Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session L07: Pais Prize Session: Helge KraghInvited Undergraduate
|
Hide Abstracts |
Sponsoring Units: FHP Chair: Michel Janssen, University of Minnesota Room: Sheraton Governor's Square 16 |
Sunday, April 14, 2019 3:30PM - 4:06PM |
L07.00001: Varying Gravity: Dirac’s Legacy in Cosmology and Geophysics Invited Speaker: Helge Kragh In 1937 the celebrated Nobel laureate and quantum theorist Paul Dirac suggested that the gravitational constant G slowly decreases in time, and on this non-Einsteinian basis he developed a cosmological model of the expanding universe. The audacious hypothesis was generally ignored but after World War II it attracted interest when it was applied to problems of paleoclimatology and global geophysics. According to Pascual Jordan, another quantum pioneer, Dirac’s G(t) hypothesis led to the consequence that the Earth expands. For a decade or so the expanding Earth hypothesis, whether based on varying gravity or not, was discussed as an alternative to the revived theory of continental drift and its development into mainstream plate tectonics. At about the same time several cosmological models based on versions of the G(t) hypothesis were proposed. Although, as seen from a modern point of view, the theories based on varying gravity were blind alleys, from a historical perspective the case is of considerable interest. For example, it illustrates the problems that may occur when scientists from two very different disciplinary traditions face the same subject matter, in this case the past of the Earth. Moreover, although Dirac’s version of the G(t) hypothesis is dead, the general idea of varying gravity is still entertained by some physicists. The talk discusses some of the main features of the debate as it evolved ca. 1950-1980. It also briefly alludes to other ideas concerning fundamental constants varying in time. |
Sunday, April 14, 2019 4:06PM - 4:42PM |
L07.00002: Is It the Same Result? Replication in Physics Invited Speaker: Allan Franklin One of the interesting issues in the philosophy of experiment is that of the replicability of experimental results. The scientific community enthusiastically endorses the idea that replication is the scientific “gold standard.” The underlying argument for this is that if an experiment has succeeded in revealing a real phenomenon or accurately measuring a quantity then that success should reappear when the experiment is repeated under the same circumstances or when it is reproduced in a different experiment. There are, however, questions concerning what constitutes a successful or failed replication. In this paper I will discuss two clear examples of successful replications: The discovery of the Higgs boson and the detection of gravitational radiation. Two failed replications will also be presented: early experiments on the Fifth Force, a proposed modification of Newton’s Law of Gravity; and attempts to measure G, the universal gravitational constant in Newton’s law. More complex episodes in which the success or failure of replication was not clear will also be discussed. These include the strange history of η+- and experiments on the pentaquark, the case of the disappearing particle. |
Sunday, April 14, 2019 4:42PM - 5:18PM |
L07.00003: Why Do the Stars Keep Shining? A Long Journey to a Satisfactory Answer Invited Speaker: Robert Smith For centuries before Hans Bethe’s path-breaking researches on fusion and stars in the late 1930s, the question of why the stars keep shining had attracted the close attention of numerous natural philosophers, astronomers and physicists. In this paper, I will review some of the answers that were advanced and how these answers helped frame the development of both physics and astronomy. |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700