Roy Smith wrote: > 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.
Narrow shoulders. I figure it just under a foot. I once attended a lecture by Grace Hopper where she handed out "nanoseconds," pieces of wire about a foot long. She said that the beaurocrats were always asking how much is a nanosecond, and couldn't imagine what a billionth was like. So she gave them something physical. -- Signature file not found -- http://mail.python.org/mailman/listinfo/python-list
