also by funkstar in a previous post: "The standard second aboard the GPS satellites is not 9192631770 beats of the particular radiation, but slightly longer in order to cancel out the predicted time contraction aboard the satellites." ========================================================== I explained that 9192631770 'beats' of the cesium ALWAYS defines a second and cannot be changed. You cannot make the atom beat slower. The quartz oscillator will synchronize the orbital clock with the Earth clock by counting more than 9192631770 beats of the cesium atom to match an Earth second, not by making the cesium atom 'beat slower'. This corrects for gravitational BLUESHIFT, not redshift. The transmitted signal is blueshifted as it falls in a gravity well. I said the light clock must agree with an unadjusted cesium clock in the orbital frame of reference. The cesium clock in high orbit beats relatively faster than a cesium clock in low Earth orbit. In case you have forgotten again, my question was how do you make a light clock in high orbit beat relatively faster than a light clock in low orbit, to slightly rephrase the question so you will not misunderstand. Is the path travelled by the light in the light clock shorter in high orbit, or does light travel faster in high orbit relative to another light clock in low orbit? The second is shorter in high orbit, so distance must also contract or light must travel faster to make the light clock run faster.