20世纪的物理学巨匠——尼尔斯·玻尔

尼尔斯·玻尔(1885-1962)是20世纪著名的物理学家,年轻时就发表了影响深远的"三部曲".本文通过其重新诠释"弗兰克-赫兹"实验结果、创建哥本哈根研究所、与爱因斯坦论战、推动创立原子能机构等几个故事展示了这位物理学大师超群的智慧、高尚的人格、伟大的爱国精神以及为人类和平奉献的崇高精神.     

Paul Ehrenfest’s Rough Road to Leiden: A Physicist’s Search for a Position, 1904–1912

Paul Ehrenfest (1880–1933) received his Ph.D. degree at the University of Vienna in 1904 and moved with his wife and young daughter to St. Petersburg in 1907, where he remained until he succeeded Hendrik Antoon Lorentz (1853–1928) in the chair of theoretical physics at the University of Leiden in 1912. Drawing upon Ehrenfest’s correspondence of the period, we first examine Ehrenfest’s difficult and insecure years in St. Petersburg and then discuss his unsuccessful attempts to obtain a position elsewhere before he was appointed as Lorentz’s successor in Leiden. Pim Huijnen is writing a doctoral dissertation in history; the present paper is based upon his Master’s Thesis, “‘Die Grenze des Pathologischen’: Het leven van fysicus Paul Ehrenfest, 1904–1912,” University of Groningen, 2003. A.J.Kox is Pieter Zeeman Professor of History of Physics at the University of Amsterdam.     

Klein,Einstein, and Five-Dimensional Unification

I examine the changing attitudes of Oskar Klein (1894–1977) and Albert Einstein (1879–1955) toward the notion of extending general relativity by an extra dimension with the aim of encompassing electromagnetism and gravitation in a unified field theory. I show how Klein developed his model of five-dimensional unification with the goal of explaining the discreteness of atomic energy levels, and how Einstein later embraced that goal. By examining the correspondence between Klein and Einstein, some of which was relayed through Paul Ehrenfest (1880–1933), I speculate that Klein’s work helped motivate Einstein to explore deterministic five-dimensional theories as a potential alternative to probabilistic quantum mechanics. Finally, I consider the contributions of Wolfgang Pauli (1900–1958) to the subject and elucidate his role in convincing Klein and Einstein that their models were not viable. Paul Halpern is Professor of Physics at the University of the Sciences in Philadelphia. He currently is a member of the Executive Committee of the Forum on the History of Physics of the American Physical Society.     

Niels Bohr's discussions with Albert Einstein,Werner Heisenberg,and Erwin Schrödinger: The origins of the principles of uncertainty and complementarity

In this paper, the main outlines of the discussions between Niels Bohr with Albert Einstein, Werner Heisenberg, and Erwin Schrödinger during 1920–1927 are treated. From the formulation of quantum mechanics in 1925–1926 and wave mechanics in 1926, there emerged Born's statistical interpretation of the wave function in summer 1926, and on the basis of the quantum mechanical transformation theory—formulated in fall 1926 by Dirac, London, and Jordan—Heisenberg formulated the uncertainty principle in early 1927. At the Volta Conference in Como in September 1927 and at the fifth Solvay Conference in Brussels the following month, Bohr publicly enunciated his complementarity principle, which had been developing in his mind for several years. The Bohr-Einstein discussions about the consistency and completeness of qnautum mechanics and of physical theory as such—formally begun in October 1927 at the fifth Solvay Conference and carried on at the sixth Solvay Conference in October 1930—were continued during the next decades. All these aspects are briefly summarized.     

Quirino Majorana’s Experiments on the Speed of Light and Gravitational Absorption

Quirino Majorana (1871–1957) was an outstanding Italian experimental physicist who investigated a wide range of phenomena during his long career in Rome,Turin, and Bologna. We focus on his experiments in Turin during 1916–1921 and in Bologna during 1921–1934 to test the validity of Albert Einstein’s postulate on the constancy of the speed of light and to detect gravitational absorption. These experiments required extraordinary skill, patience, and dedication, and all of them confirmed Einstein’s postulate and Isaac Newton’s law of universal gravitation to high precision. Had they not done so, Majorana’s fame among historians and physicists no doubt would be much greater than it is today. Giorgio Dragoni is Professor of History of Physics at the University of Bologna. Giulio Maltese is a Roman member of the Italian Society for the History of Physics and Astronomy. Luisa Atti is a Bolognese member of the Association for the Teaching of Physics.     

Richard Gans: The First Quantum Physicist in Latin America

Richard Gans (1880–1954) was appointed Professor of Physics and Director of the Institute of Physics of the National University of La Plata,Argentina, in 1912 and published a series of papers on quantum physics between 1915 and 1918 that marked him as the first quantum physicist in Latin America. I set Gans’s work within the context of his education and career in Germany prior to 1912 and his life and work in Argentina until 1925, as well as the foundation of the Institute of Physics of the National University of La Plata in 1906–1909 and its subsequent development by Emil Bose (1874–1911). I conclude by commenting on Gans’s life after he returned to Germany in 1925 and then immigrated once again to Argentina in 1947.     

