Thursday, April 28, 2005

Hans Bethe Was, So to Say, One of My Teachers

Hans Albrecht Bethe, one of the giants of 20th century physics, died on March 6, 2005. He was born in 1906 in Strasbourg, Alsace-Lorraine -- then part of Germany --, studied physics at Frankfurt, and obtained his doctorate from the University of Munich in 1928. In 1933 he moved to England, and in 1935 to America, where he held the chair of physics at Cornell from 1937 until his retirement in 1975. Bethe was one of the key figures in the Manhattan atomic bomb project during the Second World War. After the war he campaigned together with Albert Einstein against nuclear testing and the nuclear arms race. He won the Nobel Prize in Physics for 1967 for his discovery of stellar nucleosynthesis [1-5].

Students who major in nuclear or radiation physics learn the name of Bethe quite early in the lesson of their specialty. His name is associated with equations to express energy losses, due to inelastic and radiative processes, of charged particles passing through matter. Bethe's papers on these equations were published in 1930 [6] and 1934 [7]. In my young days one of the most thoroughly written textbooks on experimental nuclear physics was the one edited by Emilio Segrè [8]. In the first volume of that textbook, there is a chapter written by Bethe and Julius Ashkin (Carnegie Institute of Technology) on the passage of radiations through matter.

I had worked on the passage of fast electrons through matter for many years. So I studied the chapter of Bethe and Ashkin repeatedly. Thus Bethe was, so to say, one of my best teachers. In a humble work of mine [9] I even cited a paper authored by Bethe and his coworkers [10], because the expression in this paper for the transport mean free path of electrons in matter was essentially useful for that work. Further, a little before my retirement from a university I bought the book of Bethe's selected works [11] (see the image above) to make it one of examples of publications of my selected works I edited by myself [12]. By the way, other examples I referred to were "The Collected Papers of Albert Einstein" and "Selected Papers of Freeman Dyson with Commentary." Many scientists possibly regard Bethe as their model in that he published important academic papers at ages over 90.

It is interesting that Bethe so swiftly did the work awarded by the Nobel Prize [2,13]. In 1938 Edward Teller invited Bethe to contribute a paper on astrophysics for a conference the former was organizing. Bethe at first pleaded ignorance of the subject, but under pressure from Teller he finally agreed to search for a relevant topic. The result was the paper on energy production in stars [14].

There are two more interesting facts about Bethe's publications [15]. One is that Bethe submitted a spoof paper [16] to Die Naturwissenschaften with G. Beck and W. Riezler, and it was accepted and published. Bethe wrote [17] about that paper, "The joke was meant to make fun of papers by Eddington in which he claimed to derive the value of the fine structure constant to be 137." The other is that Bethe's name was added in the byline of a letter to the Editor of the Physical Review on the theory evolved by R. A. Alpher under George Gamow's direction [18]. It was Gamow's mischievous idea to make the list of authors, Alpher, Bethe and Gamow, sound like alpha, beta and gamma. It is funny that it is written, "Bethe did, however, contribute with Ralph Alpher to George GamowÉÜs famous 1948 alpha-beta-gamma paper on the origin of the elements and the big bang." in Biographical Encyclopedia of Scientists [2].

The American Institute of Physics had been publishing a series of books named Masters of Modern Physics. The series included a volume of Bethe [19]. I bought it, but have not read it yet. The volume is a collection of Bethe's essays written since the end of the Second World War. In the preface of this book Bethe wrote, "That President Reagan and General Secretary Gorbachev both agreed that nuclear armaments are absurdly large comes as a modest result of the arms-control effort in which I was joined by many others. Much remains to be done before the world can feel safe from a nuclear holocaust."

The 2005 NPT (the Nuclear Non-Proliferation Treaty) Review Conference will soon be held at the UN in New York (from May 2 to 27, 2005). UN Secretary-General Kofi Annan stated on the occasion of the 35th anniversary of the NPT (March 5, 2005), "Today, the NPT confronts profound challenges to its effectiveness and credibility. At the 2005 NPT Review Conference in May, these challenges will test the commitment of all States to the three pillars of the NPT: non-proliferation, disarmament, and peaceful uses of nuclear technology." We expect that the effectiveness and credibility of the NPT be strengthened at the coming review conference to respect Hans Bethe's will.
  1. Hans Bethe - Biography (
  2. J. Daintith, S. Mitchell, E. Tootill and D. Gjertsen, ed., Biographical Encyclopedia of Scientists, 2nd ed., Vol. 1, p. 81 (Institute of Physics Publishing, Bristol, 1994).
  3. Atom Bomb Designer Dies (PhysicsWeb, March 8, 2005).
  4. Hans Bethe (Wikipedia).
  5. K. Gottfried and E. E. Salpeter, Nature, 434, 970 (970).
  6. H. A. Bethe, Ann. Physik, 5, 325 (1930).
  7. H. A. Bethe and W. Heitler, Proc. Roy. Soc. (London), A146, 83 (1934).
  8. E. Segrè, ed., Experimental Nuclear Physics, Vols. I-III (John Wiley & Sons, New York, 1952-1959).
  9. T. Tabata, R. Ito and S. Okabe, J. Appl. Phys. 42, 3361 (1971).
  10. H. A. Bethe, M. E. Rose and L. P. Smith, Proc. Am. Phil. Soc. 78, 573 (1938).
  11. H. A. Bethe, Selected Works of Hans A Bethe with Commentary (World Scientific, Singapore, 1997).
  12. T. Tabata, ed., Abstracts of Selected Papers of Tatsuo Tabata and His Coworkers Vol. 1 and 2 (available as PDF files from the IDEA Web site) (IDEA, 2002, 2003).
  13. O. Klein, The Nobel Prize in Physics 1967: Presentation Speech (1967).
  14. H. A. Bethe, Phys. Rev. 55, 434 (1939).
  15. E. Mendoza, ed., A Random Walk in Science: An Anthology Compiled by R. L. Weber, pp. 24 and 70 (Inst. Phys. London, 1973).
  16. G. Beck, H. Bethe and W. Riezler, Naturwissenschaften, 19, 39 (1931).
  17. Page 185 of Ref. 11.
  18. R. A. Alpher, H. Bethe and G. Gamow, Phys. Rev. 73, 803 (1948).
  19. H. A. Bethe, The Road from Los Alamos (Amer. Inst. Phys., 1991).

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