NIST MONOGRAPH 155, FROM SUNDIALS TO ATOMIC CLOCKS, UNDERSTANDING TIME AND FREQUENCY, 19TH ED. (MARCH 1999

NIST MONOGRAPH 155, FROM SUNDIALS TO ATOMIC CLOCKS, UNDERSTANDING TIME AND FREQUENCY, 19TH ED. (MARCH 1999). It has been two decades since the first edition of this book appeared. Over that time launching artificial satellites has become routine, computers have become household items, digital messages routinely travel between cities and nations by communication satellites and optical fibers, astronomers have identified black holes, and researchers have learned to manipulate individual and small groups of atoms. These changes have had a profound impact on the arts of time keeping and distribution and on our understanding of the nature of time and space. In this new edition I have attempted to deal with these matters, and many others, by introducing six new chapters and by making numerous changes and additions to the chapters from the first edition. In the beginning I imagined this book would be of most use and interest to a general audience. In that regard it offered an eclectic, too eclectic I sometimes thought, introduction to time, timekeeping, and the uses of time, especially in the scientific and technical areas. But as I soon discovered, many of my colleagues referred to the book, on occasion, to brush up on an item here and there. Perhaps this is not surprising. The business of generating, maintaining and applying time and frequency technology is a vast enterprise. Although this second edition does not pretend to give an in-depth, textbook presentation, I hope it still maintains scientific integrity while continuing to be comprehensible to the general reader. Finally, in 1988, the National Bureau of Standards (NBS) was renamed the National Institute of Standards and Technology (NIST). Where historically appropriate I refer to NBS, otherwise the current designation, NIST, is used. James Jespersen March 1999