Hi > On Oct 5, 2021, at 11:33 AM, Tom Van Baak <t...@leapsecond.com> wrote: > > The Hafele-Keating experiment was performed 50 years ago. Starting October > 4th, 1971, Joe Hafele and Dick Keating took 4 hp cesium clocks on an airplane > trip, a very long trip, all the way around the world, twice. The purpose of > the trip was to see if they could detect predicted relativistic effects using > "flying clocks". > > At that point in history portable hp cesium clocks were just accurate/stable > enough to try this bold experiment. Subsequent work during the 70's confirmed > and refined their results. For a brief description of the experiment: > > https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment > > Here's the detailed technical paper Hafele presented at PTTI in 1971: > > "Performance and Results of Portable Clocks in Aircraft" > https://apps.dtic.mil/sti/pdfs/ADA489971.pdf > > Links to their two scientific journal articles in 1972: > > "Around-the-World Atomic Clocks: Predicted Relativistic Time Gains" > https://www.science.org/doi/10.1126/science.177.4044.166 > > "Around-the-World Atomic Clocks: Observed Relativistic Time Gains" > https://www.science.org/doi/10.1126/science.177.4044.168 > > For a collection of PDF and photos see my 50th anniversary Hafele-Keating > page: > > http://leapsecond.com/museum/HK50/ > > I've also attached a photo of their clock setup in the back of my car. Two > vintage 5061A cesium clocks, each with 1PPS and Patek Philippe clock option. > Between them a K02-5060A NiCad battery pack. Combined it's about 200 lbs of > equipment. Two of these racks were used for a total of 4 clocks. In addition > they had a hp 5360A computing counter with time interval plugin to make 4-way > clock consistency comparisons periodically during the experiment. Nearly 500 > lbs of "carry-on". You won't be able to do that today...
My recollection is that even back then, they bought one or more seats for the clock(s). The ideal location apparently was at a bulkhead (by the galley ???). It was the only place they might be able to get power to charge the batteries in flight … Bob > > For those who want a time nut introduction to cesium clocks and relativity > here's a talk at Stanford a few years ago: > > http://web.stanford.edu/group/scpnt/pnt/PNT18/presentation_files/I08-VanBaak-GPS_Flying_Clocks_and_Relativity.pdf > > /tvb > > <HK50-tvb-IMG_8802-640x640.jpg><HK50-tvb-IMG_8801-640x640.jpg>_______________________________________________ > time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an > email to time-nuts-le...@lists.febo.com > To unsubscribe, go to and follow the instructions there. _______________________________________________ time-nuts mailing list -- time-nuts@lists.febo.com -- To unsubscribe send an email to time-nuts-le...@lists.febo.com To unsubscribe, go to and follow the instructions there.
