REPORTS
New Studies of Isaac Newton's Work: APS Meeting in San Jose
An invited session sponsored by the Forum on New Studies of Isaac Newton's Work was held on March 20, 1995, at the APS meeting in San Jose, California.
Alan Shapiro, University of Minnesota, presented a paper entitled, "Artists' Colors and Newton's Colors." He demonstrated that placing Newton's theory of color in the context of the artists' tradition helps to explain why it took until the mid-19th century to develop the distinction between the additive mixing of light and the subtractive mixing of pigments. During the Renaissance, artists rejected the Aristotelian idea that a mixture of white and black, or light and darkness, could generate chromatic colors. Color mixing became a common practice, culminating in the discovery of the three painters' primaries in the early 17th century: red, yellow, and blue. Newton's discovery that sunlight is not simple and pure but a mixture of spectral colors revealed new physical properties of sunlight. But he and his contemporaries also understood his theory to be one about color mixing. That theory took its start from the artists' rejection of black and white as chromatic colors, and in turn it supported the artists' position by further distinguishing them from the chromatic colors. Newton also attempted to bring the painters' three primaries into agreement with the infinite number of "primary" colors that he discovered in sunlight. His synthesis of the two fundamentally different concepts of primary color affected the reception and understanding of his theory in the 18th century.
Subrahmanyan Chandrasekhar*, University of Chicago, spoke about, "Some Propositions of Newton's Principia," based on a book he is completing. Working through all of Newton's propositions in detail has, according to Chandrasekhar, provided him with substantial insight into how Newton thought and worked.: "For me, reading the Principia is like discovering a whole array of gems. The fact that he [Newton] existed is something that I just don't understand."
Michael Nauenberg, University of California, Santa Cruz, who organized the session, presented a paper entitled, "Newton's Early Computational Method for Dynamics." He began by observing that despite considerable historical research, very little is known about how Newton developed the mathematical theory of orbital dynamics which culminated in the Principia. A letter from Newton to Hooke, written on Dec. 13, 1679, reveals that Newton had made considerable more progress in understanding central force motion than had been previously realized. In particular a careful analysis of the original diagram which appears in this letter reveals that by then Newton understood by the fundamental symmetries of orbital motion for central forces. Moreover, the text of the letter indicates that he had developed a computational method to evaluate orbital motion for arbitrary central forces. Nauenberg went on to show that the early mathematical method Newton used to solve orbital motion for general central forces in his letter to Hooke was based on the calculus of curvature which he developed in the late 1660's. In correspondence with Newton in late 1679, Hooke suggested an alternative physical approach to which Newton gave a mathematical formulation without acknowledging Hooke (later in 1686 he wrote to Halley emphatically denying that Hooke had made any important contributions). This approach led Newton immediately to the discovery of the physical basis of Kepler's area law, which remained hidden in his earlier curvature method. The new approach is described in Proposition I, Theorem I of the Principia, and constitutes the cornerstone for the geometric methods in the book.
*Professor Chandrasekhar, who shared the 1983 Nobel Prize in Physics with William Fowler, died in Chicago on August 21, 1995, following a heart attack. Chandrasekhar, who was 84 at the time of his death, was a nephew of C.V. Raman, the 1931 Nobel Laureate in Physics.
The Centennial of X-Rays: A Celebration.: APS Meeting in Washington
The session was organized and chaired by Elizabeth Garber of the State University of New York at Stony Brook. In her introductory remarks, she noted that the 1890s marked a turning point in the history of modern physics. Within five years new phenomena were uncovered that could not be encompassed within the available principles governing explanations of physical phenomena. Radioactivity (1896), x-rays (1895) and the electron (1897) mark the importance of experiment for the development of modern physics. X-rays are now essential tools in industry, medicine and the sciences and it is fitting that we examine their disclosure the early history, and impact on physics and other sciences.
Spencer Weart cast new light on "Wilhelm Conrad Roentgen" and his work on x-rays. Rather than being a plodding experimentalist whose only significant work was in 1895 Roentgen emerged as a meticulous "measurement physicist" whose career built steadily--not an insignificant achievement given the conditions in German academia in the late nineteenth century. He trained under August Kundt, and worked on specific heats and other phenomena that seemed to offer insights into the structure of matter through the careful measurement of the physical properties of specific heats of gases, elasticity and heat conduction in solids. His work on cathode rays was a continuation of this search for probes to the structure of matter. Roentgen also had some near misses in the discovery of important phenomena, notably the Kerr effect. He was primed and sensitive to any unusual occurrences in his laboratory work. His exploration of the existence and properties of x-rays was thorough and systematic. While they may have been produced by others before him, Roentgen investigated the established their fundamental properties.
While the impact of x-rays on medicine are taken as very significant Albert Wattenberg, "Physics Experiments with X-Rays, 1895--1913," detailed some of the experiments that were done with and on x-rays in the twenty years after their discovery. Some of the earliest were done by Henri Becquerel who began to examine the fluorescent crystals he was working on for x-ray emissions. This led, in 1896, to his discovery of radioactivity in uranium salts. It did not decide the nature of x-rays themselves. One of the major impediments to the close examination of the properties of x-rays was the lack of an efficient and effective vacuum pump. The mercury pumps available in the 1890s were a "disaster" and it took four days to obtain a decent vacuum. Better equipment allowed Charles Barkla in 1912 to establish the electromagnetic nature of x-rays. Barkla had already used x-rays to establish some fundamental atomic properties of the chemical elements. Also in 1915 William Duane and F. L. Hunt used x-rays to measure Planck's constant. However, this measurement, using a method the reverse of the photoelectric effect confused the issue of the nature of x-rays further.
