The Origins Podcast with Lawrence Krauss - Barry Barish | Exploring The History of Experimental Physics

Episode Date: August 10, 2021

In this podcast episode, Lawrence Krauss reconnects with an old friend and Nobel Prize recipient, Barry Barish. They discuss a wide range of topics and explore Barry's own history as well as the history, present, and future of experimental physics. Barry Barish is an American experimental physicist and Nobel Laureate. He is a Linde Professor of Physics, emeritus at California Institute of Technology and a leading expert on gravitational waves. In 2017, Barish was awarded the Nobel Prize in Physics along with Rainer Weiss and Kip Thorne "for decisive contributions to the LIGO detector and the observation of gravitational waves". In 2018, he joined the faculty at University of California, Riverside, becoming the university's second Nobel Prize winner on the faculty. iTunes: https://podcasts.apple.com/us/podcast/the-origins-podcast/id1467481703 Website: https://www.originsprojectfoundation.org/ Twitter: https://twitter.com/OriginsProject Instagram: https://www.instagram.com/originsprojectfoundation/ Facebook: https://www.facebook.com/OriginsProject/ The Origins Podcast, a production of The Origins Project Foundation, features in-depth conversations with some of the most interesting people in the world about the issues that impact all of us in the 21st century. Host, theoretical physicist, lecturer, and author, Lawrence M. Krauss, will be joined by guests from a wide range of fields, including science, the arts, and journalism. The topics discussed on The Origins Podcast reflect the full range of the human experience - exploring science and culture in a way that seeks to entertain, educate, and inspire. Get full access to Critical Mass at lawrencekrauss.substack.com/subscribe

Hi, Lawrence Krause here and I wanted to append a brief video note to this podcast you're about to hear for a variety of reasons, but one because the person I'm having the discussion with Barry Berrish will be one of the guest speakers also on our upcoming Origins Project Foundation trip Under the Northern Lights to Greenland, September 8th to 21st, 2022. We'll travel from Reckovic to Greenland under the Northern Lights and guest speakers Barry Barish. myself and Richard Dawkins will be aboard to spend time with the travelers who come along for 14 days to spend time not just hearing the lectures but also to interact with us and the other wonderful travelers that we have coming along. We've had a great response and we have not many births left, maybe four or five. So I thought I'd invite any of you who are interested to go to our website, OriginsprojectFoundation.org and go to the travel button and and learn about the trip. $2,000 of the cost of the trip

will go as a tax-deductible donation to help support the foundation. So I hope I'll see some of you next September. And right now you can listen to me and Barry Beresh talk about some of the things that we'll discuss, just a few of the things that will discuss with some of you in Greenland next year. This episode is with an old friend of mine

and a famous and remarkable physicist, Barry Berish, who won the Nobel Prize in 2017, along with Kip Thorne and Raynor Weiss, for the discovery of gravitational waves. One of the fundamental predictions of Albert Einstein's General Theory of Relativity and a remarkable experiment that I personally thought would be impossible, and Barry helped make it happen. But what most people don't realize about Barry is that his career in physics spans a far broader area. His origins are in elementary particle physics and experiment. And so what we had to, what we were able to do in our discussion was have a discussion really about the history of experimental physics. His own history, which spans so many different

areas. And the importance of realizing that in fact you can change what you do, as he's often done, use the things you've learned in one area and apply them to another bravely, taking risks, but always reaching out for a goal which may not be achievable, but you've got to try anyway. Barry is also one of the finest human beings, I know, and it was a true pleasure to spend time talking to him. And I hope you'll find this discussion as illuminating and enjoyable as I did. So with no further ado, Barry, Barry. Okay, well, thanks, Barry, for letting me intrude on your attic there and having this discussion. I've said much too much time here.

Yeah, I know the feeling. Well, I'm here in our studio, which is nice. It's been a while since I've been back here. And although we've talked privately about it, I want to at least publicly congratulate you on the prize and Nobel Prize. And I've known you for 40 years, and I cannot think of a nicer person to get it, really, truly. So for me, I was just so happy for you.

That's great. Well, that's a nice way to start our session. Yeah. Now, let's start. Well, we're going to, so I want to talk about physics and, well, I lost science, but I want to, this is an origin. I want to start with your origins, which we're in Nebraska, right? Is that right?

Right, right. And then you moved to LA when you were young. How old were you? Right. But I was just nine, almost 10 when we moved. So it was elementary school, fifth grade. And the school that I went to where we moved in in L.A., In L.A., the neighborhood was very mixed, and that's the first thing.

So it had a lot of kids who weren't very academic and some, a few that were. We lived up in that, it's kind of, it's called Los Files area in L.A., but we lived on the end of it that there was near Sunset Boulevard, which is where there's a lot of minorities that live in. poor people, and so the school was very mixed. But there was another phenomenon then that really affected things, which is that I think ever since soon after that, and probably in your experience of most people, you've talked to kids that don't do very well in school, just get moved on. Yeah. And at that time, that didn't happen. Kids were held back. And so when I graduated from elementary school, some of the boys went into the Navy. So, you know, I was 12 and they were 16 or 7, 18, or whatever it is. So, you know, and that was the end of their schooling. So, but that made it especially a difficult environment for me. I came, I came from Nebraska and hit this school where there were kids that were, there's a big difference between teenagers and a 10-year-old. Yeah, yeah. So I spent, you know, the first semester getting changed.

home from school. Oh, great. But I could run fast, so I survived it. So. Well, did you, you didn't think you're going to the Navy. That didn't attract you, I assume. This convinced me not to go in the Navy, yeah. Now, your parents, did your parents have, I must admit, I happen to read something just

yesterday a little bit about your, your father, I guess. But, but did they have any education? Did they have any? No. No, so my, the history is my grandparents immigrated from somewhere where you can't find it on the map anymore. In Poland, somewhere. Somewhere. Yeah, exactly.

And so, you know, I've tried and I can't locate the places. And our only aunt that could have died in the meantime. So I'm not sure where, but they came around the turn of the last century. and so my father was actually born in the U.S. He was born in 1911 and my mother in 1913. So they were born in the U.S. But in and my father's family actually immigrated and didn't do what a lot of Jewish families do,

which is go to New York. Instead they came through Chicago. And at that time, there was an act in the U.S. to try to build up the farmland. So there was this homesteader act. Yeah, I know about it. I don't know too much about it, but they got land as homesteaders.

And I don't know whether it was North Dakota or South Dakota, but one of the Dakotas. And these people were not farmers, of course. Yeah, they took a lot of people from Europe who didn't know what they were, and they sold it as if it was fertile land, and a lot of it wasn't at all. It really was quite a scam.

But I don't know what they did there. because they weren't farmers, but they managed to only be there a few years and then make enough money selling the land that they moved to, first to Sioux City in Iowa. And there they opened up, I have photographs of, they opened up a store that sold everything. You know, well, only everything wasn't like a corner store. That is what I mean. It had, you know, tires, coal, Ford cars, Ford cars. Yeah. And then in 1921, I have the newspaper article, my uncle, my father's father had died. And my uncle had a Ford dealership, but Ford was very anti-Semitic. Yes. I read this.

It turns out he had a magazine that they put out in their equivalent of a showroom at that time, which was very anti-Semitic. My uncle and his brother got them into a fight with Ford and it was all over newspapers. I read one of the pieces from then. I did my research, and I was shocked. Yeah. And of course, that's all before I came along. But then they changed, moved to Des Moines, Iowa, which is kind of across the river, across the Missouri River from Omaha. and there they had kind of an all-purpose store of some sort and eventually i don't know why

they they uh moved to omaha so we so uh so i was born in in omaha uh my father's father had died when he was 12 or so this is slowly getting to the year's 11 or 12 and he had to go to and they didn't have much money so he had to actually go to work after school and uh so he never went to college and we don't know, but I never even thought about it until my brother said something that my brother suspects he didn't graduate from high school either. Yeah. So he basically started working when he was 13 or something. My mother was very smart and read a lot, and she was wanted to go to college.

had applied to the University of Nebraska and claimed and I never believed her and my brother never believed her that she had a scholarship to the University of Nebraska but her father wouldn't let her go. Oh, interesting. And it turns out that when she died

going through her papers, there was the letter from the University of Nebraska and it was a true story, which we... Wow, that's amazing. That is amazing, yeah. Wow. Well, it's interesting. We share that.

I mean, my father didn't graduate high school. My mother was, again, smarter. She graduated high school, but the family could only afford to send one, her brother to university with my uncle. And so it's now, so in, and since we kind of share that, the interesting question is, so you didn't come from a family of people who were academics

or academically inclined. Maybe your mother, did your mother instill an interesting reading or? Yeah, reading. So she read, yeah, at that, at that time, books became cheap. You didn't have to go to the library because they made pocket books all the same. And so she read crap.

She read mystery stories. My mom too. My mom too. But lots of stuff. Boxes of mystery stories and stuff. And so I used to read. So I liked reading. Well, at first I grew up where I grew up when we moved to California was basically Hollywood or West that area.

So storytelling was always a big thing in that general environment. And I liked reading and storytelling and writing from a young age. And, you know, writing, we'll try to write stories and stuff. And I was the editor of the school newspaper and things like that, starting in junior high school. So the combination of liking to read, and I'd never read anything any good because my mother read junk. Yeah. But until I was about 13 or something or 12, I don't know what age. But then I discovered somehow.

the Russian novels. Oh, I was attractive because I knew that my family came from somewhere there. So somehow that was the reason I picked them up when I got tired of reading these mystery stories. And I fell in love with literature, really, at the age of 12 or 13, and I like to write. So I thought, if you would ask me when, I don't know what age, but 13, 14, that I would be a novelist. That's what I my, not a

movie writer or playwright. Yeah, but a novelist. That's, that was my and not exactly dream but if you you know, ask me what I was aimed at, that was what I said. I always did really well because any of us to succeed in

physics are good at math. So I was kind of a whiz at math from a young age and whiz compared to all these kids I think the school with and won some math content. and so forth. But I never had even had the understanding that I could ever do anything with that when I was young. It was just that part was something I enjoyed, but I didn't have any, any, I just didn't have any guidance at all. And then the high school that I went to, which is called Marshall High School, was good in its way, but not, it didn't especially do anything from me.

From a very young age, I played serious tennis. It was the one thing that I, I was always have. athletic and I played serious tennis. So I started playing tennis when I was really young and had my parents paid for me to have some lessons. And so I actually learned how to play it right. And we didn't live far from Griffith Park, which had a huge number of tennis courts. And I'd go there after school from a very young age and just play with people. And so I played tennis competitively in tournaments and then for our high school team. And from the time, from the ninth, 10th grade, or whenever you start, the time I graduated, I was the number one player.

They make a ladder. Sure, sure, yeah. And so one anecdote is that in high school, you play these other high schools. And eventually, I was good enough so that I was all city, Los Angeles. And I was tried to play on the freshman team when I went to Berkeley as an undergraduate. So I was pretty good, but not really good. Yeah, but good enough. But anyway, I was the number one player at Marshall High School, and we always played Van Ice High School.

This is my little anecdote. Okay, I knew we were heading here. And the number one player at Van Ice High School was a little blonde kid named Bobby something or other. And it turned out, I found out years later, I had no idea. until I read something that it was Robert Redford. Oh, really? That I played against in high school for years. I learned that when I was reading at one point

and realized he played the, he was visiting Philadelphia or someplace and played with the mayor. And it was in the newspapers. And it just clicked. And then I looked up and it's true. He went to Van Nuys High School. Well, you know, when I hear things

like that, I think how lucky it is for the world that neither of you were better tennis players. Yeah. So when I went to Berkeley, I played tennis for a little while as a freshman, but then when I went, then when I went to started having labs, I just couldn't do it. They practiced in the morning. Sure, yeah. And I wasn't good enough anyway. But, yeah, I was a wrestler.

I used to wrestle and I was actually pretty good in Canada. I won't go into it. But I, but in university, I just, yeah. I just, yeah. So similar, similar kind of. Yeah, I was, yeah, at a national level I used to wrestle. But, but that way, I was one 14 and a half. It's hard to believe I ever weighed that low. I won't ask you what you're waiting now. Yeah, exactly. I don't want to tell you. So this leads me to the question, which I was in.

So why, I know why I, I mean, as we had similar backgrounds in many ways, but I know what I got interested in physics, but why you? What got you interested in science and physics? Yeah. It was all, unfortunately, I wish I could say I did it like my colleague Kip Thorne, who romantically was interested in Einstein, and then general relativity. We've compared backgrounds.

Sure. From the age of 15, he was going to do general relativity. But in my case, first I was going to be a novelist. When that died, and then I came from a rather poor family. I didn't really have any mentor in high school other than the tennis coach. Interesting. Who noticed that all the other kids on the tennis team would come to me to help, with them with their problems and this and that.

And so he got the idea that I should do something reasonable with my life and study and stuff. So he was the closest. Oh, well, that's good. Which I didn't have a personal relationship with them otherwise. But interestingly, after the Nobel Prize, one of the things I did was get invited to go back to my high school. Yeah, I hadn't been there in 50 years or whatever the number was. and but it's still there in that part of East Hollywood and less fields. And so I went back and visited and now the gym is named after my tennis coach.

Yeah. His name was Wheeler. Wheeler, yeah. So it's sort of physics name anyway, but. Yeah. Right. So anyway, once I kind of defaulted out of literature, I figured I had to do something where you used your talents and made a living.

Were your parents particularly, let me interrupt and ask, in my case, my mother wanted me to be a doctor if she decided I would be a doctor. Oh, of course, my parents wanted me to be a doctor if I couldn't be a lawyer. My brother, a lawyer, me a doctor, and my brother became a lawyer, which made it even worse. And my brother's a lawyer. Yeah, exactly. So it was a doctor or a lawyer.

And I, you know, I got the same thing near the time I was graduating from college. You're going to go to medical school now. Me too. My mother was so upset when I got a job at Harvard that I wasn't going to go. medical school. Yeah. So a similar kind of issue. But anyway, trying to be practical, I decided I should study engineering.

Oh. So at that time, and first, I had no horizon past California. That was as far as I could see. Sure. And so going to school was either going to Stanford, Berkeley, UCLA, or Caltech. and the consular at Marshall High School told me not to apply to Stanford because they had a quota. That was her statement. I don't know. It was true. It's quite likely at that time. It dissuaded me. And so I applied to Berkeley and UCLA and Caltech.

