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Armand Fizeau

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Armand-Hippolyte-Louis Fizeau (1819-1896) is reputed to be the first person to employ Christian Doppler's work in acoustics (the Doppler Effect) to light[1] and made what is considered to be the first accurate measurement of the speed of light.

From the hilltop at Montmarte in Paris, Fizeau sent a beam of light eight kilometres long to a mirror on the hill at Suresnes which returned back through a slit in a spinning wheel. Knowing the speed of the rotation of the wheel, he was able to calculate the velocity of light within 5% of modern estimations.

Fizeau also provided empirical data from his observations that light travels slower through water than through air.

Fizeau's observations and those of Foucault's were a significant piece of direct observation that was to support the wave-theory of light as opposed to the corpuscular theory that had been posited by Sir Issac Newton. Newton's theory predicted that light would travel faster though water than air.

Léon Foucault (1819-1868), a colleague of Fizeau, was to later calculate the speed of light to within 1% of modern estimations.[2]

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  1. There is no real evidence that Fizeau knew of Doppler's work which was published in 1942 and Fizeau's work, published in 1948, was evidently his own discovery. To that extent, Doppler has prior claim but Fizeau is credited with discovering the effect as well and applying it to other phenomena
  2. Gribbin, John (2002). Science: A History. Penguin Books; Christian Doppler (1803–1853) and the impact of the Doppler effect in astronomy Wolfschmidt, Gudrun. Institute for History of Science, Hamburg University