Ephraim Fischbach

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ORAL HISTORIES

Department of Physics and Astronomy, Purdue University

Interviewed by
David Zierler
Location
Teleconference
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Interview of Ephraim Fischbach by David Zierler on 2020 June 30,Niels Bohr Library & Archives, American Institute of Physics,College Park, MD USA,www.aip.org/history-programs/niels-bohr-library/oral-histories/44882

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Abstract

In this interview, David Zierler, Oral Historian for AIP, interviews Ephraim Fischbach, professor of physics at Purdue University.  Fischbach recounts his childhood in Brooklyn and the role of Judaism in his upbringing. He discusses his undergraduate work at Columbia, and he describes a number of humorous adventures in the lab that convinced him to switch to physics from chemistry. Fischbach describes his graduate work under the direction of Henry Primakoff in theoretical particle physics at the University of Pennsylvania, and his first job after Penn at SUNY-Stony Brook. He discusses his work on the strength of gravitational interactions, weak interactions, algebraic computing, and he describes his time at the Niels Bohr Institute in Copenhagen. Fischbach describes the circumstances leading to his hire at Purdue and he discusses his collaboration with Sam Aronson and the fundamental work on the “Fifth Force,” and the popular interest this work engendered.  Fischbach explains the underlying mysteries of the “Fifth Force” and its ongoing influence in both cosmology and particle physics. He describes his ongoing interests in complex calculations, radioactive decay, and neutrinos, among many projects, and in the last part of the interview, Fischbach explains his goal to protect electrical grids from solar storms, which he sees as one of the greatest threats facing modern society.

Transcript

Zierler:

Okay. This is David Zierler, oral historian for the American Institute of Physics. It is June 30th, 2020. It is my great pleasure to be here with Professor Ephraim Fischbach. Ephraim, thank you so much for being with me today.

Fischbach:

My pleasure. It's really an honor.

Zierler:

All right. So to start, tell me your title and institutional affiliation.

Fischbach:

I'm a professor of physics at Purdue University in West Lafayette, Indiana.

Zierler:

Okay, and now, let's take it back to the beginning. Not the birthplace of the universe, but the birthplace of civilization, Brooklyn, New York. Tell me a little bit about first your parents. Where are your parents from?

Fischbach:

My mother was from Poland, from Warsaw, my father was from Austria, a small city called Tluste, Austria (now Ukraine). And they were obviously both immigrants.

Zierler:

When did they come to this country?

Fischbach:

They both came in the period around World War I. At various times during the war.

Zierler:

What kind of backgrounds did they come from? What was their class?

Fischbach:

I would say they were basically middle class. My mother's father was a rabbi and teacher, and my father's father was a carpenter. I'd say middle class.

Zierler:

And they were Jewish-ly observant?

Fischbach:

That's an interesting question. And I'm going to sound like Trump here, in the definition of observant. We were not-- all our kids, we was quasi-observant. We’re not shomer Shabbat, we were traditionally close to being Jewish, but not observant. And that was true of a lot of our friends. Their friends and the kids who were in my generation. Those who would culturally identify with being Jewish, but no Orthodox Jew in Borough Park, Brooklyn would call us Orthodox. Let's put it that way. (both laugh)

Zierler:

Where did your parents meet? In the United States or in Europe?

Fischbach:

No, they met in the United States. I think I know where they met, but they met through some mutual friends in the United States. In New York.

Zierler:

And what was your father's profession?

Fischbach:

He was a lawyer, but not a rich one because he was a lawyer for a lot of Holocaust survivors. And so in that time when I was growing up, he was dealing with a lot of people who couldn't afford to pay him, so we weren't rich even though he was a lawyer. My mother was a teacher, a Hebrew teacher. My father was just a regular lawyer.

Zierler:

Now when you say he represented a lot of Holocaust victims, you mean he represented them not as Holocaust victims seeking reparations, but simply people who needed a lawyer? Locally?

Fischbach:

So it was a combination of reparations and what they could do, but it was all connected with them being survivors and what benefits they could arrive at and stuff like that. He was generally their lawyer, but most of it dealt with the problems they were having as being, you know, survivors.

Zierler:

Right, right. And what year do you come on the scene? When were you born?

Fischbach:

1942.

Zierler:

1942, okay. You have siblings?

Fischbach:

Yes. I have one brother, whose name is Marnin, also a Hebrew name, Marnin, is a psychiatrist. His background is more or less the same as mine, obviously.

Zierler:

And what neighborhood did you grow up in?

Fischbach:

I grew up in the Borough Park neighborhood of Brooklyn. Which is now maybe quasi more famous because it's close to the area where Anthony Fauci grew up in Brooklyn. He grew up maybe a 15-minute bike ride away from us. So he's another good Brooklyn boy. He's very good.

Zierler:

What-- I can ask more specific than Borough Park. What intersection?

Fischbach:

The intersection-- That's part of the story. It's the intersection of 16th Avenue and 47th Street.

Zierler:

Okay, yeah.

Fischbach:

One house away from the corner of 16th and 47th where there was a Mobil gas station. And believe it or not, that is part of my background in becoming a physicist, if you can only imagine that. But that's true.

Zierler:

Of course.

Fischbach:

There was this gas station there, and when I went through their junk in their garbage cans, I would bring something home and my dad would explain to me what a carburetor was, and what a distributor cap did, I loved spark plugs. I really had a lot of fun with spark plugs.

Zierler:

So your father was a lawyer, but he knew his way around mechanically?

Fischbach:

Yes, because his father was a carpenter, and my father was very good with his hands. He was very competent. He set up a shop in the basement, and I would go and putter around and build things. I think, as I look back, that puttering around, putting this piece of junk with that piece of junk, is part of what led me to be a physicist eventually. It seems strange, but that's what it was.

Zierler:

Now, your neighborhood, was it Hasidic?

Fischbach:

Not at that time. As kids, we used to say it was half-Irish, half-Jewish, and half-Italian, which told you a lot about our understanding of fractions. But it was mixed Irish, Jewish, mostly Italian and Jewish, but not necessarily religious Jews. Now it is. So that whole neighborhood has been taken over by very Orthodox Jews, such as those who bought our house, and it's become much more Hasidic than it was then. But it was heavily Orthodox at that time.

Zierler:

Now, your family, you would do shabbos mornings in shul, or no?

Fischbach:

Yes, every shabbos. Rain or shine, snow, whatever. My father insisted on going to shul every shabbat, whatever. Over my mother's objections, but we went anyway.

Zierler:

But your father did not go daily minyan?

Fischbach:

Absolutely not. No, we went strictly on shabbat and of course on major holidays, like Passover.

Zierler:

So he was devoutly only shabbos.

Fischbach:

Absolutely, that's right.

Zierler:

And your shul was like a shtiebel or was it a bigger, like a conservative kind of shul?

Fischbach:

That's very interesting. This goes back, I mean you can get my whole background here, but this goes back to how I became a Torah reader. This congregation was Young Israel of Borough Park, I guess it was. They were smart enough to set up a junior congregation in the Shulamith school, which is part of this enterprise, where you could go and run the service and start reading Torah at any age. I started reading Torah when I was six years old, as did all the other kids, I'm not special in any way. My brother Marnin is just as good as I am, as were all the other kids, and so we started reading Torah from age of six to bar mitzvah. Every shabbat, we were reading Torah and doing all the m'gilot and everything else.

Zierler:

This is a very unique group, I've never heard this before.

Fischbach:

Unbelievable, but these guys were smart. They figured out if they did that, they would create a generation of people like me who would be proficient in doing services. In West Lafayette where I live, I'm one of only two or three people, I think, who have this training. Maybe there are two other people who can read Torah with the same ease and proficiency that I can.

Zierler:

So I just realized, Ephraim, this is baked into the grand plan. You're doing exactly what the plan was for you as a six year old.

Fischbach:

Yeah.

Zierler:

You know the history with Young Israel? Young Israel understood that there would be branches of frum shuls all over the country, way beyond Borough Park in 1948.

Fischbach:

Yeah, that's right.

Zierler:

And so that there would be one day an Ephraim that would live in Indiana, and when it came time to leyn Torah, there you are.

Fischbach:

There I am, and I'm proud to be Jewish and I read Torah and the m'gilot. Of course, I've read not only Torah and every haftorah, every megillah from beginning to end. Everything. So, I'm the Purim megillah reader and everything. And again, I'm no different from any of the hundreds of kids who went to that congregation with me. It's much to their credit that they saw that this would work, and it did. At least in our case. Yeah, it's interesting.

Zierler:

Well, what's even more interesting, and not to corner you so early in our conversation, but at the end of the day, Torah Misinai or no?

Fischbach:

No.

Zierler:

No?

Fischbach:

No, no.

Zierler:

For sure. I'm not asking as a physicist, I'm asking to more deeply understand who you are.

Fischbach:

Yeah, I know.

Zierler:

Still no?

Fischbach:

No, no. Still no. So I have a deeper understanding of a lot of things religious: it’s a combination of yeshivah, Torah, and shul. I really am a fan of reading Tanakh. I'm not religious, but I love Tanakh as a document.

Zierler:

So let me ask, because it's an interesting thing, right? So for a rabbi, it's easy for a rabbi to believe in God. That's their job, right? They're supposed to. Is it hard for a physicist to believe in God? Is that what it's about?

Fischbach:

It's hard for me to think that the Torah was divinely inspired, let's put it that way. When I drill down and think of all of what's going on. I'm going to walk off the plank. In Exodus, after the stories of the escape from, Egypt and all that stuff, very quickly the Torah turns to all the obligations and perks of being Kohanim (Priests). And a good part of the rest of Exodus, maybe all of it, from there on, the Torah spends a lot of time on the perks of the Kohanim class, they just sort of pop up.

Zierler:

On the basis that they're going to be learning and steiging all day, and so they don't have time to go out and earn a living on their own.

Fischbach:

That's true, but we see part of that is, what in order for this to be true, they have to receive all the sacrifices and all the other foods that people are bringing them. So they elevate themselves above, and what is interesting is even in Exodous the detail that goes into it, that of the clothing of the Kohanim, and the text doesn't make any pretense about it. There's one place that says, "l'chavot ulatifarit" "these clothes are to be glorious," and so on. Well, the poor guy in the street, so to speak, he was funding all this. Now, what this does is it puts pressure on people, on the religious people, to make sure the flock stays with the flock. And it's that thing which causes a lot of tension, not only in Judaism, but I think in every other religion. It's why Catholics don't get along with Protestants and why this sect doesn't get along with another one. And why this Jewish congregation doesn't get along with that Jewish congregation. That is, there's a class of people who depend on the fact that there's a flock. And in a sense, I think religions, where this is true, have gone a little bit astray. I mean it doesn't question whether God exists or anything of the sort, but it does give you some insight into why there are tensions, because this group believes it's that way, and their rabbi says that's the way it is, and the other rabbi doesn't know what he's doing and so on. I'm sure that you understand that in Borough Park, there are fights over putting a wire around a roof, around the street. One rabbi think thinks it's okay and the other rabbi doesn't.

Zierler:

Well, the last I checked, Rav Moshe said 6,000 neshamos [i.e., souls, or people] on Ocean Parkway was too many.

Fischbach:

Yeah, right. (both laugh) So you know, I like the Tanakh for what it is. It's a great document. I love all of the things associated with it, but I'm not religious. Leave it that way.

Zierler:

Now it's a separate question. Torah Misinai is one question, and the concept of creation implying a creator is another. Is that an easier one for you to handle? Or it's the same question?

Fischbach:

It's the same question. I'm perfectly happy as a physicist to think of spontaneous symmetry breaking, a concept you've no doubt heard of, that somehow things can pop up out of nowhere. I tend not to dwell on questions which can't actually be answered, so I think about it. I have the usual questions about religion and God and all that stuff, but I'm no different from anybody else. I have a lot of friends who are Catholics, Protestents, Muslims, Hindus, Buddists and so on. We all ask the same questions, and it's become more of a cultural, social event where we all share our respective religions. I'm not angry with anybody for being pro- or con-some religion. As long as people are nice. And that's the fun I get. And we do talk Bible and Torah and I do talk now with various friends who are philosophers of religion and so on.

Zierler:

The big thing is, in the Sefer Torah, you know what's to the right of that? Nothing! And it's like the Torah is telling you, don't dwell on this. You can't understand it. And that's one place where I see that the Torah and physics truly agree.

Fischbach:

That's right, it's exactly right.

Zierler:

It's the un-dwell-able blank space.

Fischbach:

Not even space, it's nothing. It's nothing. So, and again as a physicist, I tend to worry about things which could be something.

Zierler:

Okay. Did you go to cheder or yeshivah or to public school, or how did you start off as a kid?

Fischbach:

I went to three separate yeshivas, one from one to four, and it's Yeshiva Etz Chayyim which no longer exists, but which is associated with the Young Israel of Borough Park. It's where the women went to Shulamith school. Obviously, women and men were kept separate. So, there for four years, then I went to a modern school called the Bialik School, on Ocean Parkway and Church Avenue. That didn't survive forever, but I was in the first class, and that was a more modern view. Then I went to Yeshiva of Flatbush. That's a very good school, both in terms of Judaism and in terms of secular studies. It's a terrific school. I really enjoyed it, had a lot of friends I still have, and that was it. So, by the time I got out, I knew a lot of stuff, and I think the teachers respected me because I knew things that they didn't know about Tanakh. Or some things at least.

Zierler:

Oh right. You were the rebbe in those classes?

Fischbach:

Some classes... Actually, since we're chatting, I'm going to tell you a little episode.

Zierler:

Please.

Fischbach:

Just to get you into it. I know what's going to happen, I'll explain it, but this involves understanding a little bit of Hebrew. There was a teacher called Shlomo Haramati, he's very good. And he's explaining something in Jewish history. And then he wants to paraphrase, he said, "Zot omerit." "Zot omerit" is a Hebrew word for paraphrase. That is to say, in English you'd say "Zot omerit," okay? And then he stops and he says (speaking in Hebrew), "Where are the words "Zot omerit" in the Tanakh (old testament) (speaking in Hebrew)?" You with me so far?

Zierler:

Yeah.

Fischbach:

Instantly, faster than I can think now, I realized that "Zot omerit" is not Biblical Hebrew, just like Shakespearean English isn't our English. But he's put up a challenge. I'll actually say to you-- Do you know where that is? If I ask you that, do you know where "Zot omerit" is in the Tanakh?

Zierler:

No.

Fischbach:

No. So I realized that "Zot omerit", that's a colloquialism, if you want to call it that, that's not the way they talk in the Tanakh.

Zierler:

Right.

Fischbach:

If those words are in the Tanakh, it must be that they literally mean what it is they mean. And instantly I figure out what it is. Now, the class is dead silent because nobody's at my level. And I look at the teacher, he looks at me, and he knows I know stuff, and I just nod to him. And he smiles back to me, and the class is still silent. And he says-- Now, I'm not going to give it away. He says, "Fischbach," because I'm sitting in the back of the room. And I said, "Mishpat Shlomo." Now if I give you that, do you know what that, the clue is?

Zierler:

Uh... Well--

Fischbach:

You can say no.

Zierler:

Well, it's got to be in m'lacha.

Fischbach:

I'm not going to give you any more hints. All right, you can say you would have got it a minute later. That's the phrase. Now tell me where that is. Oh, Dave, you can do it. I feel really proud of you. (laughs)

Zierler:

You would, you would.

Fischbach:

Okay, I'll give you the hint and then you can understand. (speaking in Hebrew) This is the famous case where Solomon says, "Cut the baby in half." And so Solomon, when the two prostitutes come and they're arguing about whose kid it is, and he says-- And before he makes his decision, he says, "(speaking in Hebrew)" Each one of them was saying the baby is--

Zierler:

Theirs.

Fischbach:

"The baby is mine, the live baby is mine," and so on. So "Zot omerit" literally means "she is saying" and “she is saying”... So I said this to the class. All I said was (speaking in Hebrew "Zot omerit") . That should have been a hint. Nobody in the class had the vaguest idea. And then Shlomo, the teacher said, okay, tell them the whole clue. And then it was, "Ahh, okay." So that gave me a certain street cred, that teachers knew I knew something, and obviously I remember this as one of those things, but I was cool. I was actually the president of the student body at that time. I didn't want to look like just some ordinary Joe on the street. So I had to maintain coolness. And I did it in this way, and the teacher was-- It was a little joke between me and the teacher, let's put it that way. I really understand Tanakh. I read it just once in a while for whatever it is, just for having fun and so on. So I do have that background. I would just take off some time and read some, any part of the Tanakh, just to remind myself of how incredibly intelligent it is. You know, mishlei (Proverbs) and the shir hashirim (Song of Songs), the beauty of love and thoughts like that. So notwithstanding all of this the fact is that I'm not religious.

Zierler:

Well, it's an appreciation for something incredible, even if it's only humans that created it.

Fischbach:

Absolutely. And those people were incredible. I mean, when you read the Tanakh in detail to me it's just awesome that they had this intellectual talent. And so I'm proud to pass that along and tell little stories like this, so if somebody's trying to figure out what I did as a physicist, at least they'll plunge through all of this. (both laugh)

Zierler:

They'll know where it came from, at least.

Fischbach:

I'm sure, absolutely.

Zierler:

And so in terms of where it came from, so you said at Flatbush that math and science was strong.

Fischbach:

They were, yeah, very good students and very good teaching. Of course, it's a smaller school, so we didn't have multiple levels of anything. But the students were good, the teaching was very good, and when I got to Columbia, I felt I was just as prepared as anybody else. So notwithstanding the fact that half the time we were learning Hebrew, we had a very good bunch of students who could deal with all of this material. I was very happy with both the English and the Hebrew studies.

Zierler:

Now, when you went to Columbia, were you thinking physics specifically, right from the beginning?

Fischbach:

No. That is a source of several funny stories. I'm going to tell you all these stories, because they are very interesting.

Zierler:

I'm asking you, that's the story. This is what I want to know.