In the years immediately following the discovery of x-rays theories about their nature multiplied. Nahum Kipnis, "Early Theories of X-Rays," demonstrated that early attempts to understand x-rays were a continuation of theories about the ether that originated in the early nineteenth century. The early theorists assumed x-rays were some kind of wave motion in the ether. Roentgen favored the idea that they were longitudinal ether waves, a idea shared by Lord Kelvin and George Francis FitzGerald. However, x-rays did not behave as other electromagnetic waves. They did not reflect or refract as other electromagnetic waves, nor were they polarizable. George Gabriel Stokes saw them as non-periodic transverse electromagnetic waves. J. J. Thomson viewed them as pulses of electromagnetic radiation. None of these theories was wholly convincing and adherence seems to follow national boundaries rather than significant physical arguments for one theory rather than any other. While x-rays were accepted as electromagnetic waves their precise nature was left unresolved and some experimental results suggested that they were wave packets, rather than continuous trains of wave motions.
While some physicists argued over the nature of x-rays and others tried to uncover experimentally their precise nature, physicians exploited their medical potential revealed in Roentgen's first paper with the x-ray of his wife's hand. J. S. Laughlin, "Development of X-Rays, Electrons, and Other Radiations for Treatment and Diagnosis," explored some of the aspects of this early research done by physicists rather than physicians and sketched the broadening role of x-rays especially as a diagnostic medical tool. Physicists investigated the dosages and the intensities necessary for seeing bone versus soft tissue and other medical uses. It was not until the development of the Coolidge tube that standards were established for radiology. Van der Graff developed his high voltage generator for both physical research and for use in radiotherapy for the treatment of tumors in the 1930s. The use of x-rays particularly as diagnostic tools and in metabolic studies especially of the brain have expanded their medical usefulness.
Radioactivity and Health: The Cold War Legacy APS Meeting in Washington
An invited session on, Radioactivity and Health: The Cold War Legacy, co-sponsored by the Forum on History of Physics and the Forum on Physics and Society, was held at the APS meeting in Washington, DC, on April 18, 1995. The following summary of the session is excerpted from the texts of the presentations reproduced in the July 1995 Newsletter of the Forum on Physics and Society. The Newsletter is available on-line via the American Physical Society's Forum home page (../forums.cfm)
Lois Joellenbeck of the Office of Technology Assessment presided at the session. In her introduction she suggested that:
- Traditionally, wars have driven technology development. They have also provided motivation and means for major research efforts and innovation. The result of one of the most famous U.S. wartime research efforts, the Manhattan Project, was a powerful weapon that led to both an intensification of old societal challenges and a host of new ones. . . During the Cold War, the novelty and limited understanding of radioactivity and its health effects provided another challenge to decision-making about radiation and its uses in research and industry. The effects of the Cold War have a long half-life. The three presentations at the session illustrate how, in the 1990's, scientists and society at large must still strive to address and learn from past problems. The questions raised are big ones, bigger than the topic of radioactivity alone, and not readily answered.
Mark Goodman, a research analyst with the Advisory Committee on Human Radiation Experiments, presented a paper entitled, "Human Radiation Experiments." He addressed some of the difficult ethical issues raised by human experimentation. Even under ideal circumstances, experiments carried out on human beings require vigilant attention to ethical issues. In the special circumstances of the Cold War, secrecy and the concern for national security provided additional potential for compromising the rights of study participants. "Scientific and technical training alone do not equip investigators with the tools to handle these questions, and under conditions of secrecy there is little opportunity to consider other perspectives."
Barton Hacker, Lawrence Livermore Laboratory, presented a paper entitled, "Setting Radiation Protection Standards: Science, Politics, and Public Attitudes in Historical Perspective." He considered the continuing scientific discussions about the health effects of low-level doses of radiation, the role of this controversy in setting radiation protection standards, and the evolution of public concern about radiation health effects. "Science is a process; increased understanding in a discipline requires open dialogue between researchers about the interpretation of data. This can prove frustrating to a public seeking unequivocal answers about issues of health and safety."
Marvin Goldman, University of California, Davis, and Health Physics Society, presented a paper entitled, "Radiation Lessons from Russia." Cold War research, development, and production of nuclear weapons has had a significant legacy in the former Soviet Union. Best known are the considerable releases of radionuclides from the Mayak weapons production site near Chelyabinsk in the Southern Ural Mountains. Data have also become available about high exposures to workers at this site. Goldman reviewed the findings to date from studies of health effects from both the environmental and occupational exposures in Russia, considering them in the context of other findings about health effects of radiation.
The Emergence of Modern Physics
An international conference on The Emergence of Modern Physics was held in Berlin, Germany, March 22-24, 1995, organized by Fabio Bevilacqua (University of Pavia), Dieter Hoffmann (University of Berlin), and Roger Stuewer (University of Minnesota). The event was held in conjunction with the 15th Anniversary Meeting of the Deutsche Physikalische Gesellschaft, and was co-sponsored by the Commission on the History of Modern Physics of the Division of History of Science of the International Union of History and Philosophy of Science, the Interdivisional Group on the History of Physics of the European Physical Society, and the Fachverbandes Geschichte der Physik of the Deutsche Physikalische Gesellschaft. Papers were delivered by 47 scholars from 17 countries, with total attendance being approximately 100. Most of the papers dealt with the central theme of the conference and focused on the nature and influence of the seminal discoveries in physics a century ago, namely: x-rays, radioactivity, the electron, the Zeeman effect, and Planck's constant. The organizers believe that the conference was most successful in offering a splendid venue for international scholarly collaboration and for the exchange of ideas on topics of critical significance in the history of modern physics. The possibility of publishing the proceedings is currently being explored. Additional information can be obtained from Roger Stuewer: rstuewer@physics.spa.umn.edu.
