[time-nuts] Time Dilation tinkering

Bob Camp kb8tq at n1k.org
Thu Mar 23 07:33:26 EDT 2017


Hi

Back before GPS and similar systems, hauling Cs standards on commercial aircraft was
a bit more common than it is today. One of the critical tricks of the trade was knowing where
each power outlet was on a specific plane and how close it was to this or that seat. The next
trick was knowing how to talk the crew into letting you plug the gizmo in the seat next to yours
into that outlet. Sometimes the magic worked and other times you had to depend on your 
battery pack. Needless to say, getting through the over ocean travel process with a dead
standard was not good news. 

Bob

> On Mar 22, 2017, at 10:59 PM, Bob Bownes <bownes at gmail.com> wrote:
> 
> It's not getting one past the airport authorities that's the issue. It's getting one that's powered up past them. ;)
> 
> Written from about 10,000'. :)
> 
>> On Mar 22, 2017, at 20:15, Tom Van Baak <tvb at LeapSecond.com> wrote:
>> 
>> Chris Albertson wrote:
>>> Why drive up a mountain?
>> 
>> "Because it's there" ;-)  And because there's a paved road, and it's free, and there's a place to stay overnight, and the mountain doesn't move. Plus a car makes a good portable time lab; you can share the experience with family or students or visiting time nuts; and a number of technical reasons.
>> 
>> But most importantly: you can remain at altitude as long as you want -- in order to accumulate just enough nanoseconds of time dilation to meet your experiment's S/N goal -- without running into (or much worse, going beyond) the flicker floor of your clocks.
>> 
>> There are several different ways to measure time dilation with atomic clocks. Some notes here:
>> http://leapsecond.com/pages/atomic-tom/
>> 
>> 
>>> Take the clock with you inside the pressurized cabin of a commercial airliner
>> 
>> Yes, and this has been done many times. The first (1971) and most famous of all traveling clock relativity experiments is:
>> https://en.wikipedia.org/wiki/Hafele%E2%80%93Keating_experiment
>> 
>> For vintage hp flying clock articles see:
>> https://www.febo.com/pipermail/time-nuts/2013-January/073743.html
>> 
>> Two modern examples are described here:
>> 
>> "Time flies"
>> http://www.npl.co.uk/news/time-flies
>> 
>> "Demonstrating Relativity by Flying Atomic Clocks"
>> http://www.npl.co.uk/upload/pdf/metromnia_issue18.pdf
>> 
>> /tvb
>> 
>> ----- Original Message ----- 
>> From: Chris Albertson 
>> To: Tom Van Baak ; Discussion of precise time and frequency measurement 
>> Sent: Tuesday, March 21, 2017 7:12 PM
>> Subject: Re: [time-nuts] Time Dilation tinkering
>> 
>> "flight" there is the word.    Why drive up a mountain?   Take the clock with you inside the pressurized cabin of a commercial airliner next time you are on one of those 10 hour trans=pacific flights.   You be taller then any mountain and it is actually cheaper then a weather balloon. 
>> 
>> Can you get a Rb clock past the TSA x-ray machine.   Maybe if you ask first.  There must be a way to hand cary specialized equipment.
>> 
>> On Tue, Mar 21, 2017 at 7:03 PM, Tom Van Baak <tvb at leapsecond.com> wrote:
>> 
>> But attached is one of the first plots where I put a SA.32m in a home-brew vacuum chamber and pulled down to a few inches of Hg for a few hours to simulate the low pressure of a flight up to 50 or 90,000 ft. For a high altitude relativity experiment -- where you'd like your clock to remain stable to parts in e-13 and not accumulate too many stray ns -- it's not a good sign when your clock changes by 2e-11 (that's more than 1 ns per minute) just because of ambient pressure changes.
>> 
>> 
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