[time-nuts] Pendulums & Atomic Clocks & Gravity
brooke at pacific.net
Sat May 26 22:02:29 EDT 2007
Yes, I saw a mention of that.
Sort of like crystal frequency jumps.
Dr Bruce Griffiths wrote:
> Brooke Clarke wrote:
>>Back in the 1800s clock makers found ways to temperature compensate the
>>pendulum such as putting a Mercury thermometer at the bottom, using metals with
>>dissimilar expansion coefficients (Harrison used steel and bronze (no zinc
>>then)) or materials with almost zero COE like Invar.
>>The Dent clock at Greenwich in 1885 had an arenoid type compensator to remove
>>barometric pressure effects, later clocks were run in vacuum.
> Invar and super Invar sound OK except that they are notoriously unstable
> with the dimensions changing slowly over time even at constant temperature.
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