On 25/10/2017 18:59, Gerald Kelleher wrote:
The theorists assume they are discussing time when it is really
timekeeping they are referring to. Of course this goes back to a
person who decided to define timekeeping as time itself using a
calendar based facility known as the Equation of Time -
The equation of time is just the first order correction for a whole host
of other effects that alter the spin of the Earth. The transit of the
sun makes for a very poor time standard by comparison with a star.
Astronomers realised this a very long time ago by the Babylonians.
http://www.precisedirections.co.uk/S...rly%20Days.pdf
Pragmatically people divided daylight and nighttime into 12 hours of
length which varied radically with the seasons (at least in the UK).
Monastery clock pendulums at the time were adjustable to allow longer or
shorter "hours" for day and night time away from the equinoxes.
https://en.wikipedia.org/wiki/Roman_timekeeping
--
Regards,
Martin Brown