Time Dilation and the Length of the Second

Steven D. Deines, Carol A. Williams

Abstract:	We show that the leap second is due to timescale divergence between Universal Time (UT) and International Atomic Time (TAI) because the Système Internationale (SI) second is shorter than the UT second. This is demonstrated by a thorough analysis of the procedures that were followed to produce Ephemeris Time (ET) to which the SI second was calibrated. This paper shows that time dilation is responsible for the ET second being shorter than the UT second. Over the past century, it was well documented that observed lunar and planetary positions always lagged behind calculated positions. ET was introduced to remove this discrepancy. Deceleration of Earth’s rotation contributed less than 1% of this timescale divergence, according to paleontological records of tidal fraction. Our calculation of the time dilation effect match the difference between the SI and UT seconds and also match the leap second insertion rate to within 0.2% since atomic time began in 1958. A method to convert from the TAI timescale using a scalar to obtain a precise UT timescale is given with leap seconds needed only once every 14 decades due to tidal friction.
Published in:	Proceedings of the 38th Annual Precise Time and Time Interval Systems and Applications Meeting December 7 - 9, 2006 Hyatt Regency Reston Town Center Reston, Virginia
Pages:	389 - 394
Cite this article:	Deines, Steven D., Williams, Carol A., "Time Dilation and the Length of the Second," Proceedings of the 38th Annual Precise Time and Time Interval Systems and Applications Meeting, Reston, Virginia, December 2006, pp. 389-394.
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