But I graduated from high school for at a time when high school's at mid-year graduation. So I actually graduated in January. Oh, I see. And this is why my life has randomness. I didn't really think. That's what's great. I think randomness is really important. So, you know, Caltech being a little school, took people only,

his most schools do in September. I was graduating in January. You could enter UCLA or Berkeley in January. Anyway, I see. And the admissions happened in the spring for Caltech. And I went to Berkeley instead of UCLA, so I could get away from home, basically. Of course. Yeah, why not?

Absolutely. Same. And so I went to Berkeley. Also, the tennis team was stronger at UCLA, and I thought I could make the tennis team at Berkeley, which ended up being an overestimation of what I could do. So I went to Berkeley. And by the time Caltech admitted me, actually. But before they admitted you and then they told you about scholarships later.

I see. Because I would have needed a scholarship. Sure. But by that time, I had fallen in love with Berkeley. Not with engineering, by the way. It was in 60s. Yeah. With Berkeley and with my, with this pretty serious at the moment girlfriend.

that. So it was, and, and, you know, there was no way I wanted to leave there. So I dropped out, didn't, didn't follow through with Caltech. But you, so you entered in engineering. Did you graduate in engineering or? No, no, no. So I'm going to get a long story of how I'm going to get to answer. I haven't forgotten your question. No, it's okay. So it's okay. So it had to do with how did I get in physics. So I'm kidding. So I went in engineering and freshman engineering. at that time was so bad that it basically chased me out. So I had two courses. So I had to take freshman, you know, math and physics and chemistry and engineering.

I had to take two courses as a freshman. One was engineering drafting. And now I like it because you can visualize things. Of course, now there's 3D CAD cam and I use it all the time. And I like the idea that you can see what you're building and everything. But they managed, it happened to be, at that time, first, you didn't have any computerized things. And it was very formalized. So I get criticized for my arrowheads.

This is how long. And they didn't like my arrowheads. So I didn't like that. And then I was also very shy as a freshman, you know, kind of shy. And personality-wise. And the other course was surveying. And they gave you this transit. And you went around the campus and you have an exercise to go measure, you know,

the coordinates of the Campanile or something in Berkeley. And the instrument was interesting. So I had, I didn't, I played around with cars when I was kids. I liked instruments. Sure. And so the instrument was interesting. but and looking through it and being able to recreate where something was and reconstruct it was interesting but that all took about an hour to master and then it was boring because you

had to do all the and secondly embarrassing you know standing around campus is a little freshman looking through this thing with people walking by and looking you know just kind of turned me off so so drafting and and in the meantime I have had freshman physics and my instructor was Owen Chamberlain. Oh, who I know. I know Owen. Yeah, he's a good guy. Yeah.

And this was 1958, and he had discovered the anti-proton with Segre in 19, I think, 55 or six. Had they won the Nobel Prize yet or no? But he hadn't won the Nobel Prize yet, which is part of my. okay sorry i'm jumping so no no no part of the later story so so anyway but he but they were making you know discoveries they had built the bevatron and uh they had discovered the anti proton he hadn't gotten the un Nobel prize but that wasn't all you know they were seeing resonances and things like that and uh so uh you know having uh an instructor who himself was excited by discovery

In fact, all these discoveries were happening and this fancy laboratory was up on the hill behind the lap, behind the campus. And even though, you know, I was learning boring stuff like, you know, something rolling down an inclined plane or whatever you learn. The most boring physics. Yeah. Yeah. I got very turned on by physics. It was wonderful that they had a, you know, that they didn't have just have, a lot of places just have these instructors teach first year. But to have a significant scientist teach first year as a.

nice thing you can do. Yeah, and it's just my luck. And then when I switched into physics, because I went to him, talked to him, but he became my academic advisor. Oh, wonderful.

And I didn't know that he was going to win a Nobel advisor. Yeah, when you're on your garage. Yeah, he was just the guy. I knew he worked up the radiation lab. And I was, like all of us,

I was a good student. And so I was ahead, I'd say, because in those days, students didn't get to go in the lab very much. I mean, it wasn't the system like it is now where you try to get students to join research groups. But luckily, for me, I had Chamberlain as an advisor. And so after I was a major, maybe either Southman, I think it was a. even the sophomore year except I started with this half year problem. Yeah. So it's hard to define what I was on. I took three and a half years to graduate. So then I got on the September business, but, but anyway, he suggested that I

come and partake in his research group, which was unusual because my colleagues, other students weren't doing that. It was a combination of him and the fact that I had dropped the tennis team. I had time and I was very good in classes. So I didn't have to it wasn't a problem. And so he suggested it. So in those days, you've been to the radiation lab in Berkeley, I'm sure at something like. Yeah. And it's up on this hill above the campus. Yeah. But in those days, they didn't have a shuttle bus like they do now that goes back. That's quite a walk. So you either walked or hitchhiked up. But in some way, it was. was a big deal to get up there.

As a kid, I didn't have a car. And so I'd go up there and what I remember. I go up there and a lot of the time, he was too busy for me. And, you know, now I know why it's a busy. I've had the similar period. You've made a discovery and there's a lot of noise around. And anyway, so he was too busy. At least my memory was he was like,

always too busy I'm sure it was just part of the time so I used to wander around I go up there and I went out kind of turn around and go back down this hill though I'd just either hitchhiked or walked up so I'd walk around the radiation lab and try to talk to people I was a little shy but not so shy there somehow I don't know why and the rules about radiation and things were much more relaxed in those things so I could walk around the Bebatron or around the different labs and talk to people and they would almost talk to a young kid but you know I was kidding a little bit so the Bevatron I found a little bit intimidating but I went there and then I walked further up the hill and up the hill there was the 184 inch cyclotron which was the

classic big cyclotron it was in Berkeley and Lawrence I guess yes it was the biggest one that Lawrence built just part of my story so yeah so I never knew Lawrence of course yeah but I'd wander around and talk to people with not very much you know what are they going to do with a kid but I went up the 188 4 inch cyclotron there was a control room with one guy sitting in it now you'd have to have two for safety reasons you can't do that but there was one guy old little guy sat sitting there sitting in the control room, and then somebody would be doing experiments somewhere on the outside. And it was one at that point, the M-184-inch was old enough that they had a lot of equipment

near it, and people would put together that equipment, maybe add something to it and do some measurement. But anyway, this guy in the control room, he would talk to me. So, you know, he was my go-to place when I go up to the radiation lab. and Chamberlain was too busy and I didn't have anything to do because I wasn't self. I didn't really have any momentum

that I could do more than something. Somebody told me to do a short time. So he would talk to me, so I used to go and talk to him about the, you know, about anything. He was kind of talking old. I thought of him as old. He was probably 50 or something.

And of course I became interested then in the cyclotron. This is my history of getting, I'm unusual for experimental physicists in that I understand accelerators very well. It started in that I understood accelerators before I understood. The physics experiments. And it's because I went in the 184 in Cyclotron. And so he used to sit there and run this machine. And it would have these knobs, these big knobs and oscilloscopes.

And that's all that's. So now it's all digital. Yeah, of course. I remember. And the LIGO has that. But then it was knobs. And so one knob would say, you know, energy or something. And another one would say something else.

And I would characterize it by somebody. They would have an intercom where somebody who is doing an experiment would say, would you change the energy from 100 to 150 MEP or something like that? And there was this big knob that said energy. And he would twist it, but he'd also go tweak to something else. So I asked him, why did you do that? And his answer was because it works. You know, basically this guy had grown up with a machine.

Yeah. And this was kind of typical of our conversation. in the meantime, I was trying to understand how to run this machine. My goal was to understand how to run the machine. And at the time, the only kind of vestigial tail I had gotten interested in from engineering was control theory for a reason that had to do with the fact that I had was just learning matrix, matrices and mathematics, and it was an application of matrices. Oh, okay.

In how you do control theory. So the way you do controls is you have, the way you set up the control is you have, you imagine you have the vectors that you multiply the matrix by or, you know, energy angle, this, you're seven or eight different things or a hundred different, different variables. and then the matrix itself, if you have a perfect control system is diagonal. Yeah, of course. And so what you multiply the energy,

multiplies the energy. If you have off diagonal terms, then you get this. And so what he was having was off. So this guy was complete. So I was diagramming what he was doing and putting it into my trivial knowledge was not very good about control theory and telling him that he had off-diaginal terms.

He had no idea what I was talking about. And of course, I didn't understand what he was doing either very much. And that was my entree into accelerators. And then I read about them. I found out about him later. So later, many years later, a little bit like Robert Redford. Years later, they have all these classic pictures. of Lawrence and McMillan and all these guys in the radiation lab.

And there's always often in those pictures, there's a little guy in a white coat that's sitting right with these guys with coats and ties. And it turns out it was this guy, Jimmy Vail was his name. And he was their chief technical person for Lawrence and McMillan, when they made the early cyclotrons and so forth. And then at this point, he owned. owned 184 inch and was and but I never knew that when I knew him. Of course, you know, years later.

So that's that you know, that was a lot. I mean, I think it's a wonderful thing for kids, you know, I advise young kids who were interested in science in any way to get out of the classroom and to see and to just see the research experience at some level to see what it's all about. And and you were lucky to sort of act sort of sort of fall into that, I guess. Yeah, yeah, I just fell into it. Now, you said, before we go forward, something interesting, he said, used to play with cars. I'm wondering, I want to ask, what I want to get to at the beginning is why experiment, rather than theory, but, but, because I, I was, when I,

I was a good student and, and, et cetera, but I, and I actually worked in a lab as an undergraduate, and that's what convinced me not to become an experimentalist. Yeah, yeah, but, because it just took so long. I worked on actually Spark Chambers and I was, and I was designing one and I, and it took me months and months and months to get this thing to work at all. And it just seems so slow compared to what I could

do with theory. I think that for me at the time you should have started with, you should have started with cars. Yeah, yeah. Yeah, no, I know. Cars, I want to ask you about cars and electronics. You didn't do ham radio or any of that kind of thing because that's a lot of experimentalists do that kind of stuff. I didn't do ham radio,

but I built radios. So I did as a kid, starting with a crystal set. Yeah, I had a crystal set. And, but I didn't do, I didn't do ham radios, but I built one. So that was the electronic stuff, but the mechanic stuff was cars. You played with cars. Tell me more about it. Yeah.

So, so my family, I mentioned that they were, had Ford cars and then migrated into cars. I mean, I grew up with cars because they had a car deal. The reason they came to California was to open up a new car dealership. So it wasn't Ford. It was Chrysler-Fleman. So my father's uncle, my father had died, as I said when he was young, but my father's uncle was the boss, the owner, basically. My father worked with him or for him his whole life.

And my jobs as a kid when I started working in high school were there. In my first summer, when I was in high school, I worked with the guy who balanced tires. Okay. So then when you bought a new tire, put a new tire on a car, you had to do something to make it go around in a true way. So you put these little weights on it. Yeah, I remember that. And very much it had a machine and they had some guy that did this, but he didn't understand anything. So what I had done when I was 15 or 16, because each summer my father had me do something else.

And I worked with like, the one I remember first was the guy. I worked with the guy that balanced, put on new tires or balanced the system. And I got interested in the only thing that was good from all the reading and everything is I spent a lot of time in libraries. and I understood how to answer my own, since I didn't have parents and answer my questions using libraries. And so that came about also when I had this summer job, I decided to learn about suspension systems and shock absorbers and all the whole system and how it works.

So I went to the library because that's what I was working with. So I went to the library and, you know, there were lots of books that you could read. So it wasn't long before. I knew a lot more about the suspension systems than the guy that was my boss in the summer. And interestingly, I started with suspension systems, and it's the key to making gravitational wave detection was the seismic system. Yeah, which is what you do in the car.

So my first summer doing it, I did that. And then when I learned to drive, I delivered parts that was just driving around L.A. But then I worked with a painter and did different things. But then at home, I had my first car and first cars weren't very good cars. And I took apart and rebuilt the engines and things like that. That's crucial. It's very satisfying way to start with using equipment because it is just the opposite of what you found. It's there's almost instant gratification because you do something.

There's not that many ways you can screw it up. But if you know what you're doing, you do something and it works better or fix it's something. And so working on a car has that. I mean, I didn't make hot rods or anything. And but anything you did, you know, improve things or you learned something. So there was real, working on something as simple basically as a gas combustion engine and trying to make it work better when they have flaws. because they ever eat it.

You know, I had this problem or that problem that it was fun. I didn't, I wasn't though a kid who spent an infinite amount of time on it. I was busy playing tennis. But I did do enough so it gave me. You give you satisfaction. And to answer your question, a hands-on orientation. So I always liked being around equipment.

And since you started in, Jeremy, obviously you had a practical bent. I was just wondering, did you ever, toy with doing theory or or uh yeah well my my uh my hero once i learned about physics then you develop your hero and so my my hero which was true for quite a long time probably until i was uh until i had a second one which was fine when i came to caltech i was uh enrico fermi of course great hero and and And really, no, but particularly, I think what attracted me was the fact that he did both theory and experiment. Which was my goal where I didn't succeed, but my goal as a scientist was to do both, actually.

No one succeeded in at least a fundamental particle physics after Fermi, our nuclear physics. I mean, he was the last, I think the last great person who was equally good at theory and experiment. Yeah, yeah, yeah. I mean, he did. It's amazing. He did his weak interaction theory. and six months later did the slow neutrons to yeah to and and amazing you know i gave a lecture once in this 100th anniversary at fermilab actually and boy then i discovered not only did they do that

i don't know how they did anything because he taught three classes and i mean it's a different world back then yeah yeah and he was unbelievable i think i mean just he was great yeah i never i never met him but so he was Nor I, but he was my, my idol kind of. And then later, Feynman, because I was in the same institution. But in a different way, in a different way. So I did think that that's what I was going to, at some stage, I was going to do both, like Fermi, but somehow life didn't turn out that way. Well, it's probably just as well in a way.

because what I was going to do next is that you went, you, so you in Berkeley, did you get your PhD in 1962, or did you enter, I forget when you, I have a number, 1962. Is that, is that when you got your PhD? I finished my thesis in 62. I think they gave the PhD the next year. Yeah, yeah, yeah, but it doesn't matter. The point is that, and it's probably just as well, it seems to me that you were doing, if you think of the history of physics, and now I want to move into your history of physics, which is, which is, which is the, wonderful thing I want to go through is all the different areas of physics you've gone on. I know a lot of people probably lately just have been talking about LIGO, but I've known you for a lot longer and known and the diversity of areas of physics is what I find particularly interesting. But in 62, what we would call particle physics, but nuclear particle physics, was in a theoretical turmoil, but an experimental celebration in a sense. As you say, Chamberlain and there all it was a time when all these new particles were being to had just been

discovered and if you're an experimentalist it was a heyday but as a theorist it looked like the world was ending in the sense that everything sensible was was going out the window and yeah did you get a sense of that as a student did you get a sense of that yeah even more even more complicated i think well that there was all this sense of discovery because of the particles were being discovered which is what got me into the field. As I said, starting it only accelerated from the time. From the time I was an undergraduate. And the reason, of course, that I chose to stay in Berkeley

was all these discoveries were very much centered around Berkeley. So, you know, they told me that they didn't like to, didn't want to keep their own undergraduates. But the year that I graduated, they kept three of us. So I stayed in Berkeley exactly for that. reason to discover. Along the way, it started to become a problem, not no longer a great exciting thing.

