OK. Quoting Bill Hooper <[EMAIL PROTECTED]>:
> Gavin wrote: > > I think the SI second is no longer defined as oscillations of Cesium > > atoms in > > an atomic clock, but rather as the length of time it takes a beam of > > light to > > travel a specified distance. > > Gavin, you are confusing the definition of the second with the > definition of the metre. The second is still defined in terms of the > oscillations of the Cesium atom*. It is the metre that is defined as > the distance light travels in a second. > > Regards, > Bill Hooper > Fernandina Beach, Florida, USA > > *"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 atom" (at rest and at a temperture of 0 K). > > Section 2.1.1.3 "Unit of time (second) > The International System of Units (SI) > 7th Ed. (1998) and year 2000 Supplement > >
