It's all a matter of time—literally. From the movements of the spheres to the slipperiness of relativity, the story of science unfolds through the fascinating history of humanity's efforts to keep time. Our modern lives are ruled by clocks and watches, smartphone apps and calendar programs. While our gadgets may be new, however, the drive to measure and master time is anything but—and in A Brief History of Timekeeping, Chad Orzel traces the path from Stonehenge to your smartphone. Orzel, a physicist and the bestselling author of Breakfast with Einstein and How to Teach Quantum Physics to Your Dog continues his tradition of demystifying thorny scientific concepts by using the clocks and calendars central to our everyday activities as a jumping-off point to explore the science underlying the ways we keep track of our time. For those interested in science, technology, or history, or anyone who's ever wondered about the instruments that divide our days into moments: the time you spend reading this book may fly, and it is certain to be well spent.