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Chladni

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Chladni

"Chladni" redirects here. For the lunar crater, see Chladni (crater).
Ernst Chladni
Ernst Chladni
Born 30 November 1756
Wittenberg
Died 3 April 1827
Breslau
Nationality German
Fields Physics
Known for Speed of sound
Chladni plates

Ernst Florens Friedrich Chladni (German: [ˈɛʁnst ˈfloːʁɛns ˈfʁiːdʁɪç ˈkladnɪ]; 1756–1827) was a German physicist and musician. His important works include research on vibrating plates and the calculation of the speed of sound for different gases. For this some call him the "father of acoustics".[1] He also did pioneering work in the study of meteorites, and therefore is regarded by some as the "father of meteoritics" as well.[2]

Personal life

Although Chladni was born in Wittenberg, Germany, Chladni's family was from Kremnica, a mining town now in central Slovakia, then part of the Kingdom of Hungary. This has led to Chladni as being identified in the literature as German,[3][4] Hungarian[5] and Slovak.[6]


Chladni came from an educated family of academics and learned men. Chladni's great-grandfather, Georg Chladni (1637–92), a Lutheran clergyman, had to flee Kremnica on October 19, 1673 during the Counter Reformation. Chladni's grandfather, Martin Chladni (1669–1725), was also a Lutheran theologian, and in 1710 became professor of theology at the University of Wittenberg, and from 1720–1721 was dean of the faculty of theology and later rector of the university. Chaldni's uncle, Justus Georg Chladni (1701–1765), was a law professor at University of Wittenberg.


Another uncle, Johann Martin Chladni (1710–1759), was a theologian and historian, and professor at the University of Erlangen and the University of Leipzig. Chladni's father, Ernst Martin Chladni (1715–1782), was a law professor and rector of the University of Wittenberg, where he joined the law faculty in 1746. His mother was Johanna Sophia and Chladni was an only child.[7] Chaldni's father disapproved of his son's interest in science and insisted that Chladni become a lawyer.[6][8][9]

Chladni studied law and philosophy in Wittenberg and Leipzig, and obtained a law degree in 1782 from the University of Leipzig. When his father died in 1782, Chladni began his research in physics in earnest.[8][9]

Chladni died in 1827 in Breslau, Lower Silesia, an area that is now in southwestern Poland. When Chladni died, this town was part of the Kingdom of Prussia, which was a member of the German Confederation.

Chladni figures




One of Chladni's best-known achievements was inventing a technique to show the various modes of vibration of a rigid surface. A plate or membrane vibrating at resonance is divided into regions vibrating in opposite directions, bounded by lines of zero vibration called nodal lines. Chladni repeated the pioneering experiments of Robert Hooke of Oxford University who, on July 8, 1680, had observed the nodal patterns associated with the vibrations of glass plates. Hooke ran a violin bow along the edge of a plate covered with flour, and saw the nodal patterns emerge.[8][9]

Chladni's technique, first published in 1787 in his book, Entdeckungen über die Theorie des Klanges ("Discoveries in the Theory of Sound"), consisted of drawing a bow over a piece of metal whose surface was lightly covered with sand. The plate was bowed until it reached resonance, when the vibration causes the sand to move and concentrate along the nodal lines where the surface is still, outlining the nodal lines. These patterns are now called Chladni figures.

Variations of this technique are still commonly used in the design and construction of acoustic instruments such as violins, guitars, and cellos. Since the 20th century it has become more common to place a loudspeaker driven by an electronic signal generator over or under the plate to achieve a more accurate adjustable frequency.

Musical instruments

Since at least 1738, a musical instrument called a "Glassspiel" or "Verillon" created by filling 18 beer glasses with varying amounts of water was popular in Europe.[10] The beer glasses would be struck by wooden mallets shaped like spoons to produce "church and other solemn music".[11] Benjamin Franklin was sufficiently impressed by a verillon performance on a visit to London in 1757 that he created his own instrument, the "armonica" in 1762.

