[time-nuts] Question re neutrinos and GPS

[Tom Van Baak]

> Now I read on another list, in which the subject is not timekeeping and from a 
> respectable author, that:
> 
> "The GPS is very unlikely to give an accurate speed for anything near the 
> speed of light - for there are many known effects not taken into account by the 
> GPS protocol. 
> In the end the OPERA experiment may alert people to the assumptions and 
> approximations implicit in the GPS."
> 
> This wrongfooted me. So please, does the above quoted statement have any 
> meaning for time-nuts? Don't answer "ask the author of the statement" please, I 
> would like to hear the opinion of time-nuts.

Antonio,

It's hard to respond to the vague statement by the author. If there
are "many known effects not taken into account" it would be more
instructive for the author to list each. You can send me the URL
off-line if you wish.

More to the point, GPS is not used in OPERA for anything involving
speed. It is simply used for common view calibration of stationary
clocks and fixed antennae at both sites. I mean, it's not like someone
is strapping a Garmin on a passing neutrino and reading its velocity
in flight.

One thing to keep in mind is that the OPERA experiment is not the
first to ever use GPS for precision timekeeping. There are a couple
of decades and thousands of examples of GPS working quite well
at the nanosecond level, across small and large baselines, etc. So
even if some professor makes a good case for GPS being wrong
for the OPERA experiment they also have to explain why this has not
affected every other use of satellite-based precision timing in the past.

Hopefully all this GPS-neutrino talk will calm down when other methods
to validate the synchronization of the clocks at CERN and LNGS are
done (e.g., direct fiber or traveling Cs clocks).

/tvb