[time-nuts] Shortt Clock Recent Measurements

[Tom Van Baak]

> The Wiki page for the Shortt pendulum clock has a "Recent Measurements" (1984)  paragraph that's in error.
> http://en.wikipedia.org/wiki/Shortt-Synchronome_clock#Recent_accuracy_measurement
> 
> While it's probably true that the clock is stable to 200 uS per day (i.e. 2E-9) I believe Alfred Loomis discovered the 
> effect of the moon on this clock a long time ago.

Hi Brooke,

The wiki page is correct. The heading is "Recent Measurements" and Pierre Boucheron's 1984 effort certainly qualifies. Note the wiki doesn't claim Boucheron was the first. In fact, even 30 years old, it is still the most recent, and the only Shortt experiment for which we have raw data. See http://leapsecond.com/pend/shortt/ for details.

One could try claiming that Loomis was the first to make detailed measurements of a Shortt, but it would take some digging to prove he was "first" and not just "one of the first". I mean, if you look at the list of who received the one hundred Shortt's that were manufactured, many laboratories had more than one, not to mention the ones that William Shortt himself owned at the factory. Certainly there was a lot of time measurement going on in the 20's and 30's. It would take a lot of work to uncover what was known by whom and when. Or who published first or not.

I think Loomis took it a wonderful extreme with his spark chronograph and quartz oscillator via telephone time transfer setup. And that be bought three clocks at once is classic and inspiring to any time nut! So I agree, Loomis deserves mention on the Shortt wiki page.

Unrelated to gravity and tides, is the role that vacuum pendulum and ovenized quartz clocks had in confirming that earth rotation was itself irregular at the millisecond level. Credit for that usually goes to Scheibe and Adelsberger in the late 30's, not Shortt or Loomis. And that of course blends into the story of the leap second...

See my scan/OCR historical pendulum collection: http://leapsecond.com/pend/pdf/
And my own precision pendulum-nut articles: http://leapsecond.com/hsn2006/

Some of you readers might wonder why in this GPS age, two time nuts, each with plenty of atomic clocks at home, would be talking about vintage pendulum clocks. It turns out that pendulum clocks are still extremely interesting timekeepers, from an experimental, scientific, and historical perspective.

/tvb