[time-nuts] Pulsars make a GPS for the cosmos

[J. Forster]

Yes, but to use them for interstellar navigation, as suggested, when the
propagation delays are 10,000 years or more complicates things.

What is contemplated is comparing the clocks, as they were thousands of
years ago, where they were thousands of years ago, with largely unknown
motions. You can't have a central coordinating facility that sends out
correction signals, because of the propagation delays.

Essentially you are cherry picking the data. Never mind the technical
problems with monitoring many pulsars in many different directions.

There is a similar problem with some early SETI searches. There is really
no 0,0,0 for the universe, AFAIK. Which Doppler effects do you remove?
Some? All? None?

My solution was to use the coordinate system, wherein the 3 degree K
background was the same in all directions as a standard of rest, but who
knows if that is a correct choice?

-John

=================



>> Pulsars are not infrinitely stable. They slowly decay, and, worse,
>> randomly undergto 'star quakes' which upset their timing. This was
>> proven
>> in the 1960s.
>
> John,
>
> You are correct, but it is a simple opportunity rather than a major
> problem. The solution is to monitor multiple pulsar sources. Not only can
> you detect the quakes, but you can precisely measure their magnitude as
> well. Once a quake is detected the new phase and/or frequency offset for
> that source can be entered into the ensemble equation, and you move
> forward as if nothing happened.
>
> Exactly the same thing happens at home when you monitor multiple quartz
> oscillators. You need more than one or two; three or four is better.
> Confidence grows according to the number of oscillators. N-1 oscillators
> help you detect any abnormality in 1.
>
> This is not unlike what happens with GPS SV as they come in and out of
> reception. Easy to detect; easily solved.
>
> And the same solution is used for UTC, where more than 300 clocks
> participate. Phase or frequency jumps (quakes) are easily identified and
> excluded from the ensemble mean. The mean is safe and the N-1 clocks can
> be used to precisely measure the anomaly in 1 clock.
>
> /tvb
>
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