Christian J. Doppler (1803-1853)
Jos R.T.C. Roelandt
Thoraxcenter, University Hospital, Rotterdam, The Netherlands.
This year not only marks the 50th anniversary of echocardiography but also the birth of Christian J. Doppler (Nov 29th 1803 - March 17th 1853) two hundred years ago in Salzburg (Austria). He studied mathematics at the Vienna Polytechnic Institute and higher mathematics, mechanics and astronomy at the University of Vienna. After several unsuccessful applications for a university position he made plans to emigrate to America. However, just before his final decision he received an invitation to join the Technical Secondary School in Prague where he became professor in elementary mathematics in 1841. Unfortunately, because of poor health, he had to give up this position. Nevertheless, he subsequently accepted the position of professor of mathematics, physics and mechanics at the Academy of Mines and Forests in Banska Stiavnica (Slovakia) in 1848. Two years later, the Hungarian revolution broke out and he returned to Vienna to become the first director of the New Institute of Physics at the Vienna University. This was the high point of his career.
It was in Prague that Doppler in 1842 presented his paper "on the coloured light of the double stars and certain other stars of the heavens"(Abh. Königl. Böhm. Ges. Wiss 1843;2:465-482). He described the Doppler effect in a few lines stressing both light and sound as longitudinal waves in the air and matter, respectively. The Doppler effect relates the light (or sound) frequency of a source to its velocity relative to an observer. The theory was correct although the changes of the colours of double stars are too small to be observed with the instruments of that time. However, the situation with sound was different. It was C.H.D. Buys-Ballot (1817-1890), a famous Dutch physicist and meteorologist who conducted one of the most famous experiments to confirm the Doppler shift of sound. He put a group of musicians on railway trains playing instruments holding a constant note and he took a position on the station platform. He asked the train driver to rush past him as fast as he could and was able to detect the Doppler shift as a change in pitch as the train past him (Akustische Versuche des Niederl. Eisenbahn, nebst gelegentliche Bemerkungen zur Theorie des Herrn Prof. Doppler, In: Pogg. Ann., LXVI (1845)). In 1846 Doppler presented a better version of his principle where he considered both the motion of the source and the motion of the observer. Doppler also published on many other scientific topics including electricity, magnetism and astronomy — particularly optical instruments. In 1848 he was elected as an ordinary member of the Imperial Academy of Sciences in Vienna and received a honorary doctorate from the University of Prague. In 1852 his health deteriorated and he died in Venice in 1853 where he had moved hoping that the warmer climate would bring some improvement. He is buried on the Island of San Michele near Venice.
The Doppler principle is widely used in physics and technology. Investigation on its application for measurement of the velocity of red blood cells started in 1957 with the work of the Japanese S. Satomura (1920-1960). J. Holen and colleagues showed in 1977 that the blood flow velocity measurement allowed to measure the pressure drop across a stenotic orifice by applying the Bernouilli equation.
D. Bernouilli (1700-1782) was born in Holland and worked most of its live in Basel. He showed that the total energy in a steadily flowing fluid system is a constant along the flow path — therefore, when the velocity of blood increases, its pressure decreases (Hydrodynamica, 1738). The Bernouilli equation and the Doppler principle are now the cornerstones for the non-invasive assessment of hemodynamics and myocardial tissue function.
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