[EPS12-pl] to Prof. Schafer: GPS and Celestial Mechanics

[György Szondy]

to Prof. Schafer:
Question about the relation of GPS and General Relativity based Celestial 
Mechanics.

BACKGROUND:
-----------
Kovalevsky stated about solving problems in a general fashion in the 
framework of Einstein's theory of gravity that it is conceptually possible, 
"but the mathematical difficulties encountered have by far not yet been 
solved"[1]

GPS is the most common usage of high precision relativistic calculations. 
Relativistic corrections used in GPS are qiuite simple. It is usually said 
to be based on Special and General Relativity (GR), however it is quite far 
from GR as the phenomenon of time is defined differently. "Time" in GPS 
measurements refers to coordinate time while in General Relativity "time" is 
proper time. Proper time in GPS measuremets is called "clock rate". A usual 
statement here sounds like: "clocks run at different rates when they are at 
different distances from a center of gravitation attraction." [2][3][4]

QUESTIONS:
----------
- Why do you think mathematical method used in GPS calculations is not 
really identified yet as a base of different theoretical description of 
gravitation?
- Which benefits that are expected from this approach [5] do you agree with? 
(no gravitational red-shift, synchronisation, lower mathematical complexity, 
linear addition of mass and energy)
- What do you think can make phisicists to deal with the theoretical 
background of GPS calculations? When will be worked out?

Thank you,
Gyorgy Szondy

REFERENCES:
-----------
[1] J Kovalevsky, 2000, Celestial Reference Systems - An Overview, 
Proceedings of IAU Colloquium 180 
http://aa.usno.navy.mil/colloq180/Proceedings
[2] R. A. Nelson, Relativity Fundamentals for Time Scales and Astronometry 
http://ad.usno.navy.mil/ad/forum/nelson.pdf
[3] Project A - Global Positioning System, 
http://www.eftaylor.com/pub/projecta.pdf
[4] Tom Van Flandern - What the Global Positioning System Tells Us about 
Relativity, http://www.metaresearch.org/cosmology/gps-relativity.asp
[5] Linear Relativity as the Result of Unit Transformation, 2001, 
physics/0109038


György Szondy
gyorgy_szondy@hotmail.com



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