There are approximately two billion children (persons under 18) in
the world. However, since Santa does not visit children of Muslim,
Hindu, Jewish or Buddhist (except maybe in Japan) religions, this
reduces the workload for Christmas night to 15% of the total, or 378
million (according to the Population Reference Bureau). At an average
(census) rate of 3.5 children per household, that comes to 108
million homes, presuming that there is at least one good child in each.
Santa has about 31 hours of Christmas to work with, thanks to the
different time zones and the rotation of the earth, assuming he
travels east to west (which seems logical). This works out to 967.7
visits per second. This is to say that for each Christian household
with a good child, Santa has around 1/1000th of a second to park the
sleigh, hop out, jump down the chimney, fill the stockings,
distribute the remaining presents under the tree, eat whatever snacks
have been left for him, get back up the chimney, jump into the sleigh
and get on to the next house. Assuming that each of these 108 million
stops is evenly distributed around the earth (which, of course, we
know to be false, but will accept for the purposes of our
calculations), we are now talking about 0.78 miles per household; a
total trip of 75.5 million miles, not counting bathroom stops or
breaks. This means Santa's sleigh is moving at 650 miles per
second--3,000 times the speed of sound. For purposes of comparison,
the fastest man-made vehicle, the Ulysses space probe, moves at a
poky 27.4 miles per second, and a conventional reindeer can run (at
best) 15 miles per hour.
The payload of the sleigh adds another interesting element. Assuming
that each child gets nothing more than a medium sized Lego set (two
pounds), the sleigh is carrying over 500 thousand tons, not counting
Santa himself. On land, a conventional reindeer can pull no more than
300 pounds. Even granting that the "flying" reindeer could pull ten
times the normal amount, the job can't be done with eight or even
nine of them--Santa would need 360,000 of them. This increases the
payload, not counting the weight of the sleigh, another 54,000 tons,
or roughly seven times the weight of the Queen Elizabeth (the ship,
not the monarch).
600,000 tons traveling at 650 miles per second creates enormous air
resistance--this would heat up the reindeer in the same fashion as a
spacecraft re-entering the earth's atmosphere. The lead pair of
reindeer would absorb 14.3 quintillion joules of energy per second
each. In short, they would burst into flames almost instantaneously,
exposing the reindeer behind them and creating deafening sonic booms
in their wake. The entire reindeer team would be vaporized within
4.26 thousandths of a second, or right about the time Santa reached
the fifth house on his trip.
Not that it matters, however, since Santa, as a result of
accelerating from a dead stop to 650 m.p.s. in 0.001 seconds, would
be subjected to acceleration forces of 17,500 g's. A 250 pound Santa
(which seems ludicrously slim) would be pinned to the back of the
sleigh by 4,315,015 pounds of force, instantly crushing his bones and
organs and reducing him to a quivering blob of pink goo.
Therefore, if Santa did exist, he's dead now. Merry Christmas!