For the record the units in question are: (nautical mile, knot; are, hectare; bar; ångström; barn)
For the benefit of those who have not done physics, 1 ångström is 10^-10 m (about the diameter of an atom), while a barn is 10^-28 m^2 (the approximate cross-section area of the nucleus of an atom). Since these units are only used in scientific work, it is likely that they will disappear fairly quickly. The are and hectare fill an awkward gap between the square metre and the square kilometre. The ratio of the two is 1:10^6 so there is really room for a unit between them. If the intermediate unit was 10^3 m^2, it would represent an awkward area - a square with sides of length 10*10^2 m (approx 31 m). Alternatively it could be defined as a "metric acre" - a strip 100 m long and 10 m wide. Neither is particularly satisfactory. An awkward situation all round. ----- Original Message ----- From: "Anon Anon" <[EMAIL PROTECTED]> To: "U.S. Metric Association" <[email protected]> Sent: Monday, January 02, 2006 7:09 PM Subject: [USMA:35537] Re: Happy New Year > Pat Naughtin wrote: > >I don't think that I will highlight the units > >ångstrom, are, bar, barn, hectare, > > The BIPM has three levels of "non-SI units accepted > for use with" SI. Those units are table 8, which is > the bottom level: "use is not encouraged" (was "to be > avoided"). I think the BIPM intention is that people > should stop learning about and using these units. So > you are probably acting in accordance with that > intention if you do not highlight them. > > See: > http://www.bipm.org/en/si/si_brochure/chapter4/4-1.html > > Terry > > > > > __________________________________ > Yahoo! for Good - Make a difference this year. > http://brand.yahoo.com/cybergivingweek2005/ >
