Cover image for Splitting the second : the story of atomic time
Splitting the second : the story of atomic time
Jones, Tony, 1955- (Tony)
Personal Author:
Publication Information:
Philadelphia : Institute of Physics Pub., [2000]

Physical Description:
x, 199 pages : illustrations ; 21 cm
General Note:
Includes index.
Format :


Call Number
Material Type
Home Location
Central Library QB107 .J66 2000 Adult Non-Fiction Central Closed Stacks

On Order



Until the 1950s timekeeping was based on the apparent motion of the Sun that in turn reflected the rotation of the Earth on its axis. But the Earth does not turn smoothly. By the 1940s it was clear that the length of the day fluctuated unpredictably and with it the length of the second. Astronomers wanted to redefine the second in terms of the motions of the Moon and the planets. Physicists wanted to dispense with astronomical time altogether and define the second in terms of the fundamental properties of atoms.

The physicists won. The revolution began in June 1955 with the operation of the first successful atomic clock and was complete by October 1967 when the atomic second ousted the astronomical second as the international unit of time.

Splitting the Second: The Story of Atomic Time presents the story of this revolution, explaining how atomic clocks work, how more than 200 of them are used to form the world's time, and why we need leap seconds. The book illustrates how accurate time is distributed around the world and what it is used for. It concludes with a look at the future of timekeeping.

Author Notes

Tony Jones is now a science writer and a part-time associate lecturer with the Open University.

Reviews 1

Choice Review

The measurement of time is very ancient; common to all people, it has generally served humanity in cultural and religious contexts and also is significant in the scientific description of the world. During the past half-century, time measurement has taken a giant leap: from celestial motions (ancient), pendulums (17th century), and clock dials (popular), it began to delve deeper into the atomic world where electronic transitions occur with inconceivable precision. These explorations led to the cesium clock, now the ultimate time machine of the modern age. In its current version, its precision is of the order of one second in ten million years. But more precise timekeeping is not just a personal obsession for thrills; accurate time reckoning finds umpteen applications from telephone systems to satellite technology. Astronomer Jones (Open Univ.) traces the history of the development, applications, and relevance of splitting the second. While philosophers rant about the limits of science, religionists pooh-pooh its incapacity to discern the transcendent, and naive antiscience people decry science for its nuclear wastes and rain-forest depletion, science marches on in research centers and laboratories, making slow and significant breakthroughs, sometimes silent, sometimes noisy, pushing humankind's understanding of various arenas of the world deeper and deeper. Highly recommended. All levels. V. V. Raman; emeritus, Rochester Institute of Technology

Table of Contents

Forewordp. vii
Prefacep. ix
1 Astronomers' Timep. 1
2 Physicists' Timep. 25
3 Atomic Timep. 53
4 World Timep. 69
5 The Leap Secondp. 95
6 Time Transferp. 115
7 Uses of Accurate Timep. 141
8 The Future of Timep. 161
Appendix Timekeeping Organisationsp. 183
Glossary of Abbreviationsp. 189
Indexp. 193

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