What exactly is "exact" (was Clean Singleton Docstrings)

[Marko Rauhamaa]

Ian Kelly <ian.g.kelly at gmail.com>:

> Okay, so how is that wavelength defined?
>
> If you needed to mark a meter stick, and all you had was the
> definition of c and the second, how would you do it without measuring
> anything?

I wouldn't be measuring a meter stick. To measure, say, the height of a
desk, I would bring in some caesium and shine its radiation from the
desk level down to the floor. By counting the ebbs and flows of the
radiation as it leaves the nozzle and strikes the wooden floor I make
the approximage height measurement.

However, I know *exactly* how long a meter is without making a
measurement.


Marko