As usual, you guys are great! Thanks so much for the clear explanations, the much appreciated humor, and the well written letter back to the folks who posted the article. :-)
-- Ezra ----- Original Message ----- From: "John M. Steele" <jmsteele9...@sbcglobal.net> To: "U.S. Metric Association" <usma@colostate.edu> Sent: Monday, November 30, 2009 4:20:07 PM GMT -08:00 US/Canada Pacific Subject: [USMA:46226] Re: Ergs??? You guys have ruined my visualization of this energy as 1.6 Mmol of flies doing pushups. :) As the two references to the energy differ by three orders of magnitude, at least one must be wrong. The body of my e-mail to their contact e-mail adress follows: In the news article referenced in the title, the energy of the wave is described as " packed as much energy as 2400 megatons of TNT (1029 ergs)." As the accepted conversion for TNT is 4.184 GJ/t (per NIST SP811), 2400 Mt is about 10^19 J or 10 EJ. I suspect you mean 10^29 ergs not 1029 ergs, but 10^29 ergs converts to 10^22 J or 10 ZJ. Since these are three orders of magnitude apart, at least one is wrong, and the article should be corrected. I would further point out that the erg (indeed the entire CGS system of units) is deprecated and not really accepted for use with the SI. Even those Americans who are relatively SI-aware would have to look up what an erg is, so why use it? NIST SP330 advises that if such units must be used, definitions in terms of real SI units should always be given in the article. --- On Mon, 11/30/09, James R. Frysinger <j...@metricmethods.com> wrote: From: James R. Frysinger <j...@metricmethods.com> Subject: [USMA:46223] Re: Ergs??? To: "U.S. Metric Association" <usma@colostate.edu> Cc: "U.S. Metric Association" <usma@colostate.edu> Date: Monday, November 30, 2009, 6:00 PM Blame the astronomers at NASA. The International Astronomical Union (IAU) is quite strongly in favor of using SI. I've posted their statement (from their authors' guide) here a few times before. But the American Astronomical Society (AAS) is hopelessly bogged down in cgs (don't ask me which flavor). Since the bulk of the major astronomical journals are funded and published by Americans, AAS sentiment overrules IAU sentiment. Yes, the Astronomical Almanac and similar AAS publications will provide you with the diameter of the Sun and our mean orbital distance from it, the astronomical unit, in centimeters. Jim Pierre Abbat wrote: > On Monday 30 November 2009 16:06:39 ezra.steinb...@comcast.net wrote: >> Anyone have an idea why the article (from our friends at NASA ;-) below >> would mention ergs for energy? >> >> http://www.nasa.gov/mission_pages/stereo/news/solar_tsunami.html > > Beats me. It's not out of range of prefixes applied to the joule, assuming > that "1029 ergs" is supposed to be "10^29 ergs" (10^22 joules). When I run > the megatons of TNT through the units program, however, it comes out on the > order of 10^19 joules. > > The erg is obsolete, except in the Sahara, where it is still in use, along > with the chott and the jebel. :) > > Pierre > -- James R. Frysinger 632 Stony Point Mountain Road Doyle, TN 38559-3030 (C) 931.212.0267 (H) 931.657.3107 (F) 931.657.3108
