Hippolyte Fizeau

Armand- Hippolyte -Louis Fizeau ( born September 23, 1819 in Paris, † September 18, 1896 in Venteuil at Epernay ) was a French physicist.

Fizeau employed as a private tutor in physics and astronomy. In 1860 he was inducted into the Academy of Sciences, 1878 he was elected President of the Bureau des Longitudes.

Under the influence of François Arago, Fizeau is initially turned to astronomical problems. Together with Jean Bernard Léon Foucault introduced Fizeau in 1845, the first image of the sun ago, which he founded the astronomical photography. In addition, both examined the infrared radiation from the sun and the interference effects of light. Testimony of this work are the Fizeau stripes (interference phenomena on wedge-shaped leaflets ). Independent of Doppler Christian (1842 ) said Fizeau 1848, the Doppler shift of the frequency of the light and thus of spectral advance.

1849 Fizeau took before measurements of the speed of light in different media. His first investigation was the speed of light in air to its end, he refined a invented by Galileo Galilei method. With a rotating gearwheel and by means of two scopes it has from the rotational speed of the wheel and the distance from the light path to calculate the speed (gear method). The calculated value was around five percent overestimated, was later corrected by Foucault. Also in 1849 Fizeau calculated using the method of mirror rotation, the speed of light in still water, 1851 was followed by the measurement in moving water ( " Fizeau experiment "). Based on the measurement results, Fizeau was able to show that the speed of light in water is less than in air. The dependence of the speed of light from the direction of flow of the water could not be reconciled with the law of addition of velocities in classical mechanics, which is why the Fizeau'schen measurements later by Albert Einstein as a crucial experiment ( crucial experiment ) were counted for the special theory of relativity.

Fizeau also worked in the field of thermodynamics, where he constructed a Interferenzdilatometer for measuring the thermal expansion of solids. In 1850 he measured with Gounelle Eugène ( 1821-1864 ), the propagation velocity of electricity in conductors. In 1853 he described the installation of a capacitor to increase the efficiency of induction. Then he studied the thermal expansion of solids and turned the phenomenon of interference of light to measure the expansion of crystals on.

He is immortalized in particular on the Eiffel Tower, see: The 72 names on the Eiffel Tower.

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Pictures of Hippolyte Fizeau

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