Physical Experiments With Test Bodies | V. B. Braginsky

The subject of this book is physical experiments in which the detection of an effect can be reduced to the registry of a force or moment of force. Despite the fact that classical physics began precisely with such experiments, they are still being made. The reasons for formulating experiments are of an extremely basic nature (for example, the problem of detecting gravitational radiation, the search for quarks, etc.).

In the experiments carried out today or made during recent years, the attained sensitivity is extremely high and may astonish the experimental

physicist who is not working in this field. On the other hand, the sensi­ tivity in these experiments is increasing with each passing year. About 50 years ago Millikan discovered a single Mexcessn electron (or its absence) in a droplet in which the excess electron was accompanied by 1013 nucleons; now thesamethingcanbedone"againstabackground*'of1018nucleons. P.N. Lebedev, at approximately the same time, measured the pressure of a light flux with an intensity of about 1 W; now it is possible to measure the light pressure from fluxes of tens of microwatts. During 1959-1963 Dicke, in repeating the experiments of Eotvos in checking the equivalence principle, succeeded in increasing the sensitivity by three orders of magnitude. Evi­ dently, in the future we can expect a further increase in sensitivity. The author has endeavored to describe the conditions (methodological and theoretical) necessary for increasing sensitivity, and also indicating the limitsofresolutionwhicharetheoreticallyattainable. Ithasbeenfound that these limits are to a certain extent similar to the recently discovered macroscopic quantum effects.

The book also includes descriptions of some recently performed interest­ ing experiments involving the solution of fundamental physical problems and estimates of the limiting resolution in individual experiments discussed in the literature. The selection of material in the second part of the book was governed only by the importance of the physical problems which can be experi­ mentally solved. Naturally, this selection was determined by the author's subjective point of view. Accordingly, the examples and illustrations in the second half of the book do not exhaust all the possible experiments in which it is important to detect small mechanical forces or moments of force.