I deliberately put 'everyone'  in quotes because there are some strange people
about ;-)

But I take your point - not everyone can live with SI only.  So a framework that
allowed many units systems, of which SI is just one, would be ideal.  But it
needs devising.

Paul

Paul A Bristow, Prizet Farmhouse, Kendal, Cumbria, LA8 8AB  UK
+44 1539 561830   Mobile +44 7714 33 02 04
mailto:pbristow@[...].com


| -----Original Message-----
| From: boost-bounces@[...].org
| [mailto:boost-bounces@[...].org]On Behalf Of Matthias Troyer
| Sent: Wednesday, October 22, 2003 8:51 PM
| To: Boost mailing list
| Subject: Re: [boost] Re: Physical Quantities revisited
|
|
|
| On Wednesday, October 22, 2003, at 08:51 PM, Paul A. Bristow wrote:
| >  I (and others) also expressed the prejudice that all are kept as their
| >  base
| >  unit, now that 'everyone' is using at least 64-bit doubles in their
| >  calculations
| >  (which is enough to keep everyone except the astronomers in the
| >  exponent range.
| >  And the significand precision available (15-ish decimal digits) is
| >  ample for all
| >  physical measurements.
|
| I want to disagree here. I know particle physicists who use singe
| precision (float) numbers in some of their calculations. If instead of
| a common choice of units where hbar=1 one uses SI unites, where hbar is
| about about 1e-34, there will be problems. Even worse problems come
| when hbar^2 is needed.
|
| Since for many calculations I do in quantum mechanics a natural set of
| units is where hbar, the speed of light, and the charge of the electron
| are set to one, I would not like to be forced to use SI units.
|
| Matthias
|
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