1) No known species of reindeer can fly. BUT there are 300,000
species of living organisms yet to be classified, and while most
of these are insects and germs, this does not COMPLETELY rule out
flying reindeer which only Santa has ever seen.
2) There are 2 billion children (persons under 18) in the world.
BUT since Santa doesn't (appear) to handle the Muslim, Hindu,
Jewish and Buddhist children, that reduces the workload to 15% of
the total - 378 million according to Population Reference Bureau.
At an average (census) rate of 3.5 children per household, that's
91.8 million homes. For the sake of our ensueing calculations, we
will assume that there is at least one good child in each.
3) Santa has 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
822.6 visits per second. This is to say that for each Christian
household with good children, Santa has 1.2 milliseconds to park,
hop out of the sleigh, jump down the chimney, fill the stockings,
distribute the remaining presents under the tree, eat whatever
snacks have been left, get back up the chimney, get back into the
sleigh and move on to the next house. Assuming that each of these
91.8 million stops are evenly distributed around the earth
(which, of course, we know to be false but for the purposes of
our calculations we will accept), we are now talking about .78
miles per household, a total trip of 71.6 million miles, not
counting stops to do what most of us must do at least once every
31 hours.
This means that Santa's sleigh is moving at appx 650 miles per
second, 3,000 times the speed of sound. For purposes of
comparison, the fastest man-made vehicle on earth, the Ulysses
space probe, moves at a poky 27.4 miles per second - a
conventional reindeer can run 15 miles per hour, unless being
chased by a pack of wolves.
4) The payload on the sleigh adds another interesting element.
Assuming that each child gets nothing more than a medium-sized
lego set (2 pounds), the sleigh is carrying 321,300 tons, not
counting Santa, who is invariably described as overweight. On
land, conventional reindeer can pull no more than 300 pounds.
Even granting that "flying reindeer" (see point #1)
could pull TEN TIMES the normal amount, we cannot do the job with
eight, or even nine. We need 214,200 reindeer. This increases the
payload - not even counting the weight of the sleigh - to 353,430
tons. Again, for comparison - this is four times the weight of
the Queen Elizabeth (the boat, not the person).
5) 353,000 tons traveling at 650 miles per second creates
enormous air resistance - thus heating the chain in almost the
same fashion as spacecraft re-entering the earth's atmosphere. As
a result of this friction, the lead pair of reindeer will absorb
around 14.3 QUINTILLION joules of energy. Per second. Each. In
short, they will burst into flame almost instantaneously,
exposing the reindeer behind them, and create deafening sonic
booms in their wake. The entire reindeer team will be vaporized
within 4.26 milliseconds. Santa, meanwhile, will be subjected to
centrifugal forces 17,500 times greater than gravity. A 250-pound
Santa (which seems ludicrously slim) would be pinned to the back
of his sleigh by 4,315,015 pounds of force.
In conclusion - If Santa ever did deliver presents on Christmas
Eve, he's dead now.