Okay, I've tried to research this for a few days, and seem to be running
into conflicting data.
Some articles say that UT1 is based on the IERS Reference Meridian (IRM).
Other articles say that UT1 is based on mean solar time at the Prime
Meridian (Greenwich). It can't be both! Which one is it? In other words,
which meridian would I need to stand on to indicate Solar Noon as
12:00:00.000 (UT1) on a day of the year where the equation of time is 0
seconds offset?
From what I can reckon, a 200-400 millisecond difference exists between the
two longitudes, which are separated by about ~102 meters at Greenwich. So,
if UT1 (and hence UTC) is based on the IRM and not the Prime Meridian, then
at some point did clocks have to be adjusted ~200 milliseconds "away from"
the Prime Meridian when the IRM was defined? Or was it sloppy and they
treated the two as one and the same?
Anyone know?
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