I write in support of Jim Frysinger's message below, and as a
former (10-year) NASA employee at the MSFC (including the ABMA and the
GMDD of the ABML, all under Ernst Stuhlinger in Huntsville).
Eugene A. Mechtly, College of Engineering
University of Illinois at Urbana-Champaign (UIUC)
1406 West Green Street, Urbana, IL 61801
.........................................
On Fri, 16 Feb 2001, James R. Frysinger wrote:
> ...
> Dear Dr. Phillips,
>
> I found your article at
> http://science.msfc.nasa.gov/headlines/y2001/ast15feb_1.htm
> regarding the heliomagnetic field and its recent flip to be extremely
> interesting and serendipitously timely for my Introductory Physics
> classes. I intend to distribute copies of the article to them and
> discuss it on Monday (with credits intact, of course) as part of my
> pre-test review in our study of magnetism.
>
> However, I am going to have to explain an obsolete unit that you used in
> the article -- the gauss. We no longer teach our students to use gauss;
> instead we use the SI unit, the tesla, for magnetic flux density.
> Their textbooks do not mention or define the gauss. In fact, we no
> longer mention that people once used the gauss! I'll have to convert
> this for them. In the future, though, would you please use only SI
> units and not use the obsolete cgs units that used to be common a few
> decades ago? It's bad enough that we have to put up with NASA
> information occasionally using statute miles, yards, feet, and pounds
> (especially information coming out of Johnson Space Center!), but to
> have to put up with yet a third system of units -- cgs -- would tax our
> lecture time limits. If your older instruments are still reading out in
> gauss, you would be doing educators and students a favor to convert the
> information to teslas behind the scenes and prior to release to the
> public.
>
> By the way, the SI symbol for the astronomical unit (a non-SI unit
> accepted for use with the International System) is ua, not AU.
>
> References for my comments above are:
> International Bureau of Weights and Measures (BIPM):
> http://www.bipm.fr/pdf/si-brochure.pdf
> National Institute of Standards and Technology (NIST):
> http://physics.nist.gov/Pubs/SP811/sp811.html
> American Institute of Physics (AIP):
> http://commerce.aip.org/metric.htm
> International Astronomical Union (IAU):
> http://www.iau.org/units.html
> Note especially paragraph 5.16 of the last reference which lists the
> gauss as obsolete. Inexplicably, it lists the symbol for astronomical
> unit as au (but not AU) instead of ua in Table 5.
>
> Again, my compliments and thanks for your otherwise excellent material.
>
> regards,
> James R. Frysinger
> ...
