ABSTRACT
Appealing as the notion of reduction of the unfamiliar to the familiar may be, it is not a satisfactory characterization of scientifi c explanation. The point can best be made in terms of a famous puzzle known as Olbers’s paradox – which is named after a nineteenth-century astronomer but was actually formulated by Edmund Halley in 1720 – why is the sky dark at night? Nothing could be more familiar than the darkness of the night sky. But Halley and later astronomers realized that, if Newton’s conception of the universe were correct, then the whole night sky should shine as brightly as the noonday sun. The question of how to explain the darkness of the sky at night is extremely diffi cult, and there may be no answer generally accepted by the experts. Among the serious explanations that have been offered, however, appeal is made to such esoteric facts as the non-Euclidean character of space or the mean free path of photons in space. In this case, and in many others as well, a familiar phenomenon is explained by reference to facts that are very unfamiliar indeed.
