technological breakthroughs that you and your colleagues and understanding of the ice has made?

• 21:42Speaker 04

  Yeah, uh, it depends. It's a difficult question. I, it's a question I've never answered, which is fair. Uh, the, one of the challenges, I mean, maybe the biggest challenge was to build a hot water drill. And that was such an unusual problem. It was also an exciting problem because, you know, you don't go to school and they teach you about hot water drills, right?

• 22:14Brian Keating?

  No.

• 22:15Speaker 04

  So

• 22:16Brian Keating?

  Well, in Wisconsin, they do actually, right?

• 22:18Speaker 04

  This was done by a group in Wisconsin of engineers, professors, graduate student technicians, anyone who could contribute, contributed. And it was very exciting, but I think, you know, it's car wash heaters that make the power. And the nozzle is very sophisticated. It was designed by an engineer, but it could have been done before, no doubt about it. I am not so sure about, uh, the data acquisition because, um, of course, we could have used the Amanda technique of, of just sending analog signals over, uh, the cable that brings down the high voltage, right?

• 23:03Speaker 04

  To that powers the photomultipliers. So, but the, the data acquisition of Ice Cube is a bit more sophisticated. You know, we capture the signals in, uh, in the ice, transform them to digital and then transmit them. And so that was the fact that chips that are used where the PhD thesis of a student of David Nighren at Berkeley.

• 23:34Brian Keating?

  Oh, wow.

• 23:35Speaker 04

  So that was really a bit beyond state of the art at the time. Of course, now, uh, that technology is, is, looks like archaeology, right? But, uh, this was, uh, the, the Berkeley design was made in, um, in the late 1990s because it was all in place when we submitted a proposal in 99.

• 24:04Brian Keating?

  Right.

• 24:05Speaker 04

  So it could have been done, it probably could have been done earlier, but in its present form. And for the discoveries we make, the electronics, I don't think we could have done it with Amanda analog signals. Uh, uh, it's pretty essential to have the technology that, uh, Nighren and the Berkeley group, uh, developed for the data acquisition.

• 24:31Brian Keating?

  I want to ask you, because I knew you as a, as a student of yours, uh, albeit not as a graduate student. I think that would be a, a great treat, but, um, but as a student in a class about, uh, for advanced, you know, undergraduates and graduate students on particle physics. Um, why do we conflate, um, scientific ability with educational or pedagogy ability? In other words, um, you know, someone who's a pilot may be extremely skilled at flying, but we don't ask, you know, him to like teach flying necessarily, although you, and you can actually teach flying with, I'm a pilot in my side hustle, uh, to, to, to pay the bills here at the State University of California. Uh, but I want to ask you, why is it that we do that? Do we, do they do that in Europe?

• 25:15Brian Keating?

  Is, is that common, um, you know, that we have expectation that because Francis or Brian are good at scientific research, that they're also good at teaching? Or, or is that a mistake?

• 25:27Speaker 04

  Well, I, this is one, this is one of the things I feel passionately about and never had the time to do much about it. But I think that, uh, you know, the graduate, uh, school that exists today at American universities, uh, is, uh, in a sense unfortunate. It still lives in the days that you take courses and learn all of physics and then do research. First of all, you cannot learn all of physics anymore. You cannot even learn all about some specialized subject in physics.

• 26:08Brian Keating?

  No.

• 26:09Speaker 04

  So the way I have, I, I have everything I know and the Belgian system at the time allowed you to do this, everything I know, I've, I've learned by doing research. You get interested in a problem, you have to solve it. You learn everything you need to solve that problem. And that's how you learn and you remember, by the way. And, uh, I think, uh, that's the ideal way that you, trying to get a background of all of physics before you start to doing research is an illusion, uh, which we, which we are still living in, in our present system of graduate schools.

• 26:54Brian Keating?

  Yes, yes. And it's, it seems to be, you know, sort of strange how the European system influenced the American system. You know, the, the Germanic, uh, kind of, uh, emphasis on research. And now most of the Ludwig Boltzmann or Max Planck Institute, they don't teach, as I understand it. So it's kind of ironic that the educators of the American system, um, of the, uh, they don't do any education of their own anymore. Um, so I wanted to talk a little bit about the technical details and the theoretical underpinnings of Ice Cube and, and you've been kind enough to prepare some slides. So I'll let you get set up to share the screen.

• 27:33Speaker 04

  Okay. So, uh, you know, we want to detect neutrinos from space because we want to do astronomy with neutrinos rather than with photons. And we know how to detect neutrinos. This is an experiment in Japan in a deep mine and it's a huge tank of water and light sensors. And that's how you detect neutrinos. The problem with this beautiful experiment is that the theorists in their wisdom told us that, uh, and by the way, I'm not blaming anyone, was one of them, uh, told us that this experiment

• 28:15Speaker 04

  is 10,000 times too small to, to do astronomy and catch the tiny flux of, uh, neutrinos that reach us from the universe. So to make a long story short, we build a detector that, uh, instead of water, made out of water, is made out of ice. And the photo tubes are distributed throughout the ice. And, uh, according to our wisdom as theorists, it probably had a chance to detect cosmic neutrinos, but no guarantees were given.

• 28:56Speaker 04

  And so what you're looking at, of course, is, uh, is not a real picture. But so if you go under the South Pole, you stand, the South Pole station stands on three kilometers of ice. And you go one and a half kilometer deep, uh, there are strings with, uh, the light sensors that you saw on the walls of the Japanese experiment. And so the strings are a kilometer long and there are 86 of them. So the light sensors between strings are 17 meters apart and the strings are 125 meters apart.

