Johann Christian Doppler and his effect--a brief history.

Abstract

Johann Christian Doppler whose name is so frequently honoured in modern-day technology was so little regarded by his colleagues that we know relatively little about his personality. One of his biographers describes him as humble and hard-working but he responded to the criticisms of Buys Ballot in a rather stubborn fashion and apparently his mathematic was not faultless. The only likeness we have of him (Fig. 1) is a bust set up by the University of Vienna in 1901 but it is not known how true it is to life. His career, like the early history of the effect he described and which is named after him, was checkered. He was born in Salzburg in 1805 (Fig. 2) and was the son of a master stone mason. Apparently he had some talent as a carver but did not have the physique to follow this craft. As a result of the interest of the mathematician Stampfer he was sent to the Polytechnic Institute of Vienna but after graduation he was unable to obtain a good position. He got as far as Munich on his way to emigrate to America when he was appointed Professor of Mathematics and Accounting at the State Secondary School in Prague in 1835. In 1841 he became Professor of Elementary Mathematics and Practical Geometry at the State Technical Academy in Prague and it was in this position that he wrote his famous paper entitled “On the Coloured Light of Double Stars and Some other Heavenly Bodies” (Fig. 3). The paper was given before the Royal Bohemian Society of Learning in 1842 and published in 1843. In 1847 he became Professor of Mathematics, Physics and Mechanics at the Mining Academy at Schemnitz at which time he was given an honorary doctorate by Charles University in Prague. However, he had to return to Vienna because of the industrial troubles and in 1850 he received his only prestigious appointment as Director of the new Physical Institute which had been founded for the training of teachers and became a full Professor of Experimental Physics at the Royal Imperial University of Vienna which was the first such appointment to be made in Austria. Unfortunately he had developed pulmonary troubles while in Prague which resulted in his death in Vienna shortly afterwards in 1853 at the early age of 49. It should be noted that many of the difficulties encountered in the early acceptance of the Doppler effect resulted from the fact that he worked under rather isolated circumstances since no other important physicists were working in Bohemia or Austria in the early part of the 19th century. Doppler’s famous paper begins by recapitulating the wave theory of light and explaining that the colour perceived by the eye varies with the frequency. He went on to postulate that this frequency will increase if the observer is moving towards the source and decrease if he is moving away from the source and drew an analogy of a ship moving to meet or retreat from a train of ocean waves. He went on to deduce in rather clumsy mathematical fashion the relationship: