The Babylonian Unit of Time

Stephenson, F. R.; Fatoohi, Louay

doi:10.1177/002182869402500203

Cited by 10 publications

(1 citation statement)

References 4 publications

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“…Stephenson and some researchers have identified hundreds of eclipse and occultation observations in early European, Middle Eastern and Chinese annals, manuscripts, canons and records. Also, some of them have fit a lot of records with simple polynomials to achieve best fits for describing the value of Δ T for centuries before ad 1600 (Morrison & Ward 1975; Stephenson & Morrison 1984; Stephenson & Houlden 1986; Stephenson & Fatoohi 1994; Stephenson & Fatoohi 1995; Stephenson 1997; Stephenson & Morrison 1995; Steele 1998; Morrison & Stephenson 2004). In spite of their relatively low precision, these data represent our only record of the value of Δ T during the past several millennia.…”

Section: Values Of δT and Analytical Relationsmentioning

confidence: 99%

A novel approach to delta-T from 1620 to 2010

Hakimi¹,

Setayeshi

2011

Monthly Notices of the Royal Astronomical Society

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Universal Time (ut) is a non‐uniform time‐scale based on the rotation of the Earth around its axis. Another time‐scale based on the duration of the SI second that was originally defined by the revolution of the Earth in its orbit around the Sun, is called Terrestrial Time (tt). As tt is a uniform time designed to provide continuity with the former Ephemeris Time (et), the difference between tt and ut is known as delta‐T (ΔT). The time series of ΔT values shows the variations in Earth rotation. There are several mathematical models to represent ΔT used in astronomical software and calculations. This paper discusses a new model for values of ΔT from 1620 to 2010 that uses artificial neural networks. The maximum absolute error in this model is about 0.5 SI second. The accuracy of the new model is compared with that of four prior models.

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