Hippolyte Fizeau

Armand Hippolyte Louis Fizeau (French: [ipɔlit fizo]; 23 September 1819 – 18 September 1896) was a French physicist. He did important work to measure how fast light travels.

In 1849, Fizeau used a special tool with a toothed wheel and a mirror. This helped him find the speed of light. His answer was very close to the real value, which was a big achievement at the time.

Two years later, in 1851, Fizeau did another test. He wanted to see how light’s speed changes when it goes through water. This test, called the Fizeau experiment, helped scientists learn more about light.

Fizeau’s work was very important for future physics studies. His measurements were much better than earlier ones. They showed that light moves at about 186,000 miles per second. His discoveries still help us understand light today.

Biography

Hippolyte Fizeau was born in Paris. He married into a well-known family that studied plants. He began his work by improving ways to take photographs. With ideas from scientists like François Arago and Léon Foucault, he looked at how light and heat work together.

In 1849, Fizeau made a big discovery. He measured the speed of light more accurately than anyone before him. He used a smart test with a spinning wheel and a mirror. He found that light travels about 313,000,000 meters per second. This number is very close to the real speed. He also helped find out how the color of light changes when things move. This is called the Doppler effect. Fizeau’s work was important to science. His name is on the Eiffel Tower and a crater on the far side of the Moon is named after him.