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Dennis Normile, in the first paragraph of his article “More powerful pulses please and puzzle” (Research News, [24 Jan., p. 481][1]), suggests, as do the authors of many articles about results from frontier acceleration techniques, that major progress is being made in developing accelerators that can be used for particle physics. Particle physicists would be delighted if that were so. However, even if the sorts of problems that are discussed in the article can be solved, many units have to be linked coherently to reach the high energies that would be useful for particle physics, and that raises new problems. Most important, in order to be useful for particle physics, a high energy accelerator must also have very high luminosity, because the cross sections for events of interest decrease with increasing energy. No technique I have seen discussed has demonstrated that it can get within orders of magnitude of the needed luminosity. Rather than raise false hopes in the science policy community, it would be better to not discuss the particle physics application until the values for the energy and the luminosity are nearer to those required for the physics. [1]: /lookup/doi/10.1126/science.275.5299.481

Drawing Theories Apart . The Dispersion of Feynman Diagrams in Postwar Physics. By David Kaiser . University of Chicago Press, Chicago, 2005. 489 pp. $80, £56. ISBN 0-226-42266-6. Paper, $30, £21. ISBN 0-226-42267-4. Writing for historians of science and physicists, the author explores how physicists used and adapted Feynman diagrams as well as how the diagrams influenced their research.

The News Focus article “String theory gets real—sort of” (A. Cho, 26 Nov. 2004, p. 1460) nicely describes the historical issues and separation of string theory and phenomenology, but it does not convey the recent excitement and increased activity of the emerging area of “string phenomenology.” The best documentation for that is people voting with their “feet”—last summer witnessed the third international string phenomenology meeting (in Ann Arbor), with the fourth already scheduled for Munich next summer, plus the first ever string phenomenology workshop, on which the article reported. String theory is exciting not only as a quantum theory of gravity, but because it allows us to address as research topics basic questions previously out of reach. Increasingly, many people are working in these areas and unifying different areas (such as collider physics, inflation, dark matter, quark masses, neutrino masses, and more) that could only be connected by a deep underlying theory. Whether such efforts are successful remains to be seen, but a number of people are more optimistic than they have been for a long time.