RE: Pulsar Nav accuracy

There are some issues with that. 

a) what if you're going to place that doesn't have any signals yet -
i.e. 500LY or more away from Sol?  Even early signals won't have a time
stamp (at least I don't think the orignal episodes of I Love Lucy don't)

b) Assuming advanced tech drives, non-FTL speeds could reach an
appreciable portion of the speed of light, how do you correct for the
time shift of the internal chronometers compared to the rest of the
universe? Differences of micro or milli seconds could occur if you
stayed at "high" velocities long enough.

c) Stars, systems and galaxies are all moving - tens, even hundreds of
thousands of miles per hour which would mean some systems are moving a
few light-seconds every day away from Sol.  After a year, a decade or
even a century they could be as far 2 light hours per year or 8.3 light
days per century. You'd have to measure the velocity of the star or
system to correct for any red-shift (or blue-shift for that matter)in
your timing signal.  The shift in wavelength might add to the
imprecision of the measurements. These velocities would be in refrence
to Sol, other systems might see a different velocity.

d) For a standard map to work, we'd need a good, fixed reference point
to start from - Are we going to use some sort of Galactic North Pole? or
perhaps a "True Galactic Blackhole Center" at or near the center of the
galaxy?  Does the Tufflyverse have humans getting to the center of the
Galaxy?  Or would we be Sol-centric and make Sol our reference point?  

I think that we sometimes forget that we live in a relative world.  If
you stand at the equator, you don't feel motion, even though you are
traveling 1,000 miles per hour as the earth rotates.  In addition, you
are moving 67,0000 miles per hour (+/- a thousand) as the Earth orbits
the sun.  Since everything around you is moving at the same rate, you
don't notice the effect. What happens when you jump to another system in
another part of the galaxy?

Some more material to chew on...

--Binhan   

> -----Original Message-----
> From: Indy [mailto:kochte@stsci.edu]
> Sent: Tuesday, February 26, 2002 7:51 AM
> To: gzg-l@csua.berkeley.edu
> Subject: Re: Pulsar Nav accuracy

> True. But it should not be difficult at all to determine this quite
> precisely. We already know to 1/10 ly or better the distances 
> to nearby
> stars. Once we actually *travel* to them, all we have to do is turn a
> sensitive receiver back toward Earth and pick up signals. 
> From this we can
> determine *extremely* well the distance (you know when a given signal
> was transmitted - such as, oh, a Weather Channel show which 
> carries the
> timestamp in the program - and with calibrated time 
> instruments you can
> determine to with lightseconds or tighter accuracy how long 
> it took the
> signal to reach your location, and from that, derive the distance to
> some small number).
>