Physics in Perspective最新文献

The concept of constants of nature originated in the late-nineteenth century and has since then increasingly occupied the minds of physicists. But are the constants truly constant? Inspired by Paul Dirac’s suggestion that the gravitational constant varies slowly in time, the question was addressed not only by physicists but also by astronomers, geologists, and paleontologists. Pascual Jordan in Germany and Robert Dicke in the United States formulated theories of gravitation that went beyond general relativity by incorporating a varying gravitational constant. These theories had cosmological consequences and also implications for the earth sciences. During the period 1955–1975, theories of varying gravity played a significant role in the process that led to the plate-tectonics revolution. Although the theories turned out to be wrong, this chapter in the history of interdisciplinary science deserves attention. For one thing, it changed the landscape of both the cosmological and geological sciences. For another thing, the question of varying natural constants is still unsettled and the subject of scientific investigation. The article focuses on the period from about 1930–1975, but also includes some comments of a more general nature.

Recent historiographic results in Galilean studies disclose the use of proportions, graphical representation of the kinematic variables (distance, time, speed), and the medieval double distance rule in Galileo’s reasoning; these have been characterized as Galileo’s “tools for thinking.” We assess the import of these “tools” in Galileo’s reasoning leading to the laws of fall ((v^{2} propto D) and (v propto t)). To this effect, a reconstruction of folio 152r shows that Galileo built proportions involving distance, time, and speed in uniform motions, and applied to them the double distance rule to obtain uniformly accelerated motions; the folio indicates that he tried to fit proportions in a graph. Analogously, an argument in Two New Sciences to the effect that an earlier proof of the law of fall started from an incorrect hypothesis (v?∝?D) can be recast in the language of proportions, using only the proof that v?∝?t and the hypothesis.

Karl Przibram is one of the pioneers of early solid state physics in the field of the interdependence of coloration effects and luminescence in solids (crystals, minerals) induced by radiation. In 1921 Przibram discovered the effect of radio-photoluminescence, the light-stimulated phosphorescence in activated crystals induced by gamma rays. In 1926 Przibram was the first to use the term, Farbzentrum (color center, F-center), and in 1923 he advanced the view of atomic centers as carriers of coloration. Being a pupil of Ludwig Boltzmann and Franz S. Exner, he dedicated his early work to condensation and conductivity phenomena in gases and Brownian motion. Under the influence of Stefan Meyer, he began his lifelong interest in mineralogy, setting up his own research group at the Vienna Radium Institute, which pioneered investigations on thermoluminescence and gave a first description of glow curves. Being of Jewish descent, Przibram had to leave Austria after the Nazis took power; he found shelter in Belgium and returned to Austria in 1946 as professor for experimental physics at the University of Vienna. This paper is a first attempt to give an overview of the cultural and scientific background of Przibram’s life and science in context of the cultural and political developments from 1900 to 1950 in Austria.

Trained at University of Liverpool in both theoretical and experimental physics, William Band accepted in 1929 an appointment at Christian Yenching University in Beijing, China, where he established his career through the 1930s, heading the physics department and nurturing dozens of distinguished Chinese researchers in its MSc program. Despite the Japanese occupation of Beijing in summer 1937, Band continued his work at Yenching—an American property and an oasis of freedom for Chinese students in?North China. In the wake of Pearl Harbor, Band joined a breathtaking and successful escape from Yenching, just before the Japanese raid?reached the campus. He sought refuge in Communist guerrilla bases in North China, where he taught calculus, college physics, and radio theory to radio technicians?of guerrilla forces. After trekking one thousand miles through Japanese occupied areas, escorted by Communist?guerrillas, Band arrived first in Yan’an, the Chinese Communist headquarters, where he met and?conversed with?Mao Zedong and Zhou Enlai, and then?in Chongqing, China’s wartime capital, where he served in the Sino-British Science Cooperation Office to help war-ridden Chinese scientists until his departure for Britain in December 1944. Band’s adventure provides a unique and useful lens to explore uncharted aspects of science in Republican China.

This is the third in a three-part article describing the development of the experimental program at the Thomas Jefferson National Accelerator Facility, from the first dreams of incisive electromagnetic probes into the structure of the nucleus through the era in which equipment was designed and constructed and a program crafted so that the long-desired experiments could begin. These developments unfolded against the backdrop of the rise of the more bureaucratic New Big Science and the intellectual tumult that grew from increasing understanding and interest in quark-level physics. Part 3, presented here, focuses on the period from 1990 to through 1997. During this period of continued revolutionary change, laboratory personnel and would be users labored to proceed from the approved 1990 experimental equipment conceptual design report, the official blueprint for the project, to fully constructed, commissioned, operating equipment under the watchful eye of Department of Energy officials and expert reviewers. The article ends with an assessment of the actual experimental resources and results compared with the initial scientific desires that prompted the decades-long effort to bring the project to life.

Against the background of the current drive toward diversity in modern scientific communities, this paper explores how a scientific practice might become more diverse by the inclusion of peripheral members. To demonstrate how peripheral members gain contributory expertise in the sciences in the absence of mentors and a readymade community, I present a case study of the Indian physicist C. V. Raman and his early self-training in the analysis of wave phenomena, especially in musical acoustics. Evaluating Raman’s example, I suggest that such peripheral agents might give us helpful pointers about our modern project of bringing diversity into a scientific community.