Fritz Reiche and the Emergency Committee in Aid of Displaced Foreign Scholars

I discuss the family background and early life of the German theoretical physicist Fritz Reiche (1883–1969) in Berlin; his higher education at the University of Berlin under Max Planck (1858–1947); his subsequent work at the University of Breslau with Otto Lummer (1860–1925); his return to Berlin in 1911, where he completed his Habilitation thesis in 1913, married Bertha Ochs the following year, became a friend of Albert Einstein (1879–1955), and worked during and immediately after the Great War. In 1921 he was appointed as ordentlicher Professor of Theoretical Physics at the University of Breslau and worked there until he was dismissed in 1933. He spent the academic year 1934–1935 as a visiting professor at the German University in Prague and then returned to Berlin, where he remained until, with the crucial help of his friend Rudolf Ladenburg (1882–1952) and vital assistance of the Emergency Committee in Aid of Displaced Foreign Scholars, he, his wife Bertha, and their daughter Eve were able to emigrate to the United States in 1941 (their son Hans had already emigrated to England in 1939).From 1941–1946 he held appointments at the New School for Social Research in New York, the City College of New York, and Union College in Schenectady, New York, and then was appointed as an Adjunct Professor of Physics at New York University, where his contract was renewed year-by-year until his retirement in 1958.     

Heike Kamerlingh Onnes and the Nobel Prize in Physics for 1913: The Highest Honor for the Lowest Temperatures

One century ago this year the Dutch experimental physicist Heike Kamerlingh Onnes (1853–1926) was awarded the Nobel Prize in Physics for his work in low-temperature physics, in particular for his production of liquid helium. I trace the route to his Nobel Prize within the context of his and his colleagues’ research in his laboratory at the University of Leiden, and in light of his nominators and the nominations he received in the five years 1909–1913.     

Science, Technology, and the Niels Bohr Institute in Occupied Denmark

I argue that research in the basic sciences during the German occupation of Denmark, which began on April 9, 1940, suffered considerably, while research and development in technology enjoyed improved conditions as Danish industry moved toward the requirements of the German wartime economy. Several organizations were created to further Danish–German scientific and cultural collaboration or to manifest Danish cultural identity. The staff of the Danish Technical College and the number of their publications remained largely constant although no papers appeared in British or American journals after 1941. Danish universities massively resisted collaboration and maintained an illusion of “business as usual.” At the Niels Bohr Institute, laboratory equipment continued to be constructed and developed and scientists continued to publish in Danish and other Scandinavian journals, although they were increasingly isolated owing to their inability to obtain foreign scientific journals and to correspond with foreign scientists. The Niels Bohr Institute was occupied from December 6, 1943, to February 3, 1944, a surprisingly short period, owing, I argue, to strategic compromises in following incompatible orders from the German army, security police, and civilian administration. Finally, I offer an interpretation of Niels Bohr’s vehemently negative reaction to Werner Heisenberg in their meeting in Copenhagen in September 1941.     

Duality in physical sciences and beyond

An extended meaning of duality is suggested in the context of development of major themes in physical sciences since Newton. In such a generalization,five distinct aspects of duality are sought to be identified and illustrated through concrete examples drawn from various physical concepts, old and new. These are (i) reciprocity, (ii) parallelism, (iii) alternative formulation, (iv) unification and (v) measurement incompatibility. Bohr’s view of duality and the Copenhagen Interpretation are discussed briefly in this context. Finally, duality aspects beyond physics are briefly touched upon, the philosophical link being provided by Bohr’s Complementarity Principle on the one hand, and recent attempts (notably by Capra) to draw suggestive parallels between modern science and Eastern mysticism on the other. “Be in truth eternal, beyond earthly opposites”—Bhagwat Gita. The author felicitates Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion.     

Martin J. Klein: From Physicist to Historian

To his friends, colleagues, and students, Martin Klein was a gentle and modest man of extraordinary integrity whose stellar accomplishments garnered him many honors. I sketch his life and career, in which he transformed himself from a theoretical physicist at Columbia University, the Massachusetts Institute of Technology, and the Case Institute of Technology into a historian of physics while on leave at the Dublin Institute for Advanced Study and the University of Leiden and then pursued this field full time at Yale University.     

Dick Crane��s California Days

Horace Richard Crane (1907–2007) was born and educated in California. His childhood was full of activities that helped him become an outstanding experimental physicist. As a graduate student at the California Institute of Technology (1930–1934), he had the good fortune to work with Charles C. Lauritsen (1892–1968) just as he introduced accelerator-based nuclear physics to Caltech. They shared the euphoric excitement of opening up a new field with simple, ingenious apparatus and experiments. This work prepared Crane for his career at the University of Michigan (1935–1973) where in the 1950s, after making the first measurement of the electron’s magnetic moment, he devised the g−2 technique and made the first measurement of the anomaly in the electron’s magnetic moment. A man of direct, almost laconic style, he made lasting contributions to the exposition of physics to the general public and to its teaching in high schools, community colleges, four-year colleges, and universities. I tell how he became a physicist and describe some of his early achievements.     

