The physics of Santa revisited

Scientifically, it's not possible for him to travel the world in one night

Editor's note: Parental discretion advised. The following weakens the case for the existence of a functional Santa Claus.

We all know the legend: Every year, Santa fills his sleigh with presents and, in the span of a single night, delivers them to good little boys and girls all over the world.

Perhaps the best-known analysis of the physical possibility of Santa's annual jaunt is a

1990 Spy magazine piece by Richard Waller (see sidebar). It has since found many digital homes on the Web.

Hoping to use the Christmas holiday as a means of explaining some real science, the Camera asked local scientists to consider the Spy assessment and added a bit of its own analysis.

The intervening 15 years have not improved the odds that a species of flying reindeer will be discovered by science. But molecular phylogeny - RNA-based genetic-identification techniques advanced by University of Colorado microbiologist Norman Pace and others - has elevated the number of likely living species on Earth well beyond 300,000. Jeffrey Walker, a microbiologist in Pace's CU lab, said the number of undiscovered species of microbes alone could be between the millions and tens of millions.

Could they perhaps pull a sleigh through the air?

"Well, you know, not by themselves," Walker conceded.

World population has increased 23 percent since 1990, from about 5.3 billion to 6.5 billion today. Using an estimate of 2.2 billion Christians, based on the CIA Factbook estimate of 32.8 percent of the world's population being Christian, and assuming that many of these are in the Americas and Europe, the number of households would be more like 250 million.

That assumes 22 percent of the population is under age 15 and that the average household in those regions has 1.9 children, based on Population Reference Bureau data. Even if half these households were childless, Santa would be busier than he was in 1990.

Critics have pointed out that Orthodox churches celebrate Christmas after Dec. 25, which would give Santa extra time.

Michael Dubson, a University of Colorado physics instructor, says the calculations leading to the unfortunately lethal conclusions of the rest of the Spy article are, generally speaking, in the ballpark.

But Dubson said it would be impossible to travel at 650 miles per second at sea level, which is about 100 times faster than the space shuttle re-enters the atmosphere. To get a 300-ton sleigh going even 100 miles per second would take "more energy than the human race generates in a couple of centuries."

Dubson said moving less weight at a speed of 100 miles per second would be possible but extremely expensive: It costs about $10,000 per pound to rocket things to Earth-escape velocity, which is seven miles per second.

Also, Dubson said, the calculation to figure out the amount of energy Santa and company would dissipate at massive speeds would depend on such details as flight altitude and the shape of the reindeer and is "an extraordinarily difficult calculation."

Critics have pointed out that Santa could make multiple trips, reducing the load and conceivably forestalling, slightly, his annihilation. Dubson said Santa and reindeer would inevitably burn up in such a scenario, but he could only estimate the timing within about 10 seconds based on the information given.

"That the entire team vaporized in 4.26 thousandths of a second - I don't know where that's coming from," he said.

A quantum Santa could not overcome such limitations, either, said David Wineland, who leads the National Institute of Standards and Technology's quantum-computing team in Boulder.

Even if Santa could harness weird quantum qualities of entanglement and superposition and be at every household at once, a wave-function collapse upon present delivery would mean only one lucky family would actually get the goods, Wineland said.

Santa would have other things to worry about. Ted Scambos, lead scientist at CU's National Snow and Ice Data Center, said global warming and other factors mean the North Pole could face ice-free summers by mid-century.

"He's definitely going to need a summer home somewhere on dry land," Scambos said. "He's probably speculating on land in the Antarctic for a new base of operations."