A physicist proved sound bends pitch by testing trumpeters on a moving train
Christian Doppler predicted in 1842 that a sound's pitch should rise as its source approaches and fall as it recedes. Three years later, Dutch scientist Christophorus Buys Ballot tested it by having trumpeters play a sustained note aboard a speeding locomotive while musicians on the platform judged the pitch shift by ear. It matched the prediction, and the same effect now explains redshifted starlight and police radar guns.