[time-nuts] Pendulums & Atomic Clocks & Gravity

Dr Bruce Griffiths bruce.griffiths at xtra.co.nz
Sat May 26 20:00:13 EDT 2007


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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