• 29:37Speaker 04

  And 86 of these strings fill a volume of ice with, uh, light sensors. This idea, by the way, was, uh, born in 1960. A Russian physicist Markov came up with this idea. So the idea is certainly not new. So the challenge was to

• 30:04Speaker 04

  熔化这些传感器到冰上， 所以我们开发了—— 这就是第一个巨大的挑战。 我们在威斯康森开发了技术来实现这一点。 第二大的挑战是， 这个冰足够好来作为粒子传感器工作吗？ 这是一个很长的故事， 而这个故事发生在这张图片中， 如果我通过这张图片阅读的话，我会花大部分时间。 但我们创造了我们最大的突破， 当我们意识到冰中的蓝色光 可以穿越几百甚至有时候几百米。

• 30:44Speaker 04

  所以这是70,000年前的 compacted snow 它是非常纯净的， 即使在实验室里， 你无法建立一个如此透明的蓝色光块。 所以我们不知道这一点， 这是纯粹的偶然性。 所以当这些问题被解决时， 我们建立了它们并采集了数据。 我的想法是， 你可以想象你的冰块在这里。

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• 31:27Speaker 04

  你可以想象它是一米五的深度， 它很黑暗。 所以我们做的是寻找地球通过的粒子， 只有核能能通过地球， 其他东西都没有。 这个核能不光通过地球， 它也通过你的 detector。 但偶尔， 像一亿中一个会击中冰上的核， 氢或 oxygen 的核， 并产生粒子。 它在核 interactions 的粒子， 它们被 charged， 它们让光发光， 这被称为相射率。 如果这是一个 muon 核，

• 32:11Speaker 04

  它会生成一个 muon， 它在冰上 traveled 千米。 所以这个 muon 你可以从 50 米到 在高能量 50 米之外。 这不是非常实用， 但是你理解了你的 detector 大于你的 instrument。 另一个问题是， 你有一个 telescope， 因为你不仅能 detect muon， 你还可以指向它， 因为 muon 在光的速度中 traveled 差不多，

• 32:51Speaker 04

  而冰中的光 traveled 三倍光的速度， 所以它就像一艘速度船， 它超越了它的波， 所以你会得到一个 shock wave， 就像一艘船的波， 它会指向那个 muon 来自哪里， 和那个 neutrino 来自哪里。 所以 我们建了一个 detector， 这里你可以看到一个事件。 这是一个 neutrino， 它从 horizon 11 度以下， 通过 detector 流动。 它在 detector 内部 deposit 了 2,600 TEV 的能量。 所以你必须记住，

• 33:34Speaker 04

  在 San 在 Geneva 的最高能量束， 是 14 TEV。 所以这个粒子在 detector 内部 deposit 了 2,600。 顺便说，

• 33:51Speaker 04

  我提到了 atmospheric neutrinos， 这是我们的背景。 这个事件太沉重了， 在 atmosphere 中不能产生， 太有能量了。 我们这些时候可以做 astronomy， 以 0.3 度的分辨率。 如果你没有看到图片， 这里你可以看到， 在我们的在线屏幕上， 你可以看到 muon 通过 detector， 光的速度被计算机减速。 这就是方法。 所以我们做了这些， 我们测量了 neutrinos 从宇宙， 你可以看到，

• 34:29Speaker 04

  这是 detector 收集的 neutrinos 从宇宙的能量， 作为 neutrinos 的能量。 你正在关注的这些数据点是 electron 和 neutron， 这是实际上 muon 核测量的 flux， 这个粉色的斑点是 flux， 这是我刚才展示的。 我们测量 electron 和 neutron 的其他数据点， 用不同的方法， 但是你可以看到它们一致。 所以这是通过地球的 muon flux，

• 35:12Speaker 04

  你可以看到我们从 atmosphere 中测量 flux， 当我们达到 detector 的 threshold， 就是 100 TEV， 然后我们越来越多的 background 在 atmospheric neutrinos， 当我们到达了十的TEV， 然后你看到 atmosphere 关机， 我们看到 previous 图中显示的 excess flux。 这是现在 close to 10 sigma 的测量， 我们看到了 atmospheric neutrinos 至少有四种完全不同的方式。

• 35:50Speaker 04

  这就是冰球的 status。 我有几个图片来展示我们的结果。

• 35:58Brian Keating?

  是的， 请做。

• 36:00Speaker 04

  事实上， 我们最重要的结果， 我们实际上从没有广告， 但我今天会做， 我总是个人会做。

• 36:11Speaker 04

  我展示了我们从宇宙中接收的 flux， neutrinos 中的能量 flux， 这是 astronomers 叫做 new F new。 当然，我们接收， 我们 detect 了 gamma rays， 这里你可以看到这个峰， 这个巨大的峰， 那是 CMB， 我的主持人很熟悉。 然后你通过， 它统治了宇宙， 然后你去到不同的光波束， 这是 ultraviolet 光， X 光， gamma rays， 但是然后宇宙变成了 gamma rays， 它变成了 gamma rays，

• 36:55Speaker 04

  因为它们无法通过 microwave background， microwave background 填满了宇宙， 阻止了它们到我们， 除了我们自己的 galaxy。

• 37:07Brian Keating?

  对， 实际上，Francis，我必须在这里停止你。

• 37:10Speaker 04

  是的，

• 37:10Brian Keating?

  你 你知道你的教授的绰号 Bright， Bright Wheeler 奇迹， 就是光子的相互转换， 到 positron-electron 来的 pairs， 这是只是最近发现的， 而且实际上我做了关于这个视频， 我会在这里有一个链接。

• 37:29Speaker 04

  好的， 谢谢。

• 37:31Brian Keating?

