Fizeau, Armand-Hippolyte-Louis

BornParis, France, 23 September 1819

DiedVenteuil, Marne, France, 18 September 1896

Hippolyte Fizeau was a pioneer in astrophotography and is best known for his work on the velocity of light. The eldest son of Louis Fizeau, a pathologist at the Paris Medical School, and Béatrice Fizeau, he entered his father’s school in about 1840, but dreadful migraines caused him to abandon medicine for physics. In 1853, Fizeau married Thérèse Valentine de Jussieu (daughter of the botanist Adrien de Jussieu), with whom he had four children.

Fizeau’s optical work had an impact on astronomy. While still a medical student in Paris, he improved daguerreotype contrast, sensitivity, and stability, and encouraged by François Arago in 1844/1845, he collaborated with Léon Foucault to take the first successful daguerreotypes of the Sun, which showed clear limb darkening, indicating that the solar luminous layers were gaseous. In 1848, Fizeau announced how in sound the speeds of source and observer with...