Léon Foucault

Chronicled events

1. May 6, 1850​·​Light Slows Down in Water
   #5825

   Light travels more slowly through water than through air: measured with a spinning mirror, the light that went through water comes back later. Newton’s particles, pulled into the water, would travel faster there.

2. February 3, 1851​·​A Pendulum Shows the Earth Turning
   #5815

   A long pendulum’s swing turns slowly clockwise, about 11 degrees an hour in Paris, though nothing pushes it sideways. The floor beneath it turns, with the spinning Earth. A motionless Earth can’t explain this.