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Jean Baptiste Joseph Fourier (1768 - 1830)

ECE 301 Fall 2007 mboutin Fourier.jpeg

French mathematician who discovered that any periodic motion can be written as a superposition of sinusoidal and cosinusoidal vibrations.Fourier transform is named in honor of him. He developed a mathematical theory of heat in Théorie Analytique de la Chaleur (Analytic Theory of Heat), (1822), discussing it in terms of differential equations.

Fourier was a friend and advisor of Napoleon. Fourier believed that his health would be improved by wrapping himself up in blankets, and in this state he tripped down the stairs in his house and killed himself. The paper of Galois which he had taken home to read shortly before his death was never recovered.

Fourier is credited with the discovery in 1824 that gases in the atmosphere might increase the surface temperature of the Earth. This was the effect that would later be called the greenhouse effect. He established the concept of planetary energy balance - that planets obtain energy from a number of sources that cause temperature increase. Planets also lose energy by infrared radiation (that Fourier called "chaleur obscure" or "dark heat") with the rate increasing with temperature. A balance is reached between heat gain and heat loss; the atmosphere shifts the balance toward the higher temperatures by slowing the heat loss. Although Fourier understood that rate of infrared radiation increases with temperature, the Stefan-Boltzmann law which gives the exact form of this dependency (a fourth-power law) was discovered fifty years later.

Fourier recognized that Earth primarily gets energy from Solar radiation, to which the atmosphere is transparent, and that geothermal heat doesn't contribute much to the energy balance. However, he mistakenly believed that there is a significant contribution of radiation from interplanetary space.

Fourier referred to an experiment by M. de Saussure, who exposed a black box to sunlight. When a thin sheet of glass is put on top of the box, the temperature inside of the box increases. Infrared radiation was discovered by William Herschel twenty five years later.


PLAGIARISM --mireille.boutin.1, Tue, 16 Oct 2007 22:54:03 Copying a webpage from somewhere else with small modifications without mentioning the source constitutes plagiarism. This will not be tolerated on the kiwi.

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