This book is unique and exceptional in dealing with the notion of physical time rigorously, both logically and empirically. The central theme is the intimate relation between physical time and cosmic gravity. It establishes and explains, in an accessible manner, the one crucial physical fact that has been missed in the development of modern physics—that the enormous gravity of the matter and energy in the Universe is the controller and cause of the relativistic time. The material in the book is accurate and free of the ambiguities in the discussion of time and its modifications (dilation), synchronization of clocks, and simultaneity. The contents go beyond the current theories of relativity that fail to incorporate the cosmic gravity in their structure. The discussion of clocks in satellite navigational systems (like the GPS) is the most complete and accurate. The book offers several new insights, and it is the only available treatise on the complete physical truth about time. The contents are addressed to a wide range of readers, from general readers and students to experienced researchers, and will also appeal well to philosophers and historians of physics. This book has the enabling quality to deal with difficult questions about physical time, with unprecedented clarity and without paradoxes.

C. S. Unnikrishnan is a professor of physics at the Tata Institute of Fundamental Research (TIFR), Mumbai, India. His research interests are fundamental issues in gravity and quantum physics, and novel metrology. He was a visiting scientist at the Kastler-Brossel Laboratory, École Normale Supérieure, Paris. The first Bose-Einstein condensate in India was produced in his laboratory at TIFR. Prof. Unnikrishnan’s major contribution is the paradigm of Cosmic Relativity, a theory of relativity and dynamics based on the factual gravity of the matter in the Universe, supported by many experimental results. Recently, he formulated a completion of Hamilton’s action mechanics to a universal mechanics, solving the foundational problems of quantum mechanics. Prof. Unnikrishnan is a proposer-member of the LIGO-India project, for a Laser Interferometer Gravitational-Wave Observatory in India, and a member of the LIGO Scientific Collaboration that detected the gravitational waves. His other interests are music and films, especially the structure and process of their creation.