From max@west.darkside.com Fri Jun 4 10:06:15 1993 From: max@west.darkside.com (Erik Max Francis) Newsgroups: sci.math,sci.astro Subject: SI prefixes (was Re: What ius [sic] a parsec?) Date: Fri, 04 Jun 93 03:19:30 PDT Organization: The Dark Side of the Moon +1 408 245 SPAM roland@sics.se (Roland Karlsson) writes: > All those conversion factors just disappears if you stop using archaic > units (:-) like lightyears, parsec, au, feet, inch, ounce, gallon, > mile, nautical mile, knot, etc. Use the metric system. Much more > convenient. How about using giga-km or tera-km for astronomical > distances, just as micro-meter or nano-meter for the very small ones? Definitely, though I'd qualify your use of the term "metric" to specifically mean SI, instead of more conventional meanings of the term "meric." Meters, kilograms, seconds, amperes (and other supplementary units). Who could ask for more? Though I think gigameter and terameter would be more fluid and useful (and they're already being used) than giga-kilometer and tera-kilometer, as that's just a terameter and a petameter, respectively. Anybody catch the article in _Science News_ about the extra drafted official SI prefixes? They were zempto-, yatto-, and two other analogous ones for the opposite end of the spectrum. Very, very interesting. Is this _really_ official or what? Erik Max Francis, &tSftDotIotE ...!apple!uuwest!max max@west.darkside.com __ USMail: 1070 Oakmont Dr. #1 San Jose, CA 95117 ICBM: 37 20 N 121 53 W / \ If you like strategic games of interstellar conquest, ask about UNIVERSE! \__/ -)(- Omnia quia sunt, lumina sunt. All things that are, are lights. -)(- From max@west.darkside.com Fri Jun 11 15:24:22 1993 From: max@west.darkside.com (Erik Max Francis) Newsgroups: sci.math,sci.astro Subject: Re: SI prefixes (was Re: What ius [sic] a parsec?) Date: Tue, 08 Jun 93 04:14:45 PDT Organization: The Dark Side of the Moon +1 408 245 SPAM rdc@helium.gas.uug.arizona.edu (richard d clark) writes: > I suppose this would work as long as they add enough prefixes. What power > 10 is the new&improved highest? I wish I knew for sure. There were four new prefixes, two large and two small. Two started with the letter _y_; the other two started with _z_. The smaller pair was lowercase, as is the convention -- y & z -- and the bigger pair were uppercase -- Y & Z. The names were something like _yatto_ and _zemto_, but I can't remember exactly and I don't remember how the large and small names differed, though I remember they were very similar. Other than that, I don't remember anything else that's useful. I have the _Science News_ article around here somewhere; I'll try to dig it up and post an excerpt if I can. At any rate, they fill up where exa- and atto- leave off: they take up 10^+-18 and 10^+-21. > Hmmm... 1 pc is 10 pi tera km. So we can start talking about intergalactic > distances in megaterakm. Or would that be gigaterameter. Is this the same > as a yattometer? I've lost count. A gigaterameter would be 10^9 x 10^12 m = 10^21 m, which _was_ represented by the largest new prefix, which, if I recall, was a Y, though I don't remember the name. Damn. I'm really going to search through my old issues for this thing now . . . > What do peopple think about which would be more convenient: changing the > basic time unit to one equal to about .1 sec so the day would be 1 mega of I have actually seen a metric system of time which worked at the day level. Each day was broken down into ten decidays, which were broken down into ten centidays, which in tern were broken into ten millidays. The roughly equivalent analogue is deciday-centiday-milliday to hour-minute-second. One deciday equals 2.40 hours; one centiday equals 14.4 minutes; one milliday equals 86.4 seconds (1.44 minutes). Actually, some institutions already use this system, although they don't use it _as such_. They don't talk about anything smaller than days -- and thus use decimals to represent smaller times -- but don't talk about decidays, centidays, or millidays. > Let's face