François Arago and the Birth of Interferometry

François Arago (1786-1853) was only 20 years old when the Bureau of Longitude selected him and his friend Jean-Baptiste Biot (1774-1862) to extend Le Meridien- the line of longitude passing through Paris-as far south as they could manage. In 1791, the Académie des Sciences had defined the meter as one ten millionth of the distance from the north pole to the Equator along that line, making the meridian the fundamental basis of the new metric system of measurement.