Time: From Earth Rotation to Atomic Physics

In the twenty-first century, we take the means to measure time for granted, without contemplating the sophisticated concepts on which our time scales are based. This volume presents the evolution of concepts of time and methods of time keeping up to the present day. It outlines the progression of time based on sundials, water clocks, and the Earth’s rotation, to time measurement using pendulum clocks, quartz crystal clocks, and atomic frequency standards. Time scales created as a result of these improvements in technology and the development of general and special relativity are explained. This second edition has been updated throughout to describe twentieth- and twenty-first-century advances and discusses the redefinition of SI units and the future of UTC. A new chapter on time and cosmology has been added. This broad-ranging reference benefits a diverse readership, including historians, scientists, engineers, educators, and it is accessible to general readers.

Author Biography

Dennis D. McCarthy is a former Director of Time at the United States Naval Observatory, the leading authority in the US for astronomical and timing data. He has led and been a member of various Commissions and Working Groups within the International Astronomical Union and has authored and edited numerous publications dealing with fundamental astronomy, time, and Earth orientation. P. Kenneth Seidelmann is a research professor of astronomy at the University of Virginia and is a former Director of Astrometry at the US Naval Observatory. He has led and been a member of a Division, various Commissions, and Working Groups of the International Astronomical Union, has co-authored two other books: Fundamentals of Astrometry (Cambridge, 2004) and Celestial Mechanics and Astrodynamics (2016), and is co-editor of the Explanatory Supplement to the Astronomical Almanac (2012).