[time-nuts] Re: Hafele-Keating, 50 years ago today

[Bob kb8tq]

Hi

> On Oct 5, 2021, at 11:33 AM, Tom Van Baak <tvb at 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>_______________________________________________
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