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

[Magnus Danielson]

From: "Tom Van Baak" <tvb at leapsecond.com>
Subject: Re: [time-nuts] Time Nuts at PTTI this past week
Date: Sat, 9 Dec 2006 07:43:41 -0800
Message-ID: <003301c71ba8$cdfe4fc0$129a8843 at computer>

> Hal,

Tom,

> > 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.

I assume you told the kids that yes, time does goes faster when you are
having fun!

Good practicaly physics lecturer you had there.

> > 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.

With modern locking techniques, the C-field is being steered for the feature
separations. It does not concerns itself with altitude as result of GR as far
as I know. Did you log the C-field control loop during this trip?

> 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.

Indeed.

> 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.

Remember that while you are 1340 meters up, the mountains gravity pull creates
a local compensation to a small degree, so you will not fully experience the
full altitude difference. It would have been a different exercise if you took
a hotair balloon more or less straight up from your home. It might however be
a challenge to stay up there for long enought to be comparable.

Cheers,
Magnus