Fischbach:

All right. Okay, here's the story. You and I are going to have a lot of fun here. I had an uncle, William Spindel. He was a professor variously at Rutgers and Yeshiva University, and was associated with Columbia. I became very interested in chemistry. I had built a laboratory in my attic. I threw out all the junk, built a laboratory. I was doing a lot of sophisticated experiments then. I had a cousin, Bob Kron, who became a psychiatrist at Penn. He's still around. And he gave me a high-voltage transformer. So I did a lot of interesting experiments, fortunately my parents didn't know what I was doing. But I did a lot of chemistry experiments. I became extremely interested in chemistry, and at some point, my uncle Bill Spindel gave me, among other things, a copy of the Hand Book of Chemistry and Physics, which I cherished. But I became so interested that I just was reading chemistry books the way my friends, would read comic books. And by the time I was even in the ninth grade, I went to the biology teacher, Joseph Heymont, and asked “can I take the Chemistry Regents." I don't know if you know, in New York you have to take these state-wide Regents exams to get credit for a course. They're whatever it is you do in your class, to get the real credit for the course, you have to take these exams, given several times a year including at the end of the Spring and Fall. They were the tests you have to pass to get a legitimate high school degree. That's called the New York State Regents Exams. I walked into the biology teacher and said, "Look, you don't know me, but whatever. Can I just walk in and take the chemistry Regents exam for fun?" And he said, "Yeah, I'll grade it, we'll grade it and just see what happens." So I just walked in on exam day, took the Regents exams, I got some grade in the 90s. Just walking in cold. So I arranged for my father, to go to the principal and say, "Look, Ephraim already got a 90% not doing anything. It's a waste of time for him to take the actual course." So the principal said “okay”. And I just found the letter where the principal wrote to my dad saying yes. So I was exempt from actually sitting in the class. But in a small school like Flatbush, what was I going to do? Instead of taking chemistry, which was a junior level course, I took third year French. I was the only guy in a class of all women. All the guys took chemistry, all the girls took French. I took French, okay? So then I actually took the Regents exam for credit, and I got a 96%, which really annoyed me. And the only reason I lost four points was because I answered a question correctly but not the way the regents wanted you to answer it. The teacher apologized to me for taking off four points. So at that point, I already had a large, very strong background in chemistry. And I loved chemistry, I still do. But my uncle, Bill Spindel, was collaborating with a professor, Ivan Taylor, at Columbia and he got me a job as a lab assistant in Taylor's lab. I really knew a lot more than the graduate students because I had hands-on experience. So I worked with Taylor's lab for four years in chemistry. This is the source of a whole lot of stories and we're going to talk about them. Anyway, I became a lab assistant in the chemistry department. Then certain things happened. At Columbia I only took one chemistry course, I got some sort of A. I just took one. But it was doing real chemistry research. And the research in this lab was involved in isolating the isotope nitrogen 15, which is a stable isotope, for biological purposes. But the raw ingredient was nitric acid. And nitric acid is very corrosive, very dangerous, and it came to the laboratory in kegs like you see at a beer party, these stainless steel kegs, nine of them that big. I had to unload them from a truck, bring them up, and that was going to be the raw ingredient. Well, for the rest of the four years, I learned a lot of embarrassing things that can happen with nitric acid. What it does to you and so on. One of which I will tell you now. We can get the spirit. Maybe you'll edit it out of this, if you don't want the AIP to be associated with craziness. So one day, I get home and I get undressed and I see that my undershorts just disintegrated in my hands. They were boxer shorts. And I said, oh, that's nitric acid. That is one of the things that nitric acid will do. And I just threw the pants away, I didn't think about it. The next day, I'm on the Broadway/7th Avenue subway. The subway comes down from 137th Street, where the City University is, down to 125th Street, which is a big intersection, then to 116th Street at Columbia, I get on. And so the train is completely packed. And after I stood there for about five minutes, I suddenly looked down and my pants, my chinos, had totally disintegrated and the area around my private parts was missing.

Zierler:

(laughs)

Fischbach:

I kid you not. It's true. Now, this was the early 60s. Before the nonsense of the Vietnam War took place. And it was-- I mean, you could have been arrested for that. I had a Tshirt on, so I stripped to the waist, stuffed the Tshirt in where my pants used to be, and made it home. It was a three subway ride home. The IRT to 59th Street, the A train from 59th to J Street, and what was then D train to my stop, which was, Ditmas Avenue, or 18th Avenue, depending on which stop I wanted to get off. And when I got home, my mother said, "Oh my god, what's going on over here?" But at that point I started to think that maybe this kind of life isn't good for your health. And I started thinking more seriously about switching into physics. But then this story happened, which convinced me. This was a very interesting story (laughs). Chemistry can be a very interesting realm. So I'm in this lab room, 517 Havemeyer, which had been the lab at one time of Harold Urey. Harold Urey was a Nobel prize winner who discovered heavy water. But I think he did that in Chicago. Anyway, this is part of his lab and everything was still there. So sitting in the lab were me, and this postdoc named Jeevanandam and a senior postdoc named Gupta. And we were sitting around, it's a very hot, sweaty day. No air conditioning. And I asked Jeeva, I said, "Jeeva, you've been here long enough to know how baseball is played. Can you explain to me the similarities and differences between cricket and baseball?" So he goes through the motion, a very good representation of the motion of a pitcher, and then he says, in his Indian accent, "Well, in cricket we bowl the ball like this." And he shows that in cricket you bowl the ball with some overhand motion. As he does it-- I'm going to pause for a moment. I would have wished at that moment to have done the following psychology experiment, which is you, Dave, me, anybody sit and write down every single thing that's in that room. You'd write down the desk, and the calculator and the books, and your manuals, and everything else. Nobody would have written down the thing that would preoccupy us for the rest of the day. And that thing was the safety shower in the lab. Every lab has a safety shower. You just don't pay attention to it. What your office-- I'm sitting right here. My office doesn't have a safety shower. Nobody paid attention to it. But as he swung his arm around, he caught the ring of the shower, and it triggered the shower to go on. Now, as I described this to my parents, this shower would have made Noah of Biblical fame happy. It comes down in buckets because it's meant to wash away some acid or whatever stuff you've spilled on yourself. It's not your gentle Water Pick, that's just standing at home. This shower came down in buckets. And now this is like confronting the various stages of death. The first stage is denial. This can't be, it can't be water coming down. Well, a second later, you realize, it is water coming down. I mean, that's what's going on. The next stage was trying to stop it. We would later figure out what had happened. This lab worked with so much nitric acid, which produces a gas called nitrogen dioxide, NO2, which when it recombines with water, forms nitric acid again. Well, there's so much NO2 in the air that it recombined with the humidity to form nitric acid, and simply corroded out the springs in the system. The plunger that this grabs onto is like the thing in a public restroom, you push it down, it snaps back. It didn't snap back because all the springs had corroded away. So now it was a joke. See, long before you were born, there's a program called “Beat the Clock.” It was a really silly program where people did silly things like scoop out ping pong balls with a spoon in your mouth and-- just dumb things. It was run by a guy named Bud Collier. This episode ended up being one of those things. I climbed up on a chair to try to jiggle the plunger back into place, but I slid off. That's because the chairs were broken, they'd been given by the Chemical Bank to Columbia because they didn't have wheels in the right place, and they're all the slick ones, not cushiony chairs. Then Jeeva got up, and he fell off. Then finally, I got up and Jeeva held me and I wiggled it back into place. But by this time, the place was completely drenched, everything was completely soaking wet, including all our clothes. We had sat in a regular shower. So what did I do? I took off my pants-- they were just drenched, you couldn't do anything with them. I put my shorts into the oven in the laboratory, just to dry my underwear out. But then I went home with a gown, a lab gown which itself was full of holes showing my underwear through, on the same trains. When I walked up to my mother, she just could not believe the sight of this. It was just too much. This was life at Columbia if you were a lab assistant trying to pay your way through Columbia. And I needed it to pay my tuition. So after a couple of episodes like this... And the last one I'll tell you, because this is also funny. We had to watch this experiment 24/7 to make readings, so I got the lousy shifts, midnight to eight in the morning on Saturday night and so on. But on Sunday, when nobody was around, I didn't wear pants: I decided it was so hot, I was just going to wear the lab gown. Nobody was going to see me, and I just got the pants, so they wouldn't get ruined. So one day, I'm in the lab. It's maybe three, four in the afternoon, and I hear Professor Taylor came in and says, "Adam, Adam, where are you?" Well, the secretary had told me that he knew that my name Ephraim was a biblical name, but evidently he never got too far in Sunday school! So he always called me Adam, okay? I swear to you. He calls me Adam. He says, "Adam, I want you to meet my daughter Mary." I said, "Oh my God, he's going to get-- his daughter's going--" His daughter was quite attractive, enough to be a date. I didn't know what to do. I mean, she was going to come and see me in the all together like this. Taylor would have fired me. He was a very upright professor. All that stuff. So the lab fortunately was so big that I could scoot from place to place. "No I'm over here, I'm over here." Finally, I managed to get into the corner to slip my pants on, and avoid a huge, embarrassing experience.

Zierler:

Oh my gosh.

Fischbach:

A couple of these episodes worked to convince me that maybe I didn't want my career to be dealing with this. But there was one thing which was moderately serious, which actually did help me a lot. There were two chemistry buildings at Columbia, Chandler and Havemeyer, and at the bottom where they sort of joined, there was a garbage dump for the whole university. People just dumped things there, and that's where they'd pick them up from. One of the things that was dumped in the past, which I picked up and my parents didn't appreciate, were some of the cartoons that were submitted for Pulitzer Prizes, the originals, which Columbia judged. And one of them was an original Rube Goldberg. Those things which we now associate with of Rube Goldberg. Was could now be worth a lot of money; my parents moved and just threw them out. But the part that's relevant here is that somebody had thrown out issues of the journal Science, and I picked up a couple. One of them contained the Nobel prize lectures of Lee and Yang on parity conservation. I said, boy, this is a lot more interesting than chemistry. And so eventually, at the end of my freshman year, I went to the dean and said, "I want to switch from chemistry into physics." He said, "Okay, Mr. Fischbach. We're going to switch you from physics into chemistry." I said, "No, no, you have it backwards." And he looked at me. Why'd he look at me? Because Columbia had a very well-deserved reputation in the physics department about being extremely nasty. The chemistry department was nice, the physics department was extraordinarily nasty. They had several Nobel prize winners and everybody was smarter than everybody else-- I mean, they made you feel like you're half an inch high. I said, "No, I want to be a physics major." So that was it. So I switched from chemistry into physics, and the rest of it's a whole bunch of stories about being a physics major, but that would take us forever. It was a very, very tough, competitive program, but, I wouldn't say you "rubbed shoulders with" because you rarely got close enough to these guys. There were several Nobel prize winners: T.D. Lee, was there, Polykarp Kusch, who was a professor of ours, was there. That's a source of another whole bunch of stories, but we can go into that later. I. I. Rabi, the senior guy in the department, was a famous physicist. Terrible teacher, but a famous physicist. And eventually, let's see... Some of the other guys, Jim Rainwater, eventually won the Nobel prize. He was a teacher, one of our undergraduate teachers, but not at the time. So this is a very, very tough, very, very competitive, tough hard-edge department. And they made you feel that you weren't smart enough to do anything, which, was probably true, but that was it.

Zierler:

And you came in when? As a junior?

Fischbach:

I came in as, to them, as... I guess I did as a sophomore. Sometime my sophomore year, I became as a physics major-- But it didn't make a difference, we were all taking the same physics courses, but starting as a junior, you really take all these very heavy duty courses.

Zierler:

Right. So you didn't lose any ground switching in as a sophomore.

Fischbach:

No. Because we were all taking the same introductory physics courses, so I didn't lose any ground. I was exactly in phase with the rest of my class, and I graduated with them.

Zierler:

Now, among all of these giants, who among them on the faculty would give you the time of day?

Fischbach:

Time of day? Are you serious?

Zierler:

Not one?

Fischbach:

Not really, none of them would be-- I think faculty in our generation are more personable. I certainly know that people think I'm more personable. But nobody would really give you the time of day unless you were working with them as a lab assistant.

Zierler:

You're fine, you don't have to say that nowadays it's different. Right?

Fischbach:

Yeah.

Zierler:

Richard Feynman would spend time with undergraduates. I know that because I've spoken to, I don't know how many of his students.

Fischbach:

Yeah.

Zierler:

And if Richard Feynman...

Fischbach:

Yeah. Feynman, exactly. Feynman—

Zierler:

If he could find time in his day, then I don't care about whoever else you could say, you know, well he was too famous or busy or smart.

Fischbach:

That's enough. Feynman was very different, but unfortunately wasn't at Columbia. But there wasn't anybody. There literally was nobody in the physics department, whom I knew of, who was sit and schmooze with you in that way. The way I sit and schmooze, the way Feynman did. Feynman was of course an incredible individual. Incidentally, at some point in our discussion, I want to tell you a story about my interaction with Feynman, but that's down the road. In any case, nobody in the physics department would give you time of day, and they were pretty much nasty. Here's an interesting example of nastiness. Another bunch of stories. This is with Kusch. Polykarp Kusch was an extremely good teacher. I give him credit for that. If we had cell phones in those days, which we didn't, you'd just photograph the blackboard and print it, that's how good he was. He was really extraordinary. But he was mean. So among other things, he controlled when our class would meet. That was the junior class he taught in E&M. And his class met at 8:30 in the morning, which is an ungodly early hour for us. We expected to be taking classes later, because we're juniors. We usually don't have to take these early classes. No, Kusch wanted to get the class over with. He was very, very good. Very good teacher. But really not very nice. There are just so many stories about Kusch, but he hated people who fell asleep in his class, and he hated people who came in late. And he would stop the class and yell at somebody who came in late. And he literally said to some guy, this guy is Mark Mandelkern, and he yelled at the kid and said, "You, what is your name?" The guy mumbles his name. And he said, "Where did you come from?" And the guy said, "Well, the train from, the Bronx was a little late." And Kusch has this funny way of talking, he said, "Look, last night I gave a lecture at the University of California at Berkeley." He literally would speak syllables like that. "And I made it to class on time. And why can't you bastards get here from two blocks away in the dorm?" He really used bad language. That's not me making it up. So of course, the kid was here whittled away, Kusch was putting us down in a lot of ways, and he was not very pleasant and very, very intimidating. His course was the wipe-out course in physics. That's the course that decided whether you were going to go on. Because it was junior level year now, and if you failed this course, it was the end of the story. So in the final for the first semester, his final was longer than usual, and he had the freedom to do that. It was a four-hour final. And he came into class and said, "Look to your right and look to your left. One of you will not be here next semester." And he was right. The class next semester was about half of what it was. He failed half the class.

Zierler:

It's almost like that was his job. He was weeding the field.

Fischbach:

That's exactly what his job, his self-assigned job was. He was the chairman of the department. And the professor, and everything. He said he was just going to whittle down the field, and he did. But then, then somehow or other, the heavens opened up. And the next semester, the following story happened, which is sort of the anti-Kusch thing. So we're in another room. The room, in the second semester, was about half the size of the original one. He had said in the previous, "I'm going to fail half the class." And he did. So he's now lecturing at the board in the second semester, and it's quiet in the room, and he's lecturing, "The divergence of B is equal to zero." He looks around and he sees a kid sleeping, and the kid was sleeping in the row behind me. "The curl of E is -dB/dt." He looks around and the kid's still sleeping. So he walks up with this booming voice, and he walks right up to this kid like I'm going up to you, and he said, "You! What is your name." And the kid's name was Rock. And he wakes up like this, looks at this guy next to him, “Why didn't get ahold of me, to wake me up?" Then Kusch asks, "What is your name?" And the guy says, "Rock." And he says, "What grade did you get on my course last semester?" This is a winner for Kusch, because half the class failed, 90% of the kids got Cs and Ds or whatever. "What grade did you get on my course last semester?" He's waiting for it. And the kid leans back and says in a loud voice, "A!" Just like that. (both laugh) Like the phonons reeled off, Kusch was blown back. And he didn't know what to say! He turned around walked to the board and he said little. Then he said something like this: "Well, maybe you bastards ought to sleep in my course all semester long!!” And at that moment, the whole class would have clapped, if it weren't for the fact that Kusch would have failed the whole class. And that was, one of these great stories. So Rock became the local hero. And it was just one of those great stories. But it illustrates Kusch, it illustrates some of the mentality of people then in the physics department at Columbia, that's what it was.

Zierler:

Ephraim, when did you realize that you had a head for physics?

Fischbach:

That's an interesting question. You know, the way it was taught at Columbia was all nuts and bolts and so on. I had an unusual experience. For graduate school, I went to Penn. My roommate at Columbia and I both went to Penn. And that was a completely different environment. But I really loved physics at a very deep level. I'm sure a lot of people do. These are all amusing episodes. But I want you to feel, at least, that I have a sense of humor. And that anybody generations from now will hear these stories. I tell them to my students. And so I'm telling you the same ones. Yeah, let's see, I should clarify something, if it makes it a little easier. As I was graduating from Columbia, somehow I was hired by a family called Marx. Marx Toy Company was one of the most famous toy companies at that time. And Mrs. Idella Marx had a deep interest in science, and she hired me to just have general discussions with this friends and family. This is actually helpful to you, because what I can say to you is I've had a lot of experience talking to non-experts and whomever, explaining all the exciting things that are going on in simple terms. And they loved it. So we spent a lot of time together doing things. They took me on ski trips on which they taught me how to ski, and to the virgin Islands. They would give me lessons and we would let's sit at night and talk about physics and astronomy and so on. So I had a lot of interest talking to them, but on one of these episodes… this is one of those rare episodes when you can say, "I did the right thing and it worked out." The Marx family had an estate, outside New York City, and Mr. Marx would take the whole staff to the race tracks with him. And he would give out the winning tickets to his kids, to the cook, to the gardener, whoever was there. Here's the winning ticket. So the kids would come home with something like $3600 after a typical day. And that was my entire annual salary as a graduate student at Penn! So one day, I had a double date on Saturday night, and Mr. Marx invited me to go. I said, "No, no, no, I'm not going to do that." Because I had never seen this woman, it was a first date. I said, I didn't do things like that. So I'm driving on the West Side Highway in New York in this crappy car. I had a really old Oldsmobile, and the brakes gave out on the West Side Highway. I don't know how familiar you are with the West Side Highway.

Zierler:

Very familiar.

Fischbach:

You are. All right. So just around 80th Street or whatever, the brakes gave out, but I realized because I was at Columbia—

Zierler:

You should point out that by 80th Street, you're really moving.

