The Speed of Light

Numerous measurements of the speed of light published during the last 30 years lead to widely divergent results as compared with the assigned experimental uncertainties. Because of wide diversity in the methods employed in the measurements, all of the data may not be combined effectively in a grand average. Sufficient data had been obtained by the geodimeter method to group them and derive a statistical estimate of the uncertainty in the speed of light by this method. This result, and conclusions reached from careful examination of several experiments, leads to the conclusion that the value 299,792.5 km which has been internationally adopted for use in radio propagation and geodetic work is very close to the best value and not likely to be in error by as much as one part in one million.