Enthalpy Posted November 26, 2015 Share Posted November 26, 2015 Hello everybody! Read recently in the semi-scientific press that two Galileo satellites that were put on a wrong orbit hence are declared unusable for the European positioning constellation (GPS competitor) are to be used as a test for Relativity by observing how the onboard clocks run over the elliptic orbit. Nice, fine. Though, I'm not easy with the claim and explanation by the Press paper I read. The Press paper tells that the onboard's clock, as observed from Earth's surface, changes its pace depending on the altitude, and this will be observed. As opposed, I had imagined that both the satellite's speed (its kinetic energy) and its altitude (its potential energy) influence the clock pace observed from Earth's surface, and even, that only matters the sum of both energies, telling that we should observe no change of the clock pace, which would be the test for GR. Your opinion please? Thank you! Link to comment Share on other sites More sharing options...
swansont Posted November 26, 2015 Share Posted November 26, 2015 The kinematic term does not cancel the gravitational one. What's your reasoning that you think it would? Link to comment Share on other sites More sharing options...
Enthalpy Posted November 27, 2015 Author Share Posted November 27, 2015 As I imagined it, the speed would act as a v/c term known prior to Relativity, and a v2/c2 term which is a relativistic correction at a few km/s. Doesn't this quadratic term cancel out the effect of gravitation, as the satellite is in free fall? Link to comment Share on other sites More sharing options...
swansont Posted November 27, 2015 Share Posted November 27, 2015 As I imagined it, the speed would act as a v/c term known prior to Relativity, and a v2/c2 term which is a relativistic correction at a few km/s. Doesn't this quadratic term cancel out the effect of gravitation, as the satellite is in free fall? In an orbit, mechanical energy is constant. How does KE compare to the kinematic dilation term? Link to comment Share on other sites More sharing options...
Enthalpy Posted November 27, 2015 Author Share Posted November 27, 2015 Yes, only a part of the kinetic energy is radial versus Earth or an observer, so a v2/c2 shift will be observed. Thanks! And if the observer were below or above a clock falling vertically, would he see a v2/c2 shift? Link to comment Share on other sites More sharing options...
swansont Posted November 28, 2015 Share Posted November 28, 2015 You see a kinetic shift even for a circular orbit. "Radial KE" is not an issue (and KE is not a vector, anyway) For an elliptical orbit, a smaller r means a higher speed. Both of these effects increase the magnitude of the time dilation. They don't cancel. Link to comment Share on other sites More sharing options...
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