Fischbach:

Yes. Right. So I realized that there's an exit around 96th Street, and that there's a gas station near there, and I coaxed the car into the gas station, and I left a note saying, "Please, fix the brakes and I'll pick it up tomorrow." This would have been on a Monday. And so on Monday morning, I said, "Look, instead of wasting my time, I'll just go into Columbia, wait for the car to be ready," and I looked at the preprints. And I found a preprint of something where a guy had some interesting theory, but I said I can improve on that. I can actually do something. And I wrote a paper on the quantization of space time, based on this preprint. I had another girlfriend, Lynn Penn, with whom I used to play tennis, type it up for me, and I sent it to Physical Review. And it was accepted. So as a first year graduate student, I published a solo paper in Physical Review. So in the second year, my second year at Penn, I arranged to take a course with Henry Primakoff, who would become my thesis my advisor. And in his case, the final was simply to write a term paper on something. I said, "Can I write on— I just wrote this paper." And you had to give a lecture. So he said, "Yeah, sure," and he invited another professor, Sidney Bludman, to sit in and hear this lecture. So I gave a lecture on quantization of space-time and SU(3) symmetry and all that stuff. The mere fact that I could do it impressed Primakoff, and so he took me on as a student, and I ended up being his student. Primakoff was a member of the National Academy of Sciences and the originator of the Primakoff effect, and he was a wonderful human being. He was as nice as the people at Columbia were nasty. In terms of being a human being and understanding things and so on. And so I worked with him from my third year, it was at the end of my second year that I started working with him. I worked with him for one year, and then he went on sabbatical to France, and I was on my own for another year, by myself. I had to figure everything out by myself, which is another discipline. Short story, but by the end of my second year with him, I had solved this problem, and I said, okay, now what? I'd gotten a job at Stony Brook, where the Institute for Theoretical Physics had just been established, and I said I'd like to finish, and he said, "Okay, come and meet me in St. Moritz." He was vacationing in St. Moritz. I said, okay! I'd never flown into Europe, I'd never driven a car in France, but I just said, okay, I'm going to do all these things, figure it out. Anyway, I did all this stuff, I brought my thesis along, he read it. Made corrections. He would cross out an entire page and say, "Ephraim, we could just solve it, we could just write it in this way." I said, "Oh yeah, sure. Whatever you want to do, you're the boss." If I cross out a whole page, I'm going to tell you about it and show you why it's better to do it my way. In any case, he was wonderful. He was just a saint, his wife was equally wonderful, and at the end of all this, when he finished reading my thesis, he said, "Well, how did you pay to get here?" I said, "Well, I just took all my savings and paid for the plane." And he said, "Oh no, no. That's not fair." And he gave a letter to take back to the guy who was sharing the contract with him and said, "Pay Ephraim his airline and airfare and everything else." He was just a wonderful guy. And sure enough, I came back, defended my thesis, and that was it. And then I got this postdoc at what was then the newly-started Institute for Theoretical Physics at Stony Brook, which was headed by C.N. Yang, the Nobel prize winner. Funnily enough, Yang, the individual whose paper inspired me many years before, was a Nobel prize winner who inspired me to think about physics, he was the person who ran the Institute for Theoretical Physics. Now that's another story. I may as well tell these stories too. The professor who actually had hired me was professor Ben Lee, who had been at Penn, but had been hired by Yang to be at Stony Brook. Ben said, "Fischbach is really good, hire him." And so Yang did, and that’s how I got to Stony Brook. This would have been in 1967.

Zierler:

'67.

Fischbach:

So I get to Stony Brook and I go in and I met Ben Lee, and we schmoozed a little bit. And then Ben says, "Let me take you in to meet Frank." I said, "Who's Frank?" And it took me a few seconds to realize that Frank is the way people called Yang. They didn't say Professor Yang. He went by Frank to all the physicists. He took me to see Frank. Now, this is a great story, and I wish I could find the original reference to this. I remember reading at some time the following story about a pitcher who came up to pitch against Mickey Mantle. Now the kid was (the guy who was the pitcher) maybe, 18 or something like that, but when the kid was 12, Mickey Mantle was at his peak. And he says this, he's looking at Mickey Mantle, he's about ready to pitch to him, and thinks, "I don't want to pitch to Mickey Mantle. I want to go to the plate and have him autograph the ball that I'm holding." Then he grabs himself and he says, "No, no, no. Wait a minute. You have to pitch to him." He had to realize that yes, Mickey Mantle is his hero, but now he has to deal with him as an equal, okay? And there was no way I was going to be an equal to Yang, but I had to deal with him as a professional, and I pulled myself together and we talked a little bit, and that was it. Yang is a very, very nice guy. And I really appreciated being with him and so on. He wrote a letter for me to my draft board, which basically said, "But for Ephraim Fischbach, the world of physics would collapse overnight, so defer him." I got a deferment and everything else. So it was a great experience at Stony Brook, and by that time, I knew I could do physics. I mean, I was doing real stuff.

Zierler:

And what kind of physics, Ephraim? I mean, we haven't really even talked about, first of all, theory. You're fully into theoretical physics.

Fischbach:

Yes, exactly.

Zierler:

Particle physics? Is it theoretical particle physics? That's what you land on?

Fischbach:

I would call myself a theoretical particle physicist. What we would call a high energy theorist. What I work on is the theory of elementary particle physics. So high energy is easier to say. That's it. So my thesis was on sort of the borderline of particle and nuclear physics, and hence I consider myself to be a high energy or particle theorist. Most of my work has been done there. But as you know, there's no law that says I can't work on other things.

Zierler:

Right.

Fischbach:

I've also done experiments. For example, I've done experiments testing the Pauli Exclusion Principle. I'm doing a lot of experiments now on radioactive decay, and also experiments in neutrino physics. So while I consider myself to be a high energy theorist, that's the name I put down, but I've also done things in general relativity. I've written several well-known papers in general relativity and so on. Including one calculating the next contribution to the gravitational deflection of light. The prediction that Einstein is famous for, the light bending. He calculated to the leading approximation. I calculated with a student of mine to the next approximation. It was done simultaneously by a group at Harvard, we got the same answer.

Zierler:

Which was the group at Harvard that was doing this? Was this Irwin Shapiro?

Fischbach:

Shapiro and Epstein were the guys, exactly. And by coincidence, we were both working on this problem at the same time. We did the same calculation in two completely different ways, but they both got the same answer. So they were published back to back. Bob Reasenberg knew that we were working on the same calculation, and our papers got to Physical Review within a day of each other. They were published together.

Zierler:

And this paper made Einstein more right or less right?

Fischbach:

What our papers did was to calculate what the effect would be if you went to one higher order in the strength of the gravitational interactions. Now the answer is that the experiments are not yet there in precision. At the current level of precision, you can't distinguish theories based on the next contribution from our calculation. In other words, you have to have a much more sensitive setup to be able to test it to the next order. Some other parameter enters the theory and you can't tell whether this parameter has the correct value that GR predicts, or something else, at that level of precision until you do a much better experiment than was capable then. I think right now, people are thinking of how you might do this, but you have to be able to measure light deflection much more precisely. You have to be able to know everything more precisely than you did in Einstein's time, to be able to test anything to that level of precision. But eventually people are going to do it. So I know that whatever happens, maybe 50 or 100 years from now, people will get to that precision and then our formula will be tested. I assume Einstein was right, and we will get the right answer, but at least this tested General Relativity to another level of sensitivity. Because the theory could be right in leading approximation, which is what Einstein calculated. That was sufficient at that time, because we don't have technology even now to do a more precise comparison of theory and experiment. For example, think of any mathematical function like an exponential and you want to expand it into a series of powers of some variable. You know that after a while you stop because you don't have the need to do it, or the ability to measure anything to that precision. But when they get experimentally to that level or precision, then they're certainly going to test this.

Zierler:

So in the late 1960s for you, what are the most exciting things that are happening in theoretical particle physics?

Fischbach:

Well, one of the things that is interesting—

Zierler:

I mean, are you paying attention to what happening at all the national labs and the accelerators that they're building?

Fischbach:

Sure, you just gain that as a general background, but you want to do things, you want to find your sweet spot.

Zierler:

Yeah.

Fischbach:

So what would be happening at that time, which is interesting. I'm trying to think of why it suddenly came up again. At that time, my collaborator was Jack Smith, who's unfortunately deceased now, and we shared an office together, we wanted to calculate something. At that time it became possible to do algebraic computing, what people now take for granted. But where you could evaluate very complicated expressions on a computer. This is one of the first two problems that I worked on. One, the first problem, was in that time, based on a technique called Current Algebra which was developed, and which made it possible for me to do the calculation I did in my thesis much better and much quicker. So I forgot about my thesis; I never published my thesis per se, but I did this calculation which used these current algebra techniques, which were developed by Gell-Mann to calculate something. A weak parity-violating contribution in nuclear physics. That's what I did. So my thesis was calculating parity-violating effects in nuclear physics, and how they would manifest themselves and so on. I'd done it by a cumbersome way in my thesis, which taught me a lot, but then as a practical matter, these new techniques allowed us to do it a lot faster, better, and get more precise answers, and that was my first paper. But the second paper taught me a lot of other things, and that was a very long calculation of the following process. A kaon that decays into a pi meson, an electron, a neutrino, and a photon. It's called radiative Ke3 decay. It's complicated, because there are four particles in the final state. Any case, Jack and I sat down to do this calculation, and it took us several weeks to do this very complicated Dirac algebra. After we did it, we found out from a colleague at Brookhaven, Bob Brown, with whom we were communicating for some other reason, that there's this program called Schoonschip that was developed by Veltman, who eventually won the Nobel prize. And he said, "Why don't you try it out on this?" Fortunately, the program was written in the same conventions that Jack and I were using. It did that in a fraction of a minute. What took Jack and me maybe six weeks to do, it did in a faction of a minute. I said, "Wow. This is really unbelievable." So actually the paper we wrote was sufficiently early in the field that it was cited in a computer science kind of journal, as an example of this new technology that’s been developed. You don't think of it now, you have all this stuff with Wolfram, what have you, but in those days, to be able to do these calculations by algebra? It's not just that it did it by algebra, it just did it. In a complicated expression, which would take several pages to write down, it combined all of the terms which had the same functional dependence with a net coefficient. You could have ten different places where the same combination of momenta would appear. It's sorted all out, gave you a final answer. Wow, you just go home, go to sleep, and it does all the work for you. So I learned that technology, and it was very useful. Jack and I wrote a several papers along those lines, and working with him was very wonderful. I learned a lot from him. He was my senior. And that was a springboard for me in going to the Niels Bohr Institute. Stony Brook was a wonderful place and I really learned a lot from Yang, Ben Lee, and others. There were a lot of very smart people there.

Zierler:

What was the connection between Stony Brook and Brookhaven? I mean, did Stony Brook seed its talent because of its proximity to Brookhaven? Why such a top-flight physics program at SUNY Stony Brook, of all places?

Fischbach:

Well that was smart. That's a good question. First of all, Stony Brook hired John Toll from the University of Maryland to be their president at some point. He's a physicist.

Zierler:

Right.

Fischbach:

I hope you don't get tired of all the funny stories we're going to tell, because—

Zierler:

No way. (laughs)

Fischbach:

Toll was smart, and he hired Yang to head this institute. Yang's reputation was stellar.

Zierler:

Right.

Fischbach:

The funny part is that in those days, Stony Brook was not fully completely built. The physics department was in an older building, and there were pot holes around, just everywhere. When we were talking about going from the physics building to lunch I had different paths. There was a geodesic, the shortest distance, there was a “hydrodesic”, the one that avoided most of the pot holes containing water, which were around all the time. One day one of the post docs fell into a pool and his suit got all messed up, and Toll actually gave him money for a new suit. So it was that kind of environment. But it was Yang's attraction, and that of Ben Lee, himself an extremely talented physicist. I'm not sure you know Ben Lee, who was killed in an incredible accident. Are you familiar with Ben Lee at all?

Zierler:

I'm not, no.

Fischbach:

He was a very brilliant physicist. But one summer he was driving out to Aspen and he was killed in a freak accident when a wheel left a truck, just spun off the truck, crossed the median, crashed into his car, and killed him. And it was a real tragedy. He was another really, really smart guy who was very nice to me. Bill Barden and I were witnesses, when Ben became a citizen. Any case, at Stony Brook, the connection to Brookhaven was a big attraction, because it's just, 20-minute, half hour drive, or whatever it was, and so people went back and forth between. People who were on the faculty at Stony Brook, worked at Brookhaven, and we would go back and forth as if this were one campus. So, Toll had the idea that the proximity to Brookhaven was a big asset, and it was. It brought a lot of people there because Brookhaven had both experimentalists and theorists. So it was a natural combination. But Yang didn't really press you to do anything particularly, he just hired a bunch of really smart guys, and they did whatever they did. One of my office mates, Barry McCoy, was doing statistical mechanics, and since he is a super bright guy, he could do whatever he did because Yang was interested in math and physics and everything else. My postdoc at Stony Brook provided the link to the work with Sam Aronson, and that was the starting point of the “5th force”, the work which would become the 5th force and all the searches for new forces. This work emerged from discussions that Sam and I had with Yang and so on. I think that Stony Brook was really a wonderful place, and from there I was able to get a position for a year at the Niels Bohr Institute in Copenhagen.

Zierler:

How did that come together for you, Ephraim?

Fischbach:

Well, that was another lucky break. Well, it's not lucky, it goes back to Toll. Toll hired Ben Lee and Yang, let's say, to be the particle physics faculty, and he hired G. E. (Gerry) Brown from Princeton to be the nuclear guy. Gerry Brown was a towering figure in nuclear physics who is now deceased. In the field of nuclear physics, everybody who knows him, myself included, thinks he should have won the Nobel prize. He's just done so many things. Here is another story; the building we were in, the old building we were in, wasn't air conditioned. At least the offices we were in didn't have central air conditioning. But the big professors, like Brown, did have air conditioning. Jack Smith, my collaborator knew Gerry Brown from somewhere else. So he said to Gerry, "Look, why don't you let us sit in your office and we'll answer the phone for you? We'll take two desks and we'll answer the phone for you when you're not here. In exchange for you just allowing us to sit in an air-conditioned room." So Gerry said sure. So I got to sit in this room, but then Gerry asked about my PhD work on parity-violating effects in nuclei. So we would schmooze together. He would ask me what I'm doing and he got interested in this area, and through him, I started collaborating with some real nuclear physicists, like Vagos Hadjimichael at Fairfield University. He got me the position at the Niels Bohr Institute, which was highly focused on nuclear physics. So Gerry said, why don't you go there? All he had to do was say, "Hire Fischbach," and they hired me. So that was it. Now remember, this was sort of in the middle of the Vietnam War. Money was drying up. And I realized that I really should get a job, so I got the job at Purdue and, graciously, Purdue let me defer for a year. So that was the year I was at the Niels Bohr Institute, I didn't have to worry about getting my next job, which everybody else did, because I already had a job at Purdue. And so it was a very nice year at Niels Bohr, because I explained to them weak interactions in nuclei, and that's not quite what those guys were doing. Of course, Aage Bohr and Ben Mottelson won the Nobel prize for work on nuclear structure. But I brought some new physics to their attention and they liked it and that was kind of my justification for being there.

Zierler:

What was your contribution with weak interactions at that point? What had you figured out?

Fischbach:

Well, what I had calculated was the following: if you imagine there's a force between two protons in a nucleus, and between a proton and neutron, most of that force is due to the strong interaction which keeps the nucleus together. But part of the force is that they can also exchange the weak interaction quanta, W-bosons, Z-bosons, and so on. As a result of that, the net potential energy of particles, let's say two particles in a nucleus, would have effects which would violate parity, because the weak interaction violated parity. That means they would distinguish left-handedness from right-handedness in some way. What that meant in simple terms is that any energy level of the particles in a nucleus would have a mixture of different parity states, left handed and right handed states, where, let's say, if you have a dominant right handed state, then an additional less dominant left-handed state from the weak interaction contribution. Because the states didn't have a well-defined handedness of parity, the transitions from one excited state to another state would also not have a well-defined handedness. So instead of emitting linearly polarized light, you would emit a circularly polarized light, where the left handedness or right handedness of the photon was one of the things I'd calculated. The other thing would be that if parity were conserved, you couldn't have a transition from a left handed state to a right handed state and so on. But with parity not being conserved, oxygen had an excited state where this is possible. You would emit something which had a mixture of positive and negative quanta, and that would give you a different signal from what you expected. But that would be a probe of the basic interactions, because then you'd work backwards and say, "Well, I did this experiment. This is what I saw." You could work backwards and figure out what, in retrospect, the fundamental properties of the weak interaction had to be for these kinds of processes to produce the observed effects. And that became, and still is, a big field. People are studying those kinds of effects. So I did the calculations which said, in effect, here's the fundamental theory, here's how it manifests itself in these experiments, go out and do the experiments. But you have to combine what I was doing with more detailed and sophisticated basic nuclear physics, the kinds of things that were done well at the Niels Bohr Institute. That's what those guys did.

Zierler:

Now, in terms of weak interactions and parity violations, whose work did you feel that you were building on?

Fischbach:

Good question. I think the original ideas were probably due to my advisor Henry Primakoff and Roger Blin-Stoyle in England.

Zierler:

I'm thinking more recently, like to what Shelly Glashow was doing in the early-mid 1960s.

