The Big Bang and the Horizon Problem

Abstract

Abstract Discussions from the recent astrophysics literature on observability, horizons, and the like have trickled down to the level of philosophical consciousness, at least in a folkloric way. For example, the folklore contains the wisdom that the standard big bang cosmological models contain particle horizons, that when this fact is coupled with the observed isotropy of the 3 K cosmic background radiation there arises a “horizon problem,” and that inflationary cosmology solves this problem. Like most folklore, this example contains some truth and a number of distortions. There is a need to set the record straight and to correct some fundamental misimpressions about observability and horizons in relativistic cosmoiogical theories. But more is at stake than correcting some misimpressions. The horizon problem provides an interesting test case for accounts of scientific explanation, for the perception of a “problem” in connection with particle horizons in standard big bang cosmology depends on views about what features a good scientific explanation should have. While this matter has received little attention in the philosophical literature, it has played an important role in guiding research in relativistic cosmology.