Faster, Stronger, Better In regard to your article on scientists living longer,1 could it be that scientists are just tougher all round? A similar argument (with apologies to those who are married) might explain why married people live longer than singles: They are just tougher; the less tough can't stand marriage and become (or stay) single. Leonard X. Finegold Physics Department Drexel University Philadelphia, Pa. L@drexel.edu 1. S. Sanides, "Researchers find key to long life: Doing

Seeing your "Market emerges for use of human drugs on pets"1 makes my pet and me wonder, "Are humans indeed a good animal model for animals?" Leonard X. FinegoldPhysics DepartmentDrexel UniversityPhiladelphia, PA 19104 S. Bunk, "Market emerges for use of human drugs on pets," The Scientist, 13[8]:1, April 12, 1999.

T.L. Gilbert, who thinks that scientific fact is a language-based social construct (The Scientist, Sept. 2, 1996, page 12), is actually beginning to think like a physicist. For ages, physicists have agreed with Gilbert's example that meters and seconds (and kilograms, and the imperialist feet and pounds mass) are arbitrary. Hence they use "natural" units, by taking ratios with natural constants. As an example, one measures velocities by comparing them with the greatest velocity-that of light. I