How many rain drops during a hard thunderstorm compared to a light
rain fall would occupy a 1 foot cube? Estimates are fine (obviously).

Hello and thank you for your question.

I'm going to take advantage of the reference cited in Pink Freud's
comment and state that raindrops can be approximated as spheres having
diameters that range from .02 inches for small drops to .2 inches for
big thunderstorm drops.

The volume of a sphere is 4/3 * 3.14 (pi) *  (d/2)^3  [that last term
is the radius cubed]

So the volume of a small drop is 4/3 pi (.01)^3
    = 4/3 * 3.14 * 10 ^-6  [that last term is one-millionth]
    = 4.2 * 10^-6 cubic inches
And the volume of a big drop is 
      4/3 * 3.14 * (.1)^3 [that last term is one-thousandth]
    = 4.2 * 10^-3  cubic inches    

A 1-foot cube is 12 x 12 x 12 = 1728 cubic inches.

So it takes 1728/(4.2 * 10^-6) = 412,700,000 little drops
  or
            1728/(4.2 * 10^-3) = 412,700 big drops to fill the cubic
foot.

A heavy storm provides about an inch per hour of rain, so the cubic
foot is about 12 hours' worth of heavy downpour.

That was fun!

Sincerely,
Google Answers Researcher
Richard-ga

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Request for Answer Clarification by mrsneaky-ga on 11 Aug 2003 20:15 PDT

I was thinking more in lines of if I took a picture of rain how many
drops would I see in the picture (imaginary cube in the picture). 
Although the answer was worth it!  Great Answer.

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Request for Answer Clarification by mrsneaky-ga on 11 Aug 2003 20:18 PDT

and my question upon further review wasn't that clear.  But the answer
lead me to some great information.

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Clarification of Answer by richard-ga on 11 Aug 2003 20:44 PDT

Thanks for the rating and the tip!
-R

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Clarification of Answer by richard-ga on 12 Aug 2003 04:53 PDT

Hello again:

I was thinking about your question - - the question you originally
intended.

Say there are 180,000,000 drops in that cube, and even in a torrential
rain it takes 10 hours to fill the cube.
Ten hours is 60 x 60 x 10 = 36,000 seconds
So the drops are entering the cube at 180,000,000/36,000 = 5,000 drops
per second.
And the speed of the falling drops (terminal velocity) is maybe 100
feet per second (about 60 miles per hour), so in that one second you
can picture a column of rain that's 100 feet or 100 boxes high.
That means that there's a cubic foot of torential rain is 1/100th of
the 5,000 drops or 50 drops in a cube of torrential rain as it falls.
And normally, if either the drops are larger or it's not raining so
heavily, the real number number is probably more like 5 drops in the
falling box of rain--less than I'd have guessed but probably closer to
what you see--think how when it starts to rain it takes a while for
the splattering drops to wet the surface they're falling on.  Five
drops in 1/100th of a second is 500 drops in a second falling on a one
square foot surface.  Sounds right to me!

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Request for Answer Clarification by mrsneaky-ga on 12 Aug 2003 08:06 PDT

I'm impresssed!!!  I was going to make a "similar" calculation based
on the other information.  THANKS!!!

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Clarification of Answer by richard-ga on 12 Aug 2003 08:14 PDT

--My pleasure
-R

As I understand it, your question concerns the size of raindrops,
since this would determine how many raindrops could fit into one cubic
foot.

Here is some information that may be useful:

http://hypertextbook.com/facts/2001/IgorVolynets.shtml

How many raindrops fall in a severe rainstorm? Can we think in terms
of "Noah's Ark"?

If it took 12 hrs to fill a cube, how long would it take to fill the
earth to the top of Mt Ararat?

Put another way: We "know" it rained for 40 days and 40 nights (We
also know there isn't enough water on the earth to fill the earth even
halfway up mountains) what volume of rainfall would have to fall to
fill the earth?

Could men, women, children, animals have survived on the Ark with that
volume of rain falling?