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 the Population Reference Bureau. At an average (census) rate of
3.5 children per household, that's 91.8 million homes. One presumes there exists at least one good
child in each.

3. Santa has 31 of 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 1/1000th of a second 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. This means that 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 on earth, the Ulysses space probe, moves at a poky
27.4 miles per second - a conventional reindeer can run, tops, 15 miles per hour.

4. The payload on the sleigh adds another interesting element. Assuming that each good child gets
nothing more than a medium-sized Lego set (2 pounds), the sleigh is carrying 321,300 tons, not
counting Santa, who is invariable 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.

5. 353,00 tons traveling at 650 miles per second creates enormous air resistance - this will heat
the reindeer up in the same fashion as spacecrafts re-entering the earth's atmosphere. The lead
pair of reindeer will absorb 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 thousandths of a second. Santa, meanwhile, will be
subjected to centrifugal forces 17,500.06 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.