This volume is a reference source of fundamental formulae in physics and astrophysics. In contrast to most of the usual compendia it carefully explains the physical assumptions entering the formulae. All the important results of physical theories are covered: electrodynamics, hydrodynamics, general relativity, atomic and nuclear physics, and so on. Over 2100 formulae are included, and the original papers for the formulae are cited together with papers on modern applications in a bibliography of over 1900 entries. For this new edition, a chapter on space, time, matter and cosmology has been included and the other chapters have been carefully revised.