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 <[email protected]> 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:[email protected]] > Sent: Sunday, November 28, 2021 20:09 > To: [email protected] > 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 [email protected] -- To unsubscribe > >>> send an email [email protected] To unsubscribe, go to > >>> and follow the instructions there. > >> _______________________________________________ > >> time-nuts mailing list [email protected] -- To unsubscribe > >> send an email [email protected] To unsubscribe, go to > >> and follow the instructions there. > >> > > _______________________________________________ > > time-nuts mailing list [email protected] -- To unsubscribe > > send an email [email protected] To unsubscribe, go to > and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send > an email to [email protected] To unsubscribe, go to and > follow the instructions there. > _______________________________________________ > time-nuts mailing list -- [email protected] -- To unsubscribe send > an email to [email protected] > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] -- To unsubscribe send an email to [email protected] To unsubscribe, go to and follow the instructions there.
