[om] Units example usage ?

[Bill Naylor]

On Tue, 29 Apr 2003, Bill Naylor wrote:

> Date: Tue, 29 Apr 2003 09:16:59 +1200 (NZST)
> From: Bill Naylor <Bill.Naylor at mcs.vuw.ac.nz>
> Reply-To: om at openmath.org
> To: om at openmath.org
> Subject: Re: [om] Units example usage ?
>
> On Mon, 28 Apr 2003 sal at dcs.st-and.ac.uk wrote:
>
> > Date: Mon, 28 Apr 2003 09:07:23 +0100
> > From: sal at dcs.st-and.ac.uk
> > Reply-To: om at openmath.org
> > To: om at openmath.org
> > Subject: Re: [om] Units example usage ?
> >
> > Irrelevant but:
> >
> > Glancing at the CD I see that you say the Speed of Light is approximately nnn
> > m/s. Isn't it exactly that by the definition of the second?
> >
> > 	Steve
>
> You may be correct, I'm not a physicist, I assumed (wrongly) all these
> (physical) things where approximate, anyway the definition of approximate
> is sufficiently 'woolly' that eq may be taken as a special case of approx
> (no?)
>

The NIST reference on Constants, Units and Uncertainity defines a second
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 cesium 133 atom."

however I see that the definition of the meter (according to NIST) is:

"The meter is the length of the path travelled by light in vacuum during a
time interval of 1/299 792 458 of a second."

so you still get exact equality,

Bill.
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