No known species of reindeer can fly.

However, 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 that only Santa has seen.

There are an estimated 2 billion children (persons under 18) in the world.

But since Santa doesn't - apparently - handle the Muslim, Hindu, Jewish and Buddhist children, that reduces the workload to 15% of the total - a mere 378 million, according to the Population Census Bureau.

At an average (census) rate of 3.5 children per household, that's 91.8 million homes. One presumes there is at least one good child to each home.

Santa has 31 hours of christmas to work with, thanks to the different time zones and the rotation of the earth, assuming he travels from 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 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 into the sleigh and move onto the next house.

Assuming that these 91,800,000 stops are evenly distrubuted around the earth (which, of course, we know to be false, but for purposes of our calculations we will accept), we are now talking about .76 miles per household, a total trip of 75,500,000 miles, not counting stops to do what most of us must do at least once every 31 hours.

This means Santa's sled is moving at 650 miles per second, 3,000 times faster than the speed of sound.

For purposes of comparison, the fastest man-made vehicle, the Ulysses space probe, moves at a poky 24.7 miles per second. A conventional reindeer can run, tops, 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 (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 the ability of 'flying reindeer' to pull perhaps ten times the normal amount, we cannot do the job with eight or even nine.

We need more.

Infact, we need 214,191 more. Or a total of 214,200 reindeer.

This increases the payload - not counting the weight of the sleigh - to 353,420 tons.

Again, for comparison, this is four times the weight of the ocean liner Queen Elizabeth.

This 353,000 tons travelling at 650 miles per second creates enormous air resistance, which will heat the reindeer up in the same fashion as spacecraft re-entering the earth's atmosphere.

The lead pair of reindeer will absorb 14,300,000,000,000,000,000 (14.3 quintillion) joules of energy.

Per second.

Each.

In short, they will almost instantaneously burst into flames, exposing the reindeer behind them, who will repeat the process, and they will create deafining sonic booms in their wake.

The entire reindeer team will be vapourised within 4.26 thousandths of a second.

Santa, meanwhile, will be subjected to acceleration forces 17,500.06 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 did deliver presents on Christmas Eve...

he's dead now.

Merry Christmas Everybody!