Fischbach:

You could describe the physics in what we'll call a phenomenological way. Phenomenological means that the interaction has to have a particular general form. The actual numbers that go in there will be derived from a more fundamental theory, but the question is, let's assume it has this form, right. Assume that is a starting point. What are you going to see experimentally? For example, when an oxygen nucleus decays, what are you going to see, and how is it going to work backwards to give you a more fundamental theory? I was not interested in the varieties of new theories that would give you these kinds of facts, I was just interested in whatever theory you come up with, at some point it has to pass through this narrow tunnel, and now the tunnel says that the interaction has to look like this with some number, which you're going to give me from your favorite theory. And I'm going to tell you whether your favorite theory's right, or your girlfriend's favorite theory, or your uncle's favorite theory. I'll be able to distinguish them, but you have to get to the point where you're characterizing your interaction in general. Well, we'll call it the phenomenological way. And that's what I was focusing on. Suppose you're given a general framework, then you put in the specifics later on. So what happened is, the phenomenological theory is useful, because it gives you a scale of effect. It says, if you're going to be doing anything at all, the order of magnitude of the effects is such and such. If you can do an experiment in this range, do it. If the effects are too small, five orders of magnitude or smaller, don't worry about it. You just write a paper and forget about it. So, we're trying to bridge the fundamental theory and a phenomenological theory together, so you come up with an experimental prediction. And so I was at sort of the phenomenological level, describing what these interactions would look like in general, and then trying to connect them with fundamental theories. And lead, eventually, to experiments. I was in that sort of intermediate range. But that involved, in my case, knowing both particle physics and nuclear physics at some level, and bringing them together and so on. And this has become a popular field. I mean, people are doing these calculations and experiments much more. But there were very few papers at the time when I got started. Eventually I wrote a review with my good friend Dubravko Tadić on this work, which was published in Physics Reports, which summarized knowledge in the field as of 1973. At some point, a critical calculation was done at more or less the same time by Bruce McKellar in Australia, by Dubravko Tadić in Yugoslavia, and by me. By coincidence, Tadić was at Brookhaven when I was at Stony Brook, and so we met. We became very, very close friends. Although he’s deceased now, his wife Gordana and my wife Janie and I are still close friends. Eventually, when I was at the Niels Bohr Institute Dubravko invited me to spend a month or so at the University of Zagreb in Croatia and at the Rudjer Bosković Institute which is associated with the university. So at that time we sat down and mostly wrote a lot of the material which went into Physics Reports. We're very close friends, and that's part of where this work was generated. Here's another funny story: I'll throw these funny stories out, because I want students to laugh. So, housing was very, very tight in Zagreb. It probably still is now. It was sort of a smoky scene, whatever. They got a room for me in somebody's apartment. It was February, and it was very cold and just miserable weather and so on. And my landlady, because heating is expensive, had turned off the heating in my room. The only reason I got any heat at all was because I kept the door open to the rest of the apartment. But I was staying there alone, cold and wearing a long coat. So at one point, I went down to the local fruit market. She was living in what would be the equivalent of Times Square, actually just off Times Square of this city. It's called Trg Republica. I went down and bought myself a few apples and I brought them back to my room. I was so tense that I chomped into one of these apples, and one of those really hard things that's at the core had wedged in between my teeth. I tried to get it out, I just could not. I just could not. It was very, very uncomfortable, bordering on being really painful. So right at the corner of this house, there's an apothecary and I went in to buy some dental floss. I asked the person at the counter "Do you speak English?" And he said, "Nein." Of course, I didn't speak Serbo-Croatian. Then he came back with, "Sprechen Sie Deutsch?" I said, "Parles-tu français?" "Non. Capisci l'italiano?" It went back and forth. I didn't think that Hebrew or Danish were going to help me, so in the end, I didn’t get the dental floss. Then we did this thing: I pointed to my teeth, they gave me toothpaste and no, I didn't want toothpaste. I don't need a toothbrush. They couldn't understand the concept of dental floss. So eventually I left and I was so tired and wound up that I managed to fall asleep overnight, and whatever was in my teeth eased itself out. In the morning, Dubravko picked me up, I said, "Hey, Dubravko, how do you say dental floss in Serbo-Croatian?" He says, "There isn't any word for it." What do you mean there's no word for it? "Because we don't use that." You mean you don't have dental floss in Zagreb? This is how Tom Friedman would say “the world wasn't flat then”. When I left Zagreb, and came back to Copenhagen, I swear to you, the first thing I did was to walk into an apothecary and I bought 12 dispensers of dental floss. I put them in every suit jacket, every pants pocket, every briefcase, and for years later, when I came to Purdue, I was still using Danish dental floss! And I still do that now. I have dental floss everywhere. And look, you have to understand that you take it for granted that the whole world is like you. In a similar episode around the same time, my wife Janie and I were at a conference in Trieste, Italy. It was one of those conferences, where in the middle of the week, there's a day off, you can go to the beach or whatever. I said, "Janie, why don't you go to the store down there and make some PB&J sandwiches to eat on the beach?" So later on, I said, "Well, where are the PB&Js?" She said, "We don't have it." I said, "What do you mean?" She said, she walked into the store, and she was trying to ask the guy where was his peanut butter? And the guy doesn't understand what's she is asking for, and this goes on and on, and finally, some other guy comes in who understands English, and he explains to my wife that they don't eat peanut butter in Italy. It was around 1974. Peanut butter's not a commodity in Trieste any more than Nutella was in the United States. And I used to steal all the Nutellas at breakfast, just so I had them as a snack when I came back to the United States. We take the world to be the way that it is in the United States but it's not. In this episode with the dental floss, I've never forgotten that. It was one of the most unpleasant experiences I had. In any case, the work that Tadić and I did lays out the phenomenology, what the big picture is, and this then motivated other people to do specific calculations. If I have this theory or that theory it may be hard to do the calculations, because this involves a lot of really detailed nuclear physics, but it's a big industry. People do these calculations and there are lots of papers that we cite. So that was sort of my contribution at that time. When I got to Purdue, I started doing different things, but also still working with Tadić on these questions. To that point and more generally, I'd do what I call high energy phenomenology. That is understanding theory from the point of view of making predictions to experiments. I'm always at some level closely connected to experiment, because I find experiment to be the ultimate reality. That is, if you're dealing with an experimental quantity, whatever you're writing has to be connected to reality rather than to something in 17 dimensions, although I do occasionally write papers on very, very speculative things. So that's the sort of window that I place myself in. Pretty much most of my papers are somehow connected as close as possible to experiment at some level.

Zierler:

Ephraim, what are some of the big things in physics that you learned during your time in Copenhagen?

Fischbach:

Well, first of all, just being around those guys. I mean, there's something about the atmosphere. Of course, the Danish people are extremely gracious and so on. I don't think there's any dramatic thing I learned, other than completing some calculations with Jack Smith. I wrote some nice papers with Jack and Harold Fearing which are still referred to. Pretty much it wasn't what I learned from them, as much as it was that I could convey to Bohr and Mottelson what the interest was in doing weak interactions. I don't think that most people had thought about this. So conveying to them why it's interesting, and why they should think of applying their talents in nuclear physics to doing these more sophisticated calculations in particle physics. A lot of things they do at the Niels Bohr Institute are very phenomenological. Such as, coming up with a formula that gives you the mass of every isotope, of every nucleus, or whatever. That's probably interesting for some reason, but it's not fundamental enough to be interesting to me. You're fitting data to some formula. But I think they learned something about weak interactions from me Although it wasn't that much of a learning experience, it was just a part of maturing and getting out and doing different pieces of work with other people and so on. So, it wasn't that much of a dramatic change. Social issues are also interesting to me, and the year I was there was the year of the Kent State shooting. And when we'd have lunch with the secretaries or whomever, they really ragged on us as Americans, correctly. And so when I see what happened at Lafayette Square where we had armed militias in the United States shooting against protesters in the wake of the George Floyd killing, my skin crawled, because it takes me back to the Kent State shooting where I remember how mortified I was, but how totally mortified the Danes were. That you would have teenagers, and kids in their 20s shooting other kids in their teens and 20s. I mean, it just was craziness.

Zierler:

And by "kids" you mean National Guardsmen who were young.

Fischbach:

Yes. I mean just the thought of having, let's say, the National Guardsmen in their 20s shooting kids who are in their teens and 20s. You know, that's just craziness. But the reaction of the Danish people to that was just abhorrence. I mean, they just had no words for this. What kind of a country do you live in, and so on? Of course, they knew that we as individuals were nice people, we weren't doing that, but it gave all of us sort of a queasy feeling. Mostly I learned a lot about the Danes and about the close feeling that the Jewish people, Israelis, had toward Danish people. I'll put it this way, the Danes are among the nicest people, as a bunch of people, with whom I've ever lived. As a country, almost everything about them was the way I would like it to be in the United States. It is not that everybody's perfect, but they are really a very sensitive group. Now, to be fair, the Danes also has their shortcomings. We had several Americans there, and when we would hang out in some restaurant and meet somebody from Greenland, they would tell us things that are kind of like how they are being discriminated against the way African Americans were being discriminated against here. It wasn't a perfect situation, but it wasn't ever as bad as what was going on in the South in the United States at that time. But you could see that biases of one sort or another are not uncommon, even among very nice people. I asked myself why is it that Danes are so outgoing and gracious in dealing with people? A single mom would be supported. She wouldn't be worrying about getting a job at a local pizzeria at the corner. And that's because the Danes have a feeling that must come in part from the fact that there's a certain homogeneity. It was a privilege being there and just learning about another culture where things are quite different from the way they were in the United States. I was there, the year ‘69-‘70, and things were not that good in the United States, from a social point of view. Denmark helped me to understand how much better a society could be.

Zierler:

Were you recruited to Purdue, or you had to subject yourself to the academic job market?

Fischbach:

I was recruited in a sense, because my advisor, Henry Primakoff, worked closely with Peter Rosen, who was on the faculty here. They wrote a lot of papers together. So I knew Peter, and Peter knew of me through Primakoff, and Primakoff obviously respected me and I had several other offers. But Peter wanted me to come to Purdue. I didn't just go randomly everywhere. I went to a few places, but Peter specifically recruited me to come to Purdue and it was, at the time, a surprising decision but a great decision. Purdue is in the boonies, and that's a story in itself. At the time, it seemed like why do I want to live in the country? I'm a New York City boy. But now I'll tell you, my wife Janie and I do live in the country, and we are quite happy about that. I run in the morning in the midst of farmland and I enjoy living in an environment where I feel comfortable. Although I am proud of the fact that I grew up in Brooklyn, I recently told some friends of ours who also grew up in New York that I would not want to live in Brooklyn now. It turns out to have been a good decision to come here. In part because at Purdue the pressure is a lot less than it would be at some other universities. With Peter’s help, I earned fairly quick promotions and so now I am the senior person in the department. In short, it's turned out to be a much, much better place in the long haul than I could have imagined when I came here in 1970.

Zierler:

Yeah. This is your 50 year anniversary.

Fischbach:

Exactly, Mazel Tov. Yeah, 50th anniversary. But there wasn't a whole lot of social life here when I first arrived.

Zierler:

You were married by the time you got to Purdue?

Fischbach:

No, that's the story. I was still single, and there wasn't much social life. Now here we go: if you go back to my time at Columbia, the chemistry group that I was in was headed by Professor Taylor and the secretary was a woman named Julia Barton, who's also deceased. Julia's daughter was dating seriously a guy named Dany Bernstein, whose sister is my wife. So Julia said, you ought to call up Janie and date her. Now understand, Janie was in New York City working, and I'm here in Indiana. You could tell how desperate I was: then I had an MG sports car, and I drove from here to New York to go out with her, 765 miles. Now, when I was an undergraduate at Columbia, we had the concept of GU, Geographically Undesirable. A GU girl was somebody who took more than two trains to get her home on the subway. Janie was more than GU, she was exponentially GU! But any case, we went out on the night of January 1st of 1971 and we were married in September of 1971.

Zierler:

Where were you married? In New York or Indiana?

Fischbach:

Yeah, we were married in New York where her family and my family lived. Janie is also not religious, but she's the granddaughter of a rabbi, and the niece of two other rabbis, one of whom, Irving Miller, was the rabbi at a synagogue in Long Island. He married us. So, we were married in New York where all our friends were and so on. When we got married on a Sunday, I was already teaching so the next day we drove from New York back to Indiana, and she was crying all the way, because Janie is a real New Yorker. She sang in New York Choral Society, and she said, "Why am I doing this?" We'd just been married. In time she's come to really love the place and she would never leave here. So it was the second year that I was a faculty member that we married, and then she got various jobs over here, and now we have three kids. But dragging a New York girl to Indiana? That was tough!

Zierler:

Indiana in 1971, no less.

Fischbach:

Yeah, David, here's where New York meets Indiana. It turns out there are a couple of other people who ended up here because they got a flat tire in Indiana and they couldn't move. So there are a bunch of New Yorkers, and we're trying to get the New York Times, the Sunday Times. Well, we ordered it and it got mailed to us, and the Sunday Times came in on the following Wednesday. And I said to my New York friends, "Hey, the Sunday Times came in on Wednesday. It's like Santa Claus coming in July because he couldn't quite make it to Indiana in December, and it doesn't work." The Sunday Times is meant to be read on Sunday, as you know. As a New Yorker, I drop off my date, buy the New York Times at the train station, because every train station had a stack of New York Times. I would read it on the subway while I was going home. That's the routine. The idea that New York Times would come out on Wednesday while you're in the middle of writing your lectures and 50 thousand things are going on... Alright, so what did we do? All the New Yorkers got together, and we hired a kid to drive down to Indianapolis and he would buy 20 copies of the Sunday Times. We'd pay him for, of course, all the Times, for his gas, for his time, and everything. So each copy of the Times would cost us $15, but we needed it, we were desperate. But eventually, some local store realized an opportunity because we kept pestering them, “why don't you get the Times?” And they started ordering the Times. Now you can actually get it more or less on time. But that's life in the boonies. It was very different here from what it was in New York, but we've adjusted to it, and the good things really stood out. The schools were terrific, are terrific, and our kids enjoyed it here, and loved growing up here. They could do sports more easily, everything was easier. Our kids were jocks and good students, so I think all in all our kids enjoyed being here, and that sort of framed their views where they'd like to live and so on.

Zierler:

When did you meet Sam? When did Sam Aronson some into the picture?

Fischbach:

Sam is a year younger than me. He graduated Columbia class of '64, as I recall. He and I were in a class taught by Dany Greenberg at Barnard. Greenberg was giving a course on the history and philosophy of science. Sam was taking the course for credit, but I was just sitting in, and we happened to both be physics majors. And then we got together again when he ended up at Brookhaven, and I was on sabbatical at Stony Brook. And of course, he lived near Stony Brook. As you may know, he eventually became the chairman of the Physics Department at Brookhaven, and then the director general at Brookhaven, and ultimately the president of the American Physical Society. He's a wonderful, brilliant guy, and if you know him you love him, that's it. Sam was doing an experiment at Fermilab with Telegdi. Telegdi is the big shot.

Zierler:

Right.

Fischbach:

And this is on what's called kaon regeneration. What happens is, I know you know all these things, but I'll just repeat it for anyone who's listening.

Zierler:

It's not for me, that's right. It's not for me.

Fischbach:

So you have these particles called neutral kaons. They're called K-long (KL) and K-short (KS). In some ways, they are the most interesting particles in the world. There is a phenomenon where you create these particles and the KS — short means short lifetime— decays away. Then, you have a beam of KL particles. They have a lifetime which is roughly 600 times longer than the KS. You now have a beam of KL particles. If you then send this KL beam into a target, there is this phenomenon called kaon regeneration: In a target, the KL breaks up into K0 and 0, the kaon and its anti-particle, and they interact differently in the target. As a consequence, you produce back again the KS component which had died out. Why is this interesting? It's interesting because it's a probe of how kaons interact via the strong interaction with whatever the target material is. It's the study of strong interactions of kaons in a target. That's why it's interesting. It's a very interesting experiment for that reason. Now, so far so good?

Zierler:

So far so good.

Fischbach:

Now, the theory which describes this process is called Regge pole theory. You've probably heard of that before. I had promised myself when I converted to be a theoretical physicist that I would never have anything to do with Regge theory. It was one of those areas I wanted to have nothing to do with. You know I'm saying that because I was forced to take my words back! So Sam and collaborators are doing this experiment, and what they’re interested in studying in this experiment is the rate of producing these KS particles as a function of the beam energy, because that's a test of Regge pole theory. So Sam comes to me just because I'm on sabbatical, and he knows I'm there. He says, "Ephraim, we're going to get an anomalous result. The energy isn't working out. The regeneration process has the wrong energy-dependence as predicted by Regge pole theory." Now, I knew nothing about Regge pole theory. I had wiped out those bins in my brain. I said, all right, I'm going to sit down and learn all this stuff, which I did. In the end I found that I agreed with him, that the simplest theory you can write down doesn't explain the data. And then Sam and I agree, why don't we ask Yang about this, because Yang knows everything. When we spoke to Yang he also agreed that you cannot explain the energy dependence that they were observing in terms of known Regge theory or any other theory. So that really is baffling, and was the motivation for our subsequent collaboration. It turns out that the energy dependence that Sam and collaborators were trying to measure also depends on basic fundamental parameters of the Kaon system such as the mass difference between KL and KS. Similarly, the lifetime of these particles is also relevant. But critically, it's the KL-KS mass difference amongst other things because that determines how these waves interact with each other. And somehow or other, we said, why don't we think about the fact that those parameters are actually energy-dependent? Now that's not supposed to be. They're supposed to be fundamental parameters of nature, but maybe not. Maybe there's something else going on, perhaps some new force in nature. Our collaborators at this point were Sam’s former student Greg Bock, and my student Hai-Yang Cheng. We wrote a paper for Physical Review Letters which we had a hard time getting published, since these are supposed to be fundamental constant parameters. If you forgot about the possible energy-dependence and you just say, I'm just going to come up with the final answer for the mass difference of the KL and KS, or the lifetime of the KS, or the CP-violating parameter called η+- . All of our results would seem to be slightly wrong. But eventually Phys. Rev. Letters relented and let us publish our results. But then we started thinking whether could this be an indication of some new force? We wrote a couple of papers on this. One was a very long paper with the experimental results and the theoretical implications, bringing up this issue of new forces and so on. Here is an amusing episode: One day while I was writing this paper, I was playing squash with Peter Rosen, my mentor, who brought me to Purdue. I'm saying, “Peter, this is really crazy. I'm writing a paper where one appendix is a whole description of Regge pole theory applied to these data.” It's pure strong interaction stuff. And the next appendix was a review of General Relativity (GR), whether you can get these effects in GR. I said, “Who the hell would ever write a paper where Regge pole theory and GR would be back to back appendixes?” And we both started laughing. And I'd never known anybody to do this. I mean, I said, "Are we crazy?" No, there was a point to this. In the end the referee indicated that he would accept this paper, but we would have to break it up into two separate papers. Those two appendixes are now in back to back papers. But this eventually led to us to thinking, this is in the early 80s, about new forces as a means of explaining these effects. Because the energy-dependence comes in if you imagine there's some external force, and the magnitude of the force depends on the speed of your detector relative to whatever's producing this force. That's true in electromagnetism, and everywhere else. So we wrote these papers on this formalism and then some years later, this proved to be the real start to what became the 5th force. I had learned from some friends at Los Alamos that some researchers in Australia, Stacey and Tuck, had measured the gravitational constant down a deep mine and were getting the wrong answer. Now, the idea of their experiment was this: As you know, if you imagine the Earth is just a perfect sphere, you can treat it as if all the mass were at the center, and the force falls off as the inverse square. But they had a mine about a kilometer deep, and they were measuring gravity at the surface and down in the mine. And that comparison should be one way of measuring this fundamental constant of gravity, if everything is okay. And they were getting the wrong answer.

Zierler:

What answer were they getting? What was the wrong answer they were getting?

