A Look at Christmas by the Numbers Christmas is a math-centric holiday. From the solstice to the complexities of singing the Twelve Days of Christmas to Santa counting who's naughty and nice, this time of year is all about crunching the numbers.
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A Look at Christmas by the Numbers

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A Look at Christmas by the Numbers

A Look at Christmas by the Numbers

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Christmas is a mathcentric holiday from the solstice to the complexities of singing "The Twelve Days of Christmas. By the way, is that six or seven geese a laying? Does Santa Claus counting who's naughty and nice this time of year? It's all about crunching the numbers.

Luckily, our math guy can help guide us. Keith Devlin joins us from his esteemed Stanford University studios. Keith, thanks for being with us.

KEITH DEVLIN: Hi, Scott. Seasons greetings to you.

SIMON: And also to you. First something very serious, I understand that journalists have been misusing statistics supplied by mathematicians, and it create what amounts to a great urban myth about this time of year.

DEVLIN: Oh, you're probably thinking of the myth that the suicide rate jumps up at Christmastime. A lot of people seem to think that. See, it's completely false. There's actually been an extra study carried out by some statisticians at Syracuse University, New York. They looked at 32 different studies over a 50-year period, and all of those studies show that suicides actually drop over Christmas. In fact, they dropped by as much as 40 percent.

SIMON: Do you have any idea how people made that mistake for so long?

DEVLIN: Well, you know, statisticians can't answer that one but I've got (unintelligible) suspicion. The culprit is that movie "It's a Wonderful Life." Christmas eve and George Bailey is looking over the bridge about to throw himself off into the watery depths. That scene, I think, is embedded in our cultural psyches. And I suspect that may well be the origins of this belief, this myth.

SIMON: Let me ask you about something - a good deal more trivial but important nevertheless. I gather there's a mathematical reason that when you store Christmas lights from one season to the next, they get tangled.

DEVLIN: There is indeed, and this is fairly recent work. I'm should give credit to my fellow physicists because this is a combined work of mathematicians and physicists. What mathematics did - and mathematics did this over a hundred years ago - was provide mathematical means for describing how complex knots are. It's a branch of mathematics called Knot Theory. And there's a thing called the Jones polynomial, which is a very precise algebraic expression that tells you how complicated a knot is.

Fast forward from the 19th century and now on to just a few months ago, a couple of physicists got some boxes and they put them in a mechanical shaking machine and they put lengths of string in those machines and they shook them up for different lengths of time. And when it finished, they looked at the way the string had been knotted when they took it out. And then roughly half of the times they put string in a box and shook it, it came out knotted. Then they ran a computer program to simulate what they'd observed. And that program gave them tremendous insight into how Christmas tree lights or iPod earphone cords and all these other kind of things - how they get tangled up. What we know now is that roughly half of the times when a knot forms, it begins to form within the first two or three seconds of shaking. So even if you've only taken that Christmas tree box up the stairs, into the attic, the chances are high that you're going to tangle it up.

SIMON: Let me ask you this, finally, people around the world love and revere Santa Claus. But we must note in this energy conscious times this is a man who flies around the globe and there has to be some concern for the carbon emission that he is getting - the carbon footprint that Santa Claus is leaving while acquitting his duties.

DEVLIN: Actually, I thought you might ask this, Scott, so I did some calculations last night. And here's what we've got. If you just restrict to all of those homes in the world that a part of a cultural tradition where Santa exists…

SIMON: Yeah.

DEVLIN: …you find that you've got about a hundred and eight million homes. If we assume that about 108 million homes are evenly distributed around the Earth. That means that the average distance between houses is about three-quarters of a mile. So he's going to travel 75 million miles. That means he's moving 650 miles a second, which is around 3,000 times the speed of sound.

Okay. Now, let's figure the weight that he's carrying. If each child is going to get presents that weigh two pounds, let's say. That means his sleigh is going to carry 321,300 tons. That creates much more air resistance than the Space Shuttle gets when it's reentering the atmosphere. So this thing is going to heat up big time. In fact, the lead pair of reindeer - I calculated - are going to absorb 14.3 quintillion joules of energy a second. That means that the first pair are going to spontaneously vaporize and then the next pair behind them are going to burst into flames one after the other. And the amounts of carbon dioxide that's going get, Al Gore, would have a fit if he could see what's going on when Santa is flying around the globe with his presents.

My guess is that Santa has a special magical way of doing it, and it doesn't have to put up with the regular laws of Physics like the rest of us do.

SIMON: Our merry math guy, Keith Devlin, at Stanford University. Thank you, Keith.

DEVLIN: Okay. Always a pleasure.

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