[LEAPSECS] 2 meetings on UTC and the impending ITU-R RA vote

Tony Finch dot at dotat.at
Mon Jul 11 08:43:53 EDT 2011

Michael Deckers <michael.deckers at yahoo.com> wrote:


> Before the advent of atomic time keeping, clocks were less stable than

> astronomical observations of Earth orientation, so that clock rates were

> adjusted post factum to fit the astronomical observations at each site.

Quartz clocks can be more stable than Earth rotation: see for example

The first outstanding application of the quartz clock to astronomy was
made in Germany with the installation at the Physikalisch-Technische
Reichsanstalt. This was described by Scheibe and Adelsberger in 1932 and
1934, and reports of its splendid performance continued periodically. It
was with this installation that it was possible for the first time to
observe and measure variations in the earth's rate occurring over
intervals as short as a few weeks. Previous measurements of such
variations, involving studies of motion of the moon, the planets, and
Jupiter's satellites, had required years to obtain comparable
information which, of course, by nature, could never reveal short-term

I thought this innovation was one of the reasons for moving to ephemeris
time as the basis for calibrating clocks, instead relying on transit

f.anthony.n.finch <dot at dotat.at> http://dotat.at/
Trafalgar: North or northwest 4 or 5, occasionally 6 later. Slight or
moderate. Rain or thundery showers. Moderate or good.

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