21 Jan
1999
21 Jan
'99
10:36 p.m.
> Really? The meter is defined (certain frequency
of light from a
certain
> element for so many waves yada yada). Sea level
is defined (don't know
the
> SI unit, but 780 millibars of pressure). Celcius
is defined (0 is
freezing
> point of pure water at sea level, 100 boiling
point of pure water at sea
> level) and that's all you need to define the gram: one cubic centimeter
of
water at 4C at
sea level. That also gets you volume (liters).
I thought length, mass (Kilogram), and time (seconds) were picked as the
basic SI units, and others, like temperature, were "secondary". For
electromagnetics,
a 4'th unit was required, sometimes an ampere (which can be defined from
mechanical variables), sometimes charge.
-Dave