The Science of Time 2016

1. Front Matter

   Pages i-x

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2. Cosmic Time: From the Big Bang to the Eternal Future

   • Chris Impey

   Pages 1-13

3. The Proof of the Pudding

   • William Andrewes

   Pages 15-16

4. The Role of Ephemerides from Ptolemy to Kepler

   • Owen Gingerich

   Pages 17-24

5. How Time Served to Measure the Geographical Position Since Hellenism

   • Susanne M. Hoffmann

   Pages 25-36

6. Changing Times in the Nautical Almanac Over 250 Years

   • Susan Nelmes

   Pages 37-43

7. Bond Time: The Electric Method of Time Recording

   • Donald Saff

   Pages 45-45

8. The Development and Use of the Pilkington and Gibbs Heliochronometer and Sol Horometer

   • Geoff Parsons

   Pages 47-48

9. These Are Not Your Mother’s Sundials: Or, Time and Astronomy’s Authority

   • Sara J. Schechner

   Pages 49-73

10. The History of Time

    • Dennis McCarthy

    Pages 75-75

11. “When?” It’s a Basic Question That We Ask All the Time

    • Harlan Stenn

    Pages 77-77

12. Inter-site Alignments of Prehistoric Shrines in Chaco Canyon to the Major Lunar Standstill

    • Anna Sofaer, Robert Weiner, William Stone

    Pages 79-101

13. Atomic Time Scales and Their Applications in Astronomy

    • Felicitas Arias

    Pages 103-104

14. Relativistic Time at the US Naval Observatory

    • Matsakis Demetrios

    Pages 105-118

15. Real-Time Realization of UTC at Observatoire de Paris

    • G. D. Rovera, S. Bize, B. Chupin, J. Guéna, Ph. Laurent, P. Rosenbusch et al.

    Pages 119-122

16. Time in Television Systems

    • Donald Craig

    Pages 123-124

17. From Computer Time to Legal Civil Time: IANA tz, IETF tzdist, etc.

    • Steve Allen

    Pages 125-125

18. The UT1 and UTC Time Services Provided by the National Institute of Standards and Technology

    • Judah Levine

    Pages 127-139

19. On a Redefinition of the SI Second

    • Fritz Riehle

    Pages 141-141

20. Time Scales Steered by Optical Clocks

    • T. Ido, H. Hachisu, F. Nakagawa, Y. Hanado

    Pages 143-149

The uses of time in astronomy - from pointing telescopes, coordinating and processing observations, predicting ephemerides, cultures, religious practices, history, businesses, determining Earth orientation, analyzing time-series data and in many other ways - represent a broad sample of how time is used throughout human society and in space. Time and its reciprocal, frequency, is the most accurately measurable quantity and often an important path to the frontiers of science. But the future of timekeeping is changing with the development of optical frequency standards and the resulting challenges of distributing time at ever higher precision, with the possibility of timescales based on pulsars, and with the inclusion of higher-order relativistic effects. The definition of the second will likely be changed before the end of this decade, and its realization will increase in accuracy; the definition of the day is no longer obvious. The variability of the Earth's rotation presents challengesof understanding and prediction. 

In this symposium speakers took a closer look at time in astronomy, other sciences, cultures, and business as a defining element of modern civilization. The symposium aimed to set the stage for future timekeeping standards, infrastructure, and engineering best practices for astronomers and the broader society. At the same time the program was cognizant of the rich history from Harrison's chronometer to today's atomic clocks and pulsar observations. The theoreticians and engineers of time were brought together with the educators and historians of science, enriching the understanding of time among both experts and the public.

• metrology proceedings
• science of time
• timekeeping in astronomy
• philosophy of time
• history of time
• future timekeeping standards
• Harrison's chronometer
• atomic clocks
• quantum theory and time
• pulsar observations

• Time Department, International Bureau for Weights and Measures, Sevres, France

  Elisa Felicitas Arias

• Hartebeesthoek Radio Astronomy Observatory, Krugersdorp, South Africa

  Ludwig Combrinck

• Vatican Observatory, Tucson, USA

  Pavel Gabor

• HM Nautical Almanac Office, UK Hydrographic Office HM Nautical Almanac Office, Taunton, United Kingdom

  Catherine Hohenkerk

• Department of Astronomy, University of Virginia, Charlottesville, USA

  P. Kenneth Seidelmann

Felicitas Arias, Ph.D., is Director of the Time Department, International Bureau for Weights and Measures in Sèvres near Paris.Responsible for the maintenance of Universal Coordinated Time. 


Ludwig Combrinck, Ph.D., is Acting Managing Director of the Hartebeesthoek Radio Astronomy Observatory (HartRAO), National Research Foundation, South Africa. His main interests are space geodesy and general relativity. 


Pavel Gabor, Ph.D., is Vice Director of the Vatican Observatory responsible for its observational facilities in Arizona. He is involved in the robotic upgrades of three telescopes and other astronomical instrumentation projects. As a Jesuit priest and an official of the Holy See, he also studies timekeeping, its history and symbolism. 


Catherine Hohenkerk, HM Nautical Almanac Office (HMNAO), UK Hydrographic Office, a long standing member of HMNAO, fellow of the Royal Institute of Navigation, Chair of the long standing IAU Division A
working group Standards of Fundamental Astronomy (SOFA) and President of IAU Division A Commission for Fundamental Standards. 


P.Kenneth Seidelmann, Research Professor of Astronomy at the Universityof Virginia; former director of astrometry directorate at the U.S. Naval Observatory, Co-editor of the Explanatory Supplement to the Astronomical Almanac, Co-author of books on astrometry, time, and celestial mechanics and astrodynamics, and author of many scientific papers.

Policies and ethics