  那真的很令人兴奋， 无论如何， 请继续， 对， pair production。

• 37:34Speaker 04

  对， pair production， 所以这些光子， pair 产生， 保持正负 pairs， 与 microwave 光子 interacting， 所以它们失去能量， 所以 flux 消失。 当然，这是 neutrino astronomy 的特征。 你可以看到， 一旦你超越了这个分界线， 你只能用 neutrinos 做 astronomy， 但是另一个有趣的事情是， 如果你看 gamma rays 中的 flux， 我们观察到的 flux in neutrinos 实际上比 gamma rays 中的 flux 大。 没有人曾有想到这一点，

• 38:19Speaker 04

  这也是为什么我们只用了两年的数据发现的。 所以这是一个有趣的事实， 仍然需要一些思考和解释。

• 38:37Speaker 04

  Now we have to find where these neutrinos come from. So here is a picture of one year of neutrino data in galactic coordinates. So that's the sky we see in neutrinos. We have 10 of these pictures for 10 years of data, more now. And we know from the flux we just measured that in this map there are 138,000 plus atmospheric neutrinos. 200 of them are actually cosmic. But you also saw what I explained. If you go to very high energy, the atmosphere cannot deliver neutrinos anymore. And you are in business.

• 39:20Speaker 04

  So if you look at the very highest energies, it looks like this.

• 39:25Speaker 04

  These are various methods with which we collected these cosmic neutrinos. But notice one thing, we don't see our own galaxy. Now, in any other wavelength of light or any other way of doing astronomy, the first thing you see are the sources in your own galaxy. We don't see those. We see flux at the 10% level of the flux that reaches us from the cosmos. So there are galaxies outside our, or sources outside our own galaxy that overpower the flux from the nearby sources that produce neutrinos in our own galaxy.

• 40:12Speaker 04

  We have a paper that's under review in Science that will address this question. But just to remind you, that's what the galaxy looked like in visible light and we don't see the galactic plane in neutrinos. Now, for many years, we made the cosmic neutrinos were discovered in 2013. Of course, the game was where do these particles come from? You know, we know their direction now to 0.3 degrees. And we did all kinds of things. But I'm going to just tell you about the latest.

• 40:55Speaker 04

  We actually discovered the source in a multi-messenger campaign in 2017. It was an active galaxy. And I'm going to tell you what happened since then. We collected, we looked at our 10-year map and we published a paper a year ago. And you are looking what's in this paper.

• 41:20Speaker 04

  And forget the red, just look at the blue. The blue, this is the upper limit on neutrino sources. We didn't see any by analyzing 10 years of data. And you see the dashed line is our sensitivity to sources as a function of where they are in the sky. The northern hemisphere is on the right, zero is the horizon and the left is the southern hemisphere. And we discovered however, that our map after 10 years was not quite symmetric, isotropic anymore. And it was due to these four sources.

• 42:05Speaker 04

  That we detected at almost 5 sigma discovery. But that's before the look elsewhere effect. After you imply the look elsewhere effect, the asymmetry in the map was still real, but the evidence for the sources not so great. NGC 1068 almost reached 3 sigma with all trials taken into account. So the question was, were these limits on fluctuations? And I'm not going to, I'll just give you the answer. They are not fluctuations.

• 42:39Speaker 04

  We went to a campaign to calibrate the detector better, to do improved reconstructions using machine language. We improved the point spread function of the telescope, abandoning Gaussian approximations. And with the conspiracy of all these improvements, we answered the question I just posed. And here you see NGC 1068 before the improvements. And then you see we calibrated the detector better,

• 43:19Speaker 04

  including calibrating each photo tube individually. And you see how, this is the source, the astronomical occasion. You see how with more statistics, we move towards the source. We point better at the source and our final evidence is at the level of 4.2 sigma. Now, this is the result of a blind analysis where we mathematically can compute all our trials. So this is a real, this is not a social construct, it's a real probability.

• 44:01Speaker 04

  And so I can sleep well at night with 4.2 sigma.

• 44:07Speaker 04

  So here, another way of looking at it, this is a picture of NGC 1068. It has this very active hot corona surrounding the central black hole. And here you see the simplest way to look at a signal. You see, this is the direction of NGC 1068. The orange is our background from atmospheric neutrinos. And you see, if you approach the source, the number of neutrinos increases. So we see 88 neutrinos pointing at the source

• 44:52Speaker 04

  with on average higher energy than the energy of the background, which you cannot see on this picture. So that was certainly very exciting. Here you see, let me just look at the top one. These are three analyses that confirm each other. They are slightly different. They actually use, assume different spectral indices. But you see here the 5 sigma discovery, which I showed before. And you see, this is pre-trial, you see NGC sticking out of it. You see a source TXS 506. That's the source we discovered in 2017 because it produced a neutrino of enormous energy

• 45:37Speaker 04

  that telescopes in a multi-messenger campaign pointed back at the source. N of source PKS 1424 plus 240. So the top three sources reappear with improved significant.

• 45:53Speaker 04

  Interestingly, one of these sources here on the fourth row in this analysis is NGC 4151. So here we are, you know, in 1943, Cfer discovered broad spectral lines from these two sources, published in this paper. So we reproduced these two sources in neutrinos. And now I could go forever, home forever again. But so we just, all these sources are sources that are actually activating radio, so they have an active core.

• 46:38Speaker 04

  And the core is opaque to gamma rays. So none of the stuff we see is accompanied by gamma rays. The gamma rays are shifted in the dense target that produces the neutrinos. They are shifted to MEV energy, X-ray or below.

• 46:55Speaker 00

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• 47:24Speaker 04

  And so this is where we stand. So in fact, this is multi-messenger astronomy Plan B. How do you look for sources that don't emit gamma rays? That's not so simple actually. So I'm waiting for ideas. I think that's the end of this. Yes, so this is NASA picture of NGC 1068. Yeah, sorry, this is it.

