[time-nuts] Detecting gravity with optical atomic clocks

[Neville Michie]

What I found interesting was that a pendulum, with a reasonably high Q, could acquire energy
from the seismic disturbance to shift its phase.
Now a 10Kg pendulum would require a significant amount of energy, and it can only
absorb energy of a very narrow bandwidth, which is calculable from its Q.
The energy can be calculated, I think, from the phase shift and the amplitude of the swing.
The total amount of energy over the whole spectrum must have been quite high.
Cheers, Neville Michie


> On 2 Dec 2018, at 12:45, Tom Van Baak <tvb at LeapSecond.com> wrote:
> 
> "Paul Bicknell" --
>> Any chance of a picture of your Synchronome pendulum clock and associated
>> timing / logging equipment 
> 
> Yes, I'll update that page with more info and photos at some point.
> Meanwhile there are some links to follow at the end of the page:
> http://leapsecond.com/pend/synchronome/quake.htm
> 
> ----
> 
> "Didier Juges" --
>> Tom,
>> I suspect something so sensitive gives you significant "false positives"
>> when a delivery truck goes by. I assume you try to correlate your data with
>> other enthusiasts nearby to resolve those discrepancies the way we do with
>> our clocks?
> 
> The pendulum is directly bolted to large thick basement corner wall. Local door slams or delivery trucks have no effect that I've ever seen. But a 7.0 earthquake is truly massive and it creates ground motion at the many microns to mm levels even 1500 miles away. A precision pendulum clock is affected by this level of vibration, especially when it persists for many minutes.
> 
> Yes, the pendulum data correlates in time with professional seismometer stations here and around the northwest.
> 
> ----
> 
> "Hal Murray", "Poul-Henning Kamp" --
>> And can you reverse-engineer the local ground movement from the
>> pendulum measurements ?
> 
> For quartz, rubidium, and pendulum clocks, it is possible to partially reverse-engineer effects of temperature, pressure, and humidity. These are scaler quantities and very slow moving processes.
> 
> Seismic effects on pendulums are a whole different problem. It's a 3D vector quantity. They are very dynamic (rapidly changing), with a complex power spectrum. And the interaction of ground acceleration with a swinging pendulum is extremely dependent on angles and on the instantaneous pendulum phase vs. seismic power relationship, which is changing every millisecond and lasts for minutes. Plus the pendulum reaction to some of these changes is non-linear. As Bob would say, lot's of fun.
> 
> In theory if you had several pendulums arranged around a circle, and used ultra wide band seismometers (or super high resolution accelerometers), and took measurements at 10 to 100 Hz, then I suspect computer simulations might be able to make some predictions out of the data. Which you could then back out.
> 
> /tvb
> 
> 
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