he American Physical Society celebrates its 100th birthday in 1999. As part of this celebration the APS Centennial Committee recommended several Tprojects to inform the physics community, students, and the public about the achievements of physicists in the 20th century, including a Speakers Bureau to send hundreds of physicists and historians of phys- ics to lecture at universities and laboratories. 1998 APS President Andrew Sessler suggested that lec- tures on 20th century physics would be greatly en- hanced by pictures of the physicists whose theories and discoveries were being reviewed. This CD-ROM, welcome containing images of about 200 outstanding 20th century physicists with brief descriptions of their achievements, is the result. We hope it will be use- ful to anyone giving a survey talk on any aspect of modern physics, and that it will also be interesting to other physicists who want to see the faces that go with familiar names. How were the names chosen? The selection was done by a committee chaired by past President Sessler, consisting also of physicist-historians Stephen Brush, Gerald Holton, and Spencer Weart. Their pri- mary goal was to choose names likely to be men- tioned in lectures on 20th century physics. But there were two important limitations. First, the committee did not include anyone who died before 1900, although it included a few physicists (such as Boltzmann and Roentgen) whose most important contributions, while made before 1900, had a major impact on 20th century physics. Second, it excluded persons still alive at the end of 1997. Thus you will not find here pictures of Galileo, Newton, or Maxwell; nor, unfortunately, will you find women and minori- ties represented in the same proportion as in the current generation of active outstanding physicists. On the other hand, it interpreted the term “physicist” broadly, including several mathematicians, astronomers, chemists and earth scientists whose work is widely known and highly valued in the physics community. A third constraint was that the photos had to fit on a single CD-ROM. Thus it could not include every physicist recom- mended by one of the several groups consulted for suggestions. The committee used its own judgment to eliminate many names. While we are confident that all the persons included do in fact belong in this collection, it would be surprising if we did not receive complaints about some of the many omissions. We urge you to provide your reactions and suggestions concerning this project to the APS. We are especially in interested in learning how you found the CD-ROM useful and what changes would make it more so. The production of this CD-ROM was made possible by the resources and cooperation of the staff of the Center for History welcome of Physics at the American Center for Physics in College Park, Maryland, including the Emilio Segrè photograph collec- tion. Please note that you may use the images only for projection at lectures; permission to reproduce them in publications or in any other form must be requested from the copyright owner, indicated in the credit line for each photo. The Center for History of Physics, owns the world rights to many of these photos. To obtain permission for the remainder please contact the APS. We acknowledge also the invaluable assistance of Erika Ridgway and Elizabeth Buchan-Higgins, APS staff members, and Stephen Norton, a graduate student in the History and Philosophy of Science Program at the University of Maryland- College Park, for collecting information for the captions. Selection Committee: Andrew Sessler (chair), Lawrence Berkeley Laboratory Stephen Brush, University of Maryland Celebrate Gerald Holton, Harvard University a Spencer Weart, Center for History of Physics Century of Physics SEARCH BY NAME A-L Alfvén, Hannes Olaf Gösta Bragg, William Henry Ehrenfest-Afanassjeva, T.A. Hertz, Gustav Ludwig Alvarez, Luis Walter Bragg, William Lawrence Einstein, Albert Hess, Victor Franz Anderson, Carl David Brattain, Walter Houser Ellis, Robert A., Jr. de Hevesy, George Appleton, Edward Victor Breit, Gregory Fairbank, William Martin Hilbert, David Aston, Francis William Bridgman, Percy Williams Fermi, Enrico Hodgkin, Dorothy Crowfoot Ayrton, Hertha Brillouin, Léon Nicolas Feynman, Richard Phillips Hofstadter, Robert L. Bainbridge, Kenneth T. Chadwick, James Fowler, William Alfred Houtermans, Fritz Georg Bardeen, John Chandrasekhar, Subrahmanyan Franck, James Hubble, Edwin Powell Barkla, Charles Glover Chapman, Sydney Frank, Ilya Mikhailovich Imes, Elmer Samuel Becquerel, Antoine-Henri Cherenkov, Pavel Alekseyevich Frank, Philipp Ioffe, Abram F. Bell, John Stewart Cockcroft, John Douglas Franklin, Rosalind Elsie Jensen, Johannes Hans Daniel Bhabha, Homi Jehangir Compton, Arthur Holly