[time-nuts] Einstein Special on PBS

Tom Van Baak tvb at LeapSecond.com
Sun Nov 29 16:02:02 EST 2015


A few years after my Mt Rainier trip I looked into doing the same experiment down a mine. But besides having mountains Seattle also has the Pacific ocean so there are any number of commercial and research deep sea operations around here. I thought it would fun to put a few 5071A and batteries into a bathysphere and send them down as many thousand feet as possible for a couple of days.

One advantage is that many of them have long fiber data links and so I thought it might be possible to compare clocks live during the experiment instead of having to wait for the round-trip. TDR could be used to compensate for fiber tempco.

The theory is simple. Below sea level gravity falls by 1/r and above sea level gravity falls by 1/r^2. The magic number, W0, is -6.969e-10 which how slow Earth's SI second is compared to "free space". In other words, clocks speed up on either side of mean sea level. Yes, an atomic clock can be used as a depth gauge as well as an altimeter.

You're probably thinking it would be fun to detect the difference between 1/r and 1/r^2 effects. But the problem is that the earth has a radius of 3900 miles so for a couple of miles above or below the surface, 1/r and 1/r^2 look identical. That is, you get the same blueshift: 1.1e-16/meter.


----- Original Message ----- 
From: "Chris Howard" <chris at elfpen.com>
To: <time-nuts at febo.com>
Sent: Friday, November 27, 2015 7:04 PM
Subject: Re: [time-nuts] Einstein Special on PBS

> The mountain thing has been done.
> Someone needs to take their
> clock to the bottom of the deepest mine (2.4 miles).

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