May 25, 1842 – Mathematician and physicist Christian Doppler presents his idea of frequency in relation to velocity, now known as the Doppler Effect. His breakthrough idea explained why continuous noises, such as police sirens, sound different when they are coming toward you versus going away.
Doppler explained that changes in the frequency of sound waves cause noises to sound different in relation to the observer’s position. He refined his theory by conducting an experiment that involved two sets of trumpeters. One set was stationed at the railway station, and the other was in a train car that was pulled past the station. Though both sets of trumpeters where playing the same music at the same time, the notes heard to the audience were different.
A year later, Doppler was elected to the Royal Bohemian Society. While admired in his field, his students complained that he was too strict and harsh in his examining. Listen to what the Doppler Effect sounds like here.
Words of Wisdom for May 25, 2015
“There have been applied sciences throughout the ages. … However this so-called practice was not much more than paper in nearly all of these cases, and the various applied sciences were only lacking a bagatelle, namely proper scientific practice. The applied sciences show the application of theoretic doctrines in existing events; but that is precisely what it does, it merely shows. Whereas the scientific practice autonomously puts to use these theories.”
― Christian Doppler (November 29, 1803 – March 17, 1853), Austrian mathematician and physicist. He is celebrated for his principle — known as the Doppler effect — that the observed frequency of a wave depends on the relative speed of the source and the observer.