You can only discover so many particles before it's just confusion. Yeah. And people started making crazy discoveries, a double, there was a double discovery, and if you remember, a double bump, it's something like that. And well, before I came to Caltech, must be a year or two years before, when I got my degree, Murray Galman came to Berkeley

and gave a talk on the eightfold way, which is the order to this system, which was in itself, I think, one of the, probably the most exciting development I've seen scientifically of experiment and theory coming together in some way. I mean, a little bit odd because he did it from this mathematical thing rather than some physical, rather than say a lot of what Fermi did, say, and beta theory or something came out of understanding physics.

He did it by taking group theory and applying it somehow. And, you know, it was unique in the sense. I'm just trying to give some background for others. but, you know, while Dirac had predicted a particle, he really hadn't predicted it. He didn't believe it. But I think it was the first time, I mean, and it's probably predicted neutrino, I guess, but it was the first time that I can think of were from some abstract theoretical picture, you could predict the existence of a particle.

And then, lo and behold, what do you know, it existed? It must have been amazing. It must have been truly amazing. So the way I remember it, I'm not sure I'm accurate, but I think pretty close, is that the whole picture had some blanks. The cascade particle wasn't found yet, but it was found while he was still doing this. But then once that was found, then he wrote the following paper where he predicted exactly what the omega-minus would be. It was the last missing particle in this group, and he could predict its mass and all.

the decay modes and all this. And then luck came in because there was a big race to look for it in Berkeley and in CERN and at Brookhaven. And there's only twice in my life of things that are close to me where an experiment has been definitive based on one observation. And this usually, you know, it's yeah, of course, yeah. But this was the bubble chamber picture of the omega minus, and

they were lucky because all the photons that came out converted, and so it was overly determined, and it gave exactly the mass. It was unbelievable. A normal experiment and other omega-minuses would have taken more than one, because you

didn't see all the particles. They didn't all couldn't the second time, of course, which I didn't think could possibly happen was our observation

of gravitational waves based on the first event, one event. Platinum event, yeah, yeah. Yeah. And yeah, the omega minus,

that's what led to Murray's Nobel Prize, I guess, is the ability, I mean, that omega minus must, again, it was before my time as the physicist,

but having studied the history of part of it. It was to Finn, it was just amazing because, Yeah, you pretty definitive. And he was a type who would just have played it up anyway, Murray. But, but, yeah.

Yeah. And so that was the transition time for me. It was the last part of my Berkeley time was he actually gave the seminar that, which was on the eight, what he called the eightfold way at that point. Yeah, sure. And then the discovery of the, I don't remember the year exactly, the Omega minus sealed it. And when I came to Caltech,

the same ideas, by the way, were generated by George Wyck. Yeah, yeah. But he was at CERN. He was a Caltech student. He got his Ph.D. He got hired back at Caltech, but he was on,

before he came back to be on the faculty, he was at CERN. So when I came as a postdoc to Caltech, he wasn't around. And by the time he came back, he did. decided he wasn't going to do theory anymore. So I never understood how independent, truly independent that was,

how much they interacted. It was really hard to tell as a young researcher. I just never. Yeah, well, the good thing about, you know, you never, especially with theory, that's one of the reasons by, I'll tell you, in later life, in someone, not that I regretted, but I envied, experimentalist because if you're a theorist, you really can't show something as yours very effectively.

If you're experimenting, you actually do something. You produce something. It's real. It's undeniable. There's this machine. There's this data. It's there. But if you're a theorist, it's very murky. And it's fine. And as far as I'm concerned, the more the merrier. I mean, because it is a cooperative part of science that people don't realize. And it's not individuals sitting alone at night and revelations at Blackboards. But, but, but, it is, it is interesting in, in kind, things like that. Who, who, who did what exactly? It's not, if you're a theorist, it's not so clear. And, um, but the good thing, as I say, is, go, man, if, you know, that he didn't just need the omega minus to be, to be, to be shown to be one of

the remarkable theorists of his time. Yeah. Yeah. And anyway, so you would, you, by then, of course, by the postdoc, you committed to doing experiment and you've been, and you've been lucky to be thrust at the center of particle physics, really, which was Berkeley, at a time when experimentally there was just a heyday. I mean, it was just, you know, anytime you turned on a machine, you suddenly saw a particle. And the theorists were, as I say, tearing out their hair and giving up on things like quantum field theory. In fact, it's interesting because I'll be talking to another friend of ours, David Gross soon. And, you know, he was at Berkeley around that time when the theorists were in fact doing just that, giving up on our present picture.

But then you, you, and yeah, so I looked at your PhD, you know, it's something, you know, pyons and protons and stuff. But, but, but the, when I first knew you, which is now jumping ahead, but by then you would, you would establish, you'd begin to work on my favorite particle in nature, neutrinos. And, and, and, and, and, and, and, and, and, and, and, and, and had worked on a key experiment, which, which established, which, which established, which really is, the standard model of particle physics. And it helped our good friend, Shelley Gladys, for the O'L fries. Because this theory of the weak interaction,

which had initially been his, and then Steve Weinberg, and, but he, it had predicted not just new particles, but a new kind of interaction that was like photons, but different. And the only,

and, and I guess, it was recognized. I don't know how you, I want you to explain this to me, how clearly recognized it was that neutrinos were the way to see it. And whether that was your goal, I mean, you worked on the experiment that eventually showed, there have been a lot of experiments that showed there weren't weak neutral currents and it held things back for a while in the early 70s. And I sort of entered graduate school in 1977, right around the time that we, I remember, you know, I think Weinberg was very excited because the experiments had now shown there was a week.

neutral current. And anyway, so you worked on that. You want to give the history of that a little bit? Yeah. There was a new accelerator being built. So that was what's now Fermilat. Yeah. And there had been a very important experiment with neutrinos that had been done at Brookhaven Lab. And that established that there were two kinds of neutrinos at that time. Neuon neutrino and the electron neutrino. So that was a big discovery that happened a period when I was working at Brookhead, near the period when I did some work at Brookhaven. I did an experiment there that you didn't read about because we didn't discover anything. That's right.

Like most experiments and like most theory, people don't realize it's just, you know, most of time, you're not making, you're making baby progress. It's not, anyway, go on. And I've always been someone that looked at, you know, what you can do, what happens in an experiment is there's new possibilities because there's new instruments or new techniques. Yeah. Not just new ideas, okay?

Or not just because you measured something before. So I've always been kind of opportunistic in thinking that you can apply, solve problems that couldn't be solved before, do experiments that couldn't be done before because of new instruments. So I was quite interested in just the idea that this new accelerator was going to be built at at Fermilat. Yeah, then called National Accelerator Laboratory at the beginning. And I was quite, I was quite, I. I had worked at Brookhaven on anti-proton, proton-annihilation,

which I thought was going to be the great avenue to phenomenal discoveries because it hadn't been done before. We didn't discover anything, so you haven't mentioned that. I went to Brookhaven to do that, leaving the group, which I was part of, that was doing electron scattering at Slack. And they did electron scattering, positron electron and then deep in the elastic scattering and made a discovery, I quit that experiment

to go to Brookhaven. Never could I forget that be, never could that be forgotten by Dick Taylor, who was my good friend who would take any opportunity to tell me what an idiot I was to leave because it was originally not MIT Slack, it was MIT Caltech Slack on those. Okay, I was gonna ask about,

I was gonna ask about mistakes or errors or things you overlook, Yeah, yeah. So this was, I wouldn't have won the Nobel Prize because I was younger, but I was younger. But it would have been an experiment that would. But I was a player in that experiment. Yeah, I was, I designed a lot of what's in the instrument that they used. I designed something else, which wasn't used for that, but the Positron source, which was only recently taken out of the accelerator at SLAP.

And, but I quit to go off to do something at Brookhaven. Anyway, so I was quite aware of both the scattering experiments at Slack with electrons, which we had done, and I was part of in the early days. And I was aware and admired the two neutrino experiment when it was done at Brookhaven. So I'd say the main thing for me was my eyes were open. And that Fermilab, when it was being built, provided what I viewed as a new opportunity. to do things. And I think the first thing is that I thought that neutrinos were going to be a great probe.

Why? Why? Why? Which have problems? Yeah. Well, okay. Why? I think I know why, but I'd like to hear your answer.

Well, basically that they're not shielded by a lot of other backgrounds. They basically, when they scatter, they scatter off. the things you care about and when you, the interactions are the weak interaction, which is very fundamental. And so to me it was, and they hadn't been done because you didn't have any instruments. I mean, basically the two neutrino experiment didn't use neutrinos in the same way to scatter them or do anything. So it was something that just hadn't been done at all. And having come from knowing about accelerators and so forth, I had the idea, that if you did it right, you could build a very intense neutrino beam.

It had never been done because the neutrinos that were used were always into a bubble chamber or a few into something. They didn't really have much of a neutrino bean to do Litterman's experiment. So I had an idea of how you can make a very intense neutrino beam. Not only that, how you could make it so it had defined energy. So it wasn't just neutrinos of all energy, but defined energy. And so our... I collaborated with a Frank Scully.

I don't know if you know it. I know. He was a junior faculty like me at Caltech. And the two of us basically designed this experiment and proposed to this one of the first round experiments at Fermilat. And the vision was mixed. first really exploratory I'd say you know I'm not driven by theory but this is a whole new new window yeah a new window and and that instrumentally you had a new accelerator you can make

much higher energy and we can and we know how to make this beam that you can make a beam of neutrinos yeah that would be focused and and of known energy and and uh Then there were a series of possible things you could do with it. So one was, I was aware of the neutral currents, but it wasn't on top of the list. I'd say it was third or fourth on the list of things we thought we would do. It was, of course, part of the design, one of the things we wanted to do, but I wouldn't say that that was number one. the first goal was to be able to do nutrient. We had two main goals.

One was to search and find the W boson, which at that time wasn't going to weigh 80GV, but was thought. And again, I'll interrupt just for the listeners, the W boson was one of the new particles that carried that was predicted of the theory of the weak interaction that carried the weak interaction. And indeed, people thought that it was probably light enough to dissect, right?

Yeah, yeah. They thought it was light enough to detect. And that was going to be our discovery. So to be honest with you, that was going to be our discovery. That was the first thing we wanted to look for. Sure. And the highest priority in kind of the design of the experiment was how do we find the W boson up to 5GV or something,

less than one-tenth of where it ended up. And the second goal. goal was to, so I guess maybe neutral currents or third. The second goal was to do the slack experiments with a better probe. That is with the deep-intelastic scattering, quote, again, I'm just going to translate that for people. So the thing about the slack experiment and the reason when the Nobel Prize, it was a probe of the protons that ultimately detected the existence these particles

quarks that appeared to be interacting relatively freely inside the protons, which is a real surprise. And you can use probes. You know, that's the way you do things. And you hit the proton, you see what comes out. And electrons were one probe. And so you realize that neutrinos could be another probe. Yeah, and a better probe because they basically don't have other things they do. So they scatter off these quark-like objects inside or point-like objects.

Let me, let me again, I'm just still going to translate a little bit. Yeah, yeah, yeah. Electrons interact with electromagnetically. They have charge and they interact weekly. Whereas the neutrinos for people, that's what makes neutrinos so special. They don't have charge, so they only interact with the weak interaction. Sorry, I just wanted to give people a preface. Yeah.

And so we did that and that, of course, is important. So that was the second goal. The first goal we failed that. W.B.O.S.N., that was the second. gold, the third gold is neutral currents. And you expected to see them, though. Well, I wasn't, we didn't know. I mean, there was no evidence yet.

When we designed that, there was no evidence zero. There was anti-evidence, wasn't there? I mean, when did there? There was anti-evidence a little bit later. We designed it in about 1968, 69. And so at the time, that, and so that's the thoughts at that time. In the year before we detected neutral currents, the single event was seen in the bubble chamber at a single event was seen in the bubble chamber. It wasn't definitive at CERN. And then we saw it in 1972 or 73. There was a lot of fuzziness in between. I would say the

advocates, say Weinberg, theoretical advocates, were not as definitive, merely in, you know, you're just going to find this thing as, say, Murray was about the Omega Minus, which we talked earlier.

So this was not, yes, it was a byproduct, but I don't think they were. Until, it's really quite amazing. I mean, again, in the history of physics, I mean, Weinberg's paper on the weekend, and weak interactions of part, we call leptons, particles like electrons and neutrinos, which is now one of the most cited theoretical papers in the world,

did not have a citation. He wrote in 67 for three or four years. I mean, you know, it's sort of a model, and I don't know whether, I don't, I've talked to Steve about this, but I don't remember the answer, whether he took, how seriously he took it, but didn't promote it a lot.

And it was an interesting, idea, but it wasn't, as you say, it didn't capture. It took a few years before people realized it put in a broader context and realized how natural it was. And I, you know, I don't know whether Shelley, again, you might have talked to Shelley. Again, for your audience, there was neutral currents, but they were always strangeness changing. Yeah. So what we knew was that in the decay of strange particles, there was channels that were equivalents of neutral currents. What was predicted here was you didn't have to change, have strangers. And strangeness is a quality of just a name applied to quarks. They have different colors, color, and there's the up quark,

down quark, and then there's a strange quark, and they have different names. And it's really just a quantum mechanical property. And it's also a particle property because it's K mesons and lambda. So the strain, the neutral current at that time only involved, these particles which had the strange court, but they basically were the lambda and this involved, could you have strange, strangeness changing, non-strangeness changing neutral currents. And that was the big deal. But it's interesting that you went for the W, you know, again, I'm relating because when I, when I first met you, it was 1980, I remember vividly because we were together in Scotland,

and I was a graduate student in a Scottish summer school. And you were talking about neutrinos then, by the way. But at the time, it was kind of interesting because theorists, the experimentists were looking for the top quark. And do you remember? I mean, and so the theorists would throw bones out, just like the W. Oh, you'll discover the W if you do this next experiment. It's only going to be 5GV.

