It was known long time ago that earth rotates. The rotation of planet earth around its own axis is known as earth rotation. There were many scientists who believed in earth rotation and also worked on proving it. Leon Foucault was one of them. He was known for providing an experimental proof of earth rotation using pendulum which was later called Foucault pendulum. He was also the first person to accurately determine the velocity of light.

Jean Bernard Léon Foucault was born to a publisher in Paris, on 18th September 1819. His father passed away when he was nine years old and from then he was raised by his widowed mother. Foucault lacked self-confidence and was very shy because of his unstable health.

Foucault went to college Stanislas, where his teachers called him lazy. Although he was weak in academics, Foucault showed his talent in building machines. His mother encouraged him to pursue medicine and become a surgeon because he was dexterous with his hands. Foucault studied medicine under Alfred François Donné.  Foucault showed interest in medicine, until he realized that he could not stand the sight of blood. He gradually showed interest in improvement of Louis Daguerre’s photographic process and so he carried out his experiments with his friend Armand Hippolyte Louis Fizeau. Foucault became Donné’s assistant after he left medical college.


While he assisted Donné, Foucault discovered the means of taking photographs through the lens of a microscope. In this process he also invented a strong light source for illuminating his microscopic subjects. In the year 1845, Foucault took over Donné’s position and became editor of the scientific newspaper Journal desDébats.

In the year 1851 Foucault made his first discovery by showing an experimental proof of earth rotation using pendulum (Foucault pendulum). The following year he provided a simpler experimental proof of earth rotation using a gyroscope. In the year 1855 he received Copley medal of the Royal Society for his efforts in proving earth rotation.

In the same year Foucault was appointed as physicist by the imperial Observatory where he did experiments for the improvement of telescope technology and land-surveying equipment.

Foucault became the first person to accurately determine the speed of light in the year 1862. He became the member of Royal Society of London in the year 1864.


Foucault suffered a stroke in the year 1867 because of which his work was interrupted. He was attacked with multiple sclerosis (a brain disorder) as a result he could no longer feel his hands. He died on February 11th 1868 in Paris and his body was buried in Montmartre Cemetery.

Foucault was one of the 72 persons whose name was inscribed on Eiffel Tower. He also has an asteroid named after him and it is named as the 5668 Foucault.


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