• 47:52Brian Keating?

  And thank you so much, Francis. So the other thing I wanted to pivot to was a recent paper that your team had in Nature about a limit on quantum gravity. And I wonder, first of all, do you have any slides about that?

• 48:08Speaker 04

  Yes, I do.

• 48:10Brian Keating?

  Okay, great.

• 48:10Speaker 04

  I do. You don't, I want to emphasize that.

• 48:20Speaker 04

  Wir sind ungefähr 350 Menschen, die IceCube-Data analysieren. Was ich gepräsentiert habe, die Astronomie, die ich gepräsentiert habe, ist wahrscheinlich nur ein Drittel der Menschen, die das machen. Ich weiß nicht genau, wie viele. Aber die Menschen verwenden dieses Detektor natürlich, um Glaciologie zu machen. Es gab ein Zeitraum in meiner Leben, in dem ich mehr Glaciologie-Papiere veröffentlicht habe, als Physik-Papiere, und ich bin sehr froh davon. Und eine große Fraktion sucht für Darkmater. Das ist eine lange Sache. Amanda war eigentlich sehr motiviert,

• 49:02Speaker 04

  weil wir Darkmater entdeckt hätten, wenn das Wimpern-Merkmal passiert hätte. Und leider passiert es nicht.

• 49:10Brian Keating?

  Ja, das ist richtig.

• 49:12Speaker 04

  Aber wir suchen immer noch.

• 49:13Brian Keating?

  Ja.

• 49:14Speaker 04

  Und die Menschen verwenden die Neutrinos, um die Erde zu tomografieren, Geologie. Und es geht weiter und weiter. Wir tun Neutrino-Oszillationen, mit Fermlab, mit einer anderen Teile des Detektors, die ich hier nicht hier emphasize. Aber eines der Dinge, die wir gemacht haben, ist, dass wir, weil die Gelegenheit so einzigartig ist, für Quantum-Graffit suchen. Und das ist eine sehr alte Geschichte. Es gibt tatsächlich eine ganze Gemeinschaft in Physik, die sucht für Quantum-Graffit,

• 49:59Speaker 04

  die eine Art Kompromiss mit der Alternative ist, die sucht für Verletzungen von Spezials relativität. Sie sind zusammengehalten, wie Sie sehen. Aber es ist einfach zu erklären, Sie wissen, unsere Neutrinos haben eine Masse. Wir detektieren sie über kosmische Entfernung mit enormen Energien im Vergleich zu Neutrinos, die wir an Acceleratoren machen. Also das Faktor, dass sie diese kleinen Massen haben, ist sehr wichtig für Physik, aber ist hier total relevant.

• 50:43Speaker 04

  Unsere Neutrinos sind wie Photonen. Und wenn sie durch den Vakuum von den Quellen von hier entfernt reisen, und obwohl sie ein Geschmack haben und sich in einander oszillieren, wenn sie hier erreichen, sind sie als Pakete von Elektron, Tau und Mu-Neutrinos, mit gleichem Anteil. Also ist das müde. 除非这个事情发生 und ich habe ein Artikel geschrieben, oh, zwei Jahrzehnte vorher, und ein Deutscher Künstler hat dieses Bild gemacht. Und was zeigt es? Well, es zeigt, wie der Vakuum, den unsere Neutrinos durchreisen, aussieht,

• 51:25Speaker 04

  wenn man Quantenmechanik und Gaffit verbindet. Und wenn man Quantenmechanik und Gaffit verbindet, wisst ihr, die Folie, die Mater transformt, über die Wheeler immer redet, hat jetzt Quantenfluktuationen.

• 51:46Brian Keating?

  Ja.

• 51:47Speaker 04

  Und so ist das ein Bild, wie der Vakuum aussieht. Unser täglicher Vakuum, in dem wir leben jetzt, wie es aussieht, wenn es Quanten Eigenschaften und Quantenfluktuation hat, die es hat, das muss es haben. Der Problem ist, dass in unserem heutigen Vakuum, in dem wir leben, sie von der Planckskala suppressed sind. Also sind sie klein. Und wenn ich die Planckskala in Entfernung transforme, sind sie 10 bis minus 33 Zentimeter. Also braucht man Neutrinos oder Photonen mit Wavelengths dieser Größe, um sich zu sensibel zu werden für diese Fluktuationen. Und wir tun es.

• 52:32Speaker 04

  Und wir waren bereits auf diese Sicht und haben die ersten Grenzen mit Amanda gesetzt. Ich weiß nicht, ob wir so viel Detail wollen.

• 52:43Brian Keating?

  Ja, wir sollten, ja, ich meine, die Publikum hört sehr viel Detail.

• 52:46Speaker 04

  Wie suchen wir für das? Ich meine, unsere Experimente sind ideal, diese Partikel zu sehen, die durch diese Quantenfluktuationen über kosmische Entfernung reisen. So bekommen wir Sensibilität. Dieses Effekt ist sehr klein, aber wir können es aufbauen, indem die Neutrinos sehr lange reisen. Und so tun Sie im Grunde, Sie testen, ob die Partikel dies, die klassische Spezials relativität, die dispersive Relation E² = p² + m². Und das sind die Eigenschaften dieser Neutrinos,

• 53:31Speaker 04

  wenn sie in Absenz durch den Vakuum reisen. Die m² ist wirklich nicht wichtig in unserer Energie, aber diese Relation zwischen Energie und Momentum ist modifiziert, wenn die Neutrinos beginnen, mit diesen, sie beginnen, diese Quantenfluktuation zu fühlen. Und das parametrisieren wir als eine Powerserie. Sie wissen, eine Summe von n = 1, 2, 3 und so weiter.

