Finding out how Santa manages to visit 336 million homes
'THEY'RE after me," says a voice on the end of the line, as rich and dark as figgy pudding, yet also tired and scared.
"All of 'em. The scientists have almost worked it out; everybody's trying to track me at this time of year and now they've sent this Major Tim up to get a better look," says the mystery voice, calling around midnight and sounding strangely familiar, as if we knew each other years ago.
Hang on a minute, I say. The first Briton in space for two decades is on the International Space Station to unpack cargo and examine the effects of microgravity on bone marrow. "Ho ho ho!" says the ancient-sounding voice, as if he's Father Christmas or something. "You really think so? That's cute, young man. But listen, find a scientist. Here's a name. I need people to believe in me, more than ever. We've got to stop Dark Santa."
Then the line goes dead.
All I can think of to do is ring the scientist he named, Dr Sharon George. She is an expert in climate change and green technology at Keele University, but also one of a growing number of scientists taking an interest in the big question: if Santa is real, how does he do it? Could there be an explanation worth believing in?
Within the laws of physics, how could one man and his sleigh deliver presents to the whole world on one night? "Actually, he has more than one night," says Dr George. "The Orthodox calendar puts Christmas on a different day, in January, so he has two shots at this."
Then she drops a bombshell: "Not everybody believes in Santa. Not everybody is good."
This comes from experience, having just given a public lecture on "The Science of Santa". They like to engage people of all ages with science and technology at Keele, and themes like this help with that. "I don't say: 'This is exactly how it happens.' I do say: 'This theory exists. This offers a possibility.'"
So let's hear it. There are 2.2 billion children in the world according to Unicef; Dr George divides that in half (roughly two per household). Then she divides it again to reflect the proportion of families with value systems based on Christianity, which has been crucial to the evolution of the pagan figure of midwinter into Saint Nicholas, then into the fat, jolly chap in his Coca-Cola suit.
"About a third of children believe and are good," says Dr George with a dollop of parental generosity. That leaves Santa with 366 million visits to make. His journey around the world has been calculated at 7.5 million kilometres. "That's to the Moon and back 10 times."
She divides the distance by 48 hours to calculate that he needs to move at 156,579 kilometres per hour. Scientists disagree about this - they really do, passionately; it's one of their favourite things to do at Christmas - because some want to take into account the extra hours he can get by flying west across time zones. Still, he's fast. America's fastest fighter jet, unveiled earlier this year, will fly at Mach 5.1.
By most calculations Santa's sleigh has to reach at least Mach 100. The top speed of the average reindeer is just 15 miles per hour.
Fortunately, these may not be the average reindeer. They can fly, for a start. If that seems impossible, consider this: according to a study in the journal PLOS Biology, there are 8.7 million species in the world and humans have yet to discover, categorise or name 86 per cent of them. So in theory, Rudolph could be out there.
The heat generated by all that friction would vaporise him (although Dr George believes Rudolph is actually a female reindeer, because the males have all lost their antlers by this time of year) but the Norwegian astrophysicist Knut Jorgen Roed Odegaard provides the definitive word: "Santa obviously has an ion-shield of charged particles, held together by a magnetic field, surrounding his entire sleigh."
There should, however, be a continuous series of sonic booms as Santa breaks the sound barrier many times on Christmas Eve. "That would be deafening," says Dr George. "It would wake all the children up."
Her solution has to do with a phenomenon observed in quantum physics, in which some particles appear to pass through energy barriers that should stop them. "Instead of burning up in the sky or having a magic key to get into everyone's houses, he could be using quantum tunnelling." The theory is related to Schrödinger's cat, which is a hypothetical animal inside a box, with a poison that will be released if an unpredictable source starts generating radiation. Scientists like to say the cat is both alive and dead until you open the box and see what has happened.
Dr George applies this to mean that, in theory, Santa could actually be all over the world on Christmas Eve - as long as nobody sees him. "If you observe him then the wave form collapses, your Santa is fine and he's there, but all the other Santas in the world disappear, you spoil Christmas for everybody else."
So keep your eyes shut, Major Tim, for all our sakes.
Now, what about the sack?