No, it would be 10 DV, no, at 20. And it was exactly the same with the top cork. Remember, theorists were coming up with predictions just beyond what the experimentalists could see and the next experiment wouldn't see it in the next. Do you remember that? Yeah, yeah, until it got to be so heavy that it took, that's the longest discovery paper I've ever read. It's the discovery of the top cork is a 200-page paper to make it. It's so difficult to actually isolate it when it's so easy that it's... Decades really quickly. Now, look, so this, what I wanted to clarify for people in place

they didn't know this is that that was a, that, you know, that was a, that you, you know, that your neutrino experiments were very important in helping establish the fundamental model of physics. Because again, I think for a lot of people now, because you won the Nobel Prize for LIGO, don't recognize the background of experiments that you worked on. And I think it's important. But more than that, what's intrigued me, and I knew you, you know, I also knew you at a time when I was kind of floundering and I didn't know whether I really wanted to continue to do theory. I was really not particularly happy. And you were a wonderfully pleasant, kind person to talk to. And I remember, and we'll get to it, because I remember you actually offered me a chance as I was a student in

MIT to spend a summer working on another experiment you worked on, which we'll get to called macro. And I regret that I never got to do that. I don't know whatever happened, but I think I do know what happened. But anyway, it, it, it, it, it, it, it, I didn't get to, I really wished I, you know, I wanted to have the experience of working on an experiment to see. But and the reason I, it's a segue to macro is that one of the things that I appreciated early about you, which, which I came to realize as our career, as I became a physicist and our careers sort of moved along and I got to know different aspects, is the, is the, is the, is the, is the jumping around. I mean, I remember when you went from accelerators to macro, which we'll talk about it, which is an underground physics experiment. And I remember you're just saying, yeah, well, it's just

different, you know, it's similar techniques. You try new things. And it's no big deal, but it seemed like a big deal to me. And but before we get to that transition for you, I wanted to ask you, you've chosen to work on there were neutral currents, macro, and then we'll talk about jam the LHC, the super connective super low-liter experiment, and then ultimately Ligo. Each one of them in their own way could have

been Nobel Prize winning experiments, depending about how it went. Did that have, did that affect your choice? Did you choose, I mean, it's easy after the fact, and so maybe with hindsight, you'll say,

but, you know, one can do experiments that are like bread and butter, okay, I'm going to do the experiment I've already done, but I'm going to improve it. and tweak it, and I'm going to make a career of this or that. Or you can say, you know, I'm only going to work on things that can have a dramatic impact. Did that govern your choice at all?

And the answer is, and an answer to no is fine. Well, no, of course, like all things, it's more complicated than that. I went into physics in a somewhat romantic way, as you said. So at any, and I've never been fearful of doing something that's different from what I did before. So in some sense, this romanticism carries, and I have pretty good confidence that I can do what I try to do. You know, experimentally. Yeah. If I can assess it and do it.

And so at any given time, I've basically been attracted to the most exciting and interesting thing. I think I can do. And, you know, I failed. It's quite a few. But the failing is important. People don't realize how it's incredibly important. In physics and in business. So we mentioned one already.

I failed this to find the W. Boson. We're going to talk now about Gran Saso, which was a great thing to learn about Italy and Italian and so forth. But the reason I went there goes back to when I once saw you, which is, I don't know if you know the history. The history started in Scotland. Yes. When I gave, do you know my history of that?

No, I want, I know. So you remember there were four lectures there, as I remember it. I may be wrong. And I lectured every other day. So, and Shelley lectured on the odd day that I, but it was every other day. And the lecture of my day was To hoft. Exactly. It was a good summer school, by the way, because is it,

a Tuft won the Nobel Prize after that. You won the Oafi. It was a good summer school. So he lectured before I lectured. And in those days, we used transparency. Yeah. No slides or no blackboards, but transparencies. And I used to go to his lectures, which were before mine on that day, understood not so much.

Yeah. He was talking. He's very mathematical anyway, but he was talking about grand unification. at least the part that I remember was about grandion. Not that he had any grand unification, but he was talking about how grand unification would work if you use not a billion-grade gauge theories. Basically, it was based on the same mathematics that we always use.

Which he had made, which he had, because of him, they became interesting in physics. I mean, it's one of the many things that Raritov did, but yeah, he was talking. very mathematically. And I, I've been as a student. And he was talking and whatever.

I was just going to say, as a theorist, I also didn't understand a lot of what he's talking about at the time. So, but that was perfect for me because I would finish up my, my,

polish my transparency, you want to call it, finish my talk while half listening to him. And then I would give my lecture. So, but at one point, he, uh,

at one point he showed, that if you use not a billion gauge series, it's the same mathematics, so in general, and formed a grand unified theory from it, that there were singularities that existed, that he identified as having the properties of a monopole. Magnetic monopole.

Magnetic monopole. But they would have a mass that was something like the unification mass. Which is 16 orders of magnitude larger than the mass of proton again. Yes. And so it turns out that one of the thing, one of my first kind of curiosities as a physicist that made me try to understand things as an experimentalist was the fact that the Maxwell's equations aren't symmetrical.

Yeah, sure. There are electric charges, but there are no matter. magnetic charges again I'm just filling in for rest of it otherwise is symmetrical yeah yeah yeah and to me symmetry is everywhere and why is there this asymmetry and maybe it's there not there because we just haven't found the little M that goes in a little Q so this is goes back to my undergraduate days my interest in it so I was interested always in searches for magnetic multiples they're very simple to understand yeah and they were

done from, that I knew about them from, even when I first came to Caltech, the maybe a little after they, Jerry Wasserberg in geology was, got moon rocks. And look for. And I spent time with them in geology at Caltech for a while, talking about whether they could find magnetic monopoles in the moon rocks. because the idea then was the monopoles would hit the moon and there would be a concentration of them in these moon rocks. I remember.

I remember that at the time. Because a lot of people, again, I hope you don't mind if I preface for other people listeners. Go, go, go, go. That magnetic monopoles had been interesting in physics. Obviously, the symmetry that you talked about was fascinating. Dirac was the person who made it interesting for, it sort of made them

the idea that a magnetic monopole might exist because he showed something remarkable in 1936, I think, that if a single magnetic monopole existed, you can understand why electric charge was quantized. It's a big mystery. Why do all charges come in multiples of the...

And it was a remarkable thing, and that made it interesting, but there was no guidance of whether... And people had looked for them, but there was no guidance that they should exist. But then, but then around the time when you and I were at that summer school and these things called grand unified theories had been developed a few years before, there was suddenly a prediction that these

things, if those theories were there, these particles had to be there and they would be very massive. Sorry, I just wanted to give that. Yeah, yeah. Yeah, just what you said is true. I was interested in them from before, moon rocks, searches with cosmic rays, all based on one of the first things that kind of, We all learned Maxwell's equations as students that I didn't understand, and maybe I didn't understand it because we just hadn't found it yet. So I was interested in it from the beginning.

I didn't know enough. The first I heard that these magnetic monopoles would be super massive, was in this lecture at Scotland. In Scotland, yeah. Wow. And sitting there, I had, I probe my memory and because I happened to be interested in the subject of magnetic monopoles, it quickly occurred to me that if I was right, that magnetic monopoles had,

that there had been all these searches for magnetic monopoles, but there had been basically a fundamental assumption that never appeared in the print that people made, but maybe they made subconsciously, but usually put all your assumptions before you do something, that the mass of the monopole was something like the mass of other particles, like the proton or some of the particles. And so I went through, instead of listening to those lectures after that, I was going through everything I remembered about magnetic monopoles, that is searches in cosmic rays and on accelerators. You couldn't make a heavy one on an accelerator. So I went through everything I knew and convinced myself, I thought, there was no library, if you remember,

in St. Andrews, but I convinced myself, at least close enough, that you had to, that all those searches had to be thrown away. They had nothing to do with these new kind of proposed magnetic monopoles that would be super heavy. So then I thought about how you might detect them. And I thought about something else that I happened to know at that point. It was. which is interesting. That is that because I had worked at Fermilab, I was quite familiar with the physics department at Chicago, and they had offered me a job.

So it's the one place I almost left Caltech for it was to go to Chicago because I worked at Fermilab. Because of that, I was quite familiar with the department there because it was a long courtship kind of with Cronin. And we didn't go. basically because of Samount it wasn't made because of my wife she decided that it was too much hard for her to start a new practice in psychology there but I probably would have gone if she interesting. Wow so anyway I knew the department very well and one person who intrigued me was

Parker Eugene Parker yeah and he had and he had written a paper that I had read that I remembered in Scotland, which was that, but I didn't remember the numbers, but I remember in Scotland that he had basically shown that the limits on that you have magnetic fields in the in the galaxy and in the solar system and the monopoles would eat them up. Yeah, right, right. And so if you have too many monopoles,

they would short out these magnetic fields. And you wouldn't have magnetic fields, okay, because he had the currents and shard it out. And so he had something called the Parker Bound, which meant that there couldn't be any above this level. And that I remembered, and I turned out to be pretty close to right, But I remembered it because of, you know, being connected to Chicago. These old things come about.

Sure. When I went home, of course, I looked up all this, and I had remembered it pretty much right. And the result was that you needed to make something that was very large because the flux of monopoles couldn't be very big because they would shirt out the fields. Okay. And so I took on the challenge of how do you make something very large? And in the meantime, others had gotten interested in. And one of them was a colleague that I respect very much, but he made a mistake, unfortunately.

That was Cabrera at Stanford. And we had some informal meetings of people that were interested in finding monopoles. This is like in 1981, I think. What were you in? We were in Scotland. It's a year after. Yeah, it was not.

1980 we were in Scotland. Yeah, so 1980, 1981, there were maybe... Cabrera's discovery of a monopole was... 82. 82. Valentine's Day, Valentine's Day, 1982, I remember it now.

So in 1981, it turns out there were, you know, a dozen or so physicists who were interested in Grand Unified Monopoles and formally, and we talked to each other. And of course, so I knew a lot about what Cabrera was doing. and I also had convinced myself that you needed something, you know, 10 to the fourth times bigger than what he was building this ring, which is a beautiful idea because you develop a... The monopo goes through and it makes a unique amount of current. And so I was designing something that was huge. And my idea was I'd make something.

And I had students working with me and we were trying to make something that we could put underneath. the football field that Caltech was the first idea. And then I became aware that they were making this new tunnel and laboratory in Europe. So that had the advantage that you could go deep underground and have a big space, which meant it made it much easier in terms of what kind of technical, what kind of experiment you had to do it. If you did it on the earth's surface or just under the surface, or just under the football field at Caltech,

you had to get rid of all cosmic rays that went through. But if you went deep underground, there were so few that got that deep that you did in a different way. So it migrated into that. I don't remember exactly where I was in that thinking at the time that Cabrera had found his signal, which made me, very happy on one hand and very upset.

Yeah, sure. I was upset that I had been somehow misled, misled myself, that I needed something huge when I probably did, because he got, but the experiment turned out to be wrong. Well, are they, no, has anyone ever, you know, we don't know if it's wrong. No, no. It could be one monopole in the universe and he might have discovered it. It just happened to go through that loop. You're right.

It's not wrong. It's just misleading. Yeah, yeah, it's misleading. Yeah. So it's a wonderful experiment and he's a very good scientist. Yeah, he had a former collaborator in mine too, yeah. Yeah, and so anyway, by the time his thing had come and gone and we developed the ideas further, it turned out that the place to go was Italy. So I went to discover the magnetic monopole.

That was the original reason to go. Of course, we saw other things like we were the confirming experiment to the neutrino oscillation experiment done in Japan. Maybe we should have discovered it before them, but it was a secondary goal for us. But looking for magnetic monopoles, then I spent 10 years. So that's risk, which we came back to. I spent 10 years. We didn't find any.

So, you know, I failed. that's the other thing, you know, that's the other reason I probably didn't want to become experimentalist, because you can spend, you know, big experiments like you did. Take 10 years, 20 years and then you can sometimes not see anything. And it can be, I imagine for me it would be frustrating. I remember at the time thinking, you know, you would take, it's not frustrating because it's all of it's fun. Yeah, well, that's the point. And you would tell me it was fun.

And I, and that was nice. And I mean, and I remember thinking, wow, Barry's just, you know, taking this on. And it's really amazing. I was shocked at the time could go from accelerators to non-accelioration. And it helped create a paradigm for large underground experiments, which, of course, has become a central part of physics. And I've been involved in them myself. And then, but yeah, you said, well, it's fun.

And that's what I thought, oh, well, I'll go and spend a summer and see how fun it is. And who knows what would have happened. But anyway, but I didn't. And you didn't. And then I thought, well, you know, they didn't see it. Poor Barry, that's his career. And then, and then we'll jump ahead. And then the United States decided to build a ramp before that, but that it was important for years in order to discover the real nature of the electroweak theory, the standard model, to build the definitive accelerator.

And it was going to be built in Texas, the superconducting supercollider. And so you'd have this null result, which was important. By the way, again, null results are important. And you demonstrated that, you know, at the level that one might have expected to see for the simplest grand unified theories that the monopoles didn't exist. And that was important in guiding one of the things that helped guide, guide theory. So I don't want to diminish it. But the superconduct supercollar was going to be built. It was going to be the definitive experiment, the largest accelerating the world, an amazing 62-mile machine underground in Texas.

And another significant experimentalist was going to be involved in building one of the machines. and one of the detectors and that fell through. And then I remember actually at the time, I was at Yale. I was fresh at Yale at the time. People were talking about who might do it. I remember I had my friend Charlie Baltay, who was a colleague of yours. And is it worth, you know, is it worth the gamble of seeing if the SSC is going to be built? And then someone like you decided it was worth a gamble to build this thing.

So let's take us to the SSC now. Yeah, well, the, the, the pot of gold at the end of the rainbow that we're looking for there was the Higgs boson. Yeah. And it was definitively designed to be able, unlike the CERN, by the way, which we should point out, I've always said, wasn't, you know, it was going to detect the LAC. The machine was designed for it and the experiment that I and a colleague Bill Willis. Mm-hmm. What I also knew for. Yeah. He was a Yale earlier and then he was at Columbia when I was working with him.

