Last summer, I taught the PHYS 129 Introductory Astronomy I course here at the college. This is the way I taught it. I had them learn the prefixes and taught with them. They learned how to "run up and down the scale". They were also made aware of the International Astronomical Union (IAU) position on the SI and on units in general. See http://www.iau.org/IAU/Activities/nomenclature/units.html which is posted on my Neat Astronomy Links page: http://www.cofc.edu/~frysingj/astrolinks.html Pity that the American Astronomical Union does not comply.
By the way, I received no complaints from either the students, nor from the professional astronomers (one of whom taught the second semester -- PHYS 130 Intro. Astr. II -- in the second half of that summer), nor from the department head. I just presented things matter of factly and that's the way everyone responded. This is a General Education course, one of the ones students can take to meet their science requirements for their core course requirements. In the upper division courses they teach them all the really nifty stuff, such as ergs, which has caused students to come to me to help them convert the quantities into joules. Jim Barbara and/or Bill Hooper wrote: > > on 4/26/2002 9:21 PM, Duncan Bath at [EMAIL PROTECTED] wrote: > > I grant that Pm, Tm, nm etc. can > > be handy for specialists where such numbers are dealt with frequently. > > Of course! > > No one would suggest that anyone should become familiar with these units > except those for whom they are useful. That can be said for ANY SI unit. (It > can be said for any non-SI unit as well). > > Sometimes the beautiful order and logic of SI makes us want to teach it all > to the uninitiated so that they can see how complete and orderly it really > is. It is perhaps worthwhile that people should generally be aware that a > variety of other prefixes are available, but they need only be taught to use > those that they will find useful. > > Now there are some questions as to which units and which prefixes are > useful. I think astronomers should be making greater use of terrametres > (Tm), petametres (Pm), exametres (Em), zettametres (Zm) and yottametres (Ym) > for appropriate distances, but many of them resist doing so because they are > so attached to their light-years (l.y.), parsecs (ps*),kiloparsec (kps) and > megaparsecs (Mps). That is unfortunate. > > For reference, here are the equivalents of all the above units, in order > from smaller to larger. You'll notice that the light year and parsec (even > with the commonly used kiloparsec and megaparse included) still doesn't > provide the wide range of unit sizes as SI does. > > 1 Tm = 1 x 10^12 m > 1 l.y. = 9.5 x 10^12 m > 1 ps = 3.1 x 10^13 m > 1 Pm = 1 x 10^15 m > 1 kps = 3.1 x 10^16 > 1 Em = 1 x 10^18 m > 1 Mps = 3.1 x 10^19 > 1 Zm = 1 x 10^21 m > 1 Ym = 1 x 10^24 m > > Regards, Bill Hooper > physics professor (retired), Florida, USA > > *I'm not positive of the accepted symbol or abbreviation for the non-SI > parsec. I think it is either ps or pc, or it may be something else. > > ======================== > Keep It Simple - Make It Metric! > ======================== -- Metric Methods(SM) "Don't be late to metricate!" James R. Frysinger, CAMS http://www.metricmethods.com/ 10 Captiva Row e-mail: [EMAIL PROTECTED] Charleston, SC 29407 phone/FAX: 843.225.6789
