There are approximately 2 billion children (persons under 1 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 Eve to 15% if 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, feed the reindeer any snacks left for them, jump into the sleigh and get on to the next house.
Assuming that each of there 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 Ulysees space probe, moves at a pokey 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 (900g), the sleigh is carrying over 500,000 tons, not counting Santa himself. On land a conventional reindeer can pull no more than 150kgs. Even granting that the ‘flying’ reindeer could pull 10 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, by another 54,000 tons, or roughly 7 times the weight of the Queen Elizabeth (the ship, not the monarch).
600,000 tons travelling at 650 miles per second creates enormous ar resistance – this would heat up the reindeer in the same fashion as a spacecraft re-entering the earths’ atmosphere. The lead pair of reindeer would absorb 14.3 quintillion joules of energy per second. 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 vapourised within 4.26 thousandths of a second, or right about the time Santa reached the fifth house on his trip.
Not that this matters, however, since Santa, as a result of accelerating from 0 to 650 m.p.s in .001 seconds, would be subjected to acceleration forces of 17,500 g’s. A 250 lb Santa (which seems ludicrously slim) would be pinned to the back of the sleigh by 4,315,015 lbs of force, instantly crushing his bones and organs to mush and reducing him to a quivering blob of pink goo.
Therefore, if Santa did exist, he’s dead now.