APS News

March 2012 (Volume 21, Number 3)

Letters to the Editor

Textbooks Can Get It Wrong

In his January Back Page article, “Ten Mistakes for Physicists to Avoid,” James Patterson urges physicists to go beyond secondary sources. I agree and would add another reason: all too often, textbook authors get it wrong.

Here are two common examples:
Textbooks often give the impression that the purpose of absolute temperature is to measure a system’s amount of energy (per molecule, say). In his Theory of Heat (1872), Maxwell said it correctly (although, to us, archaically): “The temperature of a body is its thermal state considered with reference to its power of communicating heat to other bodies.” In short, temperature measures hotness.

Textbooks often make a muddle of mass, matter, and inertia.  In his three-page paper of 1905, Einstein said it clearly: if a body’s energy changes by ΔE, then its inertia changes in the same sense by ΔE/c2 (in modern notation). In short, the connection is between energy and inertia.

Ralph Baierlein
Flagstaff, AZ

Thanks for an Excellent Back Page

I really enjoyed reading and got a great deal out of the January Back Page article “Ten Mistakes for Physicists to Avoid” by James Patterson. Every once in a while, you put an article back there that really knocks it out of the park. The other article which I found deeply important to academic life was the one on Violence and Knowledge. Honesty and clarity link these excellent pieces together.

Mark C. Hickey
Bedford, MA

Ed. Note: The author refers to the Back Page “The Violence of Our Knowledge: On Higher Education and Peace Making” by Parker J. Palmer, which appeared in the July 2007 APS News.

Fission Timeline Clarified

Part of the history column on Fermi in the December, 2011, issue of APS News needs clarification, at least with respect to timelines and names.

The article states “Reports of experimental evidence for nuclear fission began circulating early in 1939, in a manuscript by German chemists claiming they had detected barium after bombarding uranium with neutrons. Among those who heard the news was Lise Meitner, who realized, with her nephew, Otto Frisch, that this could be nuclear fission. The news quickly spread across the pond to American physicists, including Fermi.”

The timeline for the quoted events actually starts in late 1938.  The German chemists were Otto Hahn and Fritz Strassman with assistants Fräuleins Bohne and Müller. Hahn and Strassman could not make sense of their observations that apparently showed the splitting of the atom.

Therefore, on December 19, 1938, Hahn wrote to Meitner, an Austrian physicist who had worked with Hahn for some 30 years in Germany. She had escaped from Germany in July, 1938, to Sweden because of the Nazis and her Jewish background. In his letter Hahn wrote “Perhaps you can put forward some fantastic explanation.” and asks her to keep the information he has sent her secret.  In a second letter dated December 21 Hahn wrote “How wonderful and exciting it would have been if we could have worked on this together as we used to.”

Meitner’s nephew, Otto Frisch, usually joined his aunt for the Christmas holidays. 1938 was no exception and she showed him Hahn’s December 19 letter. The two went on a forest hike in the snow all the while discussing Hahn's and Strassman’s results. It was during this hike that they arrived at the explanation. Frisch introduced the word “fission” into the lexicon of physics.

Thus, Meitner did not learn of fission as a result of Hahn’s and Strassman’s manuscript as the APS News article implies, but rather she explained the observations (with her nephew) as a result of Hahn asking her if she could do so.

The news did not cross the Atlantic as a result of Hahn's and Strassman’s manuscript but rather as a result of an oral communication from Frisch to Bohr, who was about to leave Copenhagen for the United States.

This history, and much more related to it, can be found in Hahn's and Frisch's autobiographies:
Otto Hahn: My Life, The Autobiography of a Scientist. Herder and Herder, New York, 1970. (Translation of the 1968 German original.)
Otto Frisch: What little I remember. Cambridge University Press, Cambridge, 1979.

Fred Peet
Brentwood Bay, British Columbia

Benefits of a combined-fields background

The Back Page article in the January 2012 issue, “Ten Mistakes for Physicists to Avoid” by James D. Patterson was very candid, and well thought out. The benefits of breadth in education and work experience deserve to be added.

Looking back, there is no doubt that the smartest thing I ever did was to obtain a combined-fields background. Got that one right.  My undergraduate degree was in mechanical engineering, my PhD thesis was in particle physics.  Diversification continued in my working life, sometimes by necessity and more often by choice.  Consequently, I was able to make original contributions in five different subfields: particle physics, mechanics of solids and structures, fluid mechanics, applied physics, and acoustics of musical instruments. Often, my work on a research/development (R/D) project would involve more than one of these subfields at the same time.

James Patterson correctly points out that an academic career is no longer necessarily the path of many physics majors. Outside Academia, most R/D projects are interdisciplinary. But interdisciplinary research is coming to academia as well. A good example is the interdisciplinary approach to reconstructing European prehistory, making full use of linguistics, archaeology and genetics. Each of these disciplines by itself yields results that are only clues at best.  But taken together, they produced solid evidence which overturned previous assumptions.

Another benefit of combined-fields capability is increased employment security. If one field or subfield were to tank, a sufficiently broad person could switch much more easily.

From this experience, a combination of breadth and depth is best, even if it takes longer time to graduate and requires harder work and study later on.

Andres Peekna
Waterford, WI 

APS encourages the redistribution of the materials included in this newspaper provided that attribution to the source is noted and the materials are not truncated or changed.

Editor: Alan Chodos