From Jay Pasachoff
In a relativistic look at the BBC’s Science Hour radio show, prompted by its 55-minute duration, you remarked that the listener “needs to keep re-tuning his radio, since the signal from the moving radio station would be shifted in frequency as well”. (Feedback, 20 July).
But if the transmitter moves at a constant rate, even 40 per cent of the speed of light as your reader suggested, then the Doppler shift is constant, and once tuned the radio should stay that way.
Williamstown, Massachusetts, US
