Roger H. Stuewer

The Nuclear Electron Hypothesis

James Chadwick’s discovery of the neutron in 1932 is justifiably viewed as a watershed in the history of nuclear physics.1 It opened the way to all modern neutron-proton theories of nuclear structure and (so the story goes) simultaneously expelled the electron from the nucleus where it had become, through its increasingly contrary behavior, an embarrassing guest — part of a problem not to be thought about, like the new taxes, as Peter Debye put it in 1930.2 Chadwick’s discovery reintroduced order and simplicity into nuclear theory.

Gamow’s Theory of Alpha-Decay

George Gamow burst upon the European community of physicists like a meteor from outer space. The origin of his trajectory was distant Leningrad; his point of impact was Gottingen;. The time was mid-June 1928. The impression Gamow made has been recorded by Leon Rosenfeld. “I shall never forget,” Rosenfeld recalled, “the first time he appeared in Gottingen — how could anyone who has ever met Gamow forget his first meeting with him — a Slav giant, fair haired and speaking a very picturesque German; in fact he was picturesque in everything, even in his physics.”1 Gamow had learned German from a private tutor as a youth in Odessa with the result, he later recalled, that “I’m terribly poor inder,die,das, and my grammar is horrible, but pronunciation good.”2

Bringing the News of Fission to America

In January 1939 the news of the discovery of nuclear fission burst in America, sending physicists into their laboratories to try to confirm the startling new discovery. Some aspects of the story of how this news reached America are well known. Others, however, are not; they have remained hidden in private correspondence and other unpublished documents. By examining these materials in conjunction with the published literature, one can reconstruct the circumstances that converged to produce this historic event.

History and Physics

This paper argues that research and teaching in physics and in the history of physics are complementary in nature, and it explores some of the implications of this point of view.

The Seventh Solvay Conference: Nuclear Physics at the Crossroads

The seventh Solvay Conference, held at the Free University of Brussels from October 22–29, 1933,1 occupies a place in the history of nuclear physics similar to the one that the first Solvay Conference, held twenty- two years earlier in the Hotel Metropole in Brussels, occupies in the history of quantum physics. Both were the first to be devoted to their respective areas of physics; both were held soon after fundamental discoveries had opened up and transformed their fields; and both served to consolidate knowledge that had been gained and to expose problems that awaited solutions. Martin J. Klein has discussed the first Solvay Conference in his writings.2 In this paper, I shall examine the seventh Solvay Conference, using it as a vantage point from which to view the social and political currents and the theoretical and experimental developments that were buffeting and transforming nuclear physics in the fall of 1933.

The naming of the deuteron

The naming of the deuteron involved a protracted debate between 1933 and 1935. The principal protagonists were Harold C. Urey, Gilbert N. Lewis, Ernest O. Lawrence, and Ernest Rutherford, but others on both sides of the Atlantic entered the fray as well. This paper examines the arguments and issues that emerged in the debate, and the process by which agreement was finally achieved on the name for this new particle.

A Critical Analysis of Newton's Work on Diffraction

CONTEMPORARY PHYSICISTS, accustomed to associating Isaac Newtons name with a corpuscular theory of light, are usually surprised to discover the large number of wave concepts in Newtons optical writings. Some have consequently regarded Newtons work as a remarkable anticipation of the wave-particle duality of our century.1 Usually at this point the historian of physics intercedes, maintaining that Newtons thoughts were directed only toward the understanding of the facts available to him, which his particular wave-particle model correlated rather nicely.2 If Newton ultimately preferred particles to waves, it was largely because he was unaware of important experimental facts. The most important of these facts was that light does not always propagate rectilinearly. Newton-it is often stated-was convinced that light, unlike sound or water waves, never spreads into the geometric shadow of an obstacle placed in its path; had Newton been aware of evidence to the contrary, he would have placed a good deal less confidence in his corpuscular theory.3 Ironically, it seems that no one is to blame more than Newton himself for failing to find this evidence, because he himself missed a crucial observation: the existence of interference fringes inside the shadow of a long, narrow obstacle like a mans hair. Important historical questions therefore hinge on Newtons work on diffraction. What, precisely, is meant by the claim that Newton missed the observation of the interior interference fringes? Is it probable that Newton would have embraced the wave theory if he had observed these fringes ? In an attempt to answer these questions, I shall first examine the most important of Newtons writings on diffraction; secondly, I shall analyze Newtons diffraction experiments; and finally, I shall attempt to determine the influence of these experiments on Newtons views on the nature of light.

The Compton effect: Transition to quantum mechanics

The discovery of the Compton effect at the end of 1922 was a decisive event in the transition to the new quantum mechanics of 1925-1926 because it stimulated physicists to examine anew the fundamental problem of the interaction between radiation and matter. I first discuss Albert Einsteins light-quantum hypothesis of 1905 and why physicists greeted it with extreme skepticism, despite Robert A. Millikans confirmation of Einsteins equation of the photoelectric effect in 1915. I then follow in some detail the experimental and theoretical research program that Arthur Holly Compton pursued between 1916 and 1922 at the University of Minnesota, the Westinghouse Lamp Company, the Cavendish Laboratory, and Washington University that culminated in his discovery of the Compton effect. Surprisingly, Compton was not influenced directly by Einsteins light-quantum hypothesis, in contrast to Peter Debye and H.A. Kramers, who discovered the quantum theory of scattering independently. I close by discussing the most significant response to that discovery, the Bohr-Kramers-Slater theory of 1924, its experimental refutation, and its influence on the emerging new quantum mechanics.

On Compton’s Research Program

When Imre Lakatos sent me a copy of his and Alan Musgrave’s Criticism and the Growth of Knowledge,1 he inscribed it with the words: “With hopes for future cooperation and best wishes.” That future cooperation, to my very deep regret, never occurred owing to Imre’s sudden and premature death in February 1974. I know, however, what he had in mind. He wanted me to join with him in analyzing certain case studies in the history of physics in light of his methodology of scientific research programs. Furthermore, I know that one of the case studies Imre wanted to treat was my own on the discovery of the Compton effect, since I can vividly recall our discussing an early draft of my book, The Compton Effect: Turning Point in Physics,2 after dinner at our home in Minneapolis in the fall of 1970. Now, however, collaboration is impossible. I therefore propose to simply summarize some of the highlights of Compton’s research program here, and to invite others to consider its possible relevancy to Imre’s methodology, or to philosophical-methodological questions in general. It goes without saying that if such connections seem to exist, my detailed study must be consulted to substantiate their existence, since my present discussion constitutes only a very rough and incomplete sketch of certain sections of my book.

The Seventh Solvay Conference: Nuclear Physics, Intellectual Migration, and Institutional Influence

I discuss the founding of the Solvay Conferences in Physics by Ernest Solvay in Brussels in 1911 and then turn to the seventh Solvay Conference in October 1933. I show how it lay at the crossroads in the history of experimental and theoretical nuclear physics when new experimental techniques and instruments were being developed and new theoretical ideas and concepts were being generated, all of which were diffused to physicists in many countries of the world, some of whom were part of the greatest intellectual migration in the twentieth century, if not in history. I conclude by indicating the great influence that the Solvay Conferences exerted as a model for other conferences in physics and in the history and philosophy of physics.