On Friday 16 August 2013 10:07:12 Roy Smith did opine: > In article <520da6d1$0$30000$c3e8da3$54964...@news.astraweb.com>, > > Steven D'Aprano <steve+comp.lang.pyt...@pearwood.info> wrote: > > On Thu, 15 Aug 2013 16:43:41 +0100, Chris Angelico wrote: > > > A mole is as much a number (6e23) as the light year is a number > > > (9.5e15). > > > > Not quite. A mole (abbreviation: mol) is a name for a specific number, > > like couple (2) or dozen (12) or gross (144), only much bigger: > > 6.02e23. And I can't believe I still remember that value :-) > > I remember it as 6.022e23 :-) > > In my high school chemistry class, there was a wooden cube, about 1/2 > meter on a side, sitting on the lecture desk in the front of the room. > The only writing on it was "6.022 x 10^23". It sat there all year. > > The volume of the cube was that of 1 mole of an ideal gas at STP. > > > A light-year, on the other hand, is a dimensional quantity. Whereas > > mole is dimensionless, light-year has dimensions of Length, and > > therefore the value depends on the units you measure in: > > > > 1 light-year: > > > > = 3.724697e+17 inches > > = 0.30660139 parsec > > = 9.4607305e+12 kilometres > > Hold your hands out in front of you, palms facing towards each other, > one shoulder-width apart. That distance is about one light-nanosecond.
Or a quite noticeable color shift when you are cutting coax cables for color phase matching, which we often had to do in an analog NTSC broadcast facility. Where a 1 degree shift, may or may not have been noticeable, was the cable equivalent of 7.7601420788892939683e-10 seconds, which was for the small foam cored cables used for such, with a Propagation Velocity of 0.78*C, only a very short length of cable. I'd have figured how much but I got lost pushing buttons in kcalc just now and came up with something I'd have to use a micrometer to measure. Its been close to 30 years since I had to do such calcs on a near daily basis. Your trivia factoid for the day, and I now return you to the regularly scheduled discussion going no where specifically. :-) Cheers, Gene -- "There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." -Ed Howdershelt (Author) My web page: <http://coyoteden.dyndns-free.com:85/gene> is up! My views <http://www.armchairpatriot.com/What%20Has%20America%20Become.shtml> I suppose that in a few hours I will sober up. That's such a sad thought. I think I'll have a few more drinks to prepare myself. A pen in the hand of this president is far more dangerous than 200 million guns in the hands of law-abiding citizens. -- http://mail.python.org/mailman/listinfo/python-list
