Bulletin of the American Physical Society
APS April Meeting 2013
Volume 58, Number 4
Saturday–Tuesday, April 13–16, 2013; Denver, Colorado
Session T15: Public Policy and History of Physics |
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Sponsoring Units: FOEP FHP Chair: Brian Schwartz, Graduate Center, City University of New York Room: Plaza Court 4 |
Monday, April 15, 2013 3:30PM - 3:42PM |
T15.00001: Robert Serber's 1943 Los Alamos Primer Analysis of Fission Bomb Efficiency Cameron Reed In an analysis of the expected efficiency of a fission bomb presented in his 1943 Los Alamos Primer, Robert Serber remarked that ``it is just possible for the reaction to occur to an interesting extent before it is stopped by the spreading of the active material.'' Due to the exponential nature of the time-dependence of a chain reaction, the efficiency of the explosion can be very sensitive to parameters such as the number of neutrons liberated per fission, the fission cross-section, and the number of critical masses of material used. In this paper I examine efficiency predictions for both uranium and plutonium bombs. Had some parameter values proven only modestly different from their true values, history may well have been very different. [Preview Abstract] |
Monday, April 15, 2013 3:42PM - 3:54PM |
T15.00002: Blurring Boundaries among Physics, Chemistry, \& Astronomy: The Mosely Centenary Virginia Trimble Scientists are territorial animals, not just about our parking spaces \& seats in the colloquium room, but also about our scientific territories, from the narrowest thesis topic (``Who's been working on my Nebula and left it covered with dust?'') to the whole of physics, chemistry, or astronomy. Many 19th century astronomers resented spectroscopes invading their observatories; chemists objected to Moseley's use of X-rays outgaming their retorts and test tubes in 1913; and chemists \& physicists typically disbelieve astronomers suggesting new science on the basis of astronomical data (3 other combinations are possible). The talk will explore some of these transgressions, successes and failures. Moseley's own contributions included sorting out the rare earths, putting paid to nebulium, coronium, etc, and putting Prout's hypothesis on a firm foundation ready for the structure Cameron and B2FH would eventually erect there. Back in 1935 Gamow asked whether a new discipline should be called nuclear physics or nuclear chemistry (both now exist within APS and ACS), and 30+ years later, chemist L.S. Trimble was still complaining that physicists had grabbed the territory of atomic and nuclear composition away from chemistry. Some historians agree. [Preview Abstract] |
Monday, April 15, 2013 3:54PM - 4:06PM |
T15.00003: The Franck-Hertz Experiment and the Nature of Ionization Clayton Gearhart In 1914, James Franck and Gustav Hertz published their famous experiment in which they bombarded mercury atoms with slow electrons---the latest in a series of papers seeking both to measure the ionization potentials of different elements, and to understand the implications of the new quantum theory. They found peaks in the transmitted current separated by 4.9 volts, a result they interpreted as the ionization potential. But they also noticed that this voltage corresponded to a prominent resonance line in the ultraviolet spectrum of mercury, and immediately performed a second experiment that confirmed the presence of this spectral line. They concluded---surprisingly---that their collisions sometimes resulted in ionization, but other times in the excitation of an atomic electron that vibrated and emitted light at this wavelength. In 1914, Franck and Hertz did not know of Niels Bohr's new theory, which presented something close to our modern view of the relation between spectral terms and ionization potentials. In this paper, I will ask how Franck and Hertz, and other physicists, thought about ionization in the early years of quantum theory, before the advent of the Bohr model. [Preview Abstract] |
Monday, April 15, 2013 4:06PM - 4:18PM |
T15.00004: Erich Regener - a forgotten cosmic ray pioneer Per Carlson, Alan Watson In the 1930s the German physicist Erich Regener (1881-1955), did important work on the measurement of the rate production of ionisation in the atmosphere and deep under-water. He discovered, along with one of his students, Georg Pfotzer, the altitude at which the production of ionisation in the atmosphere reaches a maximum, often and misleadingly called the Pfotzer maximum. He was one of the first to estimate the energy density of cosmic rays, an estimate used by Baade and Zwicky to postulate that supernovae might be the source of cosmic rays. Yet Regener's name is little known largely because he was forced to take early retirement by the National Socialists in 1937 as his wife had Jewish ancestors. In this paper we review his work on cosmic rays and the subsequent influence that he had on the subject through his son, his son-in-law, his grandson and his students. He was nominated for the Nobel Prize in Physics by Schroedinger in 1938. He died in 1955 at the age of 73. [Preview Abstract] |
