http://en.wikipedia.org/wiki/Gravita..._time_dilation
"Gravitational time dilation is an actual difference of elapsed time between two events as measured by observers differently situated from gravitational masses, in regions of different gravitational potential. (...) The existence of gravitational time dilation was first confirmed directly by the Pound-Rebka experiment. (...) Gravitational time dilation has been experimentally measured using atomic clocks on airplanes. The clocks aboard the airplanes were slightly faster with respect to clocks on the ground. The effect is significant enough that the Global Positioning System's artificial satellites need to have their clocks corrected. (...) Gravitational time dilation has also been confirmed by the Pound-Rebka experiment..."
Nowadays relatively honest Einsteinians admit that the Pound-Rebka experiment did not confirm gravitational time dilation - rather, it confirmed the variable speed of light predicted by Newton's emission theory of light:
http://www.einstein-online.info/spot...t_white_dwarfs
Albert Einstein Institute: "One of the three classical tests for general relativity is the gravitational redshift of light or other forms of electromagnetic radiation. However, in contrast to the other two tests - the gravitational deflection of light and the relativistic perihelion shift -, you do not need general relativity to derive the correct prediction for the gravitational redshift. A combination of Newtonian gravity, a particle theory of light, and the weak equivalence principle (gravitating mass equals inertial mass) suffices. (...) The gravitational redshift was first measured on earth in 1960-65 by Pound, Rebka, and Snider at Harvard University..."
Accordingly, the GPS clocks are not corrected for gravitational time dilation - rather, they are corrected for the fact that, due to their acceleration, light signals from GPS satellites arrive at the ground slightly faster than they would if their speed were unaffected by gravitation.
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