The calculation of the speed of light in 1849 utilized a beam reflected from a mirror located 8,633 meters away. By passing this beam through a wheel with 720 teeth rotating at precise intervals, Hippolyte Fizeau determined a velocity within five percent of the modern value, fundamentally advancing the empirical study of light propagation during the nineteenth century.
Early Career and Photographic Processes
Born in Paris in 1819, Fizeau pursued an education at the Collège Stanislas de Paris and the Paris Medical Faculty between 1840 and 1841 before attending the Collège de France in 1842. His initial research focused on refining photographic techniques. Early collaborations with Léon Foucault, encouraged by François Arago, centered on the investigation of light and heat interference. These studies provided the foundation for his later contributions to physics, including the Fizeau–Foucault apparatus.
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Fizeau is credited with the 1851 Fizeau experiment, which measured light speed within moving water. His work intersected with the discovery of the Doppler effect, later referred to in French as the Doppler–Fizeau effect. In 1848, he predicted the redshifting of electromagnetic waves. His technical work expanded in 1853, when he described the application of a capacitor, then known as a condenser, to enhance the efficiency of induction coils. Later research involved studying the thermal expansion of solids and utilizing light interference to measure crystal dilatations.
Institutional Recognition and Legacy
Fizeau served as president of the French Academy of Sciences in 1878 and held membership in several prestigious organizations, including the Royal Society, the Royal Swedish Academy of Sciences, the Royal Prussian Academy of Sciences, and the Bureau des Longitudes. He received the Rumford Medal in 1866 and was named a Knight of the Legion of Honour in 1849. His name is one of the 72 inscribed on the Eiffel Tower. He died at the château de Venteuil in 1896.
Fast facts
- Born: 1819, Paris
- Died: 1896, château de Venteuil
- Primary Field: Physics
- Notable Awards: Rumford Medal (1866)
- Professional Positions: President of the French Academy of Sciences (1878)
- Legion of Honour: Knight (1849)
- Eiffel Tower Recognition: Name inscribed among 72 scientists
Questions readers ask
What was the significance of the 1849 light experiment?
It provided a measurement of the speed of light with unprecedented accuracy, achieving a result within five percent of the current accepted value.
Why is Fizeau's name on the Eiffel Tower?
His name is one of 72 inscribed on the tower to honor prominent French scientists, engineers, and mathematicians active in the century preceding the 1889 World's Fair.
Achievements
- Knight of the Legion of Honour — 1849
- Notable work: Fizeau interferometer
- Notable work: Fizeau–Foucault apparatus
- Educated at Collège Stanislas de Paris, Paris Medical Faculty and Collège de France
- Worked as physicist, astronomer and engineer
