Experiment, Theory Choice, and the Duhem-Quine Problem
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The fallibility and corrigibility of experimental results is well established. One need only look at a survey of the measurements of fundamental physical constants1 or at the “Review of Particle Properties,”2 a standard reference for high-energy physicists, to see that the measured values of not only particular quantities, but also of the world average of such quantities, change by far more than their cited experimental uncertainties would suggest is plausible or probable.3 A case in point is the history of measurements of η+-, the CP violating parameter in K° decay (see Figure 1). Prior to 1973, η+- had been measured six times. The results were in good statistical agreement and had a mean of (1.95 ± 0.03)× 10-3. The four succeeding measurements agreed with each other, and had a mean of (2.27 ± 0.022)×10-3. These means differ by eight standard deviations, an unlikely change if these are two sets of correct measurements of the same quantity. (The probability is 1.24×10-15). Unless one is willing to consider the possibility that η+- changed in 1973, we must conclude that at least one of these sets of measurements is incorrect.
KeywordsPhysical Review Theory Choice Rational Belief Fermi Theory Dirac Theory
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