I asked this question in another thread, but wonder about the answer I got: Question: I bought an atomic-timed clock and wondered if while I am taking off from an airport my clock would record time slower than a clock inside the airport. Since time on the clock is actually maintained by a radio signal it receives from the US atomic clock in Fort Collins, would my clock be affected the same way as if it were keeping time all by itself on board the plane? Answer: No. Your clock will run slow while on the plane, but that will not affect the synchronism of the time updates. Every time your clock receives an update from the Fort Collins WWVB 60kHz atomic-clock radio station, it will revert to Fort-Collins-synced time Follow-up Question: Why wouldn't the Fort Collins signal, once entering the plane's frame of reference, especially accelerating for take off, be affected and so give a relativity-adjusted impulse to the clock? I can see how light speed of the signal would be the same, but wouldn't the signal's oscillation rate be speeded up/shortened?