"Orchid XP v7" <voi### [at] devnull> wrote in message
news:4734b5ac$1@news.povray.org...
> KalleK wrote:
>
> >> How the HECK did they measure that o_O
> >
> > It's defined that way: one meter is the 1/299 792 458 part of what light
> > travels in one second in vacuum...
> >
> > (Well one meter was defined differently in former times...)
>
> Sweet!
>
> So how do they define 1 second? (IIRC, isn't it the amount of time it
> takes for the Sodium D-line to go through some defined number of
> oscilations or something?)

Hyperfine transition of the Caesium-133 atom, iirc

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