In 2010, Chou et al. performed tests in which both gravitational and velocity effects were measured at velocities and gravitational potentials much smaller than those used in the mountain-valley experiments of the 1970s. It was possible to confirm velocity time dilation at the 10−16 level at speeds below 36 km/h. Also, gravitational time dilation was measured from a difference in elevation between two clocks of only 33 cm.[11][12]
Nowadays both gravitational and velocity effects are, for example, routinely incorporated into the calculations used for the Global Positioning System.[13]
It later transpired that the published results were quite different from the original measurements. H&K made a number of ‘corrections’ to their data to average out the errors between the clocks used, and the variations between the clocks moving in similar directions were large enough to invalidate the overall measurements. If the experiments were as flawed as this article suggests then they cannot be used to prove or disprove time dilation.