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Talk:Theory of relativity (view source)
Revision as of 22:26, April 12, 2012
, 22:26, April 12, 2012→Why are adjustments needed to GPS?: possible 2002 reference
: It would be helpful to have a more modern reference. GPS switched to a system of daily updates to the satellites. Maybe those relativistic formulas cause errors that require daily clock synchronizations to correct. Not likely. But to prove the point we ought to find a reference that says that the satellites still use the 38 ns/day relativistic adjustments, and that the daily corrections are much smaller than that. [[User:RSchlafly|RSchlafly]] 17:18, 12 April 2012 (EDT)
: It would be helpful to have a more modern reference. GPS switched to a system of daily updates to the satellites. Maybe those relativistic formulas cause errors that require daily clock synchronizations to correct. Not likely. But to prove the point we ought to find a reference that says that the satellites still use the 38 ns/day relativistic adjustments, and that the daily corrections are much smaller than that. [[User:RSchlafly|RSchlafly]] 17:18, 12 April 2012 (EDT)
::The best I've found so far is [http://www.ipgp.jussieu.fr/~tarantola/Files/Professional/GPS/Neil_Ashby_Relativity_GPS.pdf] from Physics Today, May 2002. This confirms the initial adjustment and mentions further on page 7: "Additional small frequency offsets arise from clock drift, environmental changes, and other unavoidable effects such as the inability to launch the satellite into an orbit with precisely the desired semimajor axis. The satellite clock frequencies are adjusted so that they remain as close as possible to the frequency of the Naval Observatory's clock ensemble." Unfortunately it doesn't give the actual size of the adjustments, thought the word 'small' does indicate it as being much less than the initial adjustment. I rather like the last sentence of this paper: "Ordinary users of the GPS, though they may not need to be aware of it, have thus become dependent on Einstein's conception of space and time." [[User:RolandPlankton|RolandPlankton]] 18:26, 12 April 2012 (EDT)
== Logic and the GPS ==
== Logic and the GPS ==