Physics

So far on this blog we have covered many aspects our family history: our father's family roots in the Russian Pale, the life of the illustrious Rabbi Yitzhak Elchanan Spektor, Jewish life in Harlem and the Bronx, the rise of the American liquor industry in the 1930s, our mother's exodus from Germany and flight to America, the implementation of economic Aryanization in occupied France in the 1940s, and much more. It has been amazing to learn in some depth about these historical periods and events and how our family members' lives, and ours, were shaped by them.

We will now turn our attention to another rich subject that shaped our family and our times, nuclear physics in the postwar period, courtesy of our father Stanley Ruby, who returned home from WWII at age 22 to finish his education and start a career in that burgeoning field less than a year after the first atomic bombs had been exploded at Hiroshima and Nagasaki.

I will warn you that, unlike the histories that we have covered to date, this one will take us into some fairly difficult scientific terrain. I will do my best to make the material understandable to curious readers without dumbing it down entirely. As with the past episodes, we will see how our family member played a role in important historical events and how that involvement impacted his and our lives.

This story begins with a recent trip I made to visit Twyla and Zach at UCLA, where they are both pursuing graduate studies. Twyla's field of science history is near and dear to my own interests, and she graciously allowed me to sit in on several lectures in the class for which she is a teaching assistant this semester, an undergraduate survey of science history from the French Revolution to the fall of the Soviet Union. The professor is Theodore Porter, an expert on the development of statistics and the social sciences in the 19th century. His approach is to understand the cultural, social and political contexts of science history.

I had been reading along with the syllabus since the beginning of the term and scheduled my visit to hear his lectures about science under National Socialism, both in life science (eugenics) and the physical sciences (the Nazi atomic project and V2 rocketry). Among the readings for the week was the play Copenhagen by Michael Frayn, in which a 1941 meeting between two physics greats, Neils Bohr and Werner Heisenberg, forms the central focus. (I had seen the play together with Stan, Helga, Walter and Joanne when it ran in San Francisco in 2002.)  Twyla and I spent a good deal of time during my visit discussing interpretations of the play.

I could go on at length on this subject, but the important thing is that my visit left me thinking about the resurrection of German physics after the war. On my return train trip through California's central valley, I recalled that a number of my father's physics colleagues were German. The field that he worked in, exploring the so-called Mössbauer effect, was named for Rudolph Mössbauer, a physicist from Munich who discovered a form of nuclear resonance in 1958 and won the Nobel Prize in 1961.

Taking advantage of Amtrak's on-board Wifi service, I googled to find out if Mössbauer had been the first postwar German Nobel recipient. He was not—Walter Bothe, a participant in the German Uranium Club that became the Nazi atomic bomb project, and the developer of Germany's first cyclotron, won it in 1954, awarded together with Max Born, a Jewish physicist who had fled Germany before the war. After that, Mössbauer was the first.

This rumination led to more searches of various scientists I remembered from Stan's days at Westinghouse (Pittsburgh), Soreq (Israel) and Argonne (Chicago). Mike Kalvius was one who had visited our family a number of times, and I remembered he was also from Munich. I discovered that earlier this year he had co-edited a volume of historical papers celebrating the 50th anniversary of the Mössbauer Nobel.

There are quite a few mentions of Stan in the The Rudolf Mössbauer Story, including in a chapter by Gopal Shenoy, another frequent guest in our home, where he credits Stan for the important suggestion that synchrotron radiation could be a useful replacement for nuclear sources in Mössbauer spectroscopy. That insight, delivered in a paper at the 1974 Mössbauer Conference in Paris, is thought to be Stan's most significant career accomplishment, since synchrotron sources were later shown to be practical and are now commonly used for Mössbauer studies in various fields. (We have previously posted a copy of Gopal's obituary of Stan in Hyperfine Interactions, in which wrote that "Stan will be best remembered for his proposal in 1974 to excite the 14.4 keV Mössbauer resonance in Fe57 using synchrotron radiation rather than a radioactive source to populate the nuclear excited state.")

