# [time-nuts] Einstein Special on PBS

Bob Stewart bob at evoria.net
Fri Nov 27 12:47:32 EST 2015

```Hi Mike,
I'm far from an expert on this, but what you're missing is that time and space isn't the same between any two points that are located in different gravity gradients and/or moving at different relative velocities.  The hyperfine transitions are happening at the same local rate whether the Cs device is on planet earth, in orbit around the earth, or in close proximity to the sun or even a black hole.  But, all of these examples are happening in different space-time environments (i.e. different local frames), so that "relative" to each other, they are experiencing time at different rates.

It might help to think of it in terms of doppler effect, though this is not an exact comparison.  But, if you have two clocks that are moving away from each other, they may very well be precisely synchronous, but because of the doppler effect, any measurement you make will show them to be running at different rates.  Because of the effects of gravity, watches at different altitudes appear to run at different rates to the outsider, although to the person wearing the watch, nothing has actually changed; it is the other person's watch that is acting funny.

So, essentially, a clock sitting on the ground at sea level is running in a very slightly different space time than one that is sitting on a mountain.  And when you place a clock in orbit, you also have 14,000 odd MPH of velocity that's also having an impact on the space-time of that object.  As a result, when you bring the prodigal clock back to sea level, it will have experienced a slightly different amount of time than the one at sea level.  Note that the prodigal clock hasn't run at a different rate.  It has actually experienced time running at a different rate from that of the clock on the ground.

Bob

From: Mike Feher <mfeher at eozinc.com>
To: 'Discussion of precise time and frequency measurement' <time-nuts at febo.com>
Sent: Friday, November 27, 2015 9:37 AM
Subject: Re: [time-nuts] Einstein Special on PBS

I just do not get it. I know that now I am 70 and my good smart days are behind me, but, this should be simple. In all these clocks mentioned, time is derived from the transition of a hyperfine line of a certain atom within some element, in this case cesium, In order for any of these clocks to deviate in relative time at different heights for example, it seems to me that the period of the hyperfine transitions must change as well, to make the defined second longer or shorter. So, in these examples the elevation does not change the time, but the way the atoms behave. What obvious item am I missing, besides maybe brain capacity? Thanks - Mike

Mike B. Feher, EOZ Inc.
89 Arnold Blvd.
Howell, NJ, 07731
732-886-5960 office
908-902-3831 cell

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Tim Shoppa
Sent: Friday, November 27, 2015 9:19 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Einstein Special on PBS

Would've been more fun to see Tom and his kids going to the top of Mt Ranier in 2005 with the ensemble :-). http://leapsecond.com/great2005/

They mentioned some "6 miles per day" offset due to GPS relativity effects.
I think this is the sum of both special relativity (time dilation) and general relativity (gravitational) effects. The GR correction is 45 microseconds a day fast; the SR correction is 7 microseconds slow. 38 microseconds seconds is 11 kilometers which is indeed 6 or 7 miles. While time drifts 38 microseconds a day, I'm not sure that GPS coordinates would drift that fast - aren't most of the corrections in the same direction?

Seeing Kip Thorne describe black holes was a blast - he refused to use the word mass when describing them, just like when I took a course from him in 1990. When my advisor taught the same course, I pleaded with him, "please use coordinates!". (Kip Thorne loves coordinate-free notation, unfortunately my brain does not work that way!!! I would've failed the course if it was only GR; fortunately it also had plasma physics in the same quarter, and I was an ace at that due to some undergraduate work.)

Tim N3QE

On Fri, Nov 27, 2015 at 12:05 AM, Arthur Dent <golgarfrincham at gmail.com>
wrote:

> In the special it looks like they used two HP5071A standards, an
> SRS620 counter, and a scope. They first made sure the stds were in
> sync then took one to the building at the top of the ski lift on New
> Hampshire's Mount Sunapee at 2726' elevation for 4 days where it would
> be running a little faster because it would be slightly further from
> the center of the spinning earth. After bringing the 5071A back from
> the top of the mountain they checked the difference in the start of
> square waves displayed on the scope and detected the 5071A at altitude
> was now 20ns ahead of the 5071A kept at sea level, as predicted, if I
> understood everything correctly. They explained that the clocks in the
> GPS satellites traveling at a much higher speed had to correct for the
> speed difference which also verified Einstein's theory.
>
> My wife and I were on the top of Mt. Sunapee this summer where we
> enjoyed the views but didn't run any experiments. ;-)
>
> -Arthur
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