Johann Christian Doppler (1803–1853), the Austrian mathematician for whom the Doppler Effect is named, proposed in 1842 that the color of double stars rotating about each other would depend on whether the star was approaching or receding from Earth.The effect was too small to be measured. But in 1845 Christophorus Henricus Diedericus Buys Ballot (1817–1890) set up an experiment using had two sets of trumpeters. One set remained at rest while the other was on an open railway car traveling at the then fantastic speed of 40 miles per hour. Although both sets of trumpeters played the same note, the change in tone was clearly heard. Doppler later extended his theory to the case when both sound source and observer were moving. French physicist Hippolyte Fizeau (1819–1896) later extended Doppler’s theory to light.