Dear John and All, I have interspersed some remarks.
on 28/3/04 1:53 PM, John Hynes at [EMAIL PROTECTED] wrote: > Astronomers don't use light years because they feel "superior," Astronomers are not alone in their fondness for jargon � but they are particularly good at it. One of my favorite pieces of jargon is the 'parsec' which, I think, is 1/60th of 1/60th of 1/90th of a quarter of a circle of an 'Astronomical Unit (AU). (Wheee!) Or to put it simply so that mere mortals can understand: (see: <www.sunspot.noao.edu/sunspot/pr/glossary.html >) (Parsec is derived) from parallactic arcsecond. A parsec (abbreviated pc) is the distance at which a star or other object shows a parallax of one arcsecond due to the motion of the Earth around the Sun. One parsec is exactly equal to 648000/pi AU, and approximately equal to 206265 AU, 3.086e16 m, 1.917e13 mi, and 3.2616 lightyears. A kiloparsec (abbreviated kpc) is 1000 pc (or about 3262 lightyears), a megaparsec (abbreviated Mpc) is 1,000,000 pc (or about 3 million lightyears), and a gigaparsec (abbreviated Gpc) is 1,000,000,000 pc. (Double Wheee!) > but because > that is often more useful a unit for their field than the metre, since it's > an easy conversion from distance to age. Otherwise, they'd have to keep > saying 9.460528404846x10^15 m, or 9.460528404846 Pm. Of course, now that > we're seeing objects over 13 thousand million light years away, that's more > than 120 Ym! What's the reason for this sort of precision. With the accuracy available for these sorts of observations and calculations, using 10 yottametres to be equal to 1000 years of light travel might well be in the ball park for the required level of precision. In a way this reminds me of the electrical suppliers who use the unit kilowatt-hour to buy and sell energy. Because their unit clearly contains reference to a power unit, watt, they have successfully obfuscated the distinction between energy and power for over 100 years, > > I don't think anybody actually uses "atto-light years"; the author was just > making a point. Yes, I agree that this was probably meant as an anti-metric joke. > And I doubt that very many astronomers are anti-metric!!!! Nor are they pro-metric. They spend their night using the 'real' tools of astronomical jargon: light-years, parsecs, astronomical units, Babylonian angles and Babylonian time; and their days spent translating (dumbing down) their favored jargon measures into 'popular' measures such as 'The asteroid has a volume of 18 Olympic swimming pools'. Cheers, Pat Naughtin LCAMS Geelong, Australia -- > ----- Original Message ----- > From: "Pat Naughtin" <[EMAIL PROTECTED]> > To: "U.S. Metric Association" <[EMAIL PROTECTED]> > Sent: Saturday, March 27, 2004 3:11 PM > Subject: [USMA:29319] Prefix use outside SI > > >> Dear Bill, >> >> Take a look at: >> >> > http://www.glyphweb.com/esky/default.htm?http://www.glyphweb.com/esky/concep >> ts/lightyear.html >> >> Amongst other things, particularly check the use of 'atto-light year' at > the >> bottom of the page. >> >> 'Oh, what a wicked web we weave - when first we practise to deceive'. >> >> In this case the deceit seems to be in the earnest interests of protecting >> our precious astronomy patch (by using layering of jargon -- we are >> different - therefore we are superior!) from those pesky metricationists. >> >> Cheers, >> >> Pat Naughtin LCAMS >> Geelong, Australia >> -- >> >> on 27/3/04 6:49 AM, Bill Hooper at [EMAIL PROTECTED] wrote: >> >>> Recently Pat Naughtin suggested: >>>> 1 milliday = 86.4 s 1 new minute a bit longer than an old >>>> minute >>>> 1 centiday = 864 seconds about a quarter of an old hour >>>> 1 deciday = 8640 seconds a little under 2 1/2 hours >>> >>> I can't help feel uncomfortable using the SI prefixes with non-SI units >>> (SI prefix milli with non-metric day to make milliday). >>> >>> We may not be able to control what others do but I'm not sure those of >>> us who want to promote SI metric should encourage such bastardizing of >>> the prefixes. >>> >>> Also, I would maintain that breaking the day into smaller units of >>> millidays, centidays and decidays, where each is an odd multiple of >>> seconds, is not much of an improvement over 24 hours, 60 minutes and 60 >>> seconds. >>> >>> However, I am happy to see that Pat agrees with the importance of not >>> changing the size of the SI second in any half baked effort to simplify >>> civil (daily) time. That would cause more problems than it would solve. >>> >>> >>> Regards, >>> Bill Hooper >>> Fernandina Beach, Florida, USA >>> <><><><><><><><><><><><> >>> Make it simple; Make it Metric >>> <><><><><><><><><><><><> >>> >> >> >
