Thought-provoking nonmathematical introduction to the conceptual foundations of both Newton’s and Einstein’s theories of gravitation. Special relativity theory, general relativity theory, other topics. For this new edition, author has added updated material on gravitational radiation detectors, current problems in cosmology, singularities of the gravitational field and more. Accessible to the layman. Bibliography. 88 illustrations, including 10 photographs. Orig. ed. 1968.