Fischbach:

They were getting, I forget which way it went. It was different from the accepted value in a slight way. Not in a huge way, but in a significant enough way from the accepted value. Additionally, it was outside everybody's error bars. So something was going wrong. And that got me thinking of, maybe there's a new force? And that's how I connected back to the work with Sam. Because if there was some new external force similar to what we now would call a 5th force, it would do both of those jobs. It would produce the wrong energy-dependence if this force interacted with kaons, and also it could produce a discrepancy in the determination of the Newtonian gravity constant. Because if something else is present, it's going to mess up everything that's relevant and those two pieces of physics are both relevant. So I started thinking, and that motivated the paper that set out what's now called the 5th force. We began that paper by discussing all the experiments that were relevant to determining whether or not there is some new external force that's interacting with the system. Because we have the gravity experiment going wrong, and the kaon data are also going wrong, it remained possible that they could both be explained by some new force. So let's imagine there is a new force. We started looking at all the experiments that were around. And by and by, we came to this famous experiment, by Eötvös, Pekár, and Fekete (EPF). We ruled out a whole bunch of other experiments, and that left the EPF experiment, so I said, let’s do it. We're going to complete the job and see what happens. I was on sabbatical with my student Carrick Talmadge, and that became his PhD thesis. Carrick is a wonderful guy. You see, I'm talking about all these wonderful guys I've had the privilege to work with. It was a Friday, and I said to Carrick, "Here's how you do these calculations." What we wanted to calculate was called the baryon number-to-mass ratio. That's the relevant quantity in the EPF experiment. I explained to Carrick how to do the calculations and I gave him my notes because I had worked on the EPF experiment in some other project. Then I took off with my family to go hiking in the mountains outside Seattle. But I said, "Carrick, you stick around here and try to do these calculations." So my wife, Janie, and our three kids, went off hiking in the mountains outside Seattle. And when I came back on Monday, I asked Carrick whether he had made any progress, he had calculated where three of the Eötvös data points should fall on the relevant plot based on my notes, and those three points indeed fell along a common sloping line. Since we were not going to make a big deal out of three points falling along a line, I said to Carrick, "Look, let's take the next one, which was copper sulfate." This involved calculating what the data should look like for copper sulfate. So I puttered around a little bit, and Carrick came back about an hour later, and said, "Sorry, this point falls off the line." And I said, "Well, easy come easy go, whatever." But the physicist in me said, look I've got to check his result, even though Carrick rarely made mistakes. He's one of those wonderful students, but I felt that I had to check it out. So I said to Carrick, "What's the formula for copper sulfate?" This is the interesting thing, because now I've gone all the way back to my high school days. He said, "CuSO4." I said, “that's right; that is the formula for copper sulfate, But!” Boing! In the deep, deep, deep recesses of my mind, I said “that is indeed the formula for copper sulfate, but I'll bet that the copper sulfate that you see has water of hydration.” So, as I told you, my uncle Bill Spindel had given me this little chunky thing, the CRC handbook 38th edition, so it's always with me when I'm on sabbatical. I went to my shelf, pulled it off, and it said, CuSO4• 5H2O. As would be later poetic, 5 H2O for the yet to be discovered 5th force. So I said, "Carrick, why don't you go back, and recalculate for the correct formula and hope this works out. Put that point in where it would lie if the correct formula were CuSO4• 5H2O." And I puttered around for an hour or so, and when he came back, that point was now right on the line formed by the other three points. And I remember having this incredible rush. I said, “I don't care, this has got to be a real effect!” Even though statistically, you'd never publish this, it's got to be real. So then we started, one by one, figuring out the compositions of the other Evötös samples that we could do. One by one, each one fell along the same line. And another and another. I said “you can't make this stuff up.” This is why you want to be a physicist. So we finished all the points for which we knew what the material was, and then we were down to a couple whose compositions were unclear. One of the samples was something called schlangenholz (snakewood). Fortunately, we were at the University of Washington, which has a big forestry department, which helped us to figure out what snakewood was. Then we found in Seattle a violin maker who made violin bows out of snakewood. I bought some pieces of snakewood from him, which is one of the densest woods that is known. Then, Carrick and I took some pieces and sent them out to determine what their chemical composition was. It's a very, very different kind of wood. But it turned out, when the data came back, that for snakewood, the relevant baryon number-to-mass ratio was essentially no different from that of cellulose, which is what we were assuming, which is the basic component of wood anyway. And then we plotted it, and again, that point was right on the line too. But in the meantime, Carrick, who has a sense of humor, he's a fantastic guy, had compiled the baryon number-to-mass ratio of all the known woods. You know, pine, oak, spruce, whatever. And when we came to write this up as a paper, he said, "I want to publish this." I said, "Carrick, no referee's going to let you write in a high-energy journal the baryon number-to-mass ratios of the various woods of the world." He said, "Come on, Ephraim, do it." I said all right, go ahead, he'll throw it out. Well, the referee accepted it. And so now in Annals of Physics, there's the baryon number-to-mass ratio, I joke, of every wood that's known. Whether it is snakewood, pine, oak, spruce, whatever it is, all those woods, it turns out, fit along the same line. Whatever the difference is in their physical characteristics, they all have pretty much the same baryon number-to-mass ratio. At this point we had shown that the data published in the table of the original EPF experiment, which is what we were reading, fell along this line. I don't read German, but I can read the table and figure out what these samples were. And so I started to write up the paper. One day, I was thumbing through the paper, and I saw that there are results that the authors quote in the body of the paper, which are not in the table at the end of the paper. So I asked myself what is going on over here? Those results had smaller error bars. At that time, we were blessed by having several German postdocs there in the nuclear theory group where I was at the University of Washington, and I asked one of them what those results were. And the bottom line was that the table was some summary of their results, but the results in the body of the paper were the original raw results. And they had much smaller error bars. So I said, oh, here we go again. When you put in the smaller error bars, these points are probably not going to fall along the same sloping line. It's not going to be as dramatic. But that's what we have to do. So we started recomputing everything using the raw Eötvös data, and then miracles happened again. The points ends up fitting on the line more closely, better, into a much more dramatic effect. And the end result was that the deviation from a null result was much dramatic. These points had to fall along the line and that line had to have a non-zero slope. It couldn't be flat, it had to be along a diagonal. And that's exactly what it was. It was in the end, an eight standard deviation effect. The chance that this was a statistical accident was basically zero. And we were just totally stunned by that. So we wrote up those results, and that became by accident the first paper in the first issue of Physical Review Letter in 1986. We published this result with the graph of all those points that we could evaluate. For some of them like Talg which is fat, we didn't know quite what it was, and we left that off along with snakewood since at that point we weren't quite sure of snakewood either. And that was the paper. And there we do talk about the results of the anomalous energy-dependence in the Fermilab data and the Australian experiment, and so on. But our paper stands by itself. And we checked and rechecked it and so on. So we sent the paper off to Phys. Rev. Letters. And two things happened: The interesting thing was that we guessed correctly that it was going to Robert Dicke at Princeton, a super titanic figure. And he did something unusual, which I've done on occasion too: He wrote to us directly, acknowledging that he was the referee. He wanted us to check that our results could not have arisen from ordinary temperature effects. Why? Because in the presence of temperature gradients, you can produce just a little wind, and that wind could move their apparatus and so on. And he said, if that's the case, the data should look like such and such. And we said okay. I said, Carrick, “he wants us to do this. Let's do it quickly.” So we did the calculation for the Dicke mechanism, and we showed that it does not reproduce the data. In other words, you cannot explain the Eötvös data that way. So we wrote back to Dicke, and he said okay. And he and another referee accepted our paper, and then it was published. So we, to the extent possible, had done everything we could do. Everything had checked out. What had happened in the meantime, however, was also interesting from a psychological point of view. Going back to the story about copper sulfate crystals, I was sure that what we did was correct, but I wanted to make absolutely sure that there was no way that we were just dealing with plain copper sulfate without the water.

Zierler:

What was your concern? Did you have a hunch that this was the case?

Fischbach:

No, I was absolutely convinced, but I wanted to make sure that there was no way they could be dealing with the anhydrous form, without the 5 H2O. I asked the guys in the chemistry department to give me a bunch of copper sulfate crystals, blue crystals. I heated them up in a beaker in some other lab, drove out all the water to make the anhydrous form, so it was now white powder. And we weighed it. Even as we went from the lab in which I heated it to a balance room, the copper sulfate started to turn blue. I mean it was very humid in Seattle in those days. And it was the Fall. And I could see that the copper sulfate was absorbing water, even initially. So Carrick and I kept making measurements over several weeks. And eventually, after a long period of time, the mass of the stuff coincided with CuSO4•(4.96H2O). And I said, that's close enough to 5 H20 for me to convince myself that that's what their sample was. To start with, there's no reason why they should have cared whether it's in the anhydrous form or the hydrated form. So then I said, “Okay, I'm convinced that's the right formula and that's it.” So that was the only concern I had. And then of course, when we analyzed snakewood and realized that all woods have approximately the same baryon number-to-mass ratio, that was it. And the only other substance whose composition we didn't know, really, was T-A-L-G, which oddly enough got back to Dicke. He had thought to translate that as talc, T-A-L-C, which you rub on your baby's bottom, but that is not right. That's the one mistake he made. T-A-L-G is fat. It was suet. And so we looked at some book and figured out what Talg was and it has large error bars on it, but we don't care. So that was it. And meanwhile, people have rechecked our numbers over and over again, and everybody agrees that what we did is right. And also that it's statistically an eight sigma effect, implying that there's no way you could have messed around with the Eötvös data and obtained our result. That's why the field took off very quickly. It's also the puzzle now for the current generation, why we aren't seeing this 5th force effect. Everybody assumed we would see it. Many researchers went out and did these experiments, awesome experiments literally on land and sea and the air, if not the hedgerows, people were looking for this. And now we come to—the Feynman story.

Zierler:

Great.

Fischbach:

Our paper came out in Phys. Rev. Letters on a Monday January 6th, 1986. We had in the previous days been vacationing in California. I have to give you the whole picture, because it's funny. All of these things are funny by hindsight. In the week between Christmas and New Year, Seattle had a sort of atmospheric inversion so that it was smoky in the city, it was really nasty. We lived in Bellevue, which is in the hills above Seattle, and you could see a cloud of crud. In any case, we went on vacation, and I got sick from breathing all of this stuff, so when I came back, it was the day before the paper was published. We landed in Seattle and I was coughing and retching. The next morning is when I got the call from John Noble Wilford at the New York Times. Why is he calling me? He was writing a story on our paper. I was totally blown away. So I spoke to him in a loud coughing voice. For those people who believe that the New York Times runs the world, I can say you're right, they do. His front page story came out Wednesday January 8, 1986, two days later, and people later told me thereafter that almost every publication in the civilized world carried that story. In the middle of this week, I got a call from Bruce Winstein, who was then at Stanford, and this is on Wednesday, the worst day of all of this, when I got calls literally from four in the morning until like ten o'clock at night. The phone didn't stop ringing. Well, at one point when I was at home, my wife picked up the phone and she says to me, "The National Enquirer wants to talk to you." So I'm saying, “how am I going to explain the 5th force in terms of sex and violence?” That's literally what I said to her. And it was Bruce Winstein because I'm supposed to visit Stanford the following Monday. He wanted to make some arrangements. So I said, "Bruce, I'm tired. Please." He even said, "Oh, yeah, yeah, okay." He was funny when he got on the phone. Okay, the next day, Thursday, Carrick, my student, and I were going to the University of British Columbia. So we drove from Seattle to UBC. It was another long, long day. Of course, the CBC wanted to have an interview with me, which they did. But they said, "You can't cough." I said, "Why?" Because it's going to blow up all our microphones. I said, "Look, I can't breathe." Anyway, we drive back. It's about a three hour drive. Somehow or other, when we entered the United States, we got a top-to-bottom check-out from the customs people. I had a brand-new car, I don't know, maybe they thought I must be selling/doing drugs. We got home very late, about 10 o'clock at night, and I called Janie on Carrick's phone. We didn't have cell phones. And nobody answered, so I called the neighbor. I said, "Where's Janie and the kids?" She said Michael, our youngest, had come down with some whatever it was, but he had to be hospitalized. Some bad flu or whatever. And he's in the hospital near you. So I drove to the hospital, and I found Janie and Michael and some nurse was having trouble sticking a needle in him because he's only six years old. Anyway, that gets resolved. I got home and went to sleep. The next day was a Friday, and finally on Friday things had calmed down, and we were calm. We were all together, family's together, we're all safe. And I'm giving Michael, our youngest kid, a bath, because he'd been in the hospital. And our middle son, Jeremy, comes in and says, "Daddy, there's a Mr. Feynman on the phone for you." The probability that Feynman would call me at home on a Friday night was slightly less than the probability that Abraham Lincoln would call me in his present state, okay? Obviously it was Bruce Winstein. So I pick up the phone and said, "Bruce, it's been a very hard week. Please I'll see you on Monday." Than I heard, "This is Richard Feynman. I'm a physicist at Caltech." I knew it was a fake then, because Feynman wouldn’t have to tell me who he was. But this goes on for a few minutes. "I want to talk to you about your paper." After a couple of these exchanges, I realized that this really was Feynman because I'd seen enough films of him. So basically we talked about the paper. He congratulated us on writing the paper. He probably would have given me, let's say, a B or a B+ for the idea, and a C+ for the way I wrote it, because he was objecting to the way I characterized certain things. I said, okay, if I get an average of a B and a C from Feynman, I'm all right. But I must have irritated him a little bit, because he wrote an op-ed piece in the LA Times basically saying that I'm wrong. Now, fortunately for me, Feynman was wrong. And everybody who was working in the field realized that Feynman was shooting from the hip, and he didn't really think through the problem. This had to do with the fact that if a force had a short range, and came from the nearby environment, its effect would depend a lot on the room structure, on where there were rooms, where their labs where, where there was dirt, and stuff; more generally, on the actual matter distribution in the environment. We all realized this at that time, for which reason I had written to the people in Hungary asking for a drawing of the place where Eötvös did this experiment. As it turned out, our conversation took place about two weeks before the Challenger tragedy, which preoccupied Feynman for several months. We didn't communicate at all during this time. But after his involvement with Challenger was over, he wrote to me personally. He hand-typed a letter, which I still have. He said, "I'm typing this. So it's not my secretary, who's a lousy typist." He wrote a lot of things, and made some interesting observations, but in the end he could not point to anything in our paper that was actually wrong, or in the EPF experiment itself. That's more relevant. And that's been the story since then. That is, many people have drilled down now to the original EPF experiment, and nobody has found anything wrong. By now, many, many people have tried to find things that Eötvös could have done that would have given rise to these data, but the fact is, baryon number-to-mass ratio is a funny physical quantity. It's the first time, maybe one of the few times that anybody's really written anything about this, and it's a quantity which, because baryon number is the measure of the strength of this new interaction in the theory we wrote down, it's not a classical quantity, it's something that has nothing to do with ordinary magnetism. So the subject turned to trying to find, whether they could have done something which simulated an effect which depended on baryon number. And the answer is no. Nobody's found that. And that's one of the enigmas, one of the puzzles that keeps us working on this project. I'll just shoot ahead for a minute. So last year was the 100th anniversary of the death of Eötvös. In 2019, there was a big to-do in Budapest, and I gave a talk on the importance of the experiment. I mean, I was kind of a mini-hero in Budapest, because Eötvös is a god there. The Harvard of Hungary is named after him, it's Eötvös University, and so raising his profile made me sort of a mini-hero. And I gave a lecture on the EPF experiment a sort of a review of what we did, but also pointing out things we learned afterwards. There are other things we learned afterwards from other subtle details in the data that make it even less likely that it's an accident. So it's even more compelling an argument than we were originally able to make. And this is written up in the proceedings. Associated with this, by complete accident, there had been a discovery of the handwritten manuscript- autograph, they'd call it, of the paper that was published after the death of Eötvös. So let's go back in history. Eötvös died in 1919 just a few weeks before the Eddington light-bending experiment that made Einstein famous. This is one of the most fascinating stories which I'm going to be writing on. Einstein and Eötvös knew each other, and Eötvös is the more senior guy, and they interacted in various ways. We have documentation of Einstein thanking Eötvös for doing the earlier versions of his experiment, which established what we now call the Equivalence Principle, the statement that all objects fall in a gravitational field in the same way. Eötvös had done some of these experiments before the war, and so Einstein is thanking him. In 1915, Einstein published the General Theory of Relativity, and everything seems okay. But it turns out that what we've pointed out is a little dirty secret. Which is that if you drill down to the Eötvös data, and look at the actual data individually as we did, you find that some of their individual data points do not actually support the weak Equivalence Principle, the claim that all objects fall the same way in a gravitational field irrespective of their composition.

Zierler:

"We" is who, Ephraim? Who's "we" here?

Fischbach:

Oh, sorry. Carrick Talmadge and the various people in our group were working on that. This includes my other graduate students Daniel Sudarsky, and Aaron Szafer, who stayed behind at Purdue, and of course Sam Aronson. If you look at certain individual results, like the comparison of the accelerations of copper and water, those as individual data, differ from the expected null result by about five standard deviations. And this ties into the question of, what was Eötvös thinking about this result. Why is it that Eötvös finished his experiment in 1908, and he died about 10 years later, and never published the results of his experiment. They were published later on by his collaborators, Pekár and Fekete. And you should ask, why didn't he publish the paper? It was significantly better than any previous experiment. In fact, it was by his own recognition 300 times better than the previous experiment which was done by Bessel. Now let's come back to this to understand the story. Around 2014, somebody clearing out an office dropped a box of whatever, and out spilled the handwritten autograph that Eötvös had written, upon which the subsequent published paper was based. But that handwritten autograph tells you what he was thinking and presents all these results. So in this autograph, he notes that his sensitivity is 300 times better than Bessel, so why didn't he publish? And this goes on and on, and you have to think that he's recalculating and redoing things, recalculating his results. This goes on for approximately ten years. And he never withdraws his paper, and yet he never publishes it. So you have to think, what is going on in Eötvös’ mind? So now, in the midst of all this, Einstein comes out with General Relativity in 1915, and Eötvös was still alive. So Eötvös must be thinking, what is going on over here? I'm not showing that the Equivalence Principle works. But he still doesn't withdraw his paper. And he doesn't publish it. And it was only in 1922, after Eötvös died, that Pekár and Fekete publish the results. So now the question becomes really interesting: It's a psychodrama. Eötvös doesn't publish their results. He must be talking to Pekár and Fekete about that. But when they do publish it, Pekár and Fekete combine all the data, the raw data, into an effective comparison of each sample against platinum. Well, why would they do that? When you combine data from different measurements, say, water against copper and water against platinum, you get copper compared to platinum and you eliminate the sample in the middle. In this way they construct an effective comparison of each sample against platinum. Even though that was not what the raw data were. But in that process, their errors (uncertainties) expand. In the original paper we wrote, we point this out in a footnote and observe that the effect of combining the data the way Pekár and Fekete did is to increase the uncertainty and make the effect look less dramatic. But the raw results, the way we plotted them, those are the actual results that they had obtained. And so you can't hide the fact that those guys, Eötvös, Pekár and Fekete were actually seeing a lot of discrepancies between what they expected and what they observed. But that was never published in time for Einstein to question the Equivalence Principle, which we now believe is correct, and that's one of these real enigmas which we're now working our way through.

Zierler:

Still? It's still an enigma?

Fischbach:

Absolutely. It is a mystery wrapped in an enigma buried in a puzzle. This is the enigma now: If you look superficially at their data they did not agree with the Equivalence Principle. They didn't know about baryon number, because that depends on the neutron's contribution, and the neutron wasn't discovered until 1932. What is clear is that their data did not clearly support the Equivalence Principle. So I keep asking myself what were they thinking, what was Eötvös thinking? Why didn't Eötvös do a better experiment? In the meantime, Einstein publishes General Relativity and then four years or so later, the Eddington light bending experiment happens, and Einstein becomes the great titanic figure that he is. That's when Einstein became the Einstein who was known all over the world. And these guys may have been saying we are not going to rain on his parade. So they just published a paper with these massaged data, claiming no effect. They almost literally say, "There’s nothing here. Don't worry about it." That's kind of a Brooklyn-ese translation of the way the paper ends. But now along comes these folks like us who say, "Hey, wait a minute now. That's not what the original data show. And let's take another look at this." And then we plot their data, and construct the simplest possible theory to account for what they saw. This hypercharge theory. As I have said in the many lectures I've given on the EPF experiments, if you erase the labels on the axes, and call it a plot of current versus voltage as a test of Ohm's law, everybody would give you an A on the test. Because the plot would be in perfect agreement with Ohm's law. So now what happens is a lot of people go out and do similar experiments. This has obviously been the most significant contribution I've made to physics. Because what happened thereafter is the appearance of all the subsequent experimental and theoretical papers.

