[LEAPSECS] Pedagogy & Greenwich

[Gerard Ashton]

We all know that "Greenwich Mean Time" is commonly used to describe UTC,
UT1, and various similar time scales. Please check if I have estimated
correctly.

-The easternmost point of the London district of Greenwich is a the
intersection of two roads, Maze Hill and Charlton Way. The coordinates are
51° 28.509' N, 0° 0.602' E, which is about 36" E. Since 15" of arc equals 1
s of time, the eastern most part of Greenwich is 2 seconds of time east of
the prime meridian. So if leap seconds were to stop, the meridian where
local mean time most closely approximates UTC would fall outside Greenwich
in about three years. At such time, any correct attempt to explain what GMT
means, when used as a synonym for UTC, should mention it has nothing to do
with Greenwich.

Gerry Ashton