Frenkel Yakov Ilyich Joliot, Frédéric Bitter, Francis Condon, Edward Uhler Frisch, Otto Robert Joliot-Curie, Irène Blackett, Patrick Maynard Stuart Crookes, William Fukui, Kenichi Kamerlingh-Onnes, Heike Blau, Marietta Curie, Pierre Gabor, Dennis Kapitza, Pyotr Bloch, Felix Curie, Marie Sklodowska Gamow, George von Kármán, Théodore Blodgett, Katharine Burr Davisson, Clinton Joseph Geiger, Hans Wilhelm Kastler, Alfred Bogolyubov, Nikolai Nikolaevich DeBroglie, Louis Victor Gibbs, Josiah Willard Kemble, Edward Crawford Bohm, David Debye, Petrus Göppert-Mayer, Maria Kerst, Donald William Bohr, Niels Henrik David Dicke, Robert Henry Goudsmit, Samuel Abraham Klein, Oskar Benjamin Boltzman, Ludwig E. Dirac, Paul Adrien Maurice Grad, Harold Kramers, Hendrik A. Born, Max Du Mond, Jesse William Monroe Hahn, Otto Kurchatov, Igor Bose, Satyendra Nath Eddington, Arthur Stanley Hale, George Ellery Kusch, Polykarp Bouchet, Edward Alexander Ehrenfest, Paul Heisenberg, Werner Karl Land, Edwin Herbert SEARCH BY NAME L-Z Landau, Lev Davidovich Moseley, Henry Gwyn-Jeffreys Raman, Chandrasekhara Thomas, Llewellyn Landé, Alfred Mott, Nevill Francis Richardson, Owen Williams Thomson, George Paget Langevin, Paul Mulliken, Robert Sanderson Röntgen, Wilhelm Conrad Thomson, Joseph John Langmuir, Irving von Neumann, John Rossi, Bruno Tomonaga, Sin-itiro von Laue, Max Nier, Alfred Otto Carl Rutherford, Ernest Tuve, Merle Anthony Lawrence, Ernest Orlando Noether, Amalie Emmy Sabine, Wallace Clement Uhlenbeck, George Eugene Leavitt, Henrietta Swan Occhialini, Giuseppe Sakharov, Andrei Dmitrievich Urey, Harold Clayton Lehmann, Inge Onsager, Lars Salam, Abdus Van de Graaff, Robert J. Lemaître, Georges Oppenheimer, J. Robert Schiff, Leonard Issac Van Hove, Léon Libby, Willard Frank Patterson, Clair Cameron Schrödinger, Erwin Van Vleck, John H. Livingston, M. Stanley Paul, Wolfgang Schwarzschild, Martin Walton, Ernest Thomas Sinton London, Fritz Wolfgang Pauli, Wolfgang Schwinger, Julian Seymour Weyl, K.H. Herman Lonsdale, Kathleen Pauling, Linus Carl Segrè, Emilio Gino Wick, Gian-Carlo Lorentz, Hendrik Antoon Payne-Gaposchkin, Cecilia Serber, Robert Wideröe, Rolf Lyman, Theodore Peierls, Rudolf E. Shockley, William Wien, Wilhelm Mach, Ernst Perey, Marguerite Catherine Siegbahn, Karl Manne Georg Wiener, Norbert Marconi, Guglielmo Perrin, Jean Baptiste Slater, John Clarke Wigner, Eugene Paul Marshak, Robert Eugene Planck, Max Karl Ernst Ludwig Sommerfeld, Arnold Wood, Robert Williams Matthias, Bernd Teo Pockels, Agnes Spitzer, Lyman, Jr. Wu, Chien-Shiung McMillan, Edwin Mattison Poincaré, Jules Henri Stark, Johannes Yukawa, Hideki Meitner, Lise Powell, Cecil Frank Stern, Otto Zeeman, Pieter Michelson, Albert Abraham Prandtl, Ludwig Street, Jabez Curry Zel’dovich, Yakov B. Millikan, Robert Andrews Purcell, Edward Mills Strutt, John William Rayleigh Zernike, Fritz Minkowski, Hermann Rabi, Isidor Isaac Szilard, Leo Zwicky, Fritz von Mises, Richard Rainwater, Leo James Tamm, Igor Yevgenyevich HANNES OLAF GÖSTA Alfvén1908-1995 The Nobel Prize in Physics 1970 “for fundamental work and discoveries in magnetohydrody- namics with fruitful applications in different parts of plasma physics” Alfvén’s concepts such as magnetohydrodynamic waves and critical ionization velocity have also been useful in under- standing phenomena in the Earth’s ionosphere and else- where in the Solar System. AIP Emilio Segrè Visual Archives, Weber Collection LUIS WALTER Alvarez 1911-1988 The Nobel Prize in Physics 1968 “for his decisive contributions to elementary particle physics, in particular the discovery of a large number of resonance states, made possible through his devel- opment of the technique of using hydrogen bubble chamber and data analysis” Alvarez is well known to earth scientists as co-author of the theory that an asteroid struck the Earth about 65 million years ago, possibly resulting in the extinc- tion of dinosaurs and other species. AIP Meggers Gallery of Nobel Laureates CARL DAVID Anderson 1905-1991 The Nobel Prize in Physics 1936 “for his discovery of the positron” This confirmed Dirac’s prediction of the existence of an antiparticle for the electron. He also discovered, with S. H. Neddermeyer, the mu meson. AIP Emilio Segrè Visual Archives, W.F. Meggers Collection EDWARD VICTOR Appleton 1892-1965 The Nobel Prize in Physics 1947 “for his investigations of the physics of the upper at- mosphere, especially for the discovery of the so-called Appleton layer” AIP Emilio Segrè Visual Archives, E. Scott Barr Collection FRANCIS WILLIAM Aston1877-1945 The Nobel Prize in Chemistry 1922 “for his discovery, by means of his mass spectrograph, of isotopes, in a large number of nonradioactive ele- ments, and for his enunciation of the whole-number rule” His determination of