### Santa Claus: An Engineer's View

There are approximately two billion children (persons under 18) 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 night to 15% of 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, jump into the sleigh and get on to the next house.

Assuming that each of these 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 Ulysses space probe [at the time of this writing], moves at a poky 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 (two pounds), the sleigh is carrying over 500 thousand tons, not counting Santa himself.

On land, a conventional reindeer can pull no more than 300 pounds. Even granting that the "flying" reindeer could pull ten 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, another 54,000 tons, or roughly seven times the weight of the Queen Elizabeth (the ship, not the monarch).

600,000 tons traveling at 650 miles per second creates enormous air resistance-this would heat up the reindeer in the same fashion as a spacecraft re-entering the earth's atmosphere. The lead pair of reindeer would absorb 14.3 quintillion joules of energy per second each. 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 vaporized within 4.26 thousandths of a second, or right about the time Santa reached the fifth house on his trip.

Not that it matters, however, since Santa, as a result of accelerating from a dead stop to 650 m.p.s. in .001 seconds, would be subjected to acceleration forces of 17,500 g's. A 250 pound Santa (which seems ludicrously slim) would be pinned to the back of the sleigh by 4,315,015 pounds of force, instantly crushing his bones and organs and reducing him to a quivering blob of pink goo.

Therefore, if Santa did exist, he's dead now. Merry Christmas.

### Response from a Physicist

The analysis in the original message [above] is woefully incomplete, and thus its conclusion can't be trusted! Being written from an engineer's point of view, it completely ignores subtleties of physics and illustrates the dangers of allowing engineers to speculate on matters outside the purview of their discipline. The analysis doesn't take into account any of the following:

- Special relativity: The speed of Santa's sleigh is calculated as being a not-insignificant fraction of the speed of light, therefore time for Santa would slow down relative to time on Earth, allowing him to do much more in each 1/1000th of a second visit to a house, and giving him plenty of time to prepare the package for the next house on the way there. [See: Lorentz Transformation for the formula for calculating time saved by travelling at velocities approaching the speed of light.]
- General relativity: I don't know where the above 'physicist' grew up, but his/her assumptions about the mass of the presents seem woefully inadequate. Hell, I've received fruitcakes that weigh multiples of 2 lbs. And a single present per recipient?! This seems an extreme under-estimate. All of this ignores the weight of all the trees turned into wrapping paper and ribbon. According to WasteOnline, Christmastime generates over 3 million tons of waste, and that's just in the UK! Thus, as we approach more realistic estimates on the size of that which Santa's hauling, the mass of Santa's sleigh would become such that general relativistic effects would begin to come into play - the sleigh would have a measurable gravitational pull, thus warping space-time in its vicinity, which could change the behavior of effects such as air resistance. One interesting side effect of this is that the sleigh could act as a "gravitational lens", warping light around it so that to an Earthbound observer, the sleigh wouldn't be clearly visible. This may explain why reliable observations of Santa are difficult to come by.
- Quantum mechanics: The interface between Santa's sleigh and the Earth's atmosphere, given the special and general relativistic effects in play, could generate the quantum effect known as Hawking radiation (after Stephen Hawking, who discovered the effect). This is the mechanism whereby black holes are able to radiate energy. This could allow Santa's sleigh to dissipate the enormous friction being generated - the quantum gravitational interface would effectively act as a shield to protect Rudolph and pals from being transformed into so much well-done venison.
- Chaos theory: Without a doubt, the scene on the sleigh would be pretty chaotic. There are probably a bunch of elves in the back, sorting through packages, checking lists (twice!), bagging them, and passing them up to Santa. If you've ever seen the central FedEx package distribution facility in Memphis, you have some idea of what this must be like. This sheer chaos is enough to generate fractal disturbances in normal causality, which makes an analysis of Santa's journey based on linear time impossible - in effect, Santa travels through fractal time, which has a fractional dimension greater than one but less than two. For Santa, time and distance merge together to some extent, allowing him to perform feats that from the point of view of an outside observer appear impossible - delivering to more than one house at a time, for example.
- Finally, the analysis completely ignores the unknown effects of faith: those 378 million children who believe in Santa each possess approximately 100 billion neurons in their brain, arranged in a complex, highly interconnected neural network. This comes to a total of 37.8 million trillion neurons, of which around Christmastime, approximately 10%, or 3.78 million trillion, are devoted to maintaining a belief in Santa Claus and an unshakeable faith that there will be presents under the tree on Christmas day. The physical effects of this enormous distributed neural process are unknown, but since documented accounts exist of such effects being used to perform feats such as walking on water and parting seas, it seems reasonable to assume that Santa's abilities would be enhanced in some way by this sheer critical mass of belief.

Although the above does not prove that Santa exists, it indicates that it is not impossible for him to exist. Examining this further, quantum theory tells us that at the quantum level, any event not in violation of fundamental laws is possible, although some events have lower probabilities than others. This means that there is a non-zero probability that Santa does exist.

In quantum mechanics, non-zero probabilities have physical manifestations in virtual form, but these virtual manifestations can in fact affect the physical universe. Hawking radiation is one such example: the vacuum of space boils with the constant creation and destruction of matter-antimatter pairs of virtual particles, which spontaneously pop into existence, "borrowing" energy from the space around them, but then almost immediately annihilate each other, returning the energy to the vacuum and resulting in no net change in the energy of the universe. In the presence of a black hole, it is possible for these particle pairs to become separated by gravitational effects, resulting in one member of the virtual particle pair becoming real while the other is consumed by the black hole.

From this, we can see that since it has been proved that it is possible for Santa to exist, then quantum theory tells us that virtual Santas and anti-Santas must continually be created and destroyed. By now, it must seem rather obvious that this explains why Santa only appears for such a brief period each year: he performs his gift-delivering journey in the short period between his creation and destruction. In addition, this means when Santa is present (no pun intended), there are in fact two of him, making each of their jobs twice as easy. In fact, it is possible that multiple Santa pairs simultaneously deliver presents on Christmas day, and there is no known limit on the maximum number of Santa pairs that could do this.

The only remaining question is why the Santa effect does not operate on every day of the year. There could be a number of simple explanations for this. The most likely is that the probability of Santa pair generation increases dramatically at a particular point in Earth's orbit, due perhaps to the specific temperature and gravitational characteristics of that point in space; thus we only experience it as we travel through that location on December 25th each year.

This could be proved by sending a space probe, containing at least one good child, to that point in space at some other time of year. The spontaneous appearance of presents within the probe would constitute definitive proof of Santa-particle theory. Note that the probe will need to contain a chimney, for maximum likelihood of success, along with some mechanism for the reliable delivery of cookies and milk in a zero-g environment.