As I was enjoying this trip down memory lane, I soon received a shock when I began to see references to earlier work by Stan that I had known nothing about. It involved an experiment he had performed at Brookhaven as a graduate student, and it seems something had gone wrong along the way. I'll explain more in the next post.

The excerpts were more than intriguing:

In 1953 Brice Rustad and Stanley Ruby carried out the most important of these angular correlation experiments on the β decay of He⁶. 

Although most of the evidence from β decay was consistent with a doublet VA [vector and axial] interaction, Rustad and Ruby's angular-correlation experiment on He⁶ provided seemingly conclusive evidence that the β decay was tensor (T).

Sudarshan and Marshak noted that four experiments stood in opposition to the V–A theory, as follows: (1) Rustad and Ruby's electron-neutrino angular-correlation experiments on  He⁶ ; (2) .... The first two cases were regarded as significant problems, whereas the second two had less evidential weight .... Sudarshan and Marshak suggested that "All of these experiments should be redone...."

Feynman and Gell-Mann went even further in regard to the experimental anomalies. "These theoretical arguments seem to the authors to be strong enough to suggest that the disagreement with the He⁶ recoil experiment and with some other less accurate experiments indicates that these experiments are wrong [emphasis added by Franklin.

Rustad and Ruby themselves, and [Chien-Shiung] Wu and Arthur Schwarzchild critically reexamined the Rustad-Ruby experiment.

Wu and Schwarzchild then constructed a scale model ten times larger than the Rustad-Ruby apparatus, making the inner walls of the source volume and collimating chimney highly reflecting.

They concluded, finally, that the corrected results "are more in favor of axial vector than tensor contradictory to the original conclusion." Their work thus cast doubt on Rustad and Ruby's original conclusion, and in a postdeadline paper that Rustad and Ruby presented at a meeting of the American Physical Society in January 1958, they agreed with that assessment.*

* There are no abstracts of postdeadline papers. Ruby remembers, however that the tone of their paper was mea culpa; private communication, 1989. 

Wow! I thought I knew a little bit about my father's career in physics but most of this information was coming as a complete surprise. Wu rang a bell. I remembered Stan, or maybe Helga, speaking of a kind of dragon lady Chinese physicist who Stan had worked with. (My earliest memories date to about 1957-8, when we were living in Pittsburgh and Stan was at Westinghouse Labs.) Feynman and Gell-Mann, of course, are both famous names and future Nobelists. Marshak sounded familiar too, but none of those in a way directly connected to Stan.

I was able to login to the UCLA proxy server on the train, and soon downloaded Franklin's paper as a pdf to my iPad. I ravenously read from the 30-page paper, starting with its intriguing opening opening line, "Are the laws of nature discovered or invented?" The introduction goes on to set up the scholarly distinction between social constructionists who believe that theory drives the scientific dialog and rationalists like Franklin to whom experiment is crucial.

To illustrate his argument, Franklin then devotes the rest of the paper recounting the 25-year history of theory and experiment leading to the acceptance of a unified theory of the weak nuclear force, from Enrico Fermi's first theoretical paper on beta decay in 1934 to the successful generalization in 1958 by two independent groups of a Unified Fermi Interaction with V–A coupling that was applicable to meson particle decays as well as beta decays.

Summarizing his argument, Franklin writes:

This history is not one of an unbroken string of successes, but rather one that includes incorrect experimental results, incorrect experiment-theory comparisons, and faulty theoretical analyses. Nevertheless, at the end of the story the proposal of the V–A theory will seem to be an almost inevitable outcome.

A regular comedy of errors, it seems. Then begins a fairly deep dive into nuclear physics as it was understood in the mid-1930s, shortly after the discovery of the neutron and the proposal of a more mysterious particle, the neutrino. I settle back for a challenging read for the next leg of the train trip through Merced, Fresno and Stockton. More in the next post.

