Physics in Perspective最新文献

The occupation of the Niels Bohr Institute by German authorities in war-time Denmark has hitherto not been described or analyzed in detail, leaving a number of questions open, such as the background and purpose of the occupation, the lack of planning of the operation, formation, mandate and actual work of the “Expert Commission,” and the justification of release without conditions. These questions are addressed and answers suggested compatible with all relevant facts available.

This paper is the first investigation of the events associated with the discovery of the antiproton. The 1955 observation of the antiproton by Owen Chamberlain, Emilio Segrè, Clyde Wiegand, and Thomas Ypsilantis was “no surprise,” in Chamberlain’s words, and might therefore be understood as a classic example of an experimental proof of an existing theory—except there was no complete theory—at best it was a further validation of Dirac’s 1930 prediction of antiparticles. Instead, I argue, it became a contest between the serendipitous observations of cosmic-ray events and the deliberate observation possible with the new accelerator-based experiments. I show that the discovery was an extended event and was seen by the physicists involved as emerging from a combination of supporting experiments—the counter-based detection of antiprotons was accepted as proof of discovery only with the supporting images of antiproton annihilations.

The introductory physics course taught in American College and Universities in the twenty-first century is a descendent of the natural philosophy—later, physics—course that developed in these institutions in the nineteenth century. In the present paper, I discuss the backgrounds of a number of prominent professors of natural philosophy who taught these courses. These came, variously from experience as high-school teachers, engineers, and clergymen. Few of them planned to become faculty members, as contrasted to today’s professors who have rigorous educational and research training to prepare themselves for their task.

This paper explores the mechanical models elaborated by projectile theorists throughout the eighteenth century to explain the reflection of light. Influenced by Isaac Newton’s Opticks, these projectile theorists proposed that repulsion was the cause of reflection. My purpose is to show that their models were not unified and lacked a deeper understanding of the origin of repulsive powers. This analysis illustrates how a simple optical phenomenon was not easy for eighteenth-century theorists to explain, even when the projectile theory of light was prominent among natural philosophers.

Mindful of a stated Project 2061 goal of the American Association for the Advancement of Science, emphasizing that “scientific literacy includes seeing the scientific endeavor in the light of cultural and intellectual history,” and in the continuing spirit of narrowing the gap between the “two cultures” by enhancing STEAM awareness and education, this essay illustrates, quite literally through well-known works of Western art, the striking parallels between fundamental themes in physics and the visual arts through history. These connections include: the identification of microcosm–macrocosm analogies in prehistoric proto-science; the beginning of the appreciation in pre-classical antiquity of the lawfulness of nature under the aegis of a Divine Lawgiver; the rise of rationalism and the first theories of the architecture of matter during the so-called “Greek miracle”; the overlapping role of theology’s “handmaiden” during the emblematic medieval Age of Faith; Renaissance renovations and the triumph of the “mechanical universe” as the capstone of the scientific revolution in the early modern period; the influence on physics of the Romantic notion of an underlying unity in all of nature, and the increasing abstraction in both art and physics during the nineteenth century; and, finally, the parallels between twentieth-century art and the physics of relativity and quantum theory, concluding with examples from modern cosmology.

We consider the proposal by many scholars and by the International Astronomical Union to rename Hubble’s law as the Hubble-Lema?tre law. We find the renaming questionable on historic, scientific, and philosophical grounds. From a historical perspective, we argue that the renaming presents an anachronistic interpretation of a law originally understood as an empirical relation between two observables. From a scientific perspective, we argue that the renaming conflates the redshift/distance relation of the spiral nebulae with a universal law of cosmic expansion derived from the general theory of relativity. We note that the first of these phenomena is merely one manifestation of the second, an important distinction that might be relevant to contemporary puzzles concerning the current rate of cosmic expansion. From a philosophical perspective, we note that many of the named laws of science are empirical relations between observables, limited in range, rather than laws of universal application derived from theory.

I re-examine the raw data of the measurements of the half-life of ²¹⁰Po from the Romanian physicist ?tefania M?r?cineanu’s doctoral thesis, performed at the Institut du Radium, 1921–1923, under the supervision of Marie Curie. The half-life values reported in the thesis show relatively large divergences and a possible dependence on the (metallic) support on which the Po source was deposited. These findings influenced M?r?cineanu’s subsequent independent research, and later compelled her to claim priority for the discovery of artificial radioactivity. The present analysis of these data, performed with the least-squares method, certifies the outstanding accuracy of the experimental measurements by providing values with good agreement between the different series of measurements and an average value that is close to the currently adopted half-life value of this isotope. On the other hand, this analysis changes our perspective by showing that the rudimentary procedure M?r?cineanu used to processing the data introduced errors in her reported values, which favored a poor interpretation of the results.