Being curious here: has anyone ever taken a Cs in a submarine? E.g. the Marianatrench or so?
As a native from a mountain-deprived country I could not help wondering. Wilko > On 28 Nov 2021, at 08:14, Tom Van Baak <[email protected]> wrote: > > 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-Hobby.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.
