[time-nuts] Time Nuts at PTTI this past week

[Tom Van Baak]

Hal,

> What's the calculated value?  Lassen isn't very high.  Are the campgrounds
> higher than Denver/Boulder?

It was Mt Rainier, near here in Seattle, WA. We
went up to the 5400' level where the clocks ran on
the order of 500 ps/hour faster than at my home lab
at 1000'. We stayed up there about 40 hours. The
calculated time dilation, based on GPS logs of our
position, was around 23 ns.

> For that matter, how hard is it to do this experiment with just two clocks
at
> different elevations?  Do cesium clocks have an adjustment knob that
easily
> covers any elevation offsets?

Yes and no. One could use the C-field adjustment,
as many of us have. But better results can be had
using an external phase microstepper, or just making
corrections in software, treating the cesium more as
a paper clock.

For this relativity experiment I didn't adjust any of the
clocks - the whole point was to let them run at their
natural frequency and see how far off they had dilated
in time when they got back home.

With the differential elevation gain I had available here
(between home and Mt Rainier is 1340 meters) the
predicted relativistic effect on the mountain was about
1.5e-13. Roughly, to get a 10% accurate measurement
I needed to use clocks that were 10x more stable than
the effect I was trying to measure. Many of the older
Cs I have collected from eBay aren't stable to 1e-14 at
a day. In the end I hand picked three 5071A that were.

/tvb