[geeks] Odd (non-computer) question....

[Sandwich Maker]

" From: Mouse <mouse at Rodents-Montreal.ORG>
" 
" Suppose we have a cube of air at STP, one metre on a side.
" 
" Now, consider an ideal plane, passing through the middle of this cube,
" dividing it into two volumes each 1m by 1m by 50cm.
" 
" Question: what is the expected number of molecular bonds that plane
" intersects at any particular moment?
" 
" It's easy enough to work out how many molecules are in that cubic
" metre.  But I'm having trouble figuring out the rest of it.  Given how
" tiny a molecule is as compared to the mean space per molecule, I expect
" the number to be small, but I don't know whether it's small as in the
" expected number is .01, or as in 10, or as in 10000, or what.

if you know how many molecules are in that cube, then you know how
much space each molecule occupies, and if you pack them neatly you can
figure how many are in the boundary-crossing layer.  yes, real gas
molecules won't behave that way, but i think it's an acceptable
simplification.

then you'd have to know the actual size of the molecules* relative to
the space each occupies to make a statistical calc of how likely a
molecule is to be in the molecule-thick layer straddling the boundary
multiplied by the number of possible candidates.

this ignores orientation, but you said 'intersects', not 'cuts'.

STP will tell you density, but i don't think you need to know anything
else.  velocity won't affect the number.

* i wonder if the crc handbook has this sort of data...
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Andrew Hay                                  the genius nature
internet rambler                            is to see what all have seen
adh at an.bradford.ma.us                       and think what none thought