Monday, April 15, 2013 4:18PM - 4:30PM |
T15.00005: Minkowski and the concept of 4-space Felix T. Smith After Lorentz (1904) showed the invariance of the equations of electricity and magnetism under the Lorentz transformation (L.T.) in space and time, Minkowski in 1905 discovered how all this could be simply and symmetrically presented through the vectors and matrices in a 4-space, which he formulated as a space-time with the roles of all 4 components essentially equivalent. Poincar\'{e} did not accept this, believing other structures compatible with L.T. but with a separable 3-space and time could also be found. Minkowski himself discovered the still standard form of the relativistic 4-velocity, whose 4 components are confined to a curved 3-space by the constraint of constant $c$. A similar construction can be identified in position 3-space if the upper bound $c$ is paralleled by the upper bound of a time-dependent Hubble length. This leads to the alternative possibility of formulating a new version of special relativity in terms not of a flat 4-space, but of a negatively curved 3-space, where the 4th term arises from the Hubble expansion. [Preview Abstract] |
Monday, April 15, 2013 4:30PM - 4:42PM |
T15.00006: The Role of the 1957 Chapel Hill Conference in the History of General Relativity Paul Halpern I will examine the importance of the 1957 Chapel Hill Conference on the Role of Gravitation in Physics, placing it in the context of developments in the history of general relativity. Organized by C\'{e}cile DeWitt-Morette and Bryce DeWitt, the conference attracted notable physicists representing a wide range of backgrounds---from quantum physicists to cosmologists. I will explore how the conference helped inspire growing interest in the subjects of general relativity and quantum gravity. [Preview Abstract] |
Monday, April 15, 2013 4:42PM - 4:54PM |
T15.00007: Is there a ``theory'' for nuclear proliferation? R.J. Peterson If we take the dates of first demonstration of nuclear weapons by nations, by testing in all but the case of Israel, a smooth trend with time is noted. An assumption that the rate of growth of nuclear nations dn(t)/dt is determined by pressures, embargoes, and other nonproliferation efforts could result in a dependence on 1/n(t), where n(t) is the number of nuclear weapons states at any time. This equation gives n(t) dependent on the square root of time since 1945, and a one-parameter fit finds excellent agreement for the nine nuclear nations to date. Although the drivers of nuclear proliferation are surely much more complex than in this simple model, its success can be taken to indicate that nonproliferation efforts have indeed been succesful in limiting the growth of nuclear-armed states. The simple model even yields a date when nation number ten might be expected to demonstrate a nuclear device. [Preview Abstract] |
Monday, April 15, 2013 4:54PM - 5:06PM |
T15.00008: Effect on Public Policy from Macro to Nano Aspects of the Deadliest Illness of Mankind: Important Role of Physics Arjun Saxena The effect on public policy of macro to nano aspects of the deadliest Illness known to mankind is given. The focus is on the important role of physics which has been ignored so far to solve its problems. It is now acknowledged that the deadliest illness is actually a group of illnesses which are lumped together as mental illnesses. They are the most widespread and damaging illnesses in the world. Their impact on the entire society globally is huge because they afflict majority of the people irrespective of race, religion, sex, age, education and economic status. In USA alone, the number afflicted according to the official count is about 80 million (out of a total population of 315 million), and it is projected to increase to about 25 to 30\% of the population within two decades. A model is given in this paper to address some of the key issues from macro to nano aspects of the deadliest illness. The information given in this paper is scientific though easy to understand. It will help the elected policy makers, public, physicists, neuroscientists, doctors, and care giving personnel world wide. The model explains the missing links in the diagnosis and treatment of mental illnesses. Additional evidence from other recent studies shall also be given. [Preview Abstract] |
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