• 54:07Speaker 04

  Eine Distanz in Energie, die charakteristisch ist der Planckskala. Also die Quantengaffitsskala oder die Skala der Verletzung von Relativität, weil Sie sehen, E² = p² kann auch durch Verletzung von Spezials relativität verursacht werden. Also suchen wir für solche Terme, wenn die Neutrinos propagieren. Und so ist es ein paar Zeilen Berechnung. Also was passiert? Was passiert, ist, dass Partikel mit unterschiedlicher Energie jetzt beginnen, zu propagieren,

• 54:50Speaker 04

  verletzende zu einem anderen Ausmaß diese E² = p²-Relation. Und so werden die Partikel mit höherer Energie einen Zeitabstand bekommen,

• 55:06Speaker 04

  proportional zu Partikeln mit lowerer Energie. Diejenigen mit höherer Energie interagieren mehr, also werden sie abgelaufen. Und der Zeitabstand ist gegeben durch die Macht der Term, den Sie untersuchen, diese Powerserie. Sie wissen, wir suchen typisch für n = 2 Term. Und dann suchen wir für Term von Zeitabständen, die proportional zu der Energie Quadrat sind. Aber der Zeitabstand baut auf die größere Entfernung, die Sie an die Quelle schauen. Also obwohl das ein sehr kleiner Effekt ist,

• 55:47Speaker 04

  wenn Sie es auf lange genug Entfernung bauen, kann es beobachtbar werden. Und es ist so, im Fall von IceCube. Also, wie es hier sagt, integrieren Sie über sehr lange Entfernung. Also hier ist ein Beispiel einer Version dieser Analyse. Und ich möchte es immer mit einer Quote zeigen, mit einer Quote von Michael Turner, der sagte, dass, unlike Newtonian Physics, general relativity will not last 200 years. Also versuchen wir, ihm zu beweisen, dass es richtig ist. Aber Sie sehen, wir können Grenzen für Delta C/CS, eine Veränderung der Geschwindigkeit der Lichtung,

• 56:31Speaker 04

  oder eine Einfluss auf den gravitationellen Feld phi auf die Propagierung der Neutrinos. Und Sie sehen, wir sind sensibel für die Vario der Order 10 bis minus 28, wenn die Verbindung zum gravitationellen Feld genug stark ist. Ist gegeben durch diesen Angle, den ich nicht erklären werde. Also setzen wir Grenzen für Verletzungen von Relativität von 10 bis minus 28. Jetzt, wenn Sie hören, wie ich das erkläre, also Sie haben diese Wellepakete von drei Geschmack, die durch diese Quantenfluktuationen reisen.

• 57:17Speaker 04

  Also können die verschiedenen Geschmacke einen Wechsel in Richtung gehen, wenn sie mit diesen gravitationellen Fluktuationen interagieren. Und das creates Geschmacksozillationen, die durch die Interaktion mit diesem Feld, mit diesem quantisierten Feld gemacht werden. Und das verletzt, kann die Vorhersage, die ich vor zwei Minuten gemacht habe, dass wir Wellepakete von gleichem Geschmack erreichen. Und so, was IceCube jetzt tut, ist, und das ist ein Papier, den wir kurz veröffentlicht haben, war eine Version dieser.

• 58:00Speaker 04

  Also ist das der Anteil von Tau, Mu und Elektronenetrinos im Bein. Also müssen wir diese rote Stelle entdecken. Wenn wir irgendwo anders in diesem Plott etwas entdecken, Lorentz-Verletzung, Quantengaffit, Sie können es irgendwie interpretieren, wie Sie wollen. Und so ist unsere heutige, diese rote Stelle mit unseren heutigen Messungen des drei-Geschmack-Szenarios als systematische Fehler, die durch diese

• 58:40Speaker 04

  By this butterfly. But so if we, we can establish violations of these principles, new physics, by ending up somewhere, anywhere else in this diagram. And so this is our present measurement. This is the error bar at a sixty-eight percent level. And we are doing a dedicated effort similar to, or even bigger, to what I explained for finding the sources of the cosmic neutrinos, to squeeze these error bars. We are actually going to put in new strings upgrading the detector

• 59:23Speaker 04

  in the season twenty-five, twenty-six, which among other things will exactly focus on making this a small ellipse around the red dot. And hopefully, maybe not. So we will see. But this is a high priority of the experiment. I have two more slides to, to remind you of

• 59:49Speaker 04

  a fun fact. You may remember that the Opera experiment discovered the violation of relativity many years ago.

• 1:00:01Brian Keating?

  Yeah, it was actually the year before the Bicep two results came out, which made us very nervous that we made a blunder.

• 1:00:08Speaker 04

  Yeah, exactly. And you can see on this slide, there is another way to test relativity, which was pointed out by Glashow. That is, if your particles move at a speed of light C prime, which is bigger than the speed of light, they carry an excess energy, mc prime squared minus mc squared. And that extra energy, they can radiate away.

• 1:00:39Speaker 04

  And that radiation, for instance, can be come out as a plus, a minus pairs. But when they radiate away their energy, it means they lose energy. And at the time, Glashow and Floyd Stecker pointed out that the highest energy neutrinos had actually too high energy and were inconsistent with the Opera observation. Of course, I don't know whether the Opera has observation disappeared before the paper was published. But our highest energy events seen at the time were inconsistent with that violation of relativity. So it shows we are doing something real in a, in a very concrete way, right?

• 1:01:23Brian Keating?

  And actually, yes, I didn't, I didn't know about that. And Sheldon, Sheldon was a guest on the podcast about two years ago. And I neglected to ask him about that. Well, there's so much to talk to Sheldon about, as there is with you.

