[time-nuts] Pendulums & Atomic Clocks & Gravity

Brooke Clarke brooke at pacific.net
Sat May 26 22:02:29 EDT 2007


Hi Bruce:

Yes, I saw a mention of that.
Sort of like crystal frequency jumps.

Have Fun,

Brooke Clarke
http://www.PRC68.com
http://www.precisionclock.com



Dr Bruce Griffiths wrote:
> Brooke Clarke wrote:
> 
>>Hi Mike:
>>
>>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.
>>
>>Have Fun,
>>
>>Brooke Clarke
>>http://www.PRC68.com
>>http://www.precisionclock.com
>>  
> 
> Brooke
> 
> Invar and super Invar sound OK except that they are notoriously unstable 
> with the dimensions changing slowly over time even at constant temperature.
> 
> Bruce
> 
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