Santa's Christmas Eve

Even army of the fittest, slimmest young men would struggle to deliver presents to all of the world's children in just one evening. Yet we are continually told that a bearded, overweight, elderly chap of dubious dress sense does just that each year, with only a few elderly reindeer and a handful of elves to assist him.

Little wonder, then, that doubts have once again been raised about the existence of Santa Claus. This week a Church minister added his voice to the fray when he told a congregation of primary school children that Santa was a scientific impossibility.

To gasps of horror, the Rev Lee Rayfield declared that the ruddy-faced one and his reindeer accomplices would vaporise if they travelled at the speeds necessary to complete all their gift deliveries in time.

A few years ago, the American satirical magazine Spy made the same scurrilous assertion, and details of the report circulated widely on the internet.

Those deluded souls who believed it loftily informed friends that Father Christmas would need to travel at thousands of times the speed of sound - a velocity at which he would selfcombust - if he was to fulfil his global duties.

Fortunately, in most sane households there is annual proof of Santa's existence. Who else, after all, would deliver all those presents each Christmas Eve and quaff the glass of sherry by the fireplace? And who, if not Rudolph, would gnaw on that grubby raw carrot, so diligently left out for him?

As long ago as 1897, the editorial pages of the New York Sun were forced to dispel the rumours circulating about Santa's demise. When eight-year-old Virginia O'Hanlon wrote to the paper demanding the truth, she received this reply, which became one of the paper's most famous reports:

'Not believe in Santa Claus? You might as well not believe in fairies! Nobody sees Santa Claus, but that is no sign that there is no Santa Claus. The most real things in the world are those that neither children nor men can see.'

And every year there is a host of Christmas cards, books and novelties which clearly show his continuing rude health. But can we prove his existence scientifically? Science writer Roger Highfield, author of Can Reindeer Fly? The Science Of Christmas, certainly thinks so. In almost 300 pages of exhaustive research he makes a powerful case.

So put down the mince pies, cast away your doubts and let us present the science which proves what even the youngest child could tell you: Santa does exist.

First things first: how does Santa know where all these children live, and what they want (and don't tell me they write him letters, because I know how long the post takes, and that's before you consider the spelling mistakes, the lack of an address, the changed minds at the last minute...)

According to Professor Larry Silverberg of North Carolina State University, Santa's 'strategically placed multigrid-receiving antenna system' picks up electromagnetic signals from children's brains (for the scientifically challenged, that means he reads your thoughts, with the help of some fancy equipment).

Santa could then process the data with the aid of computers to work out where the children live and what they want (assuming, of course, that they have been good).

Such technology does exist, thanks to a technique whereby a so-called 'superconducting interference device' detects minute magnetic fields generated by the crackle of brain activity.

Similar devices are used daily in hospitals to scan the brain and monitor its activities.

Fair enough, but the man uses a rickety old sleigh and a bunch of equally dodgy reindeer to get to those houses. And if I'm not mistaken, reindeer can't fly.

Actually, they can. Thanks to centuries of selective breeding and bio-engineering, their lungs have developed in such a way that they become buoyant when filled with a specific mixture of helium, oxygen and nitrogen. So says Prof Silverberg.

Genetic changes through time also allow them to grow stabilisers, or even wings, to balance Santa's sleigh and stop it flipping over.

In studies of fruit flies, to draw an analogy, scientists have shown that a certain gene mutation can transform one body part into another, an accelerated form of evolution.

Next you'll be claiming that reindeer antlers are actually sophisticated aerodynamic devices.

Funny you should say that. At supersonic speeds, Concorde generates its upward lift by shedding a huge helical vortex (a kind of rotating whirlpool) from the tip of each wing. Reindeers do the same thing with the prongs of their antlers, according to Warwick University mathematician Ian Stewart.

Hmm, but that doesn't explain why they don't vaporise at speeds of 6.4 times the speed of sound.

They use thermal shielding, you fool! Professor Silverberg thinks the all- encompassing shield is probably 'a composite fibre encapsulated in an epoxy resin matrix' which would be lightweight, durable, very strong and cold-resistant.

Similar compounds are found in the protective coating used on space shuttles to stop them overheating when they re- enter the earth's atmosphere.

Silverberg explains: 'When going through the ionosphere (the upper atmosphere), a sleigh made of this material would glow bright red, a sight children and other reliable sources have long reported seeing in the sky on Christmas Eve.'

Talking of reindeer, why is Rudolph's nose 'oh so bright'?

The colour of Rudolph's prominent extremity can actually be traced to an infection. Hasn't your nose ever gone red with a bad case of the snuffles?

Reindeer noses offer a welcome environment for bugs because the physiology of their noses is such that they warm the air they breathe in and cool the air they breathe out, thus reducing the loss of heat and water - think of all those old movies where Santa's beard has icicles hanging from it, yet the reindeer have enviably dry nostrils.

Now, about that sleigh. It looks like something that would struggle to get down a snow-covered hill in the average playpark. How exactly does it reach great speeds and carry presents to all the world's children?

Some commentators reckon Santa relies on a rocket sleigh, but in fact the fuel consumption of such a machine would be prohibitive.

It's more likely that he employs the theory of general relativity. 'Santa Claus and his community at the North Pole,' says Prof Silverberg, 'have learned how to manipulate time, space and light.'

Santa's society, he says, has made relativity clouds that fit him, his sleigh and all of his reindeer. According to relativity theory, matter cannot move through space faster than the speed of light.

But there is no such limit on the speed at which space itself can move - and since Santa's entourage are encapsulated in a space bubble, it can travel at phenomenal speeds. In 1994, Miguel Alcubierre of Cardiff University found that if space-time can be manipulated so that it expands behind the sleigh and contracts in front of it, the craft will be propelled along as if it were riding the crest of a wave.

But there's still no way he can load all those presents onto his sleigh. UNICEF calculates there are more than 2.1 billion children in the world.

Good point. Fortunately, Santa is the proud owner of what Roger Highfield calls 'a hierarchical distributed mobile manufacturing system'. In simple terms, this means he makes the gifts on site in each child's home.

Instead of lugging round billions of toys, he uses silicon-chip based machines (small enough to fit on the head of a pin) which have each child's wish-list programmed in. The machines also grow the toys, atom by atom, from bits of snow, soot and mince pies picked up by Santa en route.

Of course, large toys require