Maurice Allais was one of the most original of France"s scientific thinkers of the 20th century. In the early 1950’s he was the author of Allais paradox in decision making under uncertainty, and in 1988 he became the only French citizen to receive the Nobel Prize in Economics for his contributions to the theory of non-equilibrium markets. Allais’s research in physics was also important, but very little known. In the mid 1950’s Allais designed and built a highly sensitive ball-borne pendulum – which he named paraconical pendulum. This apparatus reacts to the gravitational force of the Sun and the Moon, and exhibited unexpected behaviour during the solar eclipse of 30 June 1954, which was partial in Paris. This local gravity anomaly is now called the Allais eclipse effect. As a tribute to Allais on the 100th anniversary of his birth, this book concentrates on his contributions to physics, in particular to the exciting and controversial field of gravity anomalies, which may open unexpected and completely new avenues in gravity theory. In addition to a short sampling of Allais papers, the book describes experimental efforts to reproduce the Allais eclipse effect, an endeavour that has turned out to be harder than expected because all eclipses are different. Several papers describe optical and geological anomalies that also interested Allais. A final section contains theoretical essays sketching novel gravity models. The book will be of interest not only to students and practitioners of physics, but also to the informed lay public, and even to philosophers of science, and researchers studying the epistemology and politics behind scientific investigation.