Christian Doppler
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Johann Christian Andreas Doppler (November 29, 1803 – March 17, 1853) was an Austrian mathematician and physicist, most famous for the hypothesis of what is now known as the Doppler effect which is the apparent change in frequency and wavelength of a wave that is perceived by an observer moving relative to the source of the waves.
Life
Christian Doppler was born in Salzburg, Austria, as the son of a well-to-do stone-mason, Johann Evangialist Doppler and his wife, Therese. A baptismal certificate indicates that Doppler was christened "Christian Adreas." Doppler was not of strong constitution, and did not follow his father into the construction trades. Instead, he was allowed to follow an academic track. His father asked the advice of Simon Stampfer, a local educator, as too the boy's future. Stampfer recognized Doppler's potential and recommended that his father send him to Vienna.<<<Maulik, Dev. 1997. Doppler ultrasound in obstetrics & gynecology. New York: Springer. 2. ISBN 0387942408.>>> After completing high school he spent three years at the Polytechnic Institute in Vienna, and returned to Saltzburg, where he completed his studies while tutoring mathematics and physics. He returned to the Polytechnic Institute for four years, where he taught higher mathematics. It was during this period that he wrote his first papers in mathematics and electricity.
Unable to find a teaching position, he contemplated a move to the United States. But after making preparations for the trip, he unexpectedly secured a post in 1835 as professor of mathematics and accounting at the State Secondary School in Prague. In 1841, he was employed at the State Technical Academy as a mathematics professor. A year later, in 1842, he read his first work on the changes in frequency of waves through a medium measured by an observer moving with respect to the waves' source. This has come to be known as the Doppler effect. The paper, presented before the Royal Bohemian Society of Sciences on May 25, 1842, was entitled On the colored light of the double stars and certain other stars of the heavens.<<<Hennerici, M., and Stephen P. Meairs. 2001. Cerebrovascular ultrasound theory, practice, and future developments. Cambridge: Cambridge University Press. 88.>>> His work was an extension of that of James Bradley, the eighteenth century astronomer who measured the speed of light by noting the abberation that affects the apparent positions of all stars due to the orbital motion of the earth. Bradley made his calculations assuming a particle theory of light. But Doppler applied similar reasoning to show that the frequency of light would change if the observer was not stationary relative to the light source.
Doppler's work was later published under the title: On the colored light of the binary refracted stars and other celestial bodies - Attempt of a more general theory including Bradley's theorem as an integral part. In Doppler's own words, "...nothing seems to be more intelligible than that to an observer the path length and the interim durations between two consecutive breakings of a wave must become shorter if the observer is hurrying toward the oncoming wave, and longer if he is fleeing from it..." As the frequency is dependent on the number of beats per unit time, and in light is related to the color perceived, Doppler concluded that the red color of some stars demonstrates that the perceived wavelength is greater as a result of the star and the earth moving away from each other."<<<Schuster, Peter. 2005. Moving the stars Christian Doppler, his life, his works and principle, and the world after. Pöllauberg, Austria: Living Edition. 63.>>>
Besides light, Doppler also mentioned sound in his 1842 work. In this work, Doppler tried to explain the color of binary stars by conjecturing that if the earth and the binaries are rapidly approaching each other, their color should be shifted to the shorter, or violet, end of the spectrum, while if receding, to the red, or longer wave-length, end. He assumed that the normal light from all stars was light, and that any deviation was due to the relative velocity between the star and the observer.
Two investigators, Buys Ballot in 1845 and John Scott Russell in 1848, verified Doppler's prediction with respect to sound. But the former also criticized Doppler's assumptions about starlight as well. As it turns out, the relative motion between most stars and the earth is too slow to produce a pronounced color effect. Furthermore, all wavelengths would shift, with the result blending to the point where a shift in color would be difficult to observe.
Some of these points were made in a presentation by H. Fizeau in 1848, who applied Doppler's theory to the total shift in the position of raunhofer lines that appear in spectra and that mark specific frequencies of light. It is this application that was to mark the future application of Doppler's principle more than a shift in the actual color of stars. <<<Campbell, William Wallace. 1913. Stellar motions, with special reference to motions determined by means of the spectrograph. New Haven: Yale university press. 12-15.>>>
While the basic premise of his work remained, his application to the color of stars came under fire from a number of sources. this application was later the focus of criticism from a number of sources. In applying his theory to colored The Doppler effect of sound was verified by John Scott Russell in 1848. In his time in Prague as professor he published more than 50 articles in mathematics, physics and astronomy.
His research career in Prague was interrupted by the revolutionary incidents of March 1848, when he fled to Vienna. There he was appointed head of the Institute for Experimental Physics at the University of Vienna in 1850. During his presence at the University of Vienna, Doppler, along with Franz Unger, played an influential role in the development of young Gregor Mendel who later became the founding father of genetics. (Note: Gregor Mendel studied in the University of Vienna from 1851 to 1853. At that time, Doppler served as a professor there.)
He died from a pulmonary disease in Venice at age 49 on March 17, 1853. His tomb can be found just inside the entrance of the Venetian island cemetery of San Michele. (Note: In 1853, Venice was also ruled by the emperor of Austria. It was like Doppler just moved from one part of the Austrian empire to another part of the same empire. Now Venice is part of Italy and so Doppler's tomb ends up in Italy instead of in Austria.)
See also
ReferencesISBN links support NWE through referral fees
<<Need at least 3 reliable references here, properly formatted.>>
- Schuster, Peter. 2005. Moving the stars Christian Doppler, his life, his works and principle, and the world after. Pöllauberg, Austria: Living Edition.; Webpage of the author)
- Alec Eden, "The search for Christian Doppler," Springer-Verlag 1992. (An English translation of Doppler's 1842 work on the Doppler effect can be found in this book. In this book, Alec Eden also made a detailed study regarding the full name of Christian Doppler. He believed that his full name should be "Christian Andreas Doppler".)
External links
- Christian Doppler and his birthplace in Salzburg
- John J. O'Connor and Edmund F. Robertson. Christian Doppler at the MacTutor archive
- Born between Salzburg and Braunau am Inn
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