"If every household has a game console which is .01 of a metre cubed, times 366 million stops, this gives us a value of 3.66 million cubic metres," says Dr George. "That's around 332,500 elephants. Imagine herding those. It's just under the capacity of Wembley Stadium." That would be a huge sack.
"There are debates around string theory and the number of dimensions in the universe. Maybe Santa has tapped into ways of jumping in and out of different dimensions."
So the sack is a portal to another dimension where all the toys are kept? "Otherwise, if he was driving around with a sack the size of Wembley Stadium making deafening sonic booms, we'd see it. So which is more plausible?"
Fair point. Is she now a believer? "The more I do this job … When you think about space and time and how weird quantum physics is, and all the things we don't know about the universe, he could be using very advanced science."
Over the past 10 years there has been a great (and presumably quantifiable, if anyone could get funding for the study) increase in the number of serious people willing to explore the science of Santa. Dr Brian Cox, for example, speculates that if Santa can get up to the speed of light, then the theory of relativity means he will experience time 7,000 times more slowly than the children who wait for him to come (and it already seems agonisingly slow to them).
Can anything on Earth other than light move as fast as that? Well yes, says Dr Cox: the Large Hadron Collider in Switzerland throws particles around at 99.999999 per cent of the speed of light.
The work there is driven by the urge to know more about the 96 per cent of matter or energy scientists cannot otherwise see or detect. That leaves room for the possibility of a life form which exists outside of our own understanding of time and space and bestows gifts upon us. But now we're touching on Santa as a metaphor for the divine: a safe, unscary version of God. Let's go back to the facts, and a red phone ringing in a windowless room in Colorado Springs on Christmas Eve, 1955.
Colonel Harry Shoup knows it must be trouble. He's looking at a vast map of the world inside the control centre for Norad, the radar tracking centre set up to spot incoming Soviet missiles. Only the boss or the Pentagon use the red phone. But instead there's a boy on the line: "Are you really Santa Claus?"
No, says the colonel, curious. He has young children waiting at home. It turns out the boy has answered an advertisement for the chance to call Santa, but the number is wrong. Colonel Shoup explains. The boy listens then says: "Do you know where Santa is, then?"
Incredibly, the colonel plays along. The phone keeps ringing all night, and has done every year since.
The Norad website will take a billion hits on Christmas Eve, although few people can be convinced by the animations that show Santa flying. Maybe they cut a deal to keep it vague. My sources suggest he is mightily fed up with the Russians buzzing him with their jets. North Korea gets very jumpy, but he has promised the Dear Leader a new X-box with the Star Wars game. Islamic State won't be getting any presents. "He doesn't like ho-ho-holes in his sleigh," says one squeaky-voiced informant from somewhere in the wilds of Lapland.
My secret source suggests a crack team of elite surrogates called the Santa Claws has been going into war zones the world over to deliver presents. "They drop down from the sky like the Claw in Toy Story."
He also suggests the amount of safe airspace has now got so small, the old guy is piloting a solution: a worldwide network of sleeper helpers in every community. The Send A Nice Toy Annually network, or SANTA: warm-hearted people who go about their business all year then go to work at Christmas using drones. "The sort of thing Amazon would kill for."
It makes sense. Drones are suddenly everywhere. There has been a huge rise in the number crashing in British prisons, carrying drugs and phones. Nine in October alone, according to reports. Nobody knows how many get through.
But talking of dubious activity, what is Dark Santa? I'm afraid it's bad news. The elves have gone rogue. My source suggests store Santas are being used for triage, working out who's naughty or nice. Every visit to a grotto is a secret interrogation.
They've set up a huge database - it's easy to keep your servers cool in the Arctic circle - scanning Snapchat, WhatsApp and Instagram, hacking into the Pentagon, GCHQ even Facebook. You'd better watch out. You'd better think twice before posting that photo.
Everything the scientists say is consistent with fact or theory, but what my source says is just speculation. Maybe. Unless it's true. That's up to you.
All I know is that the phone rings again, and this time it is definitely the big man with the beard, breaking cover to give us all a message. "It's the only way to escape Dark Santa. You've got to tell people to get off their phones, get off their iPads. Talk to each other, properly. Face to face. Reconnect, for one day at least."
There is the deepest of sighs, before the voice of voices says: "Merry Christmas, to you and yours. Just believe."