• 1:01:36Speaker 04

  Oh, yeah. I mean, how do you pick your subjects, right?

• 1:01:41Brian Keating?

  Yeah, we could go for hours. The only thing I want to say about the Lorentz invariance, and we're looking for it in the polarization signals of distant objects as they rotate or do not rotate. And you can look for by refringence types of facts, as you talked about with the ice.

• 1:01:56Speaker 04

  By the way, you, you, you know, it's a clear quantum. But what, what I was explaining before is the analogous of gamma rays traveling through a crystal, right? And they can exchange their polarizations. There. So it's a pure quantum effect. But it's, it's very straightforward to, to look for it.

• 1:02:33Brian Keating?

  Yeah, it's very interesting. And I guess the only, you know, kind of, you know, critique that I've heard is that the results are somewhat model dependent. I mean, this, this SME framework, which I've used in my papers before as well.

• 1:02:48Speaker 04

  Yeah.

• 1:02:48Brian Keating?

  Is very, it's, it's very specific to a particular class of, you know, it's like they say about non-Gaussianity. It's like saying it's a non-dog animal. Well, there's a lot of non-dog animals in the world, right? So how do you address those, you know?

• 1:03:02Speaker 04

  Well, my answer is that this is the least model dependent you can get, right? If you have a model, you can always reinterpret it in terms of this power expansion.

• 1:03:16Brian Keating?

  That's right.

• 1:03:17Speaker 04

  This is actually a standard method that was pioneered by Weinberg, right? To, to, you have a theory and you parametrize the deviations in terms of operators with of different dimensions. And N are the dimension of these operators.

• 1:03:38Brian Keating?

  That's amazing. So I think that's the most model.

• 1:03:41Speaker 04

  So it's the most model independent you can, can get that. And any model we can reinterpret in terms of these results.

• 1:03:49Brian Keating?

  That's right. That's right. Well, thank you so much for that, Francis. I guess the, the topics I'd now like to turn to is what comes next for IceCube? There's rumors of advanced IceCube structure that will come about. Can you talk a little bit about the status of the, do you have any slides on that? Or?

• 1:04:09Speaker 04

  No, I, I don't have any slides on that.

• 1:04:13Brian Keating?

  That's fine, yeah.

• 1:04:13Speaker 04

  So I, but it's very simple. I mean,

• 1:04:20Speaker 04

  if I had given a one-hour talk, and I, I often do on IceCube,

• 1:04:27Speaker 04

  the only conclusion any reasonable listener can come to is we need better angle resolution. We need more statistics. We just don't want to deal with a few sources. We need more sources. And what do you do? You have to build a bigger detector.

• 1:04:45Brian Keating?

  Yes.

• 1:04:45Speaker 04

  Fortunately, we discovered when we build and design, when we build IceCube, we only had

• 1:04:57Speaker 04

  vague understanding of how large the absorption length actually was. Because Amanda was much smaller, right? So we had never seen ice and light propagate in ice over kilometer distance, which was necessary to measure an absorption length, which at the bottom of the detector is two hundred fifty meter for rank of light. So it's just incredible. And so we were conservative. But now we know we can space our photomultipliers further. And so this hundred twenty-five meter distance between strings of photomultipliers, we're going to increase to two hundred fifty meters.

• 1:05:42Speaker 04

  And then we can instrument eight to ten times the volume with the same number of photomultipliers.

• 1:05:50Brian Keating?

  Wow.

• 1:05:51Speaker 04

  So ten times the volume for the price of IceCube. And of course, you know, all the

• 1:06:04Speaker 04

  the

• 1:06:06Speaker 04

  data acquisition, which I discussed at the beginning, all that is improved and much cheaper. And so we really think we can build a next generation detector for the same cost as, as the original one. We actually have, we have designed this detector and submitted the design to the Decadel Review, who endorsed it. So it's not a dream anymore. And at least, unlike the first dream, at this point, we know what we're doing. It's not a gamble anymore.

• 1:06:44Brian Keating?

  Oh, that's wonderful. Well, congratulations with that. And of course, you know, it's this phenomenal treat to see not only the success of your projects and the leaders, under your leadership, but all the young people that have come out of it. My friend, Nathan Whitehorn at UCLA. And, and of course, sharing the, the space with you and, and your team down at the South Pole with so many young people. It's always so energizing to be down there and not to mention the hot tubs, which were, which were quite great. I never got to go swimming in one of the hot tubs.

• 1:07:18Speaker 04

  Yeah, I, I always show a picture of the collaboration at the end of my talk.

• 1:07:23Brian Keating?

  Yeah.

• 1:07:24Speaker 04

  But it's actually a picture and it's incredible. The age of our collaboration. I have theories why this is, but I won't go into it. It doesn't matter. The other thing I have to say is, and this was always emphasized by the late Trevor Weeks, who discovered, who, who developed gamma ray astronomy, earth-based gamma ray astronomy. Trevor Weeks used to say astronomy is not like particle physics. You need many telescopes. It's not like discovering the Higgs. You know, in principle, one detector could maybe have done it, but you need two. Even there, you need two.

• 1:08:08Speaker 04

  And so astronomy, the sky is big. There are many problems. So with a smaller telescope and the right idea, you can contribute. And so people picked, I think, the, the the biggest compliment to IceCube is that people are now planning and building detectors, building in Lake Baikal, building in the Mediterranean. Building in off the coast of Vancouver in Canada and planning a detector in China.

• 1:08:44Brian Keating?

  Yeah.

• 1:08:45Speaker 04

  So there are many and many more to come, I hope.

• 1:08:49Brian Keating?

