ABSTRACT
The evidence supporting the theory of nuclear-energy generation in stars is indirect, based largely upon observations of electromagnetic radiation emitted from the surface of stars and upon theoretical stellar models that have not been subjected to independent experimental tests. It is interesting, therefore, to try to think of a way of directly testing the theory of stellar-energy generation in stars. In order to make such a test, one would like to be able to “see” into the deep interior of a star where the nuclear reactions are believed to occur. Thus, an information carrier with a mean free path of the order of 10+11 cm (~R ʘ) is required. In the interior of a star like the sun, light has a mean free path of less than a centimeter. Only neutrinos, which have extremely small interaction cross-sections, can enable us to “see” into the interior of a star. Thus, the observation of solar neutrinos would constitute the most direct test that we can think of for the hypothesis that hydrogen-burning nuclear reactions provide the main energy source for stars like the sun. Moreover, the requirement that a theoretical solar model would have to yield the observed solar neutrino flux would provide an additional, and rather restrictive, condition on acceptable solar models.