Beta decay had been known and studied since Becquerel had discovered radioactivity in uranium in 1896. In 1934, still in Rome before emigrating to America, Fermi theorized that beta decay occurs when an atomic nucleus transitions from one element to another while simultaneously releasing a combination of electrons and neutrinos (or their antiparticles) as beta radiation. Others picked up on the idea and sought to improve on it. One group in particular modified the mathematics in order to better fit the existing experimental data. Their work met with wide acceptance but was later shown to be wrong. That's the first of Franklin's comedy of errors.

Another pair of famous names, George Gamow and Edward Teller, are next in the story, freshly emigrated to George Washington University from Russia and Hungary. They offer a more generalized version of the equations that allow for spin and angular momentum in the particle interactions. The mathematics to account these quantities becomes rather abstract, resulting in a set of five "couplings"—vector, scalar, tensor, axial vector and pseudoscalar—that can applied in combinations to describe nuclear interactions. The debate for the next dozen years or so becomes which combination of those couplings best describes the beta decay interaction.

For this first time through the material, I am going to keep it really simple and tell you that the scientific consensus by the end of the decade was that the correct solution must be some combination of scalar, tensor and pseudoscalar (S, T, P) or a combination of vector and axial vector (V, A). Meanwhile, a new experimental technique had been developed by various groups that allowed for measurement of nuclear spin and momentum. Such angular correlation experiments were designed to "calculate the angle between the direction of emission of the decay electron and that of the emitted neutrino," summarizes Franklin.

One of the researchers best known for experimental work on beta decay was the aforementioned C.S. Wu, who had come to the U.S. in 1936, studied under E.O. Lawrence at Berkeley, worked on uranium separation for the Manhattan Project, and was now a lecturer in the high-powered physics department at Columbia University, where Stan returned in 1946 to resume his war-interrupted studies.

In 1952, Stan and collaborator Brice Rustad are working in Wu's lab at Brookhaven Labs when they design an apparatus for an angular correlation experiment on an isotope of radioactive helium. Helium gas produced in a reactor is pumped into a semicylindrical volume while two detectors count the emitted particles and direction of nuclear recoil. Thus they can calculate electron-recoil angle for each event and plot a graph of angle to coincidence rate.

Franklin's Fig. 7 shows two graphs Rustad and Ruby published in their February 1955 report in Physical Review, showing the data fit to the predicted tensor values. Franklin summarizes Rustad-Ruby's conclusion: "The theoretical curves predicted on the basis of the various forms of the β-decay interaction clearly show that the tensor (T) interaction is favored."

Here I find myself wondering how it is that this first-time publication by a fairly green postgraduate achieved such attention to begin with. By now I have figured out how to log in to the journal database of the American Physical Society and can see a list of all papers by S.L. Ruby, including a list of papers to reference each of those papers. By navigating citations, you can get a pretty quick idea of how any historical paper impacted future work.

Rustad and Ruby published twice, first in a short report in February 1953 titled "Correlation between Electron and Recoil Nucleus in He6 Decay" and then in a full paper in February 1955 titled "Gamow-Teller Interaction in the Decay of He6." I see that the first has been cited 28 and the second 60 times, and that some of those citations are by names like Feynman, Goldhaber, Frauenfelder, Marshak, Wu—all names I am becoming familiar with.

So why does the experiment get such notice? Franklin doesn't say so here, but it must be because of its association with Madame Wu. Rustad had published with her previously, but this is Ruby's debut publication in the Physical Review. Also, Franklin implies that the result was easy to accept because it supported the prevailing theoretical supposition at the time.

Things changed in a hurry by the end of 1956. Research in particle interactions from cosmic radiation had identified a whole category of new middleweight particles, bigger than electrons but smaller than nucleons, called mesons—and there was a profusion of variants with names like pion, muon and others. It had turned out that mesons exhibited decay transitions very similar to radioactive beta decay, and theorists now sought to find a single explanation for both phenomena.