This takes us to where we are now in this story. I recognized that we wrote down the simplest possible theory involving this new force hypercharge, and this brings up the story I told you about my meeting with T.D. Lee. About a week after our paper was published, T. D. Lee was visiting the University of Washington, where we were, to give some public lectures. His visit had been arranged way in advance and had absolutely nothing whatsoever to do with the publication of our paper, which utilized his theory with C. N. Yang on baryonic forces. Towards the end of our meeting, I asked Lee “why didn’t you and Yang plot the data the way we did?” And he replied, that at that time, which was approximately 1955, he and Yang were working on the question of whether the weak interaction violates parity, and this one-page paper was just a short interlude in the midst of that work. But this leads to a very interesting question: What if Lee and Yang had in fact taken out another day or two to calculate the quantities needed to plot the EPF data as we did? Then they would have seen the same unexpected correlation in the EPF data that we did. Having then been confronted with actual experimental data pointing to a striking new effect, would they have then abandoned their work on parity-violation, which very few people at that time thought was very likely. The history of weak interactions in general, and neutrino physics in particular, would likely have been quite different from what we now take for granted as excepted fact.

But we plotted the data, and when you look at a plot of the data even critics would say that the result overwhelming. And then you ask what EPF could have done wrong, and it's impossible to think of a theory which could have produced some alternative picture where they could have gotten the same data and the same correlation and so on. This is because baryon number is a non-classical quantity, so it's obviously not going to affect the data in the same way Dicke thought temperature and pressure, etc. would. It's just not natural. I mean, it could be, but to get ten points to line up in that way, I don’t think so. It is, of course, possible that the EPF data represent the most amazing coincidence I have ever seen. Otherwise, it’s very hard to think of why hypercharge doesn't explain the data. Nonetheless, people have done experiments on land and sea and the air and they haven't seen evidence for a new force. So if you could ask me, what are we doing? I'm trying to say to myself, that we were lucky in picking the simplest theory which I worked out, and got it to work. But that theory may be only one of a class of theories, which could have also worked. And that's what I'm doing now, trying to construct other theories which have the same relevant characteristics but which may be different in other ways. Now that's not trivial. Because I can start by describing baryon number or hypercharge, which would be the same in this situation. Baryon number is a number of baryons, the sum of neutrons and protons in a sample. Hypercharge is the sum of baryon number and strangeness, so that adding in strangeness allows us to have a theory also capable of explaining the previously discussed kaon data, since kaons are strange particles. So by calling it hypercharge, I can tie in these things together that we talked about at the beginning. Why the kaon regeneration data look the way they do, which is unexpected. So that becomes a bigger context. But whether the property is hypercharge or baryon number, it's called the baryon number-to-mass ratio. I can think of a lot of theories which have a property where the forces also depend on some other characteristic. The characteristic that's most important is the range of the force. We talk about the influence of all these forces falling off exponentially, and the distance scale over which they fall off, is characterized by the range. That's a number we can tune in constructing theories. So if the influence of a force falls off with separation R, you could say it's R compared to λ, where λ is the range of this force. And that's a dimensionless number and that's the thing that's relevant. So literally, people have looked for this on land and sea and the air and everywhere. People have done experiments on astronomical scales, atomic scales or whatever. Nobody's found evidence for this in any experiments that have already been done. Researchers continue to do these experiments because it's mind-boggling how Eötvös could have done his experiment, not knowing about any of this stuff, and find a coincidence, a correlation, with a variable that wouldn't even be constructed until decades later. And so that's a mystery. And associated with each mystery is another layer of mysteries, and notebooks of mine are filled with conjectures about what the answer could be.

Zierler:

What's your best guess?

Fischbach:

My best guess, I used to be a big fan of Sherlock Holmes, and my best guess derives in part from the case of, The Dog that Didn't Bark. My best guess is that the answer is something that's so obvious, banal, and fundamental, that we're not paying attention to it. Or maybe another possibility is that the 5th force is catalyzed by something else.

That's what one of my current theories is. You need the 5th force, but something else is driving it. Something else that allows the 5th force to show its strength and so on. And I'm working on various theories that would allow that. But of course, any theory would be the guided or constrained by all the experiments, of which there are many. A successful theory has to fit in somewhere, where I could see. For example, if the experiment done by some Professor X didn't quite rule out a particular theory, there could be some narrow range of parameters where I could actually explain what's going on. And that's my hope at the moment. So, I'm working on some funny theories trying find a narrow opening where if the parameters were this and this, it would explain the EPF experiments, but not subsequent experiments which gave null results. I'm convinced, perhaps wrongly, that since the data kept getting better and better when I kept thinking of the data as being more and more constrained, that we must be seeing a real effect. I can't believe it's an accident. There's just no way I can believe this is an accident, but I'm willing to believe that the correct theory may be very different from what I have been thinking, and also very different from what anybody else is thinking. If I understood what the right theory was, phenomenologically, the first step would be to say, let's write down a formula which could explain whatever I want to explain without being in conflict with all the experiments that have been done already. That’s a very, very tough task. I should add that there is one experiment that actually saw some effect. That's an experiment by Peter Thieberger who was at Brookhaven, but who did this experiment in New Jersey, at the Palisades Cliffs. And he saw an effect. Oddly enough, his was the very first experiment to be carried out, and I thought, "Wow, this is great! Boy, what can be better than that?" But nobody has reproduced his experiment. So I have the following choice: Either Thieberger made a mistake, or he's in some funny situation, or there's some feature of his experiment that we have not noticed. But it's not that he knew anything special, because this all came out very fast. It's not that he knew anything that I don't know. It's just that the way the experiment was configured might have a clue in it, something I'm not paying attention to. So that's the kind of thing I think about. It's like trying to throw a dart at a board that's half a mile away and getting a bullseye. It's not easy, but I'm not giving up. Because I can't believe these data are coincidence. Other researchers have estimated the chance that the Eötvös data could have resulted from a statistical fluctuation to be roughly one-in-a trillion. It's small enough that it can't be an accident. There's something else that's going on, but I don't know what it is. And we have to figure out what it is. Is it the place, is there something special about Eötvös's location? Was something else going on over there at the time? Or more likely, something that's totally obvious and we're not paying attention to it. And that's kind of what I'm thinking about at the moment. Something that would be a catalyst, and that's my theory, but it depends on the baryon number-to-mass ratio and something else activating it. That's sort of my theory at the moment. People are still doing these experiments, including this group at the University of Washington, led by Eric Adelberger, who's become the one of the premiere experimentalists in this field. Various groups are publishing results over and over again, which get better and better and which constrain the putative 5th force more and more. So let me throw in a sense of humor here, since I want students to think of me as having a sense of humor, even in doing physics. One of the experiments that was done at the University of Washington was Boynton's group. Paul Boynton, a good friend, did an experiment in a deep tunnel. It was a tunnel that was being drilled in Index, Washington (Index is a mountain there). Oddly enough, one of my recent students, Dan Javorsek lived in Index, which is basically three bars and a gas station kind of town in the middle of Washington State. Dan knew about my work. He came to Purdue and wanted to work with me, and he wrote a brilliant PhD, a test of the Pauli Exclusion Principle and several other papers. He's just a wonderful guy. So any case, Boynton did this experiment in a tunnel that was drilled into Mount Index by some Australian drilling company just to test out their drilling equipment. It was not done for any other purpose. So Paul did this experiment and because it’s in the mountain, it is a very difficult experiment, there's water running around. But Paul would tease me once in a while, and say, "Oh, we're seeing some great effect, you've got to come." After a while, I realized it was just a joke. But towards the end of his experiment, I decide to pull one on him. This is before we had fancy copying equipment. There'd been a number of press releases from the American Physical Society about my 5th force work. I took one of them and I used a xerox and un-xeroxed it, and copied and did a bunch of things to make it look like a real AIP press release. And in the press release, I had him saying, "Oh this experiment brilliantly confirms the 5th force and Professor Boynton, thanked the drilling company for giving them a nice site with running water and a cool environment." Really, the running water's a pain in the neck, and the environment was dirty, cold, and unpleasant. I also had Professor Boynton saying, “’To my surprise, Fischbach turns out to be correct.’ And he adds ‘… there’s absolutely no doubt that our experiment established unequivocally the presence of the fifth force. It appears that Fischbach isn’t as crazy as I had thought,’ says Boynton.” And he adds … “’We hope that our next experiment will show that Einstein, Bohr, and Heisenberg are also wrong.'" And I had my secretary sign it, so it'd have a feminine handwriting to make it look authentic, and I arranged to have it sent from New York, where the American Institute of Physics is located.

 

Zierler:

Oh wow. (laughs)

Fischbach:

And Boynton went berserk. He thought it was for real. He got a big kick out of it. That's it, I remember I sent it to somebody in New York to have it trans-shipped from there. So in any case, Boynton did an experiment. And it is, again, a nice experiment. These experiments are very, very difficult. I think Adelberger has done a terrific job, and we're slowly "deconstructing" these experiments by asking how could the manner in which this experiment was done mask a real effect? And you can think about it and have some vague ideas about various experiments, and that's sort of the line of reasoning that we're pursuing. On the one hand, people say that I'm just sort of being uptight about all of this. I should just admit it's wrong. On the other hand, people you talk to also admit there's something there. You can't dismiss the EPF experiment. Following the publication of our paper, people worked very, very hard to find things wrong with the EPF experiment, but do you know what they found? They found that EPF had done their experiment even better than previously been realized. Here's one example. Clive Speake was one of these guys who did these experiments. He's at the BIPM in Paris, I think. Clive Speake made the following observation, which is very subtle and it shows you how careful you have to be. He noted that one of the experiments that EPF did involved a reaction of iron sulfate and silver sulfate mixed in solution in which the silver precipitates out of this reaction. Otherwise the reactants before and after mixing are the same. Clive did a calculation motivated by the observation that the net effect of this experiment is that after mixing, the center of gravity of the sample moves from where it was before. It is shifted because the silver that precipitates out has a relatively high mass, and so now you have to account for the fact that the center of gravity is in a different position. That would show up as an effect at the sensitivity level of the EPF experiment. And this is one place where the object of the experiment is to compare the acceleration of a mixture, the two ingredients, before and after you mix them together. It was a before and after experiment to see whether the chemical reaction changes things. Of course, the baryon number-to-mass ratio would be the same, so there shouldn't be an effect, and that’s in fact what EPF observed. There's no effect. But, Clive pointed out that if EPF not been careful, the final mixture would have see an effect, because it's not just mixing sugar water and salt water and it looks the same. Something actually physically precipitates out of this sample. And that changes the center of gravity and gravity gradients are extremely critical in this experiment. How gravity changes over short distances is important. Evidently EPF must have corrected for this, because otherwise they wouldn't have obtained a null result, which is what you expect. But they didn't report this in the paper, which suggests that this correction would have been too trivial for them to talk about. And so the fact that they made this subtle correction is extremely important in telling you, that EPF did the experiment carefully and correctly. This is one of those wow things. The paper written by Pekár and Fekete eliminated by their own acknowledgement a lot of the details of what they did. It suggests that EPF did a lot of things more carefully than are represented in the published paper even though the published paper is pretty long. They talk about how long the published paper was before they cut it down. So now in the more recent times, somebody found this hand handwritten autograph and Sam Aronson came to me and we talked whether we wanted to do something with this? And Sam said, "I know this guy, Gabor David, who's at Brookhaven, and who has a joint appointment at Stony Brook. Let's toss it to him." So Gabor, whom I did not know before, but have now met, translated the paper, the original autograph, and it is now published. We have the actual handwritten Eötvös version. And in that version, you see a much more nuanced way of Eötvös dealing with all of these questions. It has more detail in it than you would imagine in a typical modern paper. Since in those days they filled in a lot of details. And that was it. The paper as it stands now is a sort of a testimony to how carefully EPF did the experiment, how carefully it was analyzed, and to everything else. And aside from the comments that we made pointing out the significance of various results, nobody found anything wrong. I mean, there are slight typos, obvious typos and so on. So that's where things stand. The paper speaks for itself, and there's nothing in the physics that we know that's wrong. Eötvös was the master of this technology. And people don't know this, but his balances were a significant contribution to the economy in Budapest, because they were sent all over the world. They were used to measure gravity gradients in order to explore for oil, until the 40s maybe. Now we have portable gravimeters, but the Eötvös balances were used for a long time. So the experiment looks good, the results are consistent, everything predicts the existence of 5th force, except nobody else is finding it. And so, it's a puzzle, and motivates me to keep thinking about it. Although I don't work on this all the time because I also have other interests, but it motivates me to think when I'm out there running in the cornfields, when it's 100 degrees outside. I keep asking what did EPF do (or not do) that we're not paying attention to? And I'm convinced it's something like that. It's either catalyzed or there's some aspect of the experiment that's either not written about or we're not thinking about that's too obvious. Now, I'm saying that to you. If perhaps 20 years from now when I'm no longer here, you can say, "Ah, Ephraim said that. Maybe it's actually right." But I'm absolutely convinced there is an effect somewhere because nobody has pointed out anything wrong with their experiment, and it's utterly inconceivable to me that EPF could have found a correlation with a variable, baryon number, which didn't exist at that time. How can this be? And it's a perfect correlation, there is not even a single data point that falls off the line. Everything is completely lined up. How can that be? And you know that this begs for an explanation.

Zierler:

Ephraim, who coined the term, "5th force"?

Fischbach:

I'm asked that all the time. It was not us. We did not give it a name. We simply said there's a quantum number called hypercharge. That appeared in a front page story of the New York Times, on Wednesday January 8th 1986. I don't know who coined the name 5th force, I assume it's John Noble Wilford, who wrote the story. It may have been a typesetter who said, “I can't write anything else in here,” fundamental for whatever. Note "fifth" is written as "5th." It just fits in that way. I tend to write F-I-F-T-H but I'm getting lazy so I'm doing it as 5th. So this whole idea is due to the New York Times. And that was the only time that I know in history, at least in modern history, where the name of a fundamental concept was invented by a science writer for the New York Times. He, or some typesetter, invented the name. "Hey, Mr. Wilford, I can't fit the 'fifth' in here. I've got to write it as 5-T-H, okay?"

Zierler:

I mean, does it make sense to you that there would be four forces and then, of course, this would be the fifth? Does that make sense in sequence?

Fischbach:

So why is it the 5th force? Because the original force, of course, gravity, that was known for a long time. Then came electromagnetism, let's say in the 1800s, that became the second force. The third force was presumably associated with beta decay. Where does beta decay come from? That wasn't called anything at the time, and then eventually when neutrons were discovered, and we realized that there must be something binding neutrons and protons in a nucleus, somebody called it the strong force. It's not like God tells you, "Call it these things." It's just that in the course of writing a paper, you would say, well, we could talk about how the pions are responsible for the strong force. I have a theory of why the pions bind neutrons and protons to the nucleus. It just naturally came there. So, when I was talking to John Wilford, he said, "Well, what are the forces?" And I explained all of the above stuff to him. He says, "Is this a new force?" Well, it is obviously a qualitatively new force if it exists, because that just depends on what the force it distinguished by, and what is it that defines those reactions? So in the real world, all of these forces are acting simultaneously on everything. We, you, me, are being affected by gravity, by E&M, obviously the nuclei in our body are being kept together by strong force, and beta decay happens all around us anyway, so it's the real force. And there's nothing we can do about it. Right now, you are being bombarded by neutrinos, which are a manifestation of the weak force. Sometimes when I give a lecture I say, "Look at your thumbnail." And you look at your thumbnail and say 1-1000. And in that one second, more than ten billion, neutrinos just passed through your thumbnail. But in your whole lifetime, it's unlikely that more than one neutrino will actually stop in your body. One neutrino if you live 100 years. So obviously we need a new force to describe that, because neutrinos do other things. Wilford called it the 5th force, I'm happy. I want to think that some typesetter, Vinny, who lived around the corner from me wound up being a typesetter for the New York Times and said, "Heya, Mr. Wilford, I can't fit in the whole word 'fifth.'" And decides to do it as 5th, and this is the way the concept arose.

Zierler:

Listen, it's a good name.

Fischbach:

Yeah. It's stuck, because what's happened is that it's become generic like Kleenex or Frigidaire or something like that.

Zierler:

Yeah.

Fischbach:

You say, "Give me a Kleenex," and it's not a Kleenex. So "5th force" has now become generic as a description of a certain class of new interactions. Now everything's being called a "5th force", even though I don't think that any of the theories that are being proposed would have the correct fingerprint to work for the EPF experiment, but that's okay. I'm happy if the concept is useful.

Zierler:

So the saga of the 5th force is not a woulda-coulda-shoulda. It's still very much active and you know, the puzzle remains to be solved. It's not that this narrative has an end point to it.

