World record measurement of the speed of light

Ken Evenson
January 01, 1972

Using techniques they developed to produce laser light with a very stable frequency, or color, Ken Evenson and his group at NIST Boulder were able to measure the speed of light at 299,792,456.2 +/- 1.1 meters per second. This value was 100 times more accurate than the previous best measurement, which calculations showed to be almost 44 meters per second too fast.