Physics in Perspective最新文献

The concept of “fact” has a history. Over the past centuries, physicists have appropriated it in various ways. In this article, we compare Ernst Mach and Albert Einstein’s interpretations of the concept. Mach, like most nineteenth-century German physicists, contrasted fact and theory. He understood facts as real and complex combinations of natural events. Theories, in turn, only served to order and communicate facts efficiently. Einstein’s concept of fact was incompatible with Mach’s, since Einstein believed facts could be theoretical too, just as he ascribed mathematical theorizing a leading role in representing reality. For example, he used the concept of fact to refer to a generally valid result of experience. The differences we disclose between Mach and Einstein were symbolic for broader tensions in the German physics discipline. Furthermore, they underline the historically fluid character of the category of the fact, both within physics and beyond.

As the History of Science Society, which is based in America, holds its annual meeting in Utrecht, one of the key academic centers on the European continent, one may surmise that the field has returned home. Yet, this hardly reflects how today’s world of scholarship is constituted: in the historiography of science, “provincializing Europe” has become an important theme, while the field itself, as is the case across the world of academia, is centered around a predominantly American literature. At the same time, ever since historians of science emancipated themselves from the sciences a long time ago, they often have appeared, in the public eye, to question rather than to seek to bolster the authority of the sciences. How has this situation come about, and what does it tell us about the world we live in today? What insight is sought and what public benefit is gained by the historical study of science? As we try to answer these questions, we will follow a number of key mid-twentieth-century historians—Eduard Dijksterhuis, Thomas Kuhn, and Martin Klein—in their Atlantic crossings. Their answers to debates on the constitution of the early modern scientific revolution or the novelty of the work of Max Planck will illustrate how notions of “center” and “periphery” have shifted—and what that may tell us about being “in Europe” today.

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 generals how to do tactical and strategic this-and-that.” This article explores the history of this-and-that distinctions between tactical and strategic nuclear weapons in the early Cold War. The idea of tactical nuclear weapons was intertwined with the work of a small group of defense intellectuals on limited nuclear war who explicitly framed the idea of tactical nuclear weapons as “arbitrary” and “illogical,” but nonetheless crucial to the continued survival of the Free World, as they understood it. I follow several strains of this complex history to show how a subset of these theorists viewed the new category of tactical nuclear weapons as an antidote to declining civilization and the embodiment of an anti-rationalist and anti-empiricist way of making knowledge about the world.

Einstein’s life-long effort to develop a theory that unifies gravitation and electromagnetism was not a purely theoretical enterprise. The technical environment of a gyrocompass factory triggered his search for a novel connection between the rotation of an electrically uncharged body and its magnetic field. The dimensional equality of the electric unit charge and the mass of a body multiplied by the square root of the gravitational constant hinted at a nonsensical electric charge, to which he gave the name “ghost charge.” He felt that he found a fundamental unity of gravitating mass and electricity, a hitherto undiscovered law of nature. Two physicists offered to assist him in finding evidence of this peculiar electric charge. Peter Pringsheim performed experiments with deionized gases and Teodor Schlomka made measurements of the earth’s magnetic field from balloons and airplanes; Schlomka also executed a thorough literature search and placed Einstein’s efforts in their historical context.

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.