Franklin's armonica inspired several other instruments, including two created by Chladni. In 1791, Chladni invented the musical instrument called "Euphon" (not to be confused with the brass instrument euphonium), consisting of glass rods of different pitches. Chladni's euphon is the direct ancestor of the modern day musical instrument known as the Cristal Baschet.[12] Chladni also improved on the Hooke "musical cylinder" to produce another instrument, the "Clavicylinder", in 1799.[8][9][11]

Chladni travelled throughout Europe with his instruments giving demonstrations.[6]

Meteorites

In 1794, Chladni published, in German, Über den Ursprung der von Pallas gefundenen und anderer ihr ähnlicher Eisenmassen und über einige damit in Verbindung stehende Naturerscheinungen, (On the Origin of the Pallas Iron and Others Similar to it, and on Some Associated Natural Phenomena), in which he proposed that meteorites have an extraterrestrial origin.[13] This was a controversial statement at the time,[14] since meteorites were thought to be of volcanic origin. With this book Chladni also became one of the founders of modern meteorite research.

Chladni was initially ridiculed for his claims of an outer space origin for meteorites, but his writings sparked scientific curiosity that eventually led more researchers to support his theory. In 1795 a large stony meteorite was observed during its fall to earth at a cottage outside of Wold Newton, Yorkshire, England. A piece of this ordinary chondrite, known as the Wold Cottage meteorite, was provided to British chemist Edward Howard who, along with French mineralogist Jacques de Bournon, carefully analyzed the elemental composition of the meteorite and concluded that an extraterrestrial origin was likely. In 1803 a meteor shower over L'Aigle, France peppered the town with over 3000 fragments of meteorites with hundreds of witnesses to the stones falling. The L'Aigle meteor shower was investigated by French physicist and astronomer Jean Baptiste Biot, under commission of the French Minister of the Interior.[8][9] Unlike Chladni's book and the scientific publication by Howard and de Bournon, Biot's article was a popular and lively report on meteorites that convinced a number of people of the veracity of Chladni's initial insights.[13]

Other work

Chladni discovered Chladni's law, a simple algebraic relation for approximating the modal frequencies of the free oscillations of plates and other bodies.

Chladni estimated sound velocities in different gases by placing those gases in an organ pipe, playing it, and observing the sounds that emerged.[15] This built on the work of Pierre Gassendi in measuring the speed of sound in air, begun in 1635.

Bibliography

  • Entdeckungen über die Theorie des Klanges. Leipzig 1787
  • Die Akustik. Leipzig 1802, französische Übersetzung: Traite d’ acoustique, Paris 1809 und in: Neue Beiträge zur Akustik, Leipzig 1817
  • Beiträge zur praktischen Akustik und zur Lehre vom Instrumentbau. Leipzig 1821
  • Über den Ursprung der von Pallas gefundenen und anderer ihr ähnlicher Eisenmassen. Leipzig und Riga 1794
  • Über Feuermeteore. Wien 1820
  • Über die Hervorbringung der menschlichen Sprachlaute. Leipzig 1824
  • Kurze Übersicht der Schall- und Klanglehre, nebst einem Anhange die Entwickelung und Anordnung der Tonverhältnisse betreffend. Mainz 1827

See also

References

Further reading

  • Jackson, Myles W. (2006) Harmonious Triads: Physicists, Musicians, and Instrument Makers in Nineteenth-Century Germany (MIT Press).
  • Rossing T. D. (1982) Chladni's Law for Vibrating Plates, American Journal of Physics 50, 271–274

External links

  • Max Planck Institute for the History of Science
  • , 1802 by Ernst Chladni at Universities of Strasbourg
  • Video of Chladni patterns through frequency range (Accessed 5/31/08)
  • Examples with round, square, stadium plates and violin shapes
  • Chladni plates
  • Electromagnetically driven Chladni plate
  • Use of Chladni patterns in the construction of violins
  • Chladni patterns for guitar plates
  • Other pictures of Chladni can be viewed at Science and Society Picture Library.
  • Ernst Chladni at Monoskop.org

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