[time-nuts] Re: Project Great

[Andy Talbot]

I would imagine there are already several caesium clocks on board the ISS,
anyway.
Don't forget there is a velocity component in relativistic time shift, as
well as gravitational, so using a moving platform like an aircraft or the
ISS complicated things a lot

Andy
www.g4jnt.com



On Sun, 28 Nov 2021 at 10:03, Dave ZL3FJ <2c39a at silverbears.nz> wrote:

> Is the ISS a suitable platform?
> I expect getting the experiment package on there would be quite another
> matter!
> DaveB, NZ
>
>
> -----Original Message-----
> From: Tom Van Baak [mailto:tvb at LeapSecond.com]
> Sent: Sunday, November 28, 2021 20:09
> To: time-nuts at lists.febo.com
> Subject: [time-nuts] Re: Project Great
>
> Hi Thomas,
>
> Good to hear the experiment was contagious for you. If you have additional
> questions let me know.
>
> Your suggestion about Mount Evans and Pikes Peak are excellent. You will
> enjoy this 2017 paper:
>
> "An Undergraduate Test of Gravitational Time Dilation"
> https://arxiv.org/abs/1710.07381
> https://arxiv.org/pdf/1710.07381.pdf
>
> ---
>
> As for CSAC, the news is not so good. I've worked with several groups to
> explore CSAC for gravitational time dilation experiments. Those clocks are
> so cute and small, it's irresistible; but the numbers just don't add up.
> Over a day their stability is in the low e-12's vs. a "real" cesium clock
> like a 5071A in the low e-14's. So when you are doing a relativity
> experiment trying to detect a frequency shift that's on the order of e-13's
> you reach for a 5071A instead of a CSAC. The performance is nearly 100 to 1.
>
> One solution is a taller mountain. The best on the planet is Mauna Kea
> (Big Island, Hawaii) where you can literally drive from sea level to the
> summit (13,800 ft, 4200 m) in a few hours. The frequency shift up there is
> 4.5e-13, which is 40 ns per day. But still, to have even the slightest
> chance of success you'd want your clocks to be good to 1e-13 or better.
> CSAC aren't even close, and probably neither are telecom Rb.
>
> I'm currently involved with another solution -- a HAB (High Altitude
> Balloon) CSAC flight. Getting to 100,000 ft altitude is quite common. Up
> there, clocks run a whopping 3.3e-12 faster, which is 280 ns/day, or 12
> ns/hour. This is a clear case where the amazing low mass and low power of a
> CSAC is a  critical advantage. However, the numbers still aren't working
> out and the logistic and environmental conditions are brutal. I won't say
> it's impossible, but it may take years and a huge bag of tricks before it
> works or it's proved too impractical.
>
> ---
>
> Jim, I'd be interested in any Cubesat / CSAC results. They don't exactly
> land in one piece so the typical round-trip clock comparison method
> wouldn't work. A direct frequency comparison might. In that case the drift
> and re-trace specs of a CSAC are probably more important than the stability.
>
> /tvb
>
>
> On 11/27/2021 12:37 PM, Thomas Valerio wrote:
> > I think that Tom's GREAT adventure is kind of what sealed the deal
> > making me a time-nut or at least a time-nuts lurker, a lot of this
> > stuff is still little over my head, but I keep reading.
> >
> > If anyone is inclined and has the clocks and the kids ( I don't have
> > either ), there is always Mount Evans and Pikes Peak, although you may
> > have to leave the clocks behind overnight.  Mount Evans is still on my
> > bucket list but without clocks and two or three days of time to
> > monitor them, I don't think I will be doing the Mount Evans edition of
> > GREAT.  For anyone that is flush enough to afford or can beg, borrow
> > or steal access to a Microsemi chip scale atomic clock, I think a
> > Mount Evans edition would be an awesome addition to Tom's original work.
> >
> >     Thomas Valerio
> >
> >
> >> For newcomers to time-nuts, Andy is asking about my DIY gravitational
> >> time dilation experiment(s).
> >>
> >>   > What am I missing?
> >>
> >> It looks like you used the wrong value (or wrong units) for "h".
> >>
> >> The summit of Mt Rainier is 14411 ft (4400 m), but the highest point
> >> on Mt Rainier that is accessible by road is the Paradise visitors
> >> center at
> >> 5400 ft. Our house is at 1000 ft elevation so the net difference in
> >> elevation of the clocks was 4400 ft (1340 m).
> >>
> >> The clock(s) on the mountain ran fast by gh/c² = 9.8 × 1340 /
> >> (3e8)² = 1.5e-13. Fast clocks gain time. We stayed for about 42
> >> hours so the net time dilation was 42×3600 × gh/c² = 22 ns.
> >>
> >> ----
> >>
> >> For more information see the Project G.R.E.A.T. 2005 page:
> >>
> >> http://leapsecond.com/great2005/
> >>
> >> Better yet, these two recent talks from 2018 and 2020 cover all 3
> >> GREAT
> >> experiments:
> >>
> >> <http://web.stanford.edu/group/scpnt/pnt/PNT18/presentation_files/I08
> >> -VanBaak-GPS_Flying_Clocks_and_Relativity.pdf>
> >>
> >> <http://leapsecond.com/ptti2020/2020-PTTI-tvb-Atomic-Timekeeping-Hobb
> >> y.pdf>
> >>
> >> Lots of time nutty photos in both of those!
> >>
> >> /tvb
> >>
> >>
> >> On 11/27/2021 7:33 AM, Andy Talbot wrote:
> >>> Just been reading your adventures with 3 Cs clocks, a mountain and 3
> >>> kids, but I can't make the estimate of time dilation work out.
> >>> You measured ~ 23ns and say it agrees with calculation
> >>>
> >>> The equation quoted in a related reference, for "low elevations" is
> >>> g.h/c² which if you plug in g = 9.81 m/s²  and h = 4300m for Mt
> >>> Rainer gives an expected value of 4.7 * 10^-16.
> >>> Over 2 days, 2 * 86400s, that would be 81 ns in total, four times
> >>> your value
> >>>
> >>> What am I missing?
> >>>
> >>> Was just speculating what Ben Nevis at a mere 1340m height might
> >>> offer
> >>>
> >>> Andy
> >>> www.g4jnt.com
> >>> _______________________________________________
> >>> time-nuts mailing list --time-nuts at lists.febo.com  -- To unsubscribe
> >>> send an email totime-nuts-leave at lists.febo.com To unsubscribe, go to
> >>> and follow the instructions there.
> >> _______________________________________________
> >> time-nuts mailing list --time-nuts at lists.febo.com  -- To unsubscribe
> >> send an email totime-nuts-leave at lists.febo.com To unsubscribe, go to
> >> and follow the instructions there.
> >>
> > _______________________________________________
> > time-nuts mailing list --time-nuts at lists.febo.com  -- To unsubscribe
> > send an email totime-nuts-leave at lists.febo.com To unsubscribe, go to
> and follow the instructions there.
> >
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com -- To unsubscribe send
> an email to time-nuts-leave at lists.febo.com To unsubscribe, go to and
> follow the instructions there.
> _______________________________________________
> time-nuts mailing list -- time-nuts at lists.febo.com -- To unsubscribe send
> an email to time-nuts-leave at lists.febo.com
> To unsubscribe, go to and follow the instructions there.