[time-nuts] gravity controlled pendulumn clock?

Tom Van Baak tvb at LeapSecond.com
Mon Dec 12 06:33:47 EST 2011

Jim Lux writes:
> intriguing.  From your parenthetical remark, I'm assuming you move the 
> whole assembly up and down to adjust the speed?
> I was thinking about a huge mass that moves around?

Got one already -- it's called the moon!

> let's see.. period is proportional to sqrt(1/g)
> g is proportional to 1/r^2, so period is proportional to r.
> Earth is roughly 7000 km radius, so moving it 1 meter higher or lower 
> changes the period by 1part in 7million... interesting.

Yes, cool isn't it? There's an entire history of using pendulums
to measure altitude, and latitude -- and time or distance: at some
locations on earth a 1 meter pendulum is so close to a 1 second
beat there was consideration to define the meter that way.

Some articles on gravity, earth tides, and pendulum clocks:

John Allen writes:
> Hi Tom - what is HSN?

Horological Science Newsletter, http://www.hsn161.com

It's a collection of people who still find precision pendulum clocks
fascinating, a specific strain of the time nut disease. It's a small
group (officially Chapter #161, Horological Science) of the larger:

National Association of Watch & Clock Collectors, http://www.nawcc.org


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