  It's truly breathtaking and inspiring to me as one of the five or so co-leaders of the Simons Observatory, which is equally sized and is also hoping to shed some light, no pun intended, on neutrinos and their role as dark matter and as a very important budget and energy budget constituent in the cosmos. So Francis, we speak, we speak a lot on this channel to young people, graduate students, post-docs, undergraduates. And one of the favorite parts of the show is when I ask kind of non-scientific questions, which I call the existential questions are the final four. And I'd be honored if you'd answer some of them, if you don't mind, right now.

• 1:09:34Speaker 04

  I am fearless, but I am probably not a good or certainly not a typical subject for this, but let's go.

• 1:09:42Brian Keating?

  There's no difficult subject. So yes, let's go into the impossible, the final four questions I ask. So they typically have to do with the distant future, both yourself and of humanity perhaps. And then advice to your former self as a young person, because as I said, we have a lot of mostly men. I'm trying to boost that up, but mostly young men interested in science, technology. But we are, we are open for all. So the very first question that I always ask is what would you put in what's called your ethical will?

• 1:10:19Brian Keating?

  In other words, what would you like to impart as wisdom that you've learned, not scientific necessarily? It could be anything. It could be to your children or great, you know, grandchildren or many, many generations down the line. What piece of wisdom guides you, if any?

• 1:10:34Speaker 04

  Well, I, I think with the advantage of not just looking at the future, but looking back, I want to come back to my years that I was at Le Matre's Institute, writing my undergraduate thesis on quarks. And imagine this was 1967, eight, 1967, actually. And so I alluded to the fact that if you worked on cosmology at the time, you were kind of a crackpot, right?

• 1:11:17Brian Keating?

  Yes.

• 1:11:18Speaker 04

  Le Matre was not a famous person, except for the fact he was a cardinal. And he had been, you know, the president of the Papal Academy and so.

• 1:11:29Speaker 04

  But I actually, my undergraduate thesis was on quarks, another topic that nobody would touch at the time.

• 1:11:38Brian Keating?

  Right.

• 1:11:39Speaker 04

  And so first of all, the first message is just do what you're interested in. You cannot be successful if you do physics as a job. And I, I'm kind of at the edge of the generation where actually physics wasn't a job. And that was wonderful.

• 1:12:02Speaker 04

  Afraid to say the time is gone and it's rightly gone. But so that's one message. The other message is how to, you know, I don't have to predict or be a visionary. Look how exciting science is. Can you imagine that in 67, you worked on quarks and jets and on cosmology and the big bang, you were not taken seriously. In fact, you couldn't get a job, even if it was a job. And look where we are now.

• 1:12:38Speaker 04

  I'm in a black hole and the big bang and a quark jet are as real as this cup of coffee on my desk, right? Nobody questions this anymore. And this happens in my career in one, in one generation of, of a physicist. And I have no doubt that this will continue.

• 1:13:02Speaker 04

  It may not continue in the direction that we are now talking about. It may be off in a different direction, but I'm sure it will continue. Science will always be exciting.

• 1:13:13Brian Keating?

  Yes, absolutely. It's, it's, as you'll hear in just a second, I'll say what my next, my next quote comes from Sir Arthur C. Clarke, who said that any sufficiently advanced technology is indistinguishable from magic. And I want to ask you, what knowledge, either from your personal career or from all of science, or maybe, I don't know, anything from philosophy, theology, who knows? What piece of one sentence or the shortest amount of words that you could possibly describe? The thing that humanity should be most proud of?

• 1:13:57Speaker 04

  Well, I, as I always limit myself to the expertise I have. And not just humanity, my generation should be proud of what we just talked about.

• 1:14:10Brian Keating?

  Yeah.

• 1:14:10Speaker 04

  And that's something to be very proud of, I think.

• 1:14:15Brian Keating?

  I agree. Yeah. My late great colleague, Hans Parr, did you ever know Hans?

• 1:14:20Speaker 04

  Yes, yes.

• 1:14:21Brian Keating?

  So he was, he was a great influence on me. He said that general relativity, which is part of some of what we've talked about, was the pinnacle, not of just science, but of all of Western civilization. And so I agree a lot had to go into that. You had to have cooperation, language. There's a beauty, there's artistry, and there's also a hard technology. And the most important thing, which you keep emphasizing so rightfully is people. And the culture of an experiment is so important. Okay.

• 1:14:53Speaker 04

  And, and people who are really obsessed with what they are doing, those are the ones you are looking for.

• 1:14:59Brian Keating?

  That's right. Yeah. Next question, the second to last question is another quote from Sir Arthur C. Clarke. And he said, when a distinguished but elderly scientist says that something is possible, he is almost certainly right, but when he states something is impossible, he is probably wrong. So I want to ask you, Francis, what have you been wrong about, if anything?

• 1:15:29Speaker 04

  Oh, many, many things. In fact, let's go back to my, my career, career was half astroparticle physics and half particle physics, right? I lived around accelerators. And I go when we were writing Halzen and Martin. I actually gave Halzen and Martin originated because I took a semester leave at the University of Hawaii because I was working with Sandy Pagwaza. By the way, that was the time they were developing Dumont.

• 1:16:12Speaker 04

  And I had no idea what Dumont was, but I'm sure it's stuck in my brain somewhere.

• 1:16:19Speaker 04

  But at the time they asked me to give a course and they say, you just come and talk what you did the last week.

• 1:16:27Speaker 04

  I thought, I walked into the room and the whole faculty showed up.

• 1:16:31Brian Keating?

  Wow.

• 1:16:32Speaker 04

  And so I decided the, the set, the C zero had just been discovered, the weak intermediate boson. And I talked the first lecture about what a breakthrough this was. And, and so then I actually decided over the semester to, to develop what we now recognize as the standard model as lectures. And so that was the beginning of Halzen and Martin.

