[ale] OT - Portable Drive

[Michael H. Warfield]

On Tue, 2007-12-11 at 14:27 -0500, Thompson Freeman wrote:
> On 12/11/2007 01:56:01 PM, Mike Harrison wrote:
> >> though, my first device was a Trash-80. I understand the  
> >> basic
> >> principles of slide-rule function, but I've no practical  
> >> experience.
> > 
> > My advanced chemistry teacher was a slide rule nut.
> > He allowed their use in class, and if used, you only
> > had to be right to 3 significant digits.
> > 
> > If you used a calculator, you had to be right to 7
> > (not 8, he was reasonable), and yet, as people 'trusted'
> > the calculator, they made mistakes and got the answers
> > wrong due to cumulative error.

> ?? Chemistry problems to 7-8 place accuracy?? Most of the  
> times I'm familiar with the _data_ isn't really good past 3  
> places. There are calculations (equilibrium types are my  
> favorite) where you need to carry large amounts of digits  
> around in the middle of the solution process, but you can  
> also pretty much just graph your way around most of those.

	Quantitative vs qualitative chemistry.  Quantitative, in the lab, the
minimum you would use were quartz beam balances that where shielded from
minor air currents that would affect the reading.  Back in the 70's when
I took a course in quant, 7-8 significant digits would still seem to be
a bit extreme (I think we mostly did 5-6 significant digits back then,
IIRC) but not outside of the realm of possibility.  This was 300 level
quantitative chemistry at Michigan State University.  The only thing
worse were the Chemical Engineering courses.  3 places, OTOH, definitely
spells qual to me.

> Significant Figures is a pet hot button of mine, and it  
> seems that I'm often on the side of a minority opinion.

	He said advanced.  Sounds like it was a quant class.  Qual would never
get that detailed and I'm a big stickler over the difference between
accuracy and precision as well.  In fact precision exceeding accuracy is
one of my biggest pet peeves when judging science fairs (I've judged on
the state level several times and I'm judging in Gwinnett this coming
year - don't know about state yet).

	Oh, and on the slide rule issue, I have both a Pickett N4-ES Log-Log
and a Picket N16-ES Electronic (scales for electronics like reactance,
impedance, frequency domain, etc) in mint condition and even had
opportunity to use them in the last year or so.  Still handy for back of
the hand estimations and juggling.
 
	Mike

> > 
> > I used the slide rule, and often did hard manual math
> > to 4 or 5 places to double check I was using it right.
> > I got good grades, because I understood it was easier
> > to be right at 3 significant digits.
> > 
> > --And to be on Linux: Am I one of the few users of 'bc'  
> > left?
> > 
> > What a powerful tool, especially when doing weird math.
> > 
> > apt-get install bc
> > bc
> > 128^128
> > 
> > Is a good example of why it's useful. Lots of display  
> > room. :)
> 
> Just for abusive giggles and chuckles - does anybody want  
> to parse that value and write it out as an English  
> sentence?? (ie - something of the type one thousand two  
> hundred forty five).
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-- 
Michael H. Warfield (AI4NB) | (770) 985-6132 |  mhw at WittsEnd.com
   /\/\|=mhw=|\/\/          | (678) 463-0932 |  http://www.wittsend.com/mhw/
   NIC whois: MHW9          | An optimist believes we live in the best of all
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