“It’s better to forget physics”: The Idea of the Tactical Nuclear Weapon in the Early Cold War

Physics in Perspective - The American physicist John Wheeler once told his colleague Richard Feynman that, in case of war, “it’s better to forget physics and tell the admirals and...     

Nordström,Ehrenfest, and the Role of Dimensionality in Physics

In the summer of 1916, Finnish physicist Gunnar Nordström (1881–1923) arrived in Leiden to carry out research with Paul Ehrenfest (1880–1933), Hendrik A. Lorentzs successor in the chair of theoretical physics. Nordström had recently published the first five-dimensional unified model of the universe, a theory that went virtually unnoticed by the physics community. Ehrenfests personal journals reveal that Nordströms visit coincided with a flowering of Ehrenfests own interest in dimensionality, which resulted in his well-known paper on the connection between the fundamental laws of physics and the three-dimensionality of space. I examine Nordströms and Ehrenfests collaboration and explore the relationship between their ideas and the Kaluza-Klein model of five-dimensional unification.Paul Halpern is Professor of Physics at the University of the Sciences in Philadelphia. He received a Guggenheim Fellowship in 2002 to study the history of dimensionality in science.     

Resisting the Bohr Atom: The Early British Opposition

When Niels Bohr’s theory of atomic structure appeared in the summer and fall of 1913, it quickly attracted attention among British physicists. While some of the attention was supportive, others was critical. I consider the opposition to Bohr’s theory from 1913 to about 1915, including attempts to construct atomic theories on a classical basis as alternatives to Bohr’s. I give particular attention to the astrophysicist John W. Nicholson, who was Bohr’s most formidable and persistent opponent in the early years. Although in the long run Nicholson’s objections were inconsequential, for a short period of time his atomic theory was considered to be a serious rival to Bohr’s. Moreover, Nicholson’s theory is of interest in its own right.     

Mistaken Identity and Mirror Images: Albert and Carl Einstein, Leiden and Berlin, Relativity and Revolution

Albert Einstein accepted a ??special?? visiting professorship at the University of Leiden in the Netherlands in February 1920. Although his appointment should have been a mere formality, it took until October of that year before Einstein could occupy his special chair. Why the delay? The explanation involves a case of mistaken identity with Carl Einstein, Dadaist art, and a particular Dutch fear of revolutions. But what revolutions was one afraid of? The story of Einstein??s Leiden chair throws new light on the reception of relativity and its creator in the Netherlands and in Germany.     

Objective Quantum Fields,Retrocausality and Ontology

We compare different approaches to quantum ontology. In particular, we discuss an interpretation of quantum mechanics that we call objective quantum field theory (OQFT), which involves retrocausal fields. Here, objective implies the existence of fields independent of an observer, but not that the results of conjugate measurements are predetermined: the theory is contextual. The ideas and analyses of Einstein and Bohr through to more recent approaches to objective realism are discussed. We briefly describe measurement induced projections, the guided wave interpretation, many-universes, consistent histories and modal theories. These earlier interpretations are compared with OQFT. We argue that this approach is compatible both with Bohr’s quantum complementarity and Einstein’s objective realism.     

Causal stochastic interpretation of quantum statistics

The differences between Einstein and Bohr on the interpretation of quantum mechanics revolved around the question of completeness of the Copenhagen Interpretation. This fundamental problem is examined here in the light of recent neutron interference experiments which allow for novel experimental situations. Exploiting the possibility of neutron spin flip in these experiments, the inadequacy of the Copenhagen interpretation to fully understand the experimental results is brought out. Instead a causal interpretation of quantum mechanics is advocated, in which the neutron, as a particle, does always have a definite space time trajectory but also involves a wave which creates a potential affecting the particle neutron. The reestablishment of definite particle trajectories in the microscopic domain obliges us to reexamine the statistical treatment of ‘identical’ particles, as well as the problem of negative energies and probabilities in relativistic quantum mechanics.     

Quantum Humor: The Playful Side of Physics at Bohr’s Institute for Theoretical Physics

From the 1930s to the 1950s, a period of pivotal developments in quantum, nuclear, and particle physics, physicists at Niels Bohr??s Institute for Theoretical Physics in Copenhagen took time off from their research to write humorous articles, letters, and other works. Best known is the Blegdamsvej Faust, performed in April 1932 at the close of one of the Institute??s annual conferences. I also focus on the Journal of Jocular Physics, a humorous tribute to Bohr published on the occasions of his 50^th, 60^th, and 70^th birthdays in 1935, 1945, and 1955. Contributors included Léon Rosenfeld, Victor Weisskopf, George Gamow, Oskar Klein, and Hendrik Casimir. I examine their contributions along with letters and other writings to show that they offer a window into some issues in physics at the time, such as the interpretation of complementarity and the nature of the neutrino, as well as the politics of the period.