[time-nuts] Re: gravity fields affect time keeping?

[Tom Van Baak]

Don,

 > There are no mountains in New Hampshire that are equal to the task.

Well, that depends. In cases like this you must consider exactly what 
kind of clock(s) are used. The performance of an old 5061A cesium clock 
may be different than a later model 5061B and both very different from a 
5071A, the model still in use by timing laboratories around the world. 
Plus there's the high-performance option with even better performance, 
having a noise floor around 5e-15. That's what I tend to use for my 
relativity experiments.

In the short video Joe Fitzgerald posted, we see that the team used Mt 
Sunapee in New Hampshire which is about 2700 ft (0.8 km). True, that's 
not very tall and the predicted blueshift from sea level is just 9e-14. 
I can tell you that a 5061 or equivalent vintage cesium clock would not 
be adequate for that experiment.

But they didn't use a pair of surplus cesium clocks. The video makes it 
clear they used a 5071A [1] for the portable clock, and likely they used 
a H-maser [2] for the base clock (the Einstein doll is sitting on top of 
a MHM 2010 maser).

It appears the clock comparison scene was filmed at Microsemi (was 
Symmetricom, now Microchip), the company that manufacturers the 5071A 
and the maser. What you see behind the glass is their main clock room 
[3]. In other words, this was not some cheap backyard experiment from 
eBay. See also the original discussion about the video on time-nuts [4].

There's not quite enough information in the video to calculate the error 
bars, so I'll not stick my neck out too far on that point. But from what 
I can tell, the results are totally plausible, in spite of the mountain 
not being very tall. Thus I'm curious what assumptions or calculations 
you used to reach the opposite conclusion.

/tvb

[1] 
https://www.microchip.com/en-us/products/clock-and-timing/components/atomic-clocks/atomic-system-clocks/cesium-time/5071a

[2] 
https://www.microsemi.com/product-directory/active-hydrogen-maser/4123-mhm-2010-active-hydrogen-maser

[3] National labs and clock companies often have a special clock room, 
aka "house standard". The one you see in the video has roots (hp 5060 -> 
hp 5061 -> hp 5071) back this clock room 50 years ago:

http://www.leapsecond.com/history/Benchmark.htm

[4] 
https://febo.com/pipermail/time-nuts_lists.febo.com/2015-November/subject.html#start


On 1/31/2023 10:09 AM, Donald E. Pauly wrote:
> The result is worthless.  This is 6x10^-14 which is within the drift 
> of two cesium clocks.  There are no mountains in New Hampshire that 
> are equal to the task.  Mt Rainier in Washington state barely works.