Fischbach:

Absolutely not, that's exactly correct. And what's interesting to me, is the fact that the 5th force is generic, because every once in a while, I'll have the following experience. Somebody comes to give a talk, for example this professor from Columbia, who's giving a talk on some interesting experiment that she's done. "Now, here's the limit we set on the 5th force." And she has no idea where that came from, because it's so generic. And so I went up to her afterwards, and I said, "You know, we're the guys who wrote the paper that did this." She was totally surprised. I sent to her a copy of the front page of the New York Times and all that. It's so generic, it's like asking who invented Kleenex? But what's happening is that the name is being adopted, to describe a force which interacts weakly but extents over macroscopic distances. That's the part that you want. Because the 5th force, as we proposed it, had to be a macroscopic force, acting over different distance scales. Now what the scale is, we don't know. It could be anywhere from an astrophysical scale, arising from the Sun, or the most microscopic— people are doing 5th force experiments over subatomic scales. But it's something which is not a photon, which has infinite range. And the way we talk about the range of a force, for electromagnetism and gravity, is infinite. That means that there is a parameter, λ which is infinite, which implies in turn that there is no exponential damping of that force. So gravity and electromagnetism are infinite range forces. The other forces are clearly short-range forces, in fact, very short range forces because they act inside the nucleus or inside a particle. Believe it or not, there is no known force that has an intermediate range. That is the home of the 5th force. So people are continually inventing particles whose masses would allow them to mediate a new kind of force, which would be of intermediate range. Again, that means that the scale over which their effects would be most prominent would be meters or centimeters, a macroscopic scale. And that's the most interesting thing, because that's the scale in which we live. Now one of the side products of all this, which is interesting, is that when I started talking on this, I told people that you have to look to design an experiment whose natural scale is the size of the scale that you're trying to probe. That is to say, I'm not going to probe an atomic scale with a photon whose mass, (and hence length scale) is much bigger than that. So I said, you have to think that in your mind every force has a kind of secret factor of e-r/λ in it. And λ is the scale. If r is small compared to λ, then the range effectively doesn't show up. When r is big compared to λ, you can very quickly suppress forces. So we're looking into the middle. And I said, the hardest distance scale in which you want to set limits is actually the scale of this lecture hall that we're in. Because on the scale of the real world in which we live, there are so many other perturbations around that you really don't know what's influencing what. At the astronomical scale, we know the Sun is up in the sky and 93 million miles away. At the microscopic scale, we know where photons live and so on. But in some intermediate scale, it's just too cumbersome to do experiments and so all the experiments are really relatively crude. But because of that, there's room for there to be fundamental new particles whose effective range of interaction is like the size of the room or things whose size is meters and centimeters, and not either super microscopic and super macroscopic. So it turns out that super microscopic and super macroscopic experiments are a lot easier than intermediate ranges, and so somewhere in there may be something going on which might resolve our understanding of the EPF experiment, but now, that's one of the hopes. We don't know that for sure. But I keep the faith that there will be something like that discovered, and maybe a force that has nothing to do with the EPF experiment, which wouldn't explain the data, but just incidentally, there's a force over that distance scale and that's interesting. But more interesting would be a force which actually explains everything. And if I had an extra bonus, this force would explain these energy-dependent phenomena and the kaon system and so on. Who knows? But I believe there are many more forces to be discovered, and you just have to keep plugging away. Hopefully if you've motivated them, inadvertently, somebody may, although not looking for our kind of 5th force, discover it anyway. And that would be discovering a new force.

Zierler:

Ephraim, I humbly request a quick two-minute break, an intermission. I'll come back and I want to ask a follow-on question to that.

Fischbach:

Sure, absolutely. And I'll take the same break in the restroom here.

Zierler:

Excellent, excellent.

Fischbach:

Is it— you're at home now, is that right?

Zierler:

I am indeed.

Fischbach:

Is Aviva there so I can meet her virtually?

Zierler:

Yes, I can't wait to call her in.

Fischbach:

Please, I mean I guess it could be a thrill. Now, if I haven't convinced you yet that I'm crazy, I just want to touch on what I'm actually working on at present.

Zierler:

Well wait, before we get to that, I do want to— That'll be the last thing that we talk about. I do want to ask you sort of a broad question. As you know, of course, there are many particle physicists who saw a golden age in physics ending when, you know, pick your date. Late 70s, early 80s, something like that. And they say things like, you know, all of the fundamental stuff has pretty much been discovered, and many of them look for the new frontiers, right? This is why so many particle physicists have gone into cosmology. And yet if I understand correctly, from the way you're talking, that the fact that we don't know what this 5th force is has fundamental impacts, or if it would ever be discovered, has fundamental impacts both on particle physics and on cosmology, right? So I would assume you would challenge this idea that there isn't remaining fundamental work to be done in particle physics itself.

Fischbach:

I completely agree with you. I mean, since I have feet in different camps, as you'll see in a few minutes, what happens sometimes in particle physics especially, is that people get tired of not being able to solve a problem because after all, if you're a postdoc you've got to write papers. And after a while, if you can't figure out, if you do not have an idea of how to solve a problem... So people are always looking for problems to do, and a lot of people have earned PhDs based on the 5th force and so on. When there's nothing to do, problems remain, and they just stay out there. I mean, that's the way things are. If you can't solve them, you can't solve them, and there's no sense killing yourself, because you've got to write papers. So what's happened, I think your intuition is correct, is that the glory days of particle physics may be in the past. We discovered CP violation, as you know, which was unheard of. So we discovered also more than one neutrino, all those things were surprises, like the idea that there was more than one neutrino. This is part of why I ended up becoming a theorist: So I'm a freshman at Columbia and taking chemistry lab. And the TAs are guys who did chemical physics. They're doing experiments at Brookhaven. And so I remember one TA telling me, he said, "Boy, this is a real pain in the ass," because to do the Schwartz two-neutrino experiment, which eventually discovered the muon neutrino, for which they won the Nobel prize, Brookhaven shut down all other experiments. So this guy for six months wasn't doing anything, because Brookhaven was using all beam time to do that experiment. I said “I don't like that. I don't want my career to depend on something else.” That was one of the compelling reasons for me to go into theoretical physics rather than experimental physics. I didn't want to be part of a big team. I want to do my own stuff and do it on my own time. Eventually we discovered CP violation, which was a huge big deal. And more than one neutrino. That also was a huge big deal. I suppose that discovering this or that elementary particle, for example, when they discovered the Ω-, so Gell-Mann won the Nobel prize, that was a big deal. Actually, my very close friend whose office is upstairs, Virgil Barnes, was the first author on that paper alphabetically. He was working at Brookhaven. He's also brilliant, but if your name is Aardvark from Finland, and you have two A's in the last name, you get to be first author in every paper. So in some sense, I do see what we'd call in French "ennui", the kind of- I don't want to say boredom, but less enthusiasm. We're sort of doing a lot of the same things over and over again. I don't follow all those papers with 28,000 Higgs bosons and so on, some of that stuff is just not interesting to me. I don't see the sparkle that we saw in some of those other discoveries. When CP violation was discovered, people started writing a lot of papers about it. Certainly, the whole world of neutrino physics is now exploding because we have different kinds of neutrinos, and I'm working on that too. But I don't sense the same sense of excitement now that you had in those days when they discovered things that were just completely off the wall, and nor do I think some of this theoretical stuff is as exciting as well. I mean, maybe that's sort of a jaded view. If people are going after cosmology, I understand that, because that is a frontier. You always to be at a frontier, and if you can do theoretical calculations that lead to predictable things, results or effects, that's great.

Zierler:

And yet absent understanding the 5th force, though, you really can still make the case that there are frontiers that remain to be discovered in particle physics.

Fischbach:

That's my view. To some of the other guys, the Eötvös results are just a novel experimental glitch that made that pattern happen, and that's all there is. We'll figure it out, maybe Eötvös drank this coffee every morning and the smell of the coffee changed the results! I don't know. If you scratch a theorist, they'll say, yeah, there is a problem there, but yeah, it's probably some experimental effect. So everybody's dismissing the Eötvös results as some experimental glitch mostly because nobody's figured it out. I mean, let's put it this way. If somebody figured out this is what Eötvös did wrong, and that explained the data, that'd be the end of the saga. On the other hand, if nobody figures it out, that may also be the end of the saga, because people don't know what to do. I mean, I'm one of a small number of people who thinks there's enough there to keep scratching my head about, but if you can't write a paper and this field isn't exciting, you know if you're going to go off on the job market, you're going to write about Higgs bosons, and cosmology and neutrinos and... Actually, I'm also writing on multidimensional theories, what would the world look like?

Zierler:

Ephraim, do you see string theory as potentially being useful to the 5th force?

Fischbach:

Yes, because I think that that leads to new kinds of interactions, and that's what you want. New kinds of interactions with new properties that you haven't thought of before. So I do think about, the formalism of string theory. Okay, I have objections to string theory. So let me back up. My advisor, as I said, was Henry Primakoff. He read my thesis, as I told you, when I traveled out to St. Moritz, where he was vacationing in 1967. We were having dinner one night, and Henry said— you know, what's unfortunate is to see theoretical papers being written about other theoretical papers. He wants to see theoretical papers being written about experiments. But that's not the way it is now. Mostly theoretical papers are written about other theoretical papers, which are written about other theoretical papers. And so that's how the culture has changed in that way, and probably it's a response to the demands of the market. Somebody comes up with some hot idea that people are talking about. For example, I am working on information theory, and related questions that can be applied to the deeper concepts of the structure and meaning of information. But I work on that with a graduate student and we have some fun. But you have to think of some topic where they're going to hire you because it looks like it's a hot topic, and you get funding. So funding is ultimately the metric through which your value is determined. Now, that is partly a philosophical thing and partly a nuts and bolts thing, because if you get funding then the university gets a part of that for overhead. They want you to bring in funding so that you can support graduate students, and other parts of the program. So you're put under pressure to get funding. You probably don't remember this, but in the mid-90s, when they were building this superconducting supercollider in Waxahachie, Texas there was a lot of pressure on everybody to fall in line and do calculations that would be relevant for the SSC. And I really resented that we all had to do papers which, as part of the job, made the case for the Department of Energy to go to congress and say, "Yeah, all these theorists are working on SSC Physics." Even though the SSC Physics I did really wasn't great work, but we all were obliged to do that.

Zierler:

Obliged to who? Who made you feel obliged? Where'd that come from?

Fischbach:

The funders in Department of Energy. Because they were being pressured top-down to show why it was compelling to spend, I don't know, upwards of one, two, three billion dollars on SSC so, they had to show that a lot of people were interested in it. Now, a lot of people were not interested in it. I mean, that's the domain of a limited group of physicists who do that kind of physics. I was not doing that kind of physics partly because everybody else was doing it. I mean, it's very hard to find a niche unless you have some hot idea. The 5th force was a hot idea, so I could jump in and do it. But a lot of this SSC stuff that was being done, high energy scattering with some phenomenological model, I thought was boring. And my judgment was borne out in time. Those papers that were written then were just not very interesting. If I remember it correctly, some congressman from New York objected to the fact that the proposed siting of the SSC was to be in Texas, which was where Bush came from and the SSC project was eventually cancelled by Congress around 1993.

Zierler:

Sherry Bollard, maybe?

Fischbach:

I forget who it was. And because there was a joint proposal from Canada and New York, to give SSC free electricity by tapping into Niagara Falls or something like that. It was an interesting proposal, but Texas won. And again, if you looked— If New York wasn't benefiting from it, there was no reason for them to go along with it, and eventually it was killed. So I was not unhappy with that, because that meant there was, in the big pot of money, more money for doing theoretical physics, and doing the theory that we wanted to do, and not the theory that they were making us do, so a lot of lousy papers were written. And a sort of an unfortunate state of affairs, but it is what it is. And then the LHC came along. So the short answer is, I love the line in the “Ancient Mariner”, "We prayeth best, who loveth best, all things both great and small," In our case, “we writeth best if we doeth best all things we love to do.” The best thing for us to do is what we're good at doing and what we like doing, and that's it. And I think the system is better off for it. I sometimes wonder about some of the stuff that's done in the name of theory. Many years ago I was at a conference in Dubrovnik, Croatia. Some guy gave this very hairy talk on some fancy string theory. I asked him at the end, "Can you tell me how that relates to anything in experiment?” He said “no, I have no idea”. Because he was simply manipulating the formalism. Henry Primakoff would have shot the guy, as nice as Henry was. The speaker was writing on some obscure little technical thing about string theory in 17.83 dimensions which nobody cares about and so on. So that kind of physics doesn't interest me.

Zierler:

Is it, Ephraim, is it the problem that it's so abstract that it's essentially just math? Is that the issue, that it's just totally divorced from physical reality?

Fischbach:

I think that's a big part of it. And I always, in all the things that I'm doing, at least, that's my niche. All the things that I'm doing are connected in short steps to experiments. So if I can't think of an experiment, and this relates to a lot of things that I'm doing, which are other kinds of theory, I want to know what's an experiment. And this goes back to me playing around as a kid in my attic with the stuff I brought out of the garbage can in the Mobil gas station on Sunday when the gas station was closed. What can I do with these things? It's the same thing intellectually and theoretically. If I'm thinking through some theoretical idea, I'm always tied, at least ultimately, to some experiment. To some new effect that's going to come out. And that's always part of my driving force. And so it's not that I only write things where I predict some experimental number, but it's directed towards experiments eventually. So I always imagine Henry Primakoff (Henry, I love you!) looking down on me and saying, "Ephraim, keep up what you're doing. Pay attention to experiments, at least so you can see in the near horizon how you might have an experimental consequence.” I'm always looking for funny things like that. And I've written lots of papers like that. Whether it's testing the Pauli Exclusion Principle or some other idea, I like to think about experiments that will set limits on any new physics, that's what I want to do. And I also prefer what we'll call tabletop experiments, like we do here. So I've actually done experiments myself, experiments within the realm of things that I can deal with. When I sit in on these conferences which are deep into mathematics, it's not that I can't understand the math, because I teach math physics. That's the course I'm teaching. I love math. I have published papers in the Journal of Mathematical Physics, fundamental papers on mathematics. I've done a lot of pure math work in various papers that I've written, I have long appendixes on math kinds of stuff. So I love doing math formalism, but in the end, the math is directed towards doing experiments, understanding experiments, and having some experimental concept. So I've done a lot of math physics projects for one reason or another, but in the back of my mind, I’m always directed towards doing some sort of experiment, which is interesting in that way. Just to develop some theoretical formulas, and then you build on them, and then you build on, you build on. If I can't see an experiment, I'm not saying all that's bad, but if I can't see an experiment on the horizon, I'm not interested in it. I'll write a paper saying here's a new math trick for doing this and this, a better way of calculating something. That's fine, but I'm not going to spend my life studying math physics.

So I will give you an example, dealing with one of my favorite papers. All right, so here's another story. You're going to have all these amazing stories. So anyway, I'm a professor in the early 90s, and I'm getting tired of having interesting ideas which I give to my students but not getting to work them out myself. Can you imagine that? So I make a deal with myself. I say to myself that the next hot idea that comes along, I'm going to work it out as if I'm a graduate student. I want to prove to myself that I'm good enough to be my own graduate student! I was literally asking myself whether I am good enough to be my own student. So this is a very interesting paper. It has become one of my really favorite papers. You can exchange between two particles, let's say two neutrons, a neutrino/anti-neutrino pair. A neutrino/anti-neutrino pair gives rise to a force any time you exchange it, and since neutrinos are light, it gives rise to a modestly long-range force, depending on circumstances. So you originally calculate it for two particles exchanging neutrino/anti-neutrino pair. Actually, Feynman was interested in this. He asked whether that could be the origin of gravity. We know that neutrinos exist, maybe gravity's just a manifestation of neutrino exchange. In his lecture notes, he actually talks about this. Now, the first correct calculation was done by Gary Feinberg and Joe Sucher. Feinberg was at Columbia, and Sucher was at Maryland. Sucher is a friend of mine. They calculated two-neutrino-exchange force, and it falls off inversely as 1/r5 between two objects. It's a very short range force, very, very weak. I had an idea based on a paper written by my professor, Henry Primakoff, in 1939. My insight was that the topological structure of Feynman diagrams containing neutrinos is different from that of diagrams with photons. Specifically, you could have instead of just two bodies interacting, you could have four bodies interacting with one another. And actually, that's been calculated too, by James Hartle. And I started fooling around with this and I realized that very quickly, those forces get to be literally astronomically large. What's the point? Let's see if I can explain this. If you try to calculate, you're going to get a mini-lecture on nuclear physics now. One of the things you're going to calculate is the binding energy of an atomic nucleus, and one contribution is the repulsive energy of the protons in a nucleus. That's one of the limiting factors which keeps nuclei from getting increasingly large. You can do that calculation, what is the potential energy? You start by taking two protons in a sphere and just integrate over all possible positions for them. And that turns out to be (6/5)e2/R, where e denotes the electric charge, and R is the radius of the nucleus. And then there are Z(Z-1)/2 pairs, where Z is the number of protons, and that gives you the binding energy, (3/5)Z(Z-1)e2/R. That's the right answer. You can do that calculation in a number of ways, but one way which was taught to me my colleague, Al Overhauser (deceased) involves concepts from a field of mathematics called geometric probability. Geometric probability is the field of math where you ask questions like what happens if I drop a needle on the floor? What's the probability given its length that it's going to intersect one of the grid lines where the two tiles meet. That's called the Buffon Problem, and it’s one of the classic problems in this field. I actually had a student who did her PhD on geometric probabilities. You see, I love math. I'm willing to engage in this. But coming back to the story about neutrinos, I realized that the topology of diagrams with all neutrinos is very different from what you think, and that just as two protons will give you a force proportional to Z(Z-1), if you had n protons, it'd be Z(Z-1)(Z-2)… and so on. And that eventually explains why heavy nuclei are unstable. But then I had the following insight. Suppose you have a neutron star. Picture it as a big ball of neutrons. That's kind of the way we picture it, all right? In there, you could have 1057 neutrons. And if you draw the right Feynman diagrams, you could say that you got many, many more combinations. And what I realized was that even though neutrino exchange forces are very, very weak, the analog of the combinatoric factor Z(Z-1)… eventually will offset the intrinsic weakness of the neutrino-exchange forces. And that in the end, you get a catastrophically large force when you have 1057 neutrons because that combinatoric factor, which turns out to be approximately 1057 factorial, overwhelms all the other small factors from the weak interaction constant sitting there.

Zierler:

Yeah.

Fischbach:

So I asked myself... If you just do a similar calculation, for n neutrons in a neutron star, you get an unphysically large potential energy which was large enough, to upset me. And so one day I'm running, on my morning run. I'd run just about every morning. I'm passing by the elementary school where our kids go, and I had one of these ah-ha moments. The ah-ha moment here was the recognition that the only way out of this awkward situation is if neutrinos have a minimum mass. Because if neutrinos have a minimum mass, you use the same kind of fact we talked about in nuclear physics. The force has an extra factor, the exponential factor (e-r/λ), where λ is inversely proportional to the mass of the neutrino, with the Planck constant thrown in. It looks like λ could be given the correct magnitude to suppress the interaction and it could allow for physically reasonable neutrino-exchange forces. Let me put it this way. Absent neutrinos having a mass (and we don't know what mass they have) that force involving all these neutrons exchanging neutrinos, is catastrophically large. It would blow up every neutron star. But neutron stars do exist. So the only way out is to say, look, we have to minimize that force. We have to make it sure that a neutron “Vinny” at the South pole of the neutron star can't interact with “Tony” at the North pole, his cousin. And the only way to do that is to see that there's a penalty. "Hey, Tony, I can't get to you! The neutrino mass is too big. I just can't make it." You need to put in an exponential factor and by adjusting how much of a suppression that factor produces, you can make those forces become much smaller. And then I realized that what I had done was to figure out that neutrinos could not be massless. See, everybody's doing these experiments, and the neutrino mass has to be less, less, less than this. I've written the first, and so far as I know, only paper, saying that the neutrino mass has to be more than a certain specific value. It's a very long paper, almost 80-pages in Annals of Physics where I present this long calculation. I showed that the only way you can have a stable neutron star is if you can prevent “Vinny” and “Tony” (both neutrons) from interacting with each other by exchanging neutrinos. Well, you can't just say, "Don't do it." The only way to prevent them from interacting is to make them exchange neutrinos of a large mass. That's our precedent. So going back to my days in Brooklyn and Coney Island, it's like this: You're on the beach, you know, Bay 15, we're tossing around a beach ball. If the beach ball's very light, all of us 100s of yards away can toss the ball around. But that's expending a lot of energy. If I just want to toss the ball to my wife or my brother, I have to make the beachball heavy. And if it's heavy, there's only a small number of people who can interact with it. And that's the analogy that I give. So if I made the neutrinos heavy, then Vinny at the bottom can't talk to Tony at the top, they'll try to, but this contribution will be exponentially suppressed by the factor (e-r/λ), where r is the distance from the North pole to the South pole of a neutron star, divided by this constant λ . If I make λ the right number, that contribution will be exponentially damped, and nothing's going to happen. Does that make sense so far?

