On 10/30/2010 04:48 PM, Jim Lux wrote:
On Oct 30, 2010, at 3:31 AM, Javier Herrero<[email protected]> wrote:
El 30/10/2010 10:31, Hal Murray escribió:
Suppose you have to go back a zillion years. Now the fuzz on the period adds
to the fuzz on measuring an individual pulse.
Not to forget that pulsar frequencies spins down as the energy that they emits
is ultimately drawn from its rotational energy (PSR B1937+21 spins down at 1.05
x 10^-19 seconds per second). In a zillion years this could amount a bit of
time (several hundred microseconds over the 2.29 x 10e8 years life of this
pulsar if the spin down rate would have been constant - too much drift for a
real time-nut ;) )
But if the decay rate is known, you could factor that into your calculation.
In fact wouldn't specifying the time of an event as the observed phase of the
pulsars be unique. That is if something is at a time of 75%A,22%B,54%C, does
that specify a unique time and place?
If you would have constant rates and three phase observables that would
give you a unique time modulus the beating period of this oscillator
combination. To solve it you would use the chinese reminder. However,
the chinese reminder theorem does not handle case with changing rates.
Also, the ability to predict deep into the futures is severely limited
by the precision of our modelling of these sources and possible other
effects playing in on them. Also, the precision by which we makes the
measures is a limiting factor. Sorting all of this out would
Percent, here, is where the event occurred in the period between the pulses
Degrees would have helped more.
I think pulsars alone would be difficult for long-term, omni-positional
timing. We haven't even touched on stellar movements over long time periods.
Also, our observation will be in movement from the various sources, so
doppler compensation would be required.
It's not a completely unsolveable thing, but a lot of things shifting
over time throwing in massive of unknown parameters which would need to
be estimated with sufficient precision if we where to build from scratch
the time and time-scale.
Just agreeing on the definitions of the star-book to traverse cultural,
time and position boundaries would be an interesting problem.
Cheers,
Magnus
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