Metro

Yvonne Abraham

# The physics of Santa’s Christmas night journey

Like many of you, I lie awake this time of year, fretting about how Santa pulls it off.

Even allowing for different time zones, how can he possibly make it around the globe in one night, shimmying down gazillions of chimneys, dropping off gifts, scarfing what must be literally tons of cookies? Shouldn’t his sleigh be unliftable? Wouldn’t he have to travel at impossible speeds? Will he make it to my place? Who can answer these questions?

Germano S. Iannacchione.

In addition to having a name that demands its own paragraph, Iannacchione heads the Physics Department at Worcester Polytechnic Institute. Nutting out the physics of Christmas is what guys like him do for kicks.

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Slightly sick kicks, it turns out. I went to see Iannacchione last week, and he ran some of the numbers for me. Now, if you’re reading this column to your kids, or you’re a bit squeamish, you might want to skip down to the last line of this story, because things are going to get gory.

“Before we do any analysis, we have to set the stage,” said the professor, a lean, neatly attired, soft-spoken man who evokes a kindly father from a ’50s sitcom.

Earth is home to 2 billion kids under 15. If you figure three kids per household, you’re looking at 600 million homes. Taking out most of the non-Christian kids leaves you with about 240 million households.

Assuming these kids slumber between 11 p.m. and 4 a.m. (who can sleep on Christmas Eve?), Santa — traveling east to west — has a total of 31 hours, crossing time zones, to hit all of them. That gives him .00046 seconds per stop.

How much does he have to schlep? Here Iannacchione gets Grinchy, basing his calculations on the assumption that there will be only one nice child in each household, and that that child will get but one gift, weighing one kilogram. On that thoroughly un-American basis, the sleigh weighs 100 million kilos, give or take.

To get the job done, Santa would have to reach speeds of 2,800 kilometers per second — about one one hundredth of the speed of light. He’d be subject to incredible gravitational forces, pulling a billion Gs. Fighter pilots pull only 3 to 4 Gs, and they need special suits to stop the blood draining from their heads. So what would a billion Gs do to poor Santa’s body?

“It would puree it,” Iannacchione said sweetly.

That’s not even the worst of it. The physicist calculated the amount of energy Santa would require to drive his sled to just a single stop, and it turns out to be the same as that produced by a small star. This is bad news, because if you combine the sleigh’s mass with that much energy in one spot you get what cosmological types like to call a singularity.

Which is to say that, if Santa really works the way Iannacchione figures he must, his first stop would create a black hole that would destroy the planet and boom, Christmas is ruined.

“But wait a minute,” he says. “We’re still here, and presents are still appearing. So we have to question our analysis.”

Maybe we’re just using the wrong kind of physics, he offers. Instead of thinking in massive terms, why not go smaller — quantum physics small. Richard Feynman said, “If you think you know quantum mechanics, you don’t know quantum mechanics.” To which I would add, if you don’t think you know quantum mechanics, you definitely don’t. I don’t. If I think about it too hard, it makes me woozy. Iannacchione says that’s natural. He calls quantum physics a Neverland.

“When you’re outside the intuitive arena, you have to trust the math,” he says.

To put it way too simply, scientists have discovered that all matter can behave like a particle or a wave. Waves can be in a bunch of places at once. Experiments have shown that particles can quantum tunnel, or “teleport,” like Doctor Who.

Being in many places at once, teleporting — if particles can do it, why can’t His Corpulence? — Saint Nick is de-pureed and back in business! Physics explains it all, as long as you have faith in the math.

*So Santa is real, kids! All you have to do is believe.

Yvonne Abraham is a Globe columnist. She can be reached at abraham@globe.com