[time-nuts] Question re neutrinos and GPS

Jim Lux jimlux at earthlink.net
Fri Jan 6 23:53:50 UTC 2012


On 1/6/12 3:20 PM, iovane at inwind.it wrote:
> So far it seemed to me that the overall standpoint of the authoritative time-
> nuts list is that the GPS timing and geografical survey of the OPERA experiment
> are good (and hence experimental errors or artifacts, if any, should be
> searched for elsewhere).
>
> I myself, not being a deep GPS expert, joined this standpoint with confidence
> (but indeed I could have been affected by a sentimental bias).
>
> 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.
>


GPS was used as part of the surveying tools to determine the distance, 
and is as good as anything else out there.  They had to transfer the 
measured position outside down into the tunnels by conventional optical 
surveying, I should imagine.

GPS was also used as a common view time transfer (between Cs clocks at 
each end). And, a traveling clock was used as well.

There have been statements about "GPS doesn't account for relativistic 
effects", which of course, is not true. GPS satellites move more than 
fast enough that if they didn't account for relativistic effects (0.2ppb 
frequency error, for instance), you couldn't do the nav computation. 
But it's actually not relevant for the discussion here.


So we have a very accurately measured distance.  It could have been 
measured by other means: conventional surveying and triangulation, for 
instance, or astronomical methods.

And we have clocks at each end that are synchronized.

The actual velocity measurement is done by dividing measured distance by 
measured time (with GPS not actually involved in the measurement).

Now, one could raise issues about whether the particles are following 
the path that's been measured, but that's different than saying "GPS 
isn't accurate for surveying".

There, could, after all, be some sort of magic naked singularity with 
negative mass that warps spacetime so that the Euclidean straight line 
(the surveyed path) isn't actually the shortest path.  (I'm not sure 
this could actually exist.. But I was thinking of the "rubber sheet with 
a weight" conceptual 2D model of gravitationally curved space)







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