# [time-nuts] Time Dilation tinkering

Tom Van Baak tvb at LeapSecond.com
Wed Mar 22 20:15:19 EDT 2017

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"

/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.