The quantum beat

the long version

This book examines the physical principles underlying the workings of clocks - from the earliest mechanical clocks to the present-day sophisticated clocks based on the properties of individual atoms. Intended for nonspecialists with some knowledge of physics or engineering, the book treats the material in a broad intuitive manner, with a minimum of mathematical formalism. The presentation covers a broad range of salient topics relevant to the measurement of frequency and time intervals. The main focus is on electronic time-keeping: clocks based on quartz crystal oscillators and, at greater length, atomic clocks based on quantum resonance in rubidium, cesium, and hydrogen atoms, and, more recently, mercury ions.