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Kevles notes: Ch. XI, Chs. XIV-XVI Physics 3000, Fall 2015, Science and Public Policy Instructor: M. Goldman Slide 2 Atomic and nuclear physics: 1920's to 1950 Atomic Physics: all about electrons in atoms Emerging understanding of atom in early 20 th century Theory of quantum mechanics and European physics discoveries Electrons in relation to nucleus (next slide). Periodic table Emission and absorption of radiation by atomic electrons (following slide) Nuclear Physics Basic consituents of nucleus: protons and neutrons. Periodic table. Radioactivity (from nucleus) Cyclotron: Break-apart nucleus by bombardment with other nucleii, protons or electrons to determine what is in it and what holds it together Video R v/BVideo Release of nuclear energy when neutron breaks heavy nucleus apart (nuclear fission) Release of nuclear energy when light nuclei come together (nuclear fusion) Accelerators Lawrence's cyclotron: beginning of higher energy, more expensive bigger machines to accelerate particles and smash them into nuclei or other particles At higher energies nuclear physics changes to "high-energy" or "elementary particle" physics, now considered a different field of physics from "nuclear." Slide 3 States of electron with different probability clouds in quantum theory of atom Superposition states Slide 4 Emission and absorption of radiation (photons) accompanies change of electron energy state Emission Absorption time photon higher energy electron lower energy electron higher energy electron lower energy electron photon Energy conserved Slide 5 CH. XI The Impact of Quantum Mechanics How was American science after WW-I bolstered by contributions from philanthropists and philanthropic institutions. Cal Tech was created in 1921. Wealthy southern Californians who wanted to stimulate industrial development in the region created its endowment. Earlier, the University of Chicago was endowed by John D. Rockefeller and Mt. Wilson Observatory was endowed by Andrew Carnegie Lawrence's cyclotron- Rockefeller foundation: Rockefeller's notesRockefeller's notes Slide 6 CH. XI (Cont'd) Before WW-I atomic physics developed in terms of quantum mechanics by European scientists such as Einstein. What were the advances in atomic physics and quantum mechanics in the mid-20's and who made them and where? Neils Bohr, Danish, Theory of the atom (with Sommerfeld). Correspondence principle. Periodic table. Nobel Prize 1922 Arthur Compton, U.S. Postdoc in England under Rutherford. Joined faculty at Washington University, St. Louis. Applied quantum ideas to X-rays scattered off of electrons. 1922 Wofgang Pauli, Austria, States of atomic electrons and quantum numbers. Exclusion principle. 1924 Werner Heisenberg, Germany. Formulated quantum mechanics using arrays of numbers (matrices). Uncertainty principle. 1925 Erwin Schroedinger, Swiss. Formulated quantum mechanics in terms of a "wave of probability." 1926 Slide 7 Atomic Bomb, 1945 Theoretical vs. Experimental Physicists Theoretical First half of 20th century: Einstein, Heisenberg, Schroedinger, Dirac, Oppenheimer Advances in quantum mechanics, atomic physics, nuclear physics Did not require gov t support at all 2nd half 20th century, Beg. 21st: Richard Feynman, Murray Gel- Mann, Ed Witten, Lisa Randall, Frank Wilcek Advances in theory of high energy physics and low temperature physics Theorists sometimes need supercomputer support Experimental First half of 20th century: Millikan, Lawrence, J. J. Thompson Compton, Rutherford, Rabi Quantum mechanics, atomic physics, nuclear Received support from nonprofit institutions 2nd half 20th century, Beg. 21st: Mostly large groups in high-energy Low temperature: Carl Wieman and Eric Cornell (CU) -Bose Einstein Condensate (Condensed Matter) Accelerators expensive - require heavy government or intergovment funding (bigger magnets, higher voltage) Other frontier basic research is relatively small scale and does not require many $$$. Slide 8 Ch. XIV A New Center for Physics From 1919-1932 many young American physicists went to Europe for Postdoc studies. Where did their Postdoc support come from? Mostly from non-profit private institutions: Guggenheim and Rockefeller foundations, NRC During this period how did women and minorities in science fare? Women began to get degrees in the sciences