Louis Jourdan wrote in USMA 21581 >At 11:00 -0400 8/08/2002, Joseph B. Reid wrote: >>I think that M.R.Madam has read too much into the CNN report. CNN >>mentioned that the speed of light is approximately 300 000 km/s, they gave >>no other figure, nor did the despatch state how fast the speed of light is >>slowing down. Until we get more details we can only continue to use the >>accepted speed of light, which is >> c = 299 792 458 m/s. >>Since 1948 this relationship defines the metre in terms of the second, > >Was it not in 1983?
Quite right, Louis. Thanks for the correctioon. The figure for the speed of light was adopted in 1975, and that figure was used to define the metre in 1983. This was obviously one of my bad days. >>which was defined in 1968 as: >>"The second is the duration of 9 192 631 770 periods of the radiation >>corresponding to the transition between the two hyperfine levels of the >>ground state of the caesium 133 atom." > >Was it not in 1967? > >Louis The BIPM metric bible says that the latest version of the definition of the second was adopted by the 13th CGPM, 1967-1968. I did not know which date to choose, so I wrote 1968. It probably was 1967 because it was Resolution 1 of the meeting. The bible lists 6 other resolutions of the meeting. Joe Joseph B.Reid 17 Glebe Road West Toronto M5P 1C8 Tel. 416 486-6071