And he's dead, unfortunately. Yeah. I rented his house. But we designed this experiment to detect the Higgs boson and it was much more optimal than the experience. Yeah, it was good. If it was there, this was definitely lucky. The machine would have produced more, but the experiment also had, we went, we took tremendous lengths to make sure there was no material so that you could. really see this gamma-gamma mode and so forth and so on. It was called gem, right? It was a gem of a machine.

Yeah. Yeah. And then what happened? Well, the politicians canceled the dumb machine, but, but. I remember, yeah, I mean, the politicians, it was the machine that was, it was, it was the dumbest decision, one of the many dumb decisions. It was a new Congress, a new conservative Congress. They had to show that they were going to save money.

So they came in there to that. guys. And it was either going to be the, so they had to cut out something visible. And it was on the technical side, I don't know, other things too. And that was either the space station or the super collider in Texas. And it was such a mistake to keep the space station, in my opinion. But I remember it was a disaster for particle physics in this country. I had become chairman of a physics department a year before the superconduct, the super collider was canceled. And there were lots of things that way. I mean, the point is it wasn't the science.

There was punishing the Texas congressional delegation. There was all this. It was all politics. And I remember when it was canceled, I was hiring. I moved there to hire 12 new faculty, which one of the reasons I left Yale to move to the case. And I got 250 applications from scientists who'd been at the L, at the SSC. And their whole careers had left their jobs,

had left their institutions. And all of that expertise was about to die. and I do remember once again thinking, poor Barry, that's, you know, that's his career. You know, you put all his eggs in that basket and first macro, it was a brilliant, but he didn't see anything. And then the SSC, well, he's a nice guy and he'll just, you know, have a happy life. And, and, and I thought, and there were a lot of people who did leave the field because of that. But you went on to do something else. And again, it was fortunate, I guess, the accidents of life.

and I found them for me too. But you didn't go to Chicago. Had you gone to Chicago, you never would have been involved in LIGO, I assume. I mean, you know, it would have, it would have be, yeah, you wouldn't have been Caltech, which is the center. But, but tell me about the transition, because it was a while, of course, after it was,

the SSC was killed in, in, in, well, I guess the SSC was killed in 92, right? Is that right? Yeah, C was killed in 93. 93. And then, um, And you started with a big one nine to four. Yeah, there was very little time. So I'll explain it.

First, it's not that I'm lucky the SEC was canceled because we would have discovered the Higgs. Yeah, yeah, yeah. That would have been a different price. And that was a pretty important discovery. Yeah, a different price. Way before it was finally discovered. Yeah, yeah. It would have been 20 years.

We saw on the right path. Yeah. But at Caltech, Caltech is a really small place. And as you know, I mean, we were a thousand undergraduates, a thousand graduate students. Thousand faculty. And it hasn't grown. It's had a guideline of 1% a year growth for the faculty students. And since I've been there, it's grown less than that.

So, you know, I've been there that many years. It basically has almost no growth, but they have a little room for it. the trustees agree to it, basically the planning is around zero growth. There's a fundamental difficult question, which is with zero growth, how do you stay in the forefront of physics in a physics department? That's not a simple question. Sure. I'm not sure I can answer how Caltech has succeeded,

but it stayed pretty well at the forefront of physics, despite the fact that since the time I came, which is quite a long time ago now, there's been essentially zero growth. The physics department is within a couple of positions the same size as it was. And if you look at most new fields that open up or something, you do it by growth,

maybe things die away slowly. But at Caltech, it means, I don't think we have a magic formula for it, but it does mean that we're very more, more uniformly involved in new appointments. Well, yeah, there is a little bit of magic thing. It's called money. Caltech has a lot of it, but go on.

Yeah, but a number of people, well, money in terms of attracting good people. Yeah. But in terms of how you make new appointments, they're really a big department-wide. Yeah, sure, because it's a big deal. It's a big deal and there's no stickiness. If somebody retires or leaves out of one field, there's no real advantage to get somebody in the same area. That's not exactly true, but it's kind of true. So it turns out that so there's an involvement in other fields.

I started at Caltech on the faculty the same year that KIPP did. Okay, interesting. And we became friendly very early. So he was in a different field than me. Obviously, he's a theorist. I'm an experimentalist and a totally different field. Fortunately, I had taken another side thing, I had taken even though I didn't have to,

general relativity as his graduate student. I had studied general relativity. And in some ways, I found it more palatable than quantum field theory. Certainly, it's yeah. because I could understand it a little bit better. I mean, manipulate the subscripts and superscripts and stuff.

And it's not really as difficult as quantum physics, really. Yeah, sure. It makes sense unlike quantum mechanics. Yeah, anyway. Yeah. So I took it in graduate school and I knew it. So I was not uncomfortable with that, let's say, I could, you know, kind of physics side of it.

thinking about that field. And I was friendly with Kip. And then there was these, I really wasn't up on all the, you know, all the early searches, Webbers and all that's very much. But I got interested once there was interferometry as a possible way to detect gravitational waves. This is long before I got involved.

This is in the 19, maybe 1980 or something like that. Yeah, yeah. Well, yeah, Caltech wasn't involved yet. Yeah. And it was maybe in late 70s or 1980. And when we were doing the annual thing of looking for new appointments, KIP was the first to say that we should build a group in the experimental part of looking for gravitational waves, not the theoretical part. And I got intrigued mostly.

I never liked this idea of a bar. I mean, I knew about it, but I didn't like it because a bar rings at a certain frequency. And who says a gravitational wave is going to be at that frequency and it's not sensitive anywhere else. And so you need a broadband instrument. So I was critical of it from the very beginning as an instrument that was not matched to the problem. And so when interferometers were an idea, from the beginning when they were talking about it,

I was aware of that. And I was attracted to it because of its broadband ability. I had no idea how sensitive you could make it or this or that. But the fact that it could cover broadband of frequencies and gravitational waves depending on the source might be at any frequencies. you could detect on the earth. Were you, let me just interrupt for a second.

Way back earlier, were you interested? I've often wondered this, because when we were in Scotland, I mean, there was a big, eventually a key work towards building what would eventually would be a gravitation wave detector was done by people in Scotland. Did you interact? Did you meet anything at all then? No, you, that, so. Okay.

Sorry to interrupt, but I've always wondered. So in 1980, I had a slight academic interest and enough to do some. homework and support the idea that KIPP had of developing an experimental group at Caltech with the next appointments we could make. So this was a dialogue that went on for two or three years. And then eventually we got as a visitor and then a half-time appointment of Ron Drever from Glasgow. Yeah.

And that group was built up. And I served as at Caltech on the, because there was quite a bit of involvement and bad history of false discoveries in that field, Caltech was pretty rigorous about making sure there was a lot of, and KIP was a theorist that there was sufficient oversight. So we had a kind of tracking oversight group from the time the experimental effort started,

which I served on. So, so I was, part of recruiting Ron and then people after that and I was on the oversight group and you know I couldn't help but not learn all about interferometry and stuff and I'm going to add a preface here from the viewpoint from outside you know gravitation waves yeah we realized that there was a way to possibly detect and I figured there's no way in hell they'd ever be detectable and there was a long history of wrong experiments and people trying to do stuff and

And it seemed like from the outside, it seemed like, yeah, and there were theorists and involved, and it was a lot of pious stuff. And I was worried about money being wasted. I remember thinking about the NSF spending money and was it really worth it. And I remember thinking, well, okay, it's really good to try and get a real serious experimentalist, you know, who I, I guess who I trusted anyway, involved. And I knew you were beginning to get interested. And it was interesting to me to see what was happening.

And that was in the early 1990s? Or was that, I mean, you became involved directly in 1993, right? Yeah. So the work at Caltech was maybe of any substance. You know, it started in the early 80s, but mostly it was Kemp and a couple of people and mostly theoretical. But it got serious about 1990. And, of course, that's about the time that I got involved in the SS.

And I used to say that I, If I wasn't going to find the Higgs, I would look for gravitational waves during that period because it was the next frontier. I was on this oversight thing and so forth. So, you know, from my point of view, that part of it was easy. I mean, let's say it had the same kind of interest of things I liked, like looking for the Hague. You know, something that's important, an experimental challenge, something I kind of always. Although it was a very different kind of experimental challenge. At least seemed to me, I was always amazed that you were able to go into it

because it seemed to me the relevant physics of the machines. Yeah. So you said a little bit of time passed. So what happened is in October of 93, Congress killed the SSC. And so many people and many scientists and technical people involved in the SSC went to CERN, a big part of our collaborative. And, you know, we like to say that it changed the designs of those experiments and so forth. I never was attracted to do that.

I always felt that those experiments were not going to be what I had been designing. The accelerator wasn't. And somehow stepping back to something that was not, you know, if it failed, it was not what we had. I didn't want to claim it on external things. And so I wasn't going to do that. And I was also extremely busy on a very thankless job. And that is, there were a lot of, you know, a lot of mostly, let's say, middle-aged scientists and technical people that I had been responsible for attracting to the SSC that were now out of jobs. Yeah, it was terrible.

And so I was very busy helping, you know, some people managed to land or already went to CERN. but in the U.S. there was a big, you know, big, really talented people and some that I had talked out of, you know, taking the job at the SSC that had been at Fermilab or Slack or something. Yeah, yeah, no, it was just. So I was doing this task, and then we also had to do something with quite a bit of equipment and so forth that we had had a surplus, but try to not just junk, but give it to the, physics labs that could use it and so forth and so on. So I was busy with that for the period after October. In December, unbeknownst to me, I didn't know the politics at all. The NSF decided to, they hadn't funded LIGO yet, but they decided to give up on it unless Caltech changed And our Caltech and MIT changed the structure and management to something that they had been through a big review.

Sure. And it would have a series of them, but they had failed. And so without going into that, the Caltech president, the MIT president, the head of the physics department at Caltech KIP, all these people got together. I don't know. And they decided to ask me, of course, I was available in principle. and so the head of the physics department at Caltech at that time was Charlie Peck, who was the first colleague that I met when I came and took a job at Caltech. Very first person, I didn't know anybody.

So I had met him the first day I came. And he's dead now, but he actually is the one that they did their thing. I had nothing to do with it. And then he was to approach me. And so he called me. I was living in Santa Monica already. And he called me and said he'd like to come out and take a walk on the beach with me. This is, you know, this is a guy I knew in my office and stuff.

We didn't go out for drinks together. It wasn't. Yeah. And he would never venture out. I had no idea what this was about except I thought something terrible was happening. So he came and brought me to the man. message that the head of the NSF and the head of Caltech and MIT had wanted to ask me to take over LIGO. And yeah.

Wow. And was it on the beach? Was it on the beach? Yeah, I know. I know. I know your house right by our house. You know where we live. So down right here on the beach.

And we were walking on the path. And so he asked me. And then, what do you think? I didn't say no, but I didn't say yes either. What I did then was, first, I had a certain loyalty to Caltech and being in. So for me, I was going to do it to save Caltech or MIT or this NSF project. I didn't really, I really wanted to assess two things. One is, was this, could you build something that had a reasonable chance of detecting

gravitational waves, of course, I'm willing to gamble some, as you know, looking for me. So it just has to be, is it plausible or is it a stretch of your imagination in my mind? And the second, it was the technology, was the design and the capability there. Whether the team was good enough, I figured I'd redo all that anyway. So that didn't bother me. And then, but what had been proposed in the NSF in terms of resources, was that enough? So I spent the time between early December when I walked on the beach until, I think it was February or March before I decided to do it. And during that time, I just studied all the questions I just posed.

And you convinced yourself it could work. I convinced myself that it could work at the level that neutron star binary systems, which is not what we detected first, could be detected if the detections of neutron star binary systems in our own galaxy were reliable enough to make the predictions. There had only been a handful of binary systems, pulsars and binary systems seen in our own galaxy. But from that, you have to ask whether what had been seen is extrapolated, is extrapolated properly to what exists in our own galaxy and whether our galaxy is typical. Because this is not, we can't, there's not enough of them in our galaxy to see. Yeah, it's a, it's a very known. So you have to see out far enough to see them somewhere else.

So how typical is our galaxy? And I looked at all that, and then the technologies, and the level at which reasonable predictions were, was that the thing called the strain that you measure is 10 to the minus 21. Which is, I mean, again, for people, I've talked about this publicly before and so of you, but it means you're looking for changes in length by one part in 10 to the 20. which means you're looking at changes in a three-kilometer long object that's smaller than one with thousands of the size of a proton.

It's a daunting, daunting challenge. So the first thing is you can't do it on a tabletop. You have to do it. The reason it's kilometers is exactly what you said. So it's not 10 to the minus 21. It's 10 to the minus 18. Yeah. But that's still.

Yeah. Yeah. So. Did you? And we make an instrument that can do that. and how good is the prediction. And the prediction turns out to be about right. We're lucky because that was not total luck, though,

but I mean, because you can predict them, but it's not surprising that that's just because it was the one source we could estimate. I wanted something that we could estimate to give me a target that I could do, but I never thought that that necessarily was going to be the first source we'd see. Yeah, backholes were much more uncertain, but more visible, but much more uncertain, black hole collisions. Whereas neutron stars were more known and, yeah, and somewhat smart. Neutron stars have been observed in our own galaxy.

Black holes, there's almost no information from electromagnetic things, so we don't know. Now, I'm only rushing because Simone is straight of your argument, because I would spend a little longer on this. But, you know, it seemed, again, from the outside like it was a boondon. like it wasn't that different than the you know this PlayStation, some sense, and so what was interesting to me was a decision and now of course I come from particle physics

which has this a feed attitude but but I remember learning from Jim Cronin who you mentioned is a Nobel Prize when he fits a wonderful man and a great physicist when he was looking at high energy cosmic rays and I remember him telling me the problem with the way these things were done where they were hit and miss people would build these little things but the point was

to build an experiment where if they were there, you'd find them. You'd take the particle physics approach, which is damn the torpedoes, build what's necessary to see the phenomena, instead of eking here and eking there. And I guess the sense I had when you began to take over, Ligo, was that it was that mentality.

It's either building it. So that's why I said, so there was a reasonable target. The estimates could be off, but we can also make it, better. So was that the limit of what we could make? No, but it was what we wanted to be funded to do with the possibility that we could do better, which we're doing now. So I knew we could, I knew that we were not going to be limited. The Higgs, if it was smaller, you couldn't see it,

because it's a physics background, and it took a long time to build something up over a physics background. Gravitational waves if we detected them, the background and the difficulty doing it is technical, not physics. So make the detectives. better, we can see rare things. So I always knew we had a target that we designed to, but if they give us the money, we could make it better. And you know, and you know, and I would have bet a million bucks that you'd never be able. I mean, I, it's still, I mean, amazing to me they could do it.

