[LEAPSECS] Consensus building?

[Steve Allen]

On Wed 2011-02-02T16:47:22 +0000, Stephen Colebourne hath writ:

> - the SI-second is a standardised unit of measurement


which is a conventional construct that is valid in a particular
reference frame.  If I build a perfect cesium chronometer and you
build a perfect cesium chronometer those will never agree because of
our differences in relative velocity and depth in the varying
gravitational potential wells.

The only way to approach agreement is to apply corrections
to the chronometer, thus changing it into a clock.

The nature of the conventions under which the SI second is
measured and integrated into a time scale have changed
many times.


> - the current definition of the SI-second was ratified in 1967


and the length of the SI second was chosen to match the length
of the second of Ephemeris Time, which is actually a measure
of angle.


> - an SI-based-minute is formed from exactly 60 SI-seconds

> - an SI-based-hour is formed from exactly 60 SI-based-minutes and thus

> exactly 3600 SI-seconds

> - an SI-based-day is formed from exactly 24 SI-based-hours and thus

> exactly 86400 SI-seconds


Given that no two observers are in the same reference frame, the
notion of extending SI seconds into days requires delving into the
years of discussions on the meaning of relativistic time scales.


> Solar

> - a solar-day is a measured period of time


Not in the sense of metrology.

A mean solar day is a conventional measure of rotation of the
earth as differenced from a conventional reference point.
The nature of the measure of the rotation angle and the conventional
reference point have been changed many times.

Yes, in the sense of human history and culture.

--
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