• 1:17:01Speaker 04

  So I think I never, there's something called the Jim mechanism. And I couldn't believe that you could just invent another quark to fix a deep problem of the theory. And I thought that was incredibly naive. And it turned out to be right. And I remember going through this history of me being wrong, not believing the Jim mechanism. You know, Jim mechanism fixes standard model with postulating that there was a charm quark in the theory.

• 1:17:42Brian Keating?

  Right.

• 1:17:43Speaker 04

  And so it made a big impression on me in the sense that, you know, sometimes you, you shouldn't hold it against simple ideas. You, the simpler an idea, the more elegant, this was in a sense elegant. And I, I, my, my reaction was totally wrong, that something simple cannot be right in nature. That's simple. And so I learned a lot from that. It made a big impression on me too, because you know, I,

• 1:18:19Speaker 04

  I, it doesn't feel good being totally wrong about something.

• 1:18:26Brian Keating?

  No, absolutely not. But I think the mark of a good scientist is to recognize, learn from it, own up and admit.

• 1:18:33Speaker 04

  I learned my lesson from that. And I, you know, I never have, unless something is demonstrably wrong. I have very, I accept everything, basically. I mean, if you, you have to have a very open mind when you approach a problem. It's not good to be biased. That's what the thing I learned here.

• 1:18:56Brian Keating?

  Yeah. Well, that really does dovetail into the last question, which is from Arthur C. Clarke's third law, which states the only way of discovering the limits of the possible is to venture a little way into the impossible. And maybe I'll pivot because you've, you've said so much about, you know, kind of advice to your former self. Maybe if you were getting into this career or in any kind of career, you're 20 years old. You're at the University of Wisconsin, Madison, you're at UC San Diego or wherever. But what would you go into? What would you advise a young Francis Halzen to go, go and do? To do as you've done to go into the impossible?

• 1:19:35Speaker 04

  I already gave the answer to that. You go what you're interested in unless you're obsessed by the subject. I mean, being a physicist from all objective point of view is a miserable career. And I don't have to state the reasons. The only reason it's worth doing is you just enjoy this. You're obsessed by it. You love what you're doing. And so if you do it as a job, it's going to be very, very disappointing, I think. So I think this is just, and the

• 1:20:15Speaker 04

  other thing is, you know, I always lived with, don't underestimate yourself. I totally lived with, until I went on this crazy adventure of Amanda and Ice Cube. I always lived with the insecurity that I didn't belong to the circles I moved in, which I think must be true for almost every graduate student. Just get over that. And I don't know how to do this. I never did it until, you know, you go on a wild ride like we did with neutrino

• 1:20:57Speaker 04

  astronomy. Then you just, you know, surfing the waves.

• 1:21:02Brian Keating?

  Right.

• 1:21:02Speaker 04

  But at many times of my career, I think I missed opportunities because I was insecure. And so it's not always the smart people who make the breakthroughs. That's another way. That's a very parochial way of thinking about it. You know, imagination can trump intelligence. There are many angles to doing research. And so just go for it.

• 1:21:33Brian Keating?

  It's very, very wonderful that you say that. And we'll close with this. So when I interviewed Barry Barish, two or three years ago now for this podcast, I asked him that same kind of a question in the form of, have you ever experienced the imposter syndrome, which is this feeling of insecurity that you just spoke about? And he said, yes, I have it worse than ever now. What are you talking about? You have the Nobel Prize. He said, no, no, Brian, when you win a Nobel Prize, you have to go and sign this logbook in Sweden that says that I got my Nobel Prize. So Barry's incredibly curious, very imaginative. And he goes back and he looks through the previous pages and he sees, he sees Feynman and he

• 1:22:15Brian Keating?

  sees a Galman at his home institution of Caltech. And he goes farther back. He sees Maria Gephardt Mayer, maybe here at San Diego. And then he goes back to 1922 and sees Albert Einstein. He sees this guy's signature here, my favorite little sock puppet. And he says, I'm not worthy. I'm not as smart as Einstein. And I say, Barry, guess what? You know, Einstein had the imposter syndrome. You know, he wasn't always Einstein. He said, what are you talking about? He said Einstein felt that Newton did more for the human culture and civilization than any person before or since. And he said, wow, I didn't know that. I said, Barry, guess what? It gets better. Newton had the imposter syndrome. He's like, ah, you gotta be kidding

• 1:22:59Brian Keating?

  me. I said, no, Barry. Isaac Newton wrote, he said, I live in shame that I never lived up to the ideals of Jesus Christ. So we all have our imposter, you know, kind of moments when we feel we're inadequate. And then, and then he ended up writing, I don't know if you can read this, but I'll send you a copy of this book next time I'm out there. But Barry wrote the foreword to my second book, which has his interview in it. And I hope someday that-

• 1:23:27Speaker 04

  I actually read it either on your webpage or somewhere.

• 1:23:31Brian Keating?

  Yes, yes.

• 1:23:32Speaker 04

  I don't think it's unusual. I think it's also, I don't think it's a problem. It's only a problem when it prevents you from doing things.

• 1:23:43Brian Keating?

  That's right. That's exactly right. And I think you're right to have the courage and just, as you said, just do it. Well, Francis, you've been an inspiration to me as a scientist, as a teacher, as a leader, and as an author. And I'm just so glad and honored and thrilled that you were able to spend so much of your valuable time with us. Thank you so much. I hope we can see each other again. Maybe you'll come here in January and I'll go there in June and we'll go and get some cheese curds on the Capitol together.

• 1:24:11Speaker 04

  It was a pleasure.

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