A particular puzzle for meson researchers at the time was whether two identified mesons, the so-called tau and theta, were two separate particles or two forms of the same particle. One way they seemed different was that they had opposite direction of spin and parity, referring to a long-held principle that spacial reflection (parity) is conserved in force interactions. It was said that nature does not prefer left- or right-handedness—you shouldn't be able to tell the difference if you are looking directly at an event or at it through a mirror.

Conservation of parity was well proven in electromagnetism and for the strong nuclear force. In 1956, two Chinese-American physicists, C.N. Yang from Princeton and T.D. Lee from Columbia, asked if it was possible that parity is not conserved in weak interactions? They examined the literature and found to their surprise that it had never been explicitly tested. They wrote a paper that pointed out the lack of proof and proposed several experiments that could settle the question.

At first, few theorists thought there could be anything to it. Richard Feynman bet $50 that parity would be upheld; Freeman Dyson remembers thinking, "This is interesting," but he didn't pay it anymore attention. Nor did many experimenters rush to do the test, except the redoubtable Madame Wu, Lee's Columbia colleague who cancels a long-planned visit to China to do the experiment as quickly as possible.

It is a complex apparatus that requires the cryogenic expertise of a lab at the National Bureau of Standards, where by December Wu and colleagues have demonstrated that beta electrons emitted from a single layer of aligned radioactive cobalt nuclei preferred a specific direction of emission relative to the nuclear spin. Thus, there was a preferred handedness. No, the law of conservation of parity does not hold in the case of beta decays.

This was big news and before it was announced a second group of Columbia physicists obtained an independent confirmation in a test of meson decays in a cyclotron. Columbia pulled out all the stops when it made the announcement of the two confirming experiments, getting a full page of coverage in the New York Times on Jan. 16, 1957. It was all anyone was talking about at the American Physical Society annual meeting a month later, and again at the important Rochester High-Energy Physics meeting in April. Yang and Lee walked off with the Nobel Prize in October, quite possibly the fastest recognition in Nobel history.

All of that is very exciting and you might expect Stan as a Columbia man to share in the good feelings. Except for one thing. To account for parity violation, Lee and Yang now proposed a new "two-component" theory of the neutrino that predicted a muon interaction that could not be S-T-P. It had to be V–A. Here's Franklin:

By the end of the summer of 1957 parity nonconservation had been conclusively demonstrated and there was strong experimental support for the two-component theory of the neutrino. That ... led to the conclusion that the weak interaction responsible for the decay of the muon had to be a doublet VA combination. Although most of the evidence for β decay was consistent with such a doublet VA interaction, Rustad and Ruby's angular-correlation experiment on He6 provided seeming conclusive evidence that the β-decay interaction was tensor (T). 

In January 1958, Physical Review published papers by Sudarshan and Marshak and by Feynman and Gell-Mann independently proposing a Universal Fermi Interaction with a combination of vector and axial vector (V–A) terms. Both papers directly cited the Rustad-Ruby paper as contradictory evidence that needed to be reconfirmed. Feynman and Gell-Mann went further and said the experiment was likely "wrong."

Franklin's next section is called "The Removal of Experimental Anomalies," and Rustad-Ruby is exhibit one. None other than C.S. Wu, with Arthur Schwarzchild, another Columbia physicist, undertake a "critical review" of the Rustad-Ruby experiment.

Franklin writes that Wu and Schwarzschild raised several questions concerning the apparatus design—a possible variation in the size of the source volume and not considering the effects of the angle of detection—that might have led to an incorrect result. They built a ten-times larger scale model of the apparatus to test the suggestion that the source volume of gas was effectively enlarged by the pressure of gas in the chimney below it. To get the picture, here is the original schematic from the 1953 paper.

Their [Wu and Schwarzchild's] work cast doubt on Rustad and Ruby's original conclusion, and in a postdeadline paper that Rustad and Ruby presented at a meeting of the American Physical Society in January 1958, they agreed with that assessment.*

The asterisk leads to a further comment that "There are no abstracts of postdeadline papers. Ruby remembers, however, that the tone of their paper was mea culpa; private communication, 1989."