it, people in any field will use whatever units are convenient > for them. We seem to like for numbers to be 'several' +- 'a few', hence > the use of kg, km, or kton as if they were a basic unit. Recognition of > this tendency is official: the unit of volume is the liter and not the > cubic meter. That's true, of course. It'd just be nice if we could all agree on the same _base_ system -- such as SI -- to use to get all these standard units. Instead of using inches, feet, miles, or millions of miles, it would be nicer (and easier to understand each other) if you'd use an SI equivalent like cm, m, km, or Gm. Erik Max Francis, &tSftDotIotE ...!apple!uuwest!max max@west.darkside.com __ USMail: 1070 Oakmont Dr. #1 San Jose, CA 95117 ICBM: 37 20 N 121 53 W / \ If you like strategic games of interstellar conquest, ask about UNIVERSE! \__/ -)(- Omnia quia sunt, lumina sunt. All things that are, are lights. -)(- From somlo@swifty.dap.CSIRO.AU Fri Jun 11 15:24:37 1993 Newsgroups: sci.math,sci.astro From: somlo@swifty.dap.CSIRO.AU (Peter Somlo) Subject: Re: SI prefixes (was Re: What ius [sic] a parsec?) Organization: CSIRO, Division of Applied Physics, Sydney Date: Wed, 9 Jun 1993 00:13:31 GMT In article max@west.darkside.com (Erik Max Francis) writes: >rdc@helium.gas.uug.arizona.edu (richard d clark) writes: > >I have actually seen a metric system of time which worked at the day >level. Each day was broken down into ten decidays, which were broken >down into ten centidays, which in tern were broken into ten millidays. >The roughly equivalent analogue is deciday-centiday-milliday to >hour-minute-second. One deciday equals 2.40 hours; one centiday equals >14.4 minutes; one milliday equals 86.4 seconds (1.44 minutes). > In the Splus language, I have written a function which, when supplied with the eight digits before the decimal point (for: year, month, day) and with the four digits after the decimal point (for: hours, minutes), converts this number into Julian days, with decimal fraction for part-day entries. This way, accurate chronoligal plots may be produced. -- Dr Peter I. Somlo FIEEE | CSIRO Div. Appl.Phys. | "Every coin has three Head RF/Microwave Proj. | Natl. Meast. Lab. | sides - at least" FAX: 61-2-413-7383 | POB 218 Lindfield 2070| (Somlo, cca. 1985) TEL: 61-2-413-7505 | NSW AUSTRALIA | From max@west.darkside.com Fri Jun 11 15:29:48 1993 From: max@west.darkside.com (Erik Max Francis) Newsgroups: sci.astro Subject: Really big and really small metric prefixes Date: Tue, 08 Jun 93 22:04:13 PDT Organization: The Dark Side of the Moon +1 408 245 SPAM I recently replied to the "SI Prefixes" thread mentioning that I had read about four prefixes that extended the standard SI prefix set (which goes from 10^18 to 10^-18, although I forgot momentarily in that reply). My reference comes from _Science News_, Vol. 143 No. 3 (1993 January 16), "Measuring superconductor magnetic noise," page 37, in an inset. When examining voltages induced when minute magnetic fields penetrating superconductors, two researchers found that the calculated value was on the order of "milliattovolts" -- that's 10^-21 V, a very small figure. The article continues: They didn't realize that the international group charged with defining the modern matric system had anticipated such as possibility [of minute figures] and adopted apropriate prefixes. The new prefixes are: yotta- Y 24 zetta- Z 21 ... zepto- z -21 yocto- y -24 So the radius of the observable Universe (assuming it to be ten billion light-years) is 90 ym (yoctometres). The article seems to imply that these four extreme prefixes are a part of the _metric_ system, not the _SI_ system. Does anybody know whether or not these are SI-standard or just metric-standard? Erik Max Francis, &tSftDotIotE ...!apple!uuwest!max max@west.darkside.com __ USMail: 1070 Oakmont Dr. #1 San Jose, CA 95117 ICBM: 37 20 N 121 53 W / \ If you like strategic games of interstellar conquest, ask about UNIVERSE! \__/ -)(- Omnia quia sunt, lumina sunt. All things that are, are lights. -)(-