Zierler:

Yes.

Fischbach:

You're sure?

Zierler:

I'm on it, I'm on it.

Fischbach:

So then I did a very, very long calculation. Now you've got to put in numbers to these very hairy calculations, but it's aided by this technique which my collaborator, Al Overhauser taught me involving geometric probability. I was introducing this discussion to show you that, to do this calculation I had to develop a lot of techniques in mathematical physics. Not just fooling around with quarks and extra dimensions. I had to really develop formulas for doing these very complicated integrals, which I did. And the end result is, and this is dramatic, if this works out I could forget about the 5th force. When I got through I said, "Okay, here's the formula. How big must the neutrino mass be to avoid problems with neutron stars? Recall that the neutrino masses can't be zero, because then everybody interacts with everybody else, I have to keep making them bigger and bigger so I can confine the interactions of neutrons in a neutron star, so that the neutrons are pretty much confined to little neighborhoods. That's the only way they will be a finite force. Making sense so far?

Zierler:

Yeah.

Fischbach:

So I did the calculation, and it turns out, mind-blowingly, that the mass comes out to be approximately 0.4 eV. Now that's interesting— that was just dumb luck. Why? Because most of the experiments now are telling us that its mass has to be less than about 1 eV. And by a miracle, my calculation says it has to be bigger than about 0.4 eV. Now, it could be 0.3, 0.4, 0.2, but it's not 10-8 eV. And it's not 108 eV. It's a number that's exactly in the sweet spot of where the field is now. In this paper, I show that there's a very narrow range between my theoretical calculation, which says that, the masses of all neutrinos have to be more than 0.4 eV. Maybe it's 0.3 eV or 0.5 eV, but in any case, less than the current limits, which are about 1 eV and so on. So if I'm lucky, they would find the neutrino mass in the middle between 0.4 eV and 1 eV. And if it's right on my number then I'm in business. So I believe that mine is the only paper I've ever seen doing that kind of phenomenology. This is in answer to your previous question, I'm interested in doing a theoretical calculation where there's an experimental result. Because eventually, various groups are going to measure the neutrino mass down to fractions of eV. And they'll test whether I'm right or wrong. It’s an interesting story, in that it started, as I told you before, when I started wondering whether I was good enough to be my own graduate student. And that (laughs), now the funny part of it was, when I said of course I'm good enough to be my own graduate student. Why? because I teach the courses in which they would first have to learn to do all this work. But I teach their courses. Hey, this should be a couple of weekends. A couple of weekends turned into a few months, a few months turned into five years. Five years and something like 1650 handwritten pages of calculations. And I toughed it out. I said, I've got to prove to myself I'm good enough to work for me. So now, I did the calculations and the results are interesting. It’s already been cited quite a lot. But it would be cited a lot more if, God willing, we do an experiment that comes out with the results I predicted. I'm sure it's a very narrow range where neutrino mass must exist. So given all the approximations I've made, I could be forgiven for, you know, factors of two, three, and so on. But that is my calculation and it's out there. That episode tells you what kind of math I like, I like doing nuts and bolts kind of math. I'm also interested in learning new techniques. But I like substantive things where at the end of 80 pages, in Annals of Physics, I show that you can get something physically interesting out of it. And now we're waiting around to see an experimental result. But I did tough it out, so maybe nature will be good to me and let me witness the fruits of my labor.

Zierler:

I think it's sort of with string theory, if you were hopeful that string theory might have a role to play.

Fischbach:

I don't think so, but I have used string theory to motivate new kinds of ideas.

Zierler:

Do you think string theorists still have interesting things to contribute?

Fischbach:

I think so. I think string theory is generic, it's a machine for cranking out different forms of interactions. So if I want to write a paper, I wanted to say, well, nature had a force like this, such and such would happen. Now, a referee might say you just can't pick things out of a vacuum and so on. Maybe if it came out of string theory, it would seem more motivated in some way? Partly it's just a strategy for writing papers. I want to be able to convince a referee that this interaction could come out of some theory, so even if string theory's not the right answer, it gives you certain functional relationships, and that's what you’re interested in. Can objects interact in this way, have this distance dependence, this dependence on mass, etc.? And can all those factors, work together to give you the result that you want? But I don't find string theory to be, at least at this stage, something I want to work on for fundamental principles, because it's been around a long time. It's hard to think of anything that's not totally mathematical, that I could contribute. And so I work on it in the hope that maybe some new idea will come out of string theory, some sort of phenomenological recognition that we're not yet thinking about. Maybe some new kind of phenomenon will emerge from string theory. And that is one of the things that I think about.

Zierler:

Well, Ephraim before I hit end of record, and we bring Aviva in, I do want to ask about some of the current research that you're involved in.

Fischbach:

I'm glad you brought that up, because when I went to the restroom and we had that break, I noted that I completely forgot to talk to David about this and that. All right, so here it is. Let's see how this got started. I'm trying to think of the path that we got this discussion started on. It has to do with radioactive decays. The current work I'm doing is exploring the possibility that radioactive decay rates are not constant. Alburger and Harbottle at Brookhaven did an experiment measuring the half-life of Si-32. What they found was that the half-life wasn't a pure exponential as expected; it had oscillations built on top. There were periodic signals sitting on top of the expected exponential behavior. And they didn't know what to do with this, okay?

Fischbach:

I got interested in this and started looking at possibility that radioactive decay rates weren't constant. Now, this is sort of insanity. It is absolutely rock-bottom dogma that radioactive nuclei decay, according to the exponential decay law: N(t) = N0(e-λt), where λ = ln2/t1/2 where t1/2, the half-life, is a fundamental characteristic of the particular nucleus. That's the premise of all this. So when people calculate the decay rates of particles or nuclei or whatever, λ is a quantity that somebody's calculated for his thesis, and that's the way it is. So I started looking at their data, and I set up an experiment over here, along with my colleague Jerry Jenkins. One thing that happened which was totally astonishing is, we were just taking on the decay of manganese-54, and there was a solar storm on December 13th, 2006. The solar storm was very interesting, because in measuring the decay rate of this isotope, we noted that, a few hours before the storm happened, the decay rate started to change. The solar storm was a big event, in part because at that moment, when the solar storm happened, two astronauts were outside the International Space Station, and they were hit by the radiation from this storm. You get a lot of radiation from those storms. Now fortunately, they weren't hurt, because it was a low-level storm. They rate them on a 1-5 scale like tornadoes or hurricanes. If it had been a more serious storm, they could have been killed. So that became an interesting question. How are you going to know in advance when the storm happens? But our data supplied information on how this would happen, because we saw a precursor signal about eight hours before. That means that if we can capitalize on this, we could have warned them before the Sun blew up. It's giving us a warning, like the canaries in the mine (or the canaries in my lab in chemistry) and we patented this. We have a patent on this technology. And we have a similar signal many times over. When we submitted our paper on this event to a journal, they said to us “you're crazy.” Why? Because radioactive decay rates are not supposed to change, but they do. And since then, we've been studying this phenomenon. This is really what I spend most of my time on. We have very many indications that this is in fact exactly what happens. That there's something extra coming from the Sun when there is a solar storm. We tend to think of this as being neutrinos, because they do come out of the Sun, but people say radioactive decay rates are fundamental constants. However, it turns out that if you go back to the literature, Ray Davis, who won the Nobel prize for detecting solar neutrinos in this chlorine experiment, pointed out that when there was a storm on a certain day, he got more neutrinos coming through. So if you assume that neutrinos are produced during the solar storm, you can then make the connection that neutrinos somehow tickle the nucleus, kick it a little bit, and cause it to decay faster. There it is, you've got a mechanism. So now, as a phenomenological theory, we've seen many events like this. And oddly enough, instead of this being the craziest thing I'll bring out a very interesting reference to you. The craziest of all crazy things is that we found in going through the literature, a paper by a German group at the PTB in Germany, and in this paper, they see oscillations, annual oscillations, over a period of approximately 15 years. Now, in the midst of all this, we read what appears to be the first paper on this subject written by Eckhard Falkenberg who had the following idea: We live in a bath of neutrinos, which are all around us. He said, what if it's the case that there's no such thing as spontaneous decay? Nuclear decay, particle decay, anything? He said his philosophy was, what if it is that decays, that we call spontaneous decays, aren’t spontaneous at all? What if neutrinos, solar neutrinos, astrophysical neutrinos, etc. are responsible for stimulating why decays happen in the first place? And he set out to show this, which he did via an experiment with tritium. And if that's the case, then there should be present day-night oscillations. You're on the wrong side of the Sun. And he showed using this sort of simple apparatus, that there is in fact an oscillation in the decay rate of tritium, superimposed on the exponential decay. Now everybody thought he was nuts, I'm sure. We never communicated with him because he was deceased by the time we got involved. But you could see in his writing that this is what he was thinking about. Although this was not a high-tech experiment, the amplitude of these oscillations and their phase coincide with what other researchers have obtained subsequently. He's one researcher who's been way, way, underrated. We should make sure to give him credit. But his work got us interested in this business, because in fact, a lot of people see these oscillations, and we do ourselves. And so the question is, why are we seeing those oscillations? The naysayers who may be right say, look, your apparatus has a certain dependence on temperature and pressure and other factors. And they have a day/night effect too. That is, line voltages change in the day and night. The line voltages change when air conditioners are turned on, etc. So you get line voltage changes, your apparatus is sensitive to the voltages coming in and this is what you are seeing. It's not because the phenomenon itself is changing, it's because your detector efficiency is changing. And that's a very, very plausible idea. But that does not explain why we saw what we saw in 2006 during the solar storm. Because it wasn't a change in outside conditions. It was over a very short time period, and it began and ended when the solar storm happened. Either that's the most amazing coincidence, or there's a physical effect present. And so we have been pursuing that as a physical effect. In short, many researchers see a lot of anecdotal experimental data, which indicate that this is true. Seasonal effects are seen in the radioactive decay data, that are not associated with temperature and whatever, because we measure temperature and whatever. It doesn't happen all the time. It doesn't happen in all nuclei. It's another one of these effects which motivate what the right experiment is to do. Just like the EPF experiment. How do I want to do the experiment? In the EPF experiment it was their choice of samples, here's your choice of nuclei. Again, a choice of samples. What am I doing when I'm not working with the 5th force? I'm worrying about this. Because this has not only enormous theoretical consequences, but also practical consequences, because if we can predict solar storms we can save a lot of lives. People have gone back to what’s called the Carrington Event. Carrington was a British astronomer who documented a solar storm in 1859. Now in 1859, we had something which ran electricity, it was the telegraph. And a lot has been written about that, it was September 1st of 1859. So what happened was the storm caused fluctuations in line voltage, which burned out telegraph offices, where people came to send telegrams. Telegraph operators were almost electrocuted by the sparks on their line generated by the solar storm. What happens during the solar storm, is that the magnetic field lines of the Earth, which normally deflect charged particles from the Sun, are knocked out during the solar storm. This then allows charged particles to come directly to the Earth and they create a current in the ground. The ground transmits current, as do pipelines. And that current can go across the entire United States in a few minutes. And people like the Lloyds of London have said, well, what would the consequences be if that happened in our time? You're talking about millions of lives lost because you knock out all the power grids along the way, and from that and the fact that there's no electricity. So a solar storm, in simple English, is the most devastating of all natural phenomena. Way worse than hurricanes, earthquakes, tornadoes, small comets, and phenomena like that, because you can affect the entire United States at once, wipe out basically the whole electric grid. And if you live out in the country, where I do, there is a place two miles from us in a little fenced in area where the transformers are, and you have this power grid, that would burn down. And these transformers don't sit it on the shelf anywhere. You have to construct them from scratch. It takes maybe a year or so to make one and costs a half a million dollars. It follows that if we can predict solar storms, that's a big plus for our society. So now I'm asking myself how to construct a theory which explains why it is that we see what we do, as in the case of the EPF experiment. To start with, not all nuclei exhibit these effects. Some nuclei respond and some do not. So if you have thousands of nuclei, building a catalogue of these nuclear decays is important, and this is something we are doing now. Certain nuclei are very responsive, tritium being one of them. Manganese-54 is another. And there are other isotopes which clearly see these effects. So I'm trying to understand what theory is it that that could describe all the phenomena that we are seeing. And how we can improve on our technology. At present there are a lot of people doing these experiments and I expect this to continue. This is something that's going to be a big deal because it not that hard to do these experiments, looking for oscillations in nuclear decays and so on. But many experiments have seen similar effects, but not everybody, and we're trying to understand why, and what the phenomenology is. But this has a practical consequence since predicting solar storms would be an enormous boon to society, if we can do that. If you have nothing to do some night, there is a history channel or docudrama, sort of a dramatic reenactment the effects of a solar storm. As would be appropriate for me it starts with a satellite falling out of the sky into a cemetery in Brooklyn. Probably the cemetery, outside of which, I played stickball when I was a kid. I can tell you when the ball would get into the cemetery, we didn't care about getting it out. We're just not going to run in. But the satellite falls out of the sky. It's spotted by a policeman. Somebody points this out to the mayor of New York, and says that happens because during a superstorm, there's expansion of the atmosphere. And the atmosphere gets bigger, and so the air resistance is more, and that's why this satellite just falls out of the sky. But that's a precursor to the actual stuff coming from the Sun. That takes maybe a day so. So he tells the mayor and she shuts down Brooklyn. So Brooklyn is disconnected from the grid. And then, when it's all over, Brooklyn reboots the city, the country, the world, and all that. Brooklyn saves the world. What could be a better story? But if you can get that docudrama, it gives you some insight to what solar storms do. But they are potentially the most devastating of all storms in the sense that can shut down the whole country if they wipe out the electric system, the electric grid. This is clearly worse than a tornado or a hurricane in some localized region. And so that's the other project in which I've been heavily involved. Now, the craziness of all of this is that in the most recent thinking that I'm doing. I am trying to build a model where the mechanism that allows us to predict solar storms is also responsible for the 5th force.

Zierler:

Woah.

Fischbach:

Now it's a good thing my brother's a psychiatrist, because I get free treatments from him.

Zierler:

(laughs) This would be like megalomania, where it all revolves around you.

Fischbach:

That's right. But my name would have to be Trump for it to make any sense. (both laugh) But since by now you hopefully have at least some measure of respect for me, I can't go into details now because it's very complicated and I'm not sure of all the links together. But, it's slowly dawning on me that maybe I can think of a mechanism. You know, I like this picture. If you remember, if you've ever been to the Sistine Chapel, there's a picture of God creating Adam, and Eve.

Zierler:

Right, they touch. Right.

Fischbach:

That's right, exactly. But the point is this. When I was an undergraduate at Columbia we had to take a fine arts course. As the professor pointed out, notice God isn't actually touching Adam. God doesn't have to touch— He's just (makes straining noises) close enough to meet Adam. So you know, I can see that these two conceptual worlds, the 5th force and radioactive decay, have a slight, slight connection, but that might be enough. It might be crazy enough to be true. We'll put it that way. In which case, I could connect these two. Now it's not just that I got up this morning and said, hey, I'm going to entertain David with this cockamamy idea. No. It's been worked out enough in my notes so that it's not the total insanity. It's probably not completely right, because getting any one idea right is a major task. But it's probably not completely wrong either. And so if I could connect these things in some way, which I'm trying to do with my postdocs and students, we could have something there. And so that's the connection.

Zierler:

Well, Ephraim, I know before I get Aviva, I was going to ask, my last question before I get her was going to be if you had to choose, would you, for the rest of your career, if you could choose one more achievement to fulfill, would it be the 5th force or would be being able to detect these solar storms? But what it sounds like is, your answer is you don't have to choose because it's the same answer.

Fischbach:

That's right. That could be. If it didn't work out, then I would certainly work on the solar flares, because this could prevent people from dying. We can save people’s lives if we make that work.

Zierler:

Yeah, yeah.

Fischbach:

And I mean that since I have children and grandchildren, obviously, when I look at my grandchildren, I'd do anything to help them out. I would obviously want to make that work. And we actually have a company, SNARE, that's started up to do all these things, and we're getting some funding from the government to do it. SNARE is an acronym for Solar Neutrino Advanced Research and Engineering.

Zierler:

And this is one of those things, we're all thinking about coronavirus right now, but a solar flare, this is like the big thing nobody's thinking about right now.

Fischbach:

Nobody's thinking about it, and what's interesting, to bring it back, to show you all the connections among different ideas, I told you about this graduate student who came to work with me, Dan Javorsek, who was living in Index, Washington where this 5th force experiment was done. That's how he knew about me, he came to work with me, does his experiment on the accelerator, mass spectrometer, and we became very close friends. He became, and he probably still holds, the Purdue record for the fastest PhD. Because I started him working on his PhD as an undergraduate. When he was a sophomore and he worked on this project, he's super bright, and so by the time he got a bachelor's degree in aero-engineering, and came to physics as a formal graduate student, he had already done his experiment. He'd actually done two experiments with me. So all he had to do was write them up and he got out in two years. Bachelors to PhD in two years. Time went on, and now the story gets a bit crazier. He was in the Air Force and he was supported by the Air Force. He was one of these top gun pilots. He was a super jock in a plane, and he had fantastic coordination. We went together, funded by the Air Force, our whole team, to measure radioactive decays during a solar eclipse in Amami Japan, on July 22, 2009. He was one of those guys. His coordination is amazing. The reason he was able to work for me at all was that the plane he was supposed to fly, or that model plane, was having problems and so the Air Force gave him two years to finish his PhD, which is crazy but we got it done.

Zierler:

Well, there's only one thing I can say. (inaudible 22:08)

Fischbach:

Thank you very much.

Zierler:

So I'm going to hit end on the recording here, and I'm going to go get my wife.

Fischbach:

Sure, absolutely.

Zierler:

Okay.

Acknowledgement:

I wish to thank all of my many colleagues for the many insights they have transmitted to me, relating to the work I have described here. Additionally, I wish to extend my deepest thanks and appreciation to Megan McDuffie for her extraordinary efforts and invaluable comments which, along with her unending encouragement and humor, helped me to bring this project to completion.