Subject: Really big and really small metric prefixes

From: [email-masked] (Erik Max Francis)
Date: Tue, 08 Jun 93 22:04:13 PDT

I recently replied to the "SI Prefixes" thread mentioning that I had 
read about four prefixes that extended the standard SI prefix set 
(which goes from 10^18 to 10^-18, although I forgot momentarily in 
that reply).  My reference comes from _Science News_, Vol. 143 No. 3 
(1993 January 16), "Measuring superconductor magnetic noise," page 37, 
in an inset.  When examining voltages induced when minute magnetic 
fields penetrating superconductors, two researchers found that the 
calculated value was on the order of "milliattovolts" -- that's 10^-21 
V, a very small figure.  The article continues:

    They didn't realize that the international group charged with 
    defining the modern matric system had anticipated such as 
    possibility [of minute figures] and adopted apropriate prefixes.

The new prefixes are:

    yotta-   Y   24
    zetta-   Z   21
        ...
    zepto-   z   -21
    yocto-   y   -24

So the radius of the observable Universe (assuming it to be ten 
billion light-years) is 90 ym (yoctometres).

The article seems to imply that these four extreme prefixes are a part 
of the _metric_ system, not the _SI_ system.  Does anybody know 
whether or not these are SI-standard or just metric-standard?

Erik Max Francis, &tSftDotIotE ...!apple!uuwest!max [email-masked]  __
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