The speed of light

John Clark (
Sun, 18 Jul 1999 14:02:12 -0400

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Ron Kean <>

> In the 1980s, the meter was redefined in terms of the speed of light,
>whereas earlier it had been defined as a certain number of wavelengths of
>a certain spectral line of Krypton 86. The meter is now defined as the
>distance light travels in 1/299,792,458 second.

OK, but how long is a second? Is it the time it takes light to travel 299,792,458 meters? This sort of thing could give circular definitions a bad name.

>That means we no longer have to wonder what is the exact
>speed of light. It is 299,792,458 >meters per second,
>exactly, by definition.

Light also moves at 340753049509845930845 meters per clognee. I will leave it as an exercise for the reader to fugue out exactly how long a "clognee" is.

John K Clark

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