Time dilation
Combined effect of velocity and gravitational time dilation

The coordinate time t c {\displaystyle t_{c}} is the time that would be read on a hypothetical "coordinate clock" situated infinitely far from all gravitational masses (U = 0 {\displaystyle U=0}), and stationary in the system of coordinates (v = 0 {\displaystyle v=0}). The exact relation between the rate of proper time and the rate of coordinate time for a clock with a radial component of velocity is:
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