As part of the “C à Paris” exhibition at the Observatory from 1st October until the 4th December 2005…

The “C” exhibition in Paris retraces the history of the first astronomers and scientists to mesure the speed of light at the Observatory. It explains the largest experiments made during the 19th Century in order to calculate the speed of light, by showing the instruments and documents of Hippolyte Fizeau, Léon Foucault and Alfred Cornu. The exhibition will also show how astronomers and geodesists (specialist mathematicians) used to measure the dimensions of the Earth before the speed of light was used for more precision.

The spectacular laser projected between the Observatory and Montmartre will also show how to calculate the speed of light, in a modern reproduction of a an experiment conducted by Hippolyte Fizeau in 1849. The experiment, reconstructed with the help of the Pierre and Marie Curie University and the Paris Observatory, uses an optical-acoustic method which ressembles Fizeau’s toothed wheel approach.

– the first blast will be during the “Nuit Blanche”, from 7pm 1st October until 2am 2nd October.
– laser blasts will then be on Wednesdays, Fridays and Saturdays from 7pm to 11pm.
– the laser will also be operating for the Science Festival, 16th October, from 7pm to 11pm.