[time-nuts] UTC and leap seconds

Hal Murray hmurray at megapathdsl.net
Fri Jun 11 17:39:20 EDT 2010


>> Wikipedia says 2 ms/100 years and that it was noticed by
>> Halley in 1695 and confirmed by Dunthorne in 1749.  I
>> assume they were using the Earth's orbit around the sun
>> as their reference clock. 

> how exactly would that work?  Are they measuring the number of "days" in  a
> "year"?  How would one do that? See when the sun crosses in front of a
> specific star (to get the "day") (or an equivalent measurement at night  of
> some sort) 

I'm not sure.  I'd guess they were more likely to use the orbits of the 
planets.

One of the ideas competing with Harrison was observing Jupiter's moons.  They 
knew enough to correct for the speed of light across the Earth's orbit.  (I'm 
not sure if they knew why it was important, but they were doing it.)


People have been fascinated by the seasons for a long time.  Stonehenge was 
~2500 BC.  So solstice data might be useful.



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