The 17th General Conference on Weights and Measures ends.
The conference passed a resolution defining a meter as the distance traveled by light in vacuum during a time interval of about three hundred millionth of a second. Before this, the meter or metre was assigned several different definitions. In 1793, it was defined as one ten-millionth of the distance between the Earth’s Equator and the North Pole. In 1960, it was once again redefined by the 11th General Conference of Weights and Measures as equal to “1650763,73 wavelengths in vacuum of the radiation corresponding to the transition between the levels 2p10 and 5d5 of the krypton 86 atom.”