but had difficulty getting employment at major universities like Harvard. Flapper mentality may have been disincentive for women to become scientists. APS Women and Minorities Programs Low scientific quality of American Catholic schools discouraged Catholics from becoming scientists; many could not afford a scientific education. Jews were almost as underrepresented in American Science as Catholics, while they dominated European science (Einstein, Pauli, others). Antisemitism operated at every level of the industry and academia. Isidor Rabi slowly made his way to acceptance as a top U.S. physicist J. Robert Oppenheimer was another example. In 1932, the Institute for Advanced Study at Princeton attracted Einstein to U.S. Attitudes began to change Slide 9 Assigned: Ch. XV, Miraculous Year Why was 1932 a miraculous year in U.S. science? Because of research advances in nuclear physics eventually leading to five Nobel Prizes, three of them for work done in United States Lawrence (cyclotron), Urey (deuterium), Anderson (positron) What is nuclear physics? The study of the forces and particles in the nucleus of an atom. The nucleus can be studied by looking at radioactive decay of, say, radium and by accelerating particles and nuclei to high energies so that they can collide with targets. Discoveries: neutron, isotopes of hydrogen (deuterium), meson, positron (anti-electron) Who was Earnest Lawrence and what did he do? He conceived of the cyclotron and constructed the first such high energy accelerator which reached 1 million volts of particle energy in 1932 He was a Professor at Berkeley. Lawrence Berkeley Laboratories and Lawrence Livermore Laboratories are named after him. Slide 10 Ch. XVI: Revolt Against Science What was the nature of the revolt? Depression in 1930s caused Federal and industrial allocations to research to be slashed Philanthropic monies turned to psychology and biology instead of physics. (Pg. 249) Companies like GE furloughed half their technical staff by 1933. (Pg. 250) Legislatures became unsympathetic towards research at public expense (Pg. 250) A coalition of budget-cutting conservatives and socially purposeful reformers had reduced appropriations for scientific luxuries in 1930s in (as well as1890s). (Pg. 251) What in science should really interest us today [1930s]? Not the verification of Einstein's theory of relativity, Atterbury declaimed. In the present state of affairs all that seemed "brilliantly useless, especially when you consider the millions who cannot afford decent homes because none of our great minds has ever focused on the basic everyday problem of human shelter... With a small amount of such brains as are now focused on the speed with which the neutron penetrates the nucleus of the atom... the cost of the poor man's housing today could be cut in half." Quote (pg. 247) from Grosvenor Atterbury, architect, town planner and pioneer in prefabricated housing Slide 11 Ch. XVII: New Deal & Research (1933-38) What was the New Deal? Who was Karl Compton? President of MIT. Appointed chair of newly formed Science Advisory Board (without teeth). A conservative scientist In the 1930's what was the difference between a conservative scientist and a New Dealer or liberal scientist? Conservative scientists believe in laissez-faire capitalism attitude towards business and industry with trickle-down benefit to public. They believe in low taxesbut also (at this time) that research can lead to development and prosperity.. New Dealers believed in strong regulation of industry and in "taxing and spending." More activism in social programs and economic reform. Advocates of socially purposeful science more than basic research. Karl ComptonVannevar Bush Slide 12 Assigned: Ch. XVIII, Recovery in Physics (1935-39) What developments occurred in science during the recovery? Beginning of patent activities in research Universities New appreciation and popularity of science (Einstein lectures) Development of practical technologies: television, nylon stockings, plastics, air-conditioning, commercial air travel, sulfanamide drugs, X-rays in crime detection. Neutron and positron discovered. Larger cyclotrons. Nuclear energy. Neutron and radioactive therapy for cancer treatment Increased academic income and government agency budgets (NBS). More jobs. The American Physical Society: "A Century of Physics"