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.

There are 2
billion children (persons under 18) in the world. BUT since Santa doesnt (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, thats 91.8 million homes. One presumes theres at least one good
child in each.

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 1/1000th 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.

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 0.78 miles per
household, a total trip of 71.604 million miles, not counting stops to do what most of us
must do at least once every 31 hours, plus feeding etc. This means that Santas 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.

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.

353,000 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 earths 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, hes been vaporized by now!