[time-nuts] Time Dilation tinkering
Tom Van Baak
tvb at LeapSecond.com
Tue Mar 21 04:58:46 EDT 2017
Hi Hugh,
> If I do the math correctly that's about 14ns difference per 24h the
> clocks are separated by that altitude. [1]
That's correct. For your 1500m elevation gain, the gravitational redshift, the df/f frequency change, will be about 1.6e-13. To be able to measure with any confidence you'll want your clocks to be stable to about 2e-14, at tau 1 or 2 days.
> This got me to wondering if a Rubidium based standard might do the trick
> - the Efratom SLCR-101s seem readily available for ~USD$200 mark.
There are tricks and technical factors, but the main one is how stable these are at tau 1 day. Buy or borrow a few of them and see if they are mutually stable to the level required. I suspect not. But perhaps other time nuts could comment on how stable their surplus Rb are out to tau 1 day.
There are lots of other details; some to your advantage, some not. But if the surplus Rb can't perform down in the -14's at a day, even in laboratory conditions, then the rest of the discussion doesn't matter.
Yes, the TAPR TICC counter would work well for this experiment. But to be honest, any old nanosecond-level counter is good enough. I say this not to discourage you from a good excuse to buy a TICC, but to encourage you to do the ADEV math to see how clocks and counters and tau can interact in your favor.
/tvb
----- Original Message -----
From: "Hugh Blemings" <hugh at blemings.org>
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com>
Sent: Monday, March 20, 2017 7:38 PM
Subject: [time-nuts] Time Dilation tinkering
> Hi,
>
> I've been mostly lurking on the list for some time now and follow with
> interest the many discussions. Very much at the early stages of my
> time-nut journey, but enjoying it so far :)
>
> I'd like to have a go at re-creating the efforts of Tom (and I gather
> others) in taking a clock up a mountain for a while and seeing if I can
> measure the relativistic changes.
>
> Being based in Australia gives me a couple of challenges, for one we
> don't really do mountains in the same sense as much of the rest of the
> world - so the highest peak I can readily get to from Melbourne is about
> 1,600m ASL. I live at 80m ASL - so a delta of around 1,500m altitude
> and several hundred km drive.
>
> If I do the math correctly that's about 14ns difference per 24h the
> clocks are separated by that altitude. [1]
>
> We also lack quite the same surplus market here as the US, so purchasing
> a Caesium based standard is well beyond my means.
>
> This got me to wondering if a Rubidium based standard might do the trick
> - the Efratom SLCR-101s seem readily available for ~USD$200 mark.
>
> Clearly there'd need to be a bunch of extra gubbins [2] added to the
> 10MHz standard to turn it into an actual clock/counter including battery
> backup and so forth. And would need a pair of everything.
>
> Before I delve too far into the planning, I'd be interested in feedback
> as to whether this style of Rb standard is likely to be up to the task
> of being the core of such an endeavour or not ?
>
> Oh I should add - my plan was to build the systems such that they
> function as nice standalone time/frequency references once this
> experiment is concluded :)
>
> Thanks in advance,
>
> Kind Regards/73,
> Hugh
> VK3YYZ/AD5RV
>
>
>
> [1] gh/c^2 x 3600 x 24 Where h is 1500, g and c the usual values :)
>
> [2] I presume at a minimum a counter running at a 5ns or less "tick" fed
> from a frequency source locked to the 10MHz of the Rb standard. This
> counter would need to be latched for reading from an external signal so
> that it can be compared to the second clock. Not sure but seems the
> TAPR TICC might have role here :)
> _______________________________________________
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
> and follow the instructions there.
More information about the time-nuts
mailing list