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Measuring Time

Frequency measurements and related developments in physics
Masatoshi Kajita


This fascinating book recounts the importance of precise measurements and their inherent uncertainty, before telling the story of humankind's efforts to define and measure time with increasing accuracy and the effect this has on science. The effort to master time culminated in the development of modern atomic clocks. The most accurate clocks ever constructed. These advanced devices are accurate to one second in 15 billion years and now act as the primary standard for time and frequency measurement. Our improvements in the accurate measurement of time have played a pivotal role in the development of modern science, including the confirmation of Einstein's theory of relativity and the recent detection of gravity waves. Furthermore, the precise measurement of time and frequency afforded by atomic clocks, and other mechanisms, is being used to examine key questions about the fundamentals of our universe, such as the possibility of symmetry violation or the idea that there may be variation of the fundamental constants over time.

About Editors

Masatoshi Kajita graduated from the Department of Applied Physics at the University of Tokyo in 1981 and obtained his PhD from the Department of Physics at the University of Tokyo in 1986. After working at the Institute for Molecular Science, he joined the National Institute of Information and Communications Technology (NICT), formally Communications Research Laboratory (CRL), in 1989. In 2009 he was guest professor at the Université de Provence in Marseille, France.

Table of Contents

1. Standards of physical quantitles
2. Historical role of precision measurements of time and frequency for the development of physics
3. Fundamentals of atomic clocks
4. Role of precision measurements in future developments in physics
5. Role of atomic clocks
6. Conclusion
Appendix: Laser cooling


Hardback ISBN: 9780750321228

Ebook ISBN: 9780750321242

DOI: 10.1088/978-0-7503-2124-2

Publisher: Institute of Physics Publishing


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