I also check Franklin's citation for the Wu-Schwarzchild information and see that it was published in an internal Columbia University Report, April 1958 titled "A Critical Examination of the He6 Recoil Experiment of Rustad and Ruby." (It will sure be interesting to read that full report, I think to myself.)

Finally, Franklin wraps up the section by reporting that one other group at the University of Illinois redid the He6 experiment and concluded that the axial-vector interaction is dominant in beta decay. "One of the experimental anomalies for the V–A theory had been removed," writes Franklin. One more for his comedy of errors.

Whew, this post has gone on way too long. There is still much to come, but for now we end with the train heading through the Sacramento Delta and Allan Franklin restating his inevitability thesis.

The history of the development and articulation of the theory of β decay from its inception in 1934 to the proposal and acceptance of the V–A theory in the late 1950s is an example of what I mean by the inevitability of the laws of physics.... This was not a history of an unbroken string of successes.... Physicists can overcome errors.  

Would it have been possible for some physicist or physicists to propose an alternative explanation of β decay? Logically, of course, the answer is yes. But, as we have seen, theoretical principles and calculations and experimental results—Nature—introduced constraints, so that the development of the V–A theory of the weak interaction seems to have been almost inevitable. 

By the time my train arrived at Oakland's Jack London station well past midnight, late due to delayed bus connections in Bakersfield, the main outlines of the story of the reversed experiment had become clear. But a big question loomed: Should this new information change our understanding of Stan's reasons for leaving the nest at Brookhaven and Columbia, as he did sometime in 1953 or '54, to work for industrial labs at IBM and Westinghouse?

The next day I spoke to Walter and Joanne to compare notes on the chronology. I was born on Long Island December 12, 1952. Stan submitted his paper with Rustad on December 31. Stan and Helga moved to Vestal near Binghamton when Stan went to work for IBM after that, some time before Joanne was born there in October 1954. Walter reminded me that they then returned to Long Island for a time following that, living in Massapequa before making the move to Pittsburgh in 1957.

I recalled something about a big storm impacting the move to Vestal. Walter knew right away I was referring to Hurricane Hazel, a Category 4 storm that swept through the lower tier of New York State on October 15, 1954, four days after Joanne's birth on October 11. There were sustained winds of 72 mph in Binghamton.

Okay, but that doesn't get us closer to knowing when they moved to Binghamton, or to a bigger question, why. Was it closer to my birth date or Joanne's? Certainly they wouldn't have moved immediately prior to Joanne's birth, so they must have been settled in Vestal no later than, say, June of 1954, but it could have been any time after January 1953. Still some work to do here.

Nevertheless, I fairly quickly came to see that the timing of the move from Brookhaven could not have been related to possible problems with the experiment. Following Franklin's chronology, which I had confirmed by now by downloading all the relevant scientific papers, the Rustad-Ruby experiment is considered golden at least until 1956. The first suggestion that it might be problematic doesn't come until after the hubbub over parity violation in January 1957. Wu's critical re-examination is in April 1958.

Unless time and effect can run backwards, as relativistic physics allows, then there is no way that something that happens in 1957 and '58 can cause an event four years earlier. No, Stan decided to move on from his post-graduate position at Brookhaven and embark on his career at industrial laboratories for reasons other than a discredited experiment.

Very likely, the reason that we have always understood for the move still applies. With a wife and two sons, and another child on the way, he needed a real salary and future prospects more than he needed the prestige of working on fundamental physics in a world class lab. He was freshly minted grad ready to go out and make his own way in the world of applied physics.

That said, his relationship with Madame Wu bears more study. It is said she was a task-master. Possibly she was immune to dad's charm, and went hard on him. Walter's first email reaction to the revelations was to write, "Screw Wu," but I'm not ready to go there yet. For one thing, we don't yet have access to her critical reexamination, which is held privately at Columbia. Franklin's paper gives us the technical gist of it, but it would be helpful to see the full document to see what else can be gleaned from it.

That to-do goes on my list for pursuing the investigation.