[time-nuts] Time of death-Again

[Marshall Eubanks]

On Oct 30, 2010, at 6:31 AM, Javier Herrero 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 ;) )
> 

I was assuming that the spin periods of the pulsars was the actual clock in question for the million year time scale. If the knowledge of
our date system is lost it is highly probably that the pulsar phase will also be lost, so there is no chance of doing sub-second timing, but from the spin period of epoch it should be possible to date the elapsed time to order a year, even over a million years.

If you then included information the orbital state of the planets at a specified data in this epoch the finders might be able to use the pulsars to figure out the elapsed time to within a few years and then use the planet data to figure out what the elapsed time is to better than a day and thus get the actual date. (Planetary alignments tend to repeat, so you need some source of absolute time to do this.)  I have no ideas short of burying a working clock on doing any better than that. (The change in the UT1 approaches a day even over historic time, and will be many days in a million years, so you will really be getting ET / TAI not UTC out of this.)

Regards
Marshall


> Regards,
> 
> Javier
> 
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