Long out of print, this classic book investigates the experimental determination of one of the fundamental constants of astrophysics and its significance for astronmy. The Expanding Universe offers a unique sidelight on the history of ideas and Eddington's artistry; his evident enjoyment of writing and exposition shine through. Astrophysicists and historians of science will find that this reissue sheds fascinating light on one of Britain's greatest scientists. Sir William McCrea has supplied the Preface.