And that's one of the reasons I'm a theorist, but I said, there's no way these guys are going to do it. But on the other hand, I guess I felt that if it was going to be done, If it was going to be done, your experience of accelerating, building large object machines that were incredibly complicated to do a difficult task was the way it was going to be done. So I guess I knew in my own mind that if I felt that it was going to be successful, I mean, it was a new technology and there are lots of people

who developed technologies under credit, but to make it happen is more than just physics. It's someone who can run a big enterprise and that you had experience doing. So since I have to go, can we end with me asking you a question related to this? Yeah, okay. I was going to ask you one too about what the future of the ILC are, but we can talk about it. You ask me. All right.

Okay. So one of the problems we have, we made this observation you recall in September. Oh, yes. And then we made an announcement in February. So we had months in between. You want to ask me about my leak? So for us, there's a good reason why we took the time we took. Sure.

The first was whether what we saw was right or we were fooling ourselves or being fooled. Yeah. And then the second that took us some time is if we were really seeing something, we wanted to have the pleasure, I wanted to especially, of understanding what it was on our own. Sure. And it's hard with Einstein's equations and with the fit and get parameters and so before we just release some observation, those wiggles and other people do it. And so, you know, and then, you know, writing an article and so forth.

And, of course, keeping privacy when you have a thousand collaborators is a difficult thing. But during that period, you were one of the people who spread rumors. I was the one. I'm the culprit. but let me now let me give you my side of the story okay and i think i did you an immense favor and i've convinced kip of this fact okay first of all i've been i've known experiments that have been about to announce big results and collaborators have told me the result and said don't say anything and i've never violated that i've never violated i remember with the original um

uh uh inflation or gravitation ways i was i was led in on because they asked me to write a companion article but never talked about it there were rumors in the scientific community about a potential thing. And I also felt if you have social media and they're rumors, then if as long as you express it, it's a rumor, why should it just be scientists who were getting excited about it? Why not get the public?

So I had no problem with that. I was told by two people individually over a two-month period, neither of whom who had any relationship with the experiment. None of them were on the experiment. And they told me about a result, and it seemed to be clear. And my feeling was, well, you know, if that's the case, I'm not, I'm not violating anything by talking to anyone who's ever been in the experiment.

And moreover, even though I know it caused incredible hassle because then the journalists started bugging people when you were trying to do other work, what it did do, in my experience in popularization of science is journalists have like one day to explain a scientific result. They take the, they take the press release and they just do. And what this gave was a thousand journalists around the world a month. or two months time to prepare to write incredibly comprehensive and good articles. And so I have no hesitation. I just explained to the public that the scientific community was interested. I didn't violate any confidence of anyone in the result. And I feel it was the right thing to do.

And even though I knew it would cause a hassle. Yeah. No, I'm not attacking it. No, no, but I'm defending. My fear was that the actual result, what we saw. would come out early. A rumor that we saw something is not, didn't matter. Exactly. Yeah, that's my feeling actually. And I figured I also wasn't worried about stealing your thunder because it's saying that there's a rumor is not, it's not the same as saying

here's what they saw. Yeah, no. But if, you know, we start having to defend the specific result because it got out, that was our, that's what I didn't want. Oh yeah, yeah, yeah. And that would have been awful. And it was wonderful that I, in my mind, it worked the best possible way. because people were primed. The rumors never had any specificity that we then had it respond to. It was perfect. I wonder if you've had this experience I have, where you have a good idea, you really will have a goal that you want to get to,

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As I mentioned in my earlier introduction, we met again to complete a discussion of the present and future. And that discussion became very wide ranging. And so we made it into a second part of this podcast. And it's fascinating because we talked about the really challenges of the LIGO discovery itself. And then the future of gravitational waves. And then, in a complementary sense, another aspect of what Barry's been working on is the future of particle physics. So it gives a sense of the thrill and challenge of discovery and the possibilities of future discoveries. So I hope you enjoy part two. Take care.

Thanks, Barry, for coming back. We had to quit a little suddenly. And there are a few issues I just wanted to cover with you. And so I really appreciate your indulgence to come back and spend a little more time talking. I'm happy to have a second chance. Yeah, it's always nice to talk. And I want to mostly talk about the future, but I do want to hit on some things.

We hit on LIGO very quickly. And you talked about how you basically made that decision to take the job on over three months when you were sort of looking at it and deciding if it was doable. What convinced you that it was doable? Do you remember? what was the, what was the, it was no technology for you, right?

I mean, maybe I'm wrong, but this was, you probably had to bring yourself up to speed on the technology itself, right? Yeah, yeah, I did. But, but I think you can, in this particular experiment, I looked at two things, I think. One is, is the technology realizable that's being proposed, you know, to what extent is it a dream or to end? people are extrapolating. They can do better into what extent of things been proven. And so we came to the strategy to do this in two steps. So that's where the name advanced Lego came from. We called it LIGO 1 and LIGO 2. Ligo 1 using technologies that we had tested.

It's one way or the other, you know, not a long scale, but test interferometers. And in the lab, or we're known to be technologies that worked. We weren't extrapolating. And that was pushed to the level where it was, the words I used at the NSF at the National Science Board, when they talked to it, when they were evaluating us, was that detections were possible, meaning it was at a level where we weren't breaking any physical laws

and where you could plausibly imagine sources that were strong enough. Okay. But I think as I said last time we had, we used as a target because we could calculate it, neutron star binaries. Yeah, you did mention that. And there, there were a handful that had been seen in our own galaxy. And so with that, you can extrapolate how many, not, Systematically, of course, they were just discovered when he looked at pulsars.

So extrapolating to how many there are in our galaxy was, it had a big error on it, but within that air. And then the second question is we're not going to see it in our own galaxy. We're going to have to see it in some galaxies further out to get enough array. And how typical is our galaxy compared to other galaxies for binary pulsars? Okay. With that in mind, there's a pretty big range of sensitivities that you might need or have. And what we did is more or less target the central value. And that's where the 10 to the minus 21 comes from.

So the 10 of the minus 21 was the central kind of calculated value using the binaries that had been seen in our own galaxy. and that was not attainable with the initial version of LIGO. We knew we had to improve a whole bunch of things, but hadn't done the technologies to do that. So we said we wanted to do LIGO in two steps. LIGO 1 were detections were possible, and LIGO 2 word detections were probable. Okay, that was the words I used with the National Science Board.

And that was your strategy. Did you, let me ask. Yeah, yeah, that was my strategy. And they bought off on that, but asked us to change the names. They didn't like the idea of anything being called LIGO 2 when we were just being approved for LIGO 1. Yeah. Which made it sound like there's going to be a LIGO 3 and 4. So they asked us to change the name.

So we called it initial LIGO and Advanced LIGO. So that's where the name Advanced LIGO came from. Oh, okay. So they came up with it. Now we're doing something which you'll see around called A plus. What that is is going beyond advanced LIGO. So we're doing some things that will give us another factor or two or so. Another factor.

I was going to ask about the future. But before I get to the future, the other thing I wanted to ask was what was the biggest single challenge that you think of, either in LIGO or advanced LIGO, maybe in each, in LIGO, what was what was what? you thought the biggest challenge would be? And was it what it turned out to be? That's a very good question. But first I'll say the biggest challenge in anything like this is the human challenge. It's not the technical challenge.

I mean, this was having, holding a group with a needed expertise together for 20 years or so. Yeah. It is the biggest challenge. So the human challenge is the biggest one. I think you're referring to the technical challenges. But let me, before we get to the technical challenge, I think, I mean, you won't say this, but be fair to you, that was, there were a number of reasons that LIGO happened

because of your participation in it. But I think you would say that your experience in large scale particle physics experiments served you in good stead in terms of that human challenge, I assume, right? I mean, that, that had been, that was really important. Yeah, yeah, yeah. I think I had a lot of experience knowing what people of different expertise, different reasons there in something. I had a fair amount of experience and on a scale that's large enough where everybody doesn't know everything and so forth.

So this was, you know, a long time scale and maybe more varied in terms of, in terms of the type of expertise that people had in the collaboration, then a particle physics. Sure. I mean, this varies from general, even on the theoretical side, from astronomers to kind of fundamental physicists to general relativist. Yeah, to atomic physicists. And then on the experimental side, there's precision engineering.

and there's a lot of, we push the technology, say, for lasers, so that's a speciality. The people who know the best and most about lasers aren't really physicists that are one of us, search for gravitational ways necessarily, except the romance. And so putting that whole group together and making it sing if you want to disparate parts was, I'd say the biggest challenge.

For the most part, we succeeded. Yeah, sure. Okay, so that was the human challenge, but now let's say the experimental challenge. What did you expect? And was it what turned out to be the challenge? Yeah. First, I'm a bit of an optimist.

I thought we would see gravitational waves with initial LIGO, or what we call it enhanced LIGO, which is putting a little bit beyond that in. That's always good to be optimistic to keep yourself going. I was optimistic in a way that turns out to be true, which is that the strongest source wasn't neutron star binaries. So I didn't think that we would necessarily reach the most extreme projections you'd make of that,

but that something else would be seen first. And something else was. And you couldn't predict its rate. So I was optimistic that we would do it. When we didn't quite reach it, we did something we could. called Enhanced LIGO, which is a cheat to kind of put some of the already by that time developed advanced LIGO into initial LIGO and have one more run before we took four years to build an upgraded detector.

The main challenge, I think, was isolating from the Earth, a mundane technical challenge. and that is we the two challenges for LIGO if you want to put it in the thumbnail are to do interferometry itself much much better than people have done before you know if you go into

a freshman or sophomore laboratory you see fringes and some interferometer that they make you do and you can probably one part in 10 or one part in 20 or something split a fringe is the word that you might

remember gets used. And, you know, high-level interferometers that are used in laboratories or in equipment might be 10 times better than that. So people have done interferometry at the level of 10 to the 3 or 10 to the 4. We had to do it to split a fringe to one part in 10 to the 12 to get to the 10. So that's 100 million times improvement. Yeah. Now, basically, much of that comes with root 4.

brute force meaning a powerful laser using, we use Fabri Perrault arms, which bounce the bean back and forth and get more power even than the lasers. There's tens of bounces. And so brute force is part of it. Brute force also making the arms long. But the rest of it was innovations in interferometry. of those innovations were on the table by the time I came into this and it's the reason I could see that we could do it.

They weren't all proven in the lab and some of them couldn't be proven on smaller scales, but there was a 40 meter in a ferometer at Caltech and a 30 meter that had existed in Germany before that that did a lot of the work. Of course, 40 meters is a factor of 100 less than we build. There's a rule of thumb that you never experienced. extrapolate more than a factor you like to do experimentally a factor of two you're semi-crazy when you do a factor of a hundred and we were a factor of 10 I mean and we were doing you know a factor of 100 which did seem crazy to me that's one of the things that seemed

crazy in advance but but that's the interferometry itself the second was a what seems like a mundane technical problem but it's really tough and It's the one that in advanced LIGO enabled the discovery. And that is what we did in LIGO. Well, what we have to do is to isolate LIGO from the ground. Here we're on the earth, but we can't have the earth shake so much that you can't do interferometry at this level is impossible. So you have to basically isolate it from the earth in the frequency bands that we worry about. So we're in the frequency band.

We have nothing to do with audio, but the place where the earth is a quiet is the audio ban, 10 to 10,000 hertz basically. If you go below that, the earth shakes like crazy. If you go above that, it's almost impossible to work because you're at such high frequencies. So our ears have figured out by evolution where you can make them work to communicate with each other. other, and that's from tens of hertz to thousands of hertz or 10,000 hertz. So that's the laboratory that's available on the earth. But the earth shakes much too much to do in our ferometry at the level that we're talking

about. Yeah, no, I used to say, sorry, go on. Yeah, go ahead. When I was lecturing on this early or later, I can't remember, I used to say, I made it up, but I don't know, I used to say that if a, if a truck 20 miles away hit a, hit a hit a bump and you didn't isolate from it, it would produce a signal much bigger than the signal you were looking for. That's the problem.

So in fact, like the first problem we had in Louisiana on initial LIGO, not advanced LIGO, was that we're, LIGOs in a commercial pine forest. And so they come around with these big yellow things and chop down trees and then that part of the forest regrows in 20 years and they rotate around this big forest. And the trees falling, even though they weren't anywhere we could see them, but they're somewhere on this land, would knock the interferometer out of occupation. So your little stories essentially right.

So we had to isolate ourselves from the earth. The technologies are really mundane. what we did for initial IGO was basically do something. I don't know. I can't remember if we talked about my childhood last time. We did. I was going to say it. I told you my first job was aligning tires and wheels.

Yeah. Okay. So one thing I understood very well because I went to the library when I was 14 or 15 is shock absorbers, how they work. Okay. Shock absorbers in your car. So a shock was a ride in your car. If you didn't have them, the ride would be pretty bad.

Yeah. But instead, you go over a bump and it's pretty damn smooth. You can barely tell you've done it unless it's bumps to keep you from going fast down a road. And Santa Monica, try to keep you. So anyway, the way that's done is to basically take and absorb the high frequency shock. You can't get rid of the energy, of course. And so it gets transferred to lower energy. And that's what a shock absorber does.

It basically moves the shock, which would make us bump up and down in the car, moves it to lower energy. So all we really did is take this mundane technology that I knew as a kid and make the best shock absorbers that ever existed. Okay. That is just the right squishiness. So they were made like... Shockers over and cars don't look this way, but they're made by like springs. And hollow springs and inside the spring,

we put some goop that made it just the right squishiness. So the materials and the goop made it just the right squishiness. But we couldn't isolate ourselves well enough from the earth to get to the level where we detected gravitational waves. we and especially at this is really a problem at low frequencies

so it turns out the shaking of the earth falls off I don't know why you might know why like frequency to the fourth power that's fast yeah yeah that's fast

so that's a good problem to think about yeah so our ears cut off at you know tens of hurts and if you go just a little bit below that, it's really noisy. The earth is moving around and shaking and making noise.

