jinx110ga,
Believe it or not, it looked like pretty much a dead heat, at first,
which surprised me, because I would have put my money on raindrops.
But then, at the finish line, one of the contenders sprinted ahead and
took first place.
Let's have a look...
According to:
http://www.hawaii.edu/suremath/jsand.html
Number of grains of sand in the world
There are 7.5 x 10^18 grains of sand on the world's beaches. They've
laid out their assumptions and calculations rather nicely.
According to:
http://members.optusnet.com.au/~darrengiles/articles/factsandfigures.htm
The total amount of precipitation to fall to earth in one year is
5,000 million million tonnes.
Now, that's the same as 5 trillion tonnes = 10 quadrillion kg = 10^15 kg = 10^18 g
Holy orders of magnitude! 10^18 grains of sand! 10^18 grams of rain.
As this site tells us:
http://www.simetric.co.uk/si_medical.htm
there are 15 to 16 drops to 1 ml of liquid, which is the pretty much the same as 1g
So summing up, we have a world with:
7.5 x 10^18 grains of sand, and
about 15 x 10 ^ 18 drops of rain (in a year).
Raindrops look to have the lead, but given the obvious wiggle room in
these numbers, I'd certainly be tempted to say it's a tie, except...!
You didn't just ask about sand on the beaches. You specifically
mentioned "...deserts, beaches, underwater, and underground sand...".
Even without knowing the specifics, that's a lot more than simply the
sand on the beaches of the world, which  when you get right down to
it  occupy only very narrow, shallow strips of territory along the
shore. Deserts, and ocean bottoms, and underground sand occupy huge
expanses and volumes, and my guess would be that they overwhelm the
amount of sand on beaches alone.
So, if we up the quantity of sand by a factor of 10 or 100, to allow
for all the nonbeach sand, then we're dealing with an order of
magnitude amount of 10^19, or 10^20 grains of sand, and that puts sand
on top of raindrops.
In sum:
sand on the beaches  7.5 x 10^18 grains
annual # of raindrops  15 x 10^18 drops
all sand in the world  10^19 or 10^20 or more grains
Sand wins.
Let me know if there's anything else you need on this one.
pafalafaga
search strategy  Google searches on:
number grains of sand in the world
annual rainfall in the world 
Clarification of Answer by
pafalafaga
on
03 Nov 2005 17:09 PST
OMG! As rracecarrga noted in the comment below, there are some more
than minor missteps in my calculations (and this while I'm helping my
6th grade sone with his exponential notation homework!).
My thanks for the comment, and my humble apologies for the mistakes.
Recalculating, the 5,000 million million tonnes of rainfall every year becomes;
...the same as 5,000 trillion tonnes = 5 quadrillion tonnes = 5 x
10^18 kg = 5 x 10^21 g
Now that's a horse of a different color. A number on the order of
10^21 grams of rain, or somewhere around 10^22 to 10^23 raindrops, is
a lot bigger than the 10^18 grains of sand that were estimated for the
sand on the beaches.
And it's bigger too  but not so much bigger  that the 10^20 number
that I guessed at as the number of grains of sand in toto.
But that last number was simply a guess, and probably a pretty
conservative one at that. I have never seen an estimate of *all* the
sand in the world, and frankly, I don't think anyone really knows how
extensive sand deposits in dunes, ocean bottoms, underground, and
elsewhere really are.
Without some parameters to work with, one is hardpressed to come up
with reasonable upper bounds for the total number of sand grains in
the world.
But when estimates this big differ by only two or three orders of
magnitude  especially when the estimates are sort of looseygoosey
to begin with  then it becomes hard to convincingly say that there
are more raindrops than sand grains, or vice versa.
There's simply an awfully large number of both, and the differences in
the numbers are not that great that one emerges as the clear victor.
I hope this revised calculation isn't a let down.
Please review the overall information provided, and let me know if it
suits you as an answer, or if you still feel in need of additional
input on this topic.
Thanks,
pafalafaga
