Is time an endlessly repeating circle, or is it a descending path leading to decay and destruction? Is it a uniform stream, or is it made of tiny discrete parcels? Drawing from literature, biology, philosophy, psychology, and theology, this intriguing work explores each of these possible models and relates them to our own subjective impressions of time. Theoretical physicists are now striving to unlock the very structure of time itself. But the quest to understand time has never been the exclusive domain of science. From the Hindu notion of cosmic rebirth to Stephen Hawking's recent studies, philosophers and scientists alike have sought to answer time's riddle. Here is the first accessible, math-free introduction to the competing models of time that demonstrates how today's theories mirror ancient debates over the "shape" of time. This book explores such provocative concepts as synchronicity, time travel, black holes, and artificial intelligence. It probes the ultimate questions of science and philosophy, surveys the frontiers of theoretical physics, and finally, demonstrates how our own personal views on mortality must affect our choice of a scientific model of time.