So our ears have learned to keep the noise away, and they cut off there. But the problem of trying to do it in these springs is the final, even though we get rid of it, it's still we're getting rid of something that's falling like frequency to the fourth power. So by not having a good enough shock absorber I guess or spring

shock absorber it basically means that we're not as good at low frequency as we might be and at the higher frequencies we weren't down to the 10 to the minus 21 yet okay that was advanced LIGO so the reason we didn't make detections in initial LIGO was a combination of, but primarily because it cut off at low frequencies. And we weren't good enough yet to do neutron stars at higher energy. Because the detections we made, which were black hole mergers that were heavier, the neutron stars, don't go to high frequency. So the whole detection, the reason it only makes a few wiggles in our detector is,

it barely gets up to the frequencies that can be detected in our detector. And by 100 hertz, there's no signal that are gone. I mean, they merge together. So we needed to make better seismic isolation. We did as good as I could imagine doing passively. We made these great squishy things. We made four very independent layers. So what got by the first one, did cut screen by the second, third, and fourth.

you probably know that LIGO is on a pendulum. Yeah. Okay, that's part of the same reason. It's a suspended mass. And if you hold a pendulum, you don't like this, and you move the top, it doesn't do much to the bottom. Right? Yeah, I can't go like that.

Yeah, yeah, yeah. So the combination of a pendulum, which kind of eliminates sideways motions and shock absorbers, which get rid of the vertical motions, are you designed a little more complicated than that, but that basically enables us to get things down, but it wasn't down far enough. So we just had taken the mundane shock absorbers from a car

and made a little better ones. And that was, but we didn't detect gravitational waves. That's up to 2009 or 2010 or so. And so we had to add something else, and that was, again, sealing another good idea, which instead of inventing one, which is, I mean, you take air, planes all over the place and you probably own a pair of bows.

Yeah. Yeah. So you use on an airplane. So what does that do? That actually senses the ambient noise from the engines on the airplane and cancels it. And that's different in the frequency things when a stewardess comes around and asks you, do you want coffee, to hear a drink or something? You hear her, but you don't hear the engines anymore.

So it's like magic. It works very well. It's amazing. So basically we wanted to basically use the same idea. Get rid of the residual ambient motion. So what that involved is bearing inside of this big seismic, passive seismic system like your car, but fancier. a whole array of seismometers pointing in all directions.

Our problem is harder than the one in the plane because there you don't care about direction. But we have to not only see that there's some motion getting by our passive system, but what direction it's going, and then we push against it. So we basically have this array of sensors, seismic sensors. And when it senses something, we then push against it.

and that gave us another factor of 100 or so. Which is what you mean. And the final isolation from the earth is the same factor, another factor of 10 to the 12th. So to do LIGO, you just have to do a factor of 10 to the 12th twice. Once in interferometry, do interferometry at the level of one part in 10 to 12th of the wavelength of the light you're using. And isolate yourself from the ground, a pretty mundane problem, but it's a technical. one. Both those are just technical. They're not limited by physics. Yeah. And one part and 10 of the 12. So yes, two parts, two times 10 to the 12th. That's why

I would have looked at it in 2000. I would have said, good luck, guys. And, but I will say one thing that makes me feel. Both of them, I always worried more about the Higgs because the difference of being our discovery in the Higgs and the difference being what's happened afterwards is a result of the fact that in the case of the Higgs, the background is physics, and it's there. The Higgs is a 1 or 2% thing on top of that. So you can see, if you do well enough and get enough data, you can see this little thing statistically, and then it's hard to go beyond that. It's still a 2% effect on top of the huge background.

Well, in our case, the background is technical, so we can keep improving it. It's just a question of how good we are, if we can improve it. and how good you are, how much patience you are. Yeah, well, it's much easier to have the patients now. Once you made the discovery, then there's motivation. Yeah, yeah. So each step now we take, you know, six months. In fact, we'd like to be off more.

Trouble is people have this mentality that, so we have a huge amount of pressure from the community and from the NSF to run all the time. Yeah, which is good. I'd be hard for an experiment. But we're better off. if we spend, you know, three quarters of our time improving the damn thing. Because we gain so fast, if we get a factor of two sensitivity, it means we look out a factor of two further.

And then you got eight times more events. Yeah, so there's a huge payoff. And it's not like the Higgs where you keep running and running and running and running, running to get enough statistics. In our case, you want sensitivity. Yeah, not statistics. Well, that's amazing. The, you know, there are two things.

interesting about it. One is, well, one, I thought it was interesting, and you already said it, but I thought it was interesting that the big problem harkened back to what you studied in the library and you're 14, which I thought was hysterical. The other was, I'm happy about this, by the way, because I always thought the big problem would be seismic isolation. That was my gut feeling, so it makes me feel better to know my gut feeling. But you're right. Once you have a discovery, it's amazing, you know, I've realized this is a theorist, too. It's an interesting fact about discoveries in physics, you take things more seriously once you've discovered them. So, I mean, if I've been a theorist, I've written papers that I could have written before

the discovery of something, but never thought seriously enough about it. And you get just so motivated. And, you know, another example in astrophysics is the cosmic microwave background, which is another, well, a Nobel Prize in discovery. The fluctuations in it, they were so close, but no one really believed they were there. But within a short time after the Colby experiment first saw them, all these ground-based experiments, basically had sort of almost seen it or seen it, but just discounted it, suddenly could look for it. It's really amazing what a discovery does and how it changes.

It does. It really does. For an experimentalist, actually, you know, the other side of the coin is I spent 20 years since 1994, in 1999, more than 20, 22 years before we made the discovery on this project. So it's natural that people, when they interview me, asked me, you know, did you lose, did you think it was going to fail at some time or get discussed it or this or that? And the answer is that somehow, as an experimentalist, there's a lot that's, I mean, I'll misuse the word that's fun. It's just fun to solve all these problems.

I remember you telling me that when I was a graduate student, that you liked the fact that one day you could be thinking about this and another day you could be thinking about that. And if you got tired of thinking about this, there's all these problems. Yeah, and it goes back to, you know, as a kid fixing a car. I mean, there's a great satisfaction. I didn't make custom cars or anything, but it was a great satisfaction in making my old jalopy work better.

Yeah. And, and again, to be fair, as a theorist, I think it's good we're having this discussion. I often tell people, you know, who criticize, you know, take string theory, for example, okay, it hasn't, you know, said anything about the real world yet. And people say, well, you know, isn't that, doesn't that, you know, but these people believe that it will. And I say, well, sure, if you're going to spend 10 or 20 years as a theorist, you know, tackling this complex problem, you've got to have some initial, you know, optimism.

and at the same time have fun along the way. Exactly. You have to have fun along the way. I mean, you know, compared to a lot of professions or whatever, as physicists, we have more patience probably than. Yeah, well, some of us do. I'm not very patient myself. Well, I don't know if you need instant gratification,

but, you know, it's a problem my wife deals with all the time. So we don't need it quite much, but we do need it. Yeah, you do need it. And as an experimentalist, you have to get a, to be a successful one. I think you have to get an enjoyment out of solving a lot of challenging, but little problems. It's just fun to do. It's little problems and also accepting that things don't work. I mean, you know, as a theorist, you know, I've written many papers and they're wrong, but not because they were wrong, but nature just decided not to, you know, if everything you did was right, it wouldn't be, you know, it wouldn't be anyone could do it, I guess.

So it's a combination of lots of things. You know, it is interesting and personalities. I think I said this at the beginning of, maybe at the beginning of our discussion, but I tend to, there's some theorists I know who tend to work on the same problem for 20 years, and that's not a bad thing. I mean, some of them made big strides,

but they focus on it. And I tend to be, I like to sort of hit and run a little bit. I like to work on lots of different kinds of physics. and look for something and learn something new and then do something. And then I don't have the patient sort of to, once I've sort of proposed a new thing, I like to move on to something else. Anyway, it's just me. But anyway.

Well, I'm more like you than my most experimentalists stay in the same field and get better and better. And you certainly. Yeah. I mean, part of it, you focused on, you know, I'm I afraid of new technologies for the different things. I think once you're a good experimentalist, that's not a lot of. a big issue, but changing always is learning. Learning's fun. Learning and it's invigorating. It's invigorating. Well, look, okay, so last thing on LIGO, and then I want to move to the future particle physics and then it'll be almost on, is what's next for LIGO? So what's,

you told me A plus. So I think the big deal is that you gain, there's two things. If we look at the future, one is we're not limited by physics, we're limited by technology. We're limited by technology. So you can do better. And there's, I think, strong reason to do better. And that isn't collecting statistics. Right now we see one, we're now seeing one, when we turned off last for the pandemic last March, in that run we were seeing one merger a week.

When we turned back on in what was supposed to be, a 15-month break, but it's going to end up being 30 because of the pandemic. It's just the distancing problem working on close optics and stuff is taking us that. We'll be seeing one a day. Okay. That's not the right figure of merit. Yeah.

To me, okay. But what matters to us more is looking further out and looking at basically getting to some finite red shift. Because for me, I think the future, other than trying to understand where these black holes come from and blah, which is related, is to start getting in the region where you can do cosmology with gravitational waves. To me, that's the great future, other than picking maybe some single problems, but it's the great future as a feel. Sure. And can you get to where you're not doing astrophysics with gravitational waves, which is great? but can we start doing cosmology where you have, you don't have this 300,000 year barrier that you do with electronic wind.

You don't have the rate problem that exists with neutrinos. So in principle, you can see back to the very first instance of the Big Bang. And whether that's doing it directly by seeing those sarcastic signals or in the equivalent of the cosmic microwave background for gravitational waves. Anyway, the long-term, I think, future that excites me, although it's past my active time, is to get to where you can do cosmology,

start to do cosmology with gravitational waves. So we can talk about what things in detail, but that's, okay, so to do that, it's not, we have to go beyond an incremental, incremental steps on the LIGO we have now, where we get factors of two, every five years by fixing some of the technological limitations. We need a new detector.

So the future is a new detector, new detectors. The concept for it is not agreed upon it yet. I mean, it's interferometry, but we don't have something better. Some people look at atomic interferometry, but it's not realistic at this point. I'm not sure it will be. So it's interferometry, but basically beyond what we can do on the present systems. So the Europeans have done a rather extensive job of designing a next generation experiment that they call the Einstein Telescope. And yet I'm worried is too expensive, but nevertheless, it's a concept.

it's got the following features. You go deep underground. It gets rid of the seismic noise to a large extent and other things that happen on the Earth's surface. They're deeper than LHC, 300 meters down where anything from the surface doesn't propagate, basically. There's two sites that they talk about that they're looking at, one in Holland and one in Sardinia,

both 300 meters, more or less, underneath the ground. and under the ground at that depth, and they've designed kind of the fanciest interferometer system you can imagine a triangle, and it's like the one in space instead of, which gives you redundancies, and the light can go around both ways, clockwise and counterclockwise,

10 kilometers on the side. And technically the biggest improvement you can make, single improvement, which we could try to do on the, on the present LIGO, but it's too, there's too much involved, I think, to waste it on that, and that is to go cryogenic. We're presently limited by the fact that we're at room temperature, and the mirrors themselves have KT noise, brownian motion.

So if you want to cool it, cooling it means you have to cool it without shaking it at all. Yeah. That's hard, technically. But you have to also change all the materials, the same material we use. from mirrors on the surface is no good at low temperature. You have to use different materials. What temperature do you go to? What's the coating you used to make it a mirror and so forth?

So we're working on those R&D, and the simplest solution without any R&D is to go to very low temperature, which we're trying not to do in our design, but the Europeans. Well, you're probably lucky too. I mean, working, everyone I know works at very low temperature. It's a different, there's a host of new problems.

Working room temperature is a luxury, I suppose, at some level. Well, room temperature is a luxury. It's hard as Ligo. But the European design goes to low temperature at present and uses sapphire for the material for the news. We present and use silicon, fuse silicon. and they don't know what the coating is. We're looking at somewhat higher temperatures, not quite so cold,

where we can use maybe crystalline silicon. Will there be, I mean, when you say we, will there be, again, will there be two? Will there be a European and an American, or is it just too expensive? So we don't know. So right now, it's healthy right now because nobody's going to fund it today and we don't know what to build quite. Yeah.

So there's a plan in Europe to build, which is further along. The reason is there was a lot of money available through the European Union or EC, I don't know, for R&D over the past decade. And so between 205 and 2011 or so, they did this design in Europe. They've refined it since then.

We weren't allowed to do anything visible that went beyond advanced LIGO by the NSF. if we even smell that we were using somebody to do something, they'd want to take away our money in the lab. And the idea was okay. You know, you promised you're going to build this thing and make it work and detect gravitational waves or try to. And here you're spending your effort designing yet another.

So we couldn't do anything until we detect your gravitational waves. So we have a much later start than the Europeans because we weren't allowed. but we're looking at something where we can make several. The idea is to not make something so expensive and deep underground as the Europeans are talking about, but rather something that's more of a cookie cutter kind of design, something you can duplicate, so we can have several around the world to be able to point like we do now.

We're talking about 40 kilometers instead of 4 kilometers. Wow. on the earth's surface, but cryogenic, and with all the modern technologies that we're not, you know, putting into LIGO itself, or we hope not to put in. And there we can, for, for black hole,

for these black hole binaries, we can go back all the way to the edge of the universe. Wow. We think with that kind of design, not quite so far with neutron version, star mergers, but, but anyway, we can get into the cosmological region. Yeah, where you can measure redshift factors and all sorts of other things,

and distance redshift, the Hubble constant. So what kind of time frame we're talking about? What we'd like, and I think would be possible if it was technically driven, is to be contemporaneous with this space experiment. I mean, there's good reason to try to be working at the same time, and those have finite lifetimes. So the lease of the space experiment is presently scheduled for 2034. So we're talking about the mid-2030s, which means we'd have to start building at 2025 or so.

So the work now is preliminary to us really going with a proposal. Wow. Okay. I would go with a proposal in 2025 or so to probably both the NSF and DOE to do a joint with at that stage. Sure, yeah, yeah. Well, I look forward to our discussion in the 2030s about... Right. And fortunately, there's people like me and Ray and a few others that can afford to spend their time doing that now because otherwise everybody wants to exploit what we've got. Yeah, sure, sure. And you can spend the time thinking about the future, yeah, which is great.

I mean, it's a one, and it takes all kinds to do science well. Yeah, so I think it's just great. But you've always thought about the future. Now, speaking of the future, now, speaking of the future, future. During LIGO, you weren't exactly resting on, on, on, on, well, either your laurels or on the, on the, on the challenges of LIGO. You also had, I think headed, if I'm right, in you, in your, in your home territory, the particle physics, research on what, what, what, what, uh, many people thought might be, or I, and still think might be the, the, the future of, of accelerators, uh, and something called the International Linear Collider. So I think was that a beginning around 2004 or 2003 or something that we began to work on that?

Well, yeah, what happened? I mean, I backed into it. First, I have a background in accelerators, which I think I met in. Yeah, you mentioned. Very few particle physicists do. That's right. Yeah. So I'm even in the accelerator division of the APS.

And so I'm unusual and I've worked on accelerators. from the beginning. So I'm in that community as a practicing experimentals. So the problem is, you know, particle accelerators have one variable, go to higher energy. Yeah. We've had for 50 years or so a wonderful synergy between using electrons and positrons and using protons.

and protons. Adron collisions and how we have seen particle physics advance. The proton machines are easier and give you a good picture, but very difficult to do any precision measurements because they're not very selective in what they pick up. That example is the Higgs. I'll come to, but I mentioned it's only a 1% effect. Yeah. So the electron positron machines have played a big role, but they've gotten harder to do because electrons are so light that you lose by the fact that when they go around in a circle, they radiate away their energy. So it's really hard to make a next generation of quibolent of LHC with electrons. It's just a really tough problem because the electrons radiate away their energy.

energy. So in order to go to the next generation, you need to get around that problem. If you wanted to do electrons and positrons, I'll give you the motivation in a minute. And that means you have to go to not bending them because these accelerations is what makes them radiate away by synchrotron radiation and all their energy that you put into it. So you need a straight line. That means that that's where the idea of having a linear collider comes. Of course, the problem with it, one of the problems with it, but the most obvious one is then these two rifles

are shooting a bullet at each other, and they get one chance to hit each other, and then it's gone. In a particle accelerator like CERN, these beams go, two beams go counterclockwise and clockwise. And if they don't intersect the first time around, they get the second, third, and then, so forth, and you keep focusing them,

and you use the articles going around over and over again. So an electron machine has to be so good that you can do it on one pass and somehow also then get rid of the beams and stuff, which is a technical problem on one pass. And this requires doing a kind of machine that no one's ever done before, and you're doing it as the nth generation accelerator. So it's a tough challenge. I mean, LIGO is a tough challenge, but this is in the sense that we didn't use linear colliders at lower energy.

I mean, there was a fake one at Slack. Yeah, it was a fake one at Slack. It wasn't a linear collider. Yeah. So it was a hard problem. They were working on the technologies to do that in R&D, much like before I was in LIGO at three places at Slack, at K-E-K Lab in Japan. and at the DESE Laboratory in Hamburg, Germany. And during the 1990s, so during the 1990s, they did this.

If you had asked me if we were doing this interview sometime in the 1990s, probably as late as late 1990s, and you asked me what I thought about this when it was being done in these labs, I probably would have said it's a great idea, but it's too hard, a little bit like what you said about. gravitational waves. But the R&D, those labs are really good, and they have really good people.

And the R&D that was done at Slack and KK and Germany, not only more or less demonstrated in principle of feasibility by about the two year 2000, but too many, you know, too many, riches to there were two different schemes that both basically proved themselves one was to do it at room temperature and something like the slack accelerator and the other was to make a superconducting version which is quite it sounds like it's just cold versus warm but it is just quite different the whole scheme by which you make superconducting cavities to accelerate is a different concept

And so by the year 2000, it was possible before that. So this is a little bit like LIGO. It was successful R&D to prove feasibility that you could do such a machine. In about the year 2000 or 2001, I led us the high energy physics, long-range planning that I do every few years with John Bagger from. at that time from John Thomas. And he was a theorist. I was the experimentalist and we read, did this study in the future for DOE of high energy physics.

And the number one recommendation we made was build a linear collider. I was busy doing LIGO, of course. We were just commissioning LIGO. So it wasn't for me, but I had done just to say I knew the background. I knew the R&D, I knew accelerator physics. I had studied the physics potential, which I'll come to an minute. And then, interestingly, the worldwide community, which is done through an organization called ICFA International Committee for Future Accelerators, which has more or less the lab directors of the big labs.

They meet now and then they decided the next machine should be a linear collider. This is 2000 or probably should be. And they commissioned a big study to do the, to decide whether if they pursue it, it should be a superconducting accelerator or a room temperature accelerator. Why did they have to make the choice then? Because the R&D at this stage, the concept have been done, but now you had to build real prototypes that were some size. The technologies are completely different.

The cost for doing R&D for something like this is very, very expensive. So it's essential to do a decision. Do you build a machine that's room temperature? Do you do a machine that's cold? And they followed the study that Bagger and I did in the ICFA priorities. So they put together a committee in the way that experimental physicists like to do it, find the experts in the world and put them together to make this decision. You really want a technical decision to be made by technical experts, not by others.

And so they put together a committee and it included a lot of the principals who had worked on these technologies at Slack or Berkeley and DESE and some other places, but put them all together. And they ended up writing, they met kind of twice I mean two times they did the study they ended up writing a big long report 600 pages which tells you something already

yeah yeah something bad yeah yeah it's right 600 pages they were put together to make a decision and it was being 600 pages I didn't even look at it I was making LIGO work so I was pretty much not looking at it at all They convened the committee a second time because this 600-page report didn't really make a choice. So they tried to make them make a choice.

Well, they had people on both sides. They didn't make a choice. So this is when I got myself involved. I got approached by Jonathan Dorfan, who was the head of ICFA at that time, and to make a new committee. which is not the kind of committee that I think should do it. They weren't all experts, but were people who knew something and had their heads screwed on right. Yeah, yeah. To decide between the two technologies.

And I was chair of that. And they gave us a year to decide. And we had a pretty intense time where we decided in six months. And, well, I wanted to get back to LIGO on. You can do this. We were making LIGO work. And we decided in six months that the best choice, and it wasn't easy actually, was to use the more modern technology, which is to be superconducting. There's a lot of reasons why, but I would say the two most important weren't that one would perform better than the other in an initial version of linear collider, but that there was much more future in a superconducting machine.

and more other uses. So rather than just be for high energy physics, we were developing something that could be used for making pharmaceuticals and all kinds of things that need particle accelerators. So we decided on coal technology, and I went back to LIGO, and that was all fine. And then they had a,

they had a process which I don't know, but a year or two later they came back and asked me if I would organize what I would run this thing. And it just happened to be okay for me because it was the time we had proposed and gotten conceptual approval for advanced LIGO. but we had a wait in a queue to get funded for a few years and then we would start the building. So I felt I had a roughly four or five year period that I could do this. So that was basically the rationale. And then they wanted to do it all like the central design had been done for the Super Collider,

where it was done in Berkeley by Mori Tigner. And this was going to be done in Vancouver. I didn't want to move to Vancouver, although I like it very much as a place. But it wasn't that. It wasn't, or moving some, it wasn't that. It was because to do this,

I thought it was such a hard problem, in many ways harder than LIGO. I needed to do what I had done in LIGO, which is to bring absolutely the best experts and all the areas together to work on it. And you're not going to get them all to move to Vancouver, even for three years. So it had to be done from a distance,

and I had to jump around the world to do it. But for example, the expertise on positrons, which you have to do with electrons and positrons, existed in France and in Germany, and not so much in the U.S. and so forth. And so basically where was the expertise was the real problem for me. And we put together a really strong group of accelerator people, but it was fine.

And we worked from a distance and had meetings twice a year where we got together, but otherwise I traveled around like crazy. And we did the design. So the design passed all the hurdles. it was done by 2011 or so and then they made us go through the usual review after review after review after review from outsiders to make sure they validated it

and they did. And then at that point it was 2012 I said goodbye and went back, which was always my plan, went back to Ligo and they replaced me with Lynn Evans. Lynn Evans is the guy who built the LHC. Yeah, I know. And so they replaced me with somebody who was better, and that's good.

So he came in. He had been serving as chair of the technical committee that was evaluating us along the way. So I had gotten in one pretty well. And he was, as an outsider, as up to speed as you could be, and of course, had all the right background. Yeah. So he came in. And at that point, the Japanese looked like they were going to make a decision quickly.

They still haven't as of today. So it's, you know, eight years later. So you can ask me whether it should still be done or, you know, where it stands. Now, I can't judge the politics. I really can't. I've learned that trying to judge Japanese politics. politics or anything is really difficult. Is it clear that if it'll be done, it'll be done in Japan?

I think if it's done at all, it'll be done in Japan. And the cost of it will be about? They'll make a reduced version at the beginning, that it'll do the Higgs, but not go to half a TV where you can do the self-coupling, for example, of the Higgs. So it'll be a Higgs factory as the first stage and be roughly, I would say, $5 billion. And then the ultimate thing as we proposed it was more like 10, which is the cost of the LHC. Which costs the LACC.

I mean, I tend to think it was $10 billion as a quantum now for a new. And you can just say how big is it, how many pieces are there and this and that. And, you know, it's the same as, you know, it's the same as the LHC. as big and well it is when you take the length and stuff but if you just take all the number of parts and things it makes sense and if you add it up in detail comes out about that yeah yeah so to build a machine and like that it's about 10 billion dollars it's presently in the japanese system the japanese are impossible to read but they have agreed in principle to make the next step which is to form what they call a pre-lab.

So it's not a lab yet, that it's in Japan, but they are wanting more assurances of international participation. Well, that's next I was going to ask. I mean, so this is so expensive. It will be, there will require international cooperation funding, not just scientifically, but funding-wise.

Yeah, yeah, absolutely. It'll be done maybe not like CERN, which is a huge treaty-based organization with a certain amount contributed, but it'll have major contribution from the U.S. and from Europe and then some from others. Okay, and then, sorry, go on. And that isn't in the bag yet. So where it stands today is the U.S. is pretty close if the government if the present government gives the same support that this government that I didn't support very much,

but the last government did, they were supporting it. So the U.S. part was supported by the Trump administration for whatever their reasons were. There's a lot of reasons for the U.S. to have various ways to, besides military, to put people and to put resources in Japan and Japan. here and so forth. So there's there's kind of a very high level trading that's done. And this fits into that as part of the U.S. contribution. Now for the public, okay, they're going to say, okay, great. Now why? Big deal. What do you want to build another big one for? Why? I would say the, the, you don't, if you knew everything, you wouldn't build.

Yeah, of course. But I would say the, the, but I would say the, the, the, simplest way to is the following. The biggest and most important discovery made in particle physics in the last 20 years or so is the discovery of the Higgs boson. For a reason that I said earlier, it's very hard to pursue that because the Higgs boson is only a 1% effect on top of the background in the CERN machine, VLHC. So no matter how much they pursue it, it's basically dominated by background. We barely can show that the Higgs has been zero, which is what's expected, let alone anything else. Are there any partners? Does it behave?

How does it behave? It is the one particle that's different than everything else in, let's say, describing Einstein's E equals MC squared. How do we create mass out of energy? And so this is a lot of. tremendously important concept. We presently don't understand it beyond the fact that we appear to be on the right track and that Mr. Higgs and people who had that idea 50 years ago. And the particular idea that there's a particle associated with this seems to be right.

But it's really hard to pursue. And that's as much because of the tools we have as it being a hard problem. If you pursued the Higgs boson and wanted to pursue it in detail, you need a machine that can see it cleanly and can concentrate on it, whether it's seeing all that's decay modes, whether there's a partner, whether seeing important features like it's self-coupling and so forth is features of the Higgs boson.

So to me, just going up and higher energy in particle physics, you don't know that you're going to see anything. beyond, but we already have a great discovery and we're not able with the present devices to pursue it. So I think the original motive, my own feeling is the original motivation to build something, which is basically a Higgs factory, something to really study the Higgs, is a really good way to go for the future of particle physics. It's also, yeah, okay. And it also, as you pointed out, and it has been the case, not uniquely, but a number of cases.

is if you're looking for new particles, because electron, positrons are so clean, it's easier to see new particles above the background rather than protons, which are made of lots of stuff and the collisions are more complicated. And so that's certainly a factor in terms of the discovery factor of things you don't know, the known unknowns versus... Discovering things, depending on what energy in the path,

whether there's anything beyond the standard model, or even understanding our heaviest quart. So we know we can barely see and prove that it's there, the top cork, which is so heavy. But to pursue it, you need again to measure all the couplings and everything about the heaviest court that we have, the best tool would be an E plus E minus machine. And so I think it has, it's a very,

it may not be as much a discovery machine or oriented as a discovery machine is pursuing some things that we knew know and we might also have discoveries, but going to higher energy doesn't look like necessarily. The next factor of two or even decade in energy is where you're going to break through. Yeah, well, we know, I mean, it's important to mention for people. The big, you know, maybe people say big deal, new particles or whatever, but we know this standard model, which is the fundamental model that describes the university, isn't complete. We know it's not complete. We don't know where we're going to get the fundamental

understanding that drives us to maybe not to solve that problem, but at least know what the right direction is. And without experiment, we'll never know because theorists will just keep hallucinating and inventing wilder and wilder things, most of which are wrong. And I guess the other thing I would say is that, well, I've always said, is that if you have the resources and it's, you know, $10 billion for the whole world, I would argue, is doable. But every time we've been fortunate that every time we've opened a new window on nature, whether it's the cosmic background or LIGO or whatever, you're surprised. Nature continues to surprise us.

And unless we keep looking, you know, as I say, you can't just do it in a room with a piece of paper. because whatever you come up with is not going to be what nature did, generally. As a theorist, I can say that for sure. We need to keep looking. As you said earlier, and actually, you know, I recently was talking to David Gross and he agreed.

I mean, we have to emphasize that physics is an experimental science. The theorists get all the, you know, it sounds sexier, but science is experimental. And if the experiments aren't there, then the science just ends. And I think we either, and let me I remember

vividly when I was at Harvard and our good friend Shelley Glass Show was there arguing to go you know to actually to build a machine that was eventually discovered W&Z I remember but I think it was and he said I remember him saying do you want to walk or do you want to fly

and and and and Shelly. Yes Shelley and so you know we don't know there You're right. In order to figure out where the issues are the standard model, the one messenger is the Higgs,

the one least understood part, and it's the thing that's worth studying. And I think as a civilization, if we stop asking those questions, it says something about us. But to do it, you need people who are willing to take risks, do new things,

be bold, but be realistic. And that's why I have enjoyed so much our discussion, because you are the perfect example of that. in so many, in so many, so many cases. And I think for the people who've been listening to this, who aren't physicists, I hope that's one of the things they're going to get out of this, what it takes. And I'm just so thankful to you to have spent the time and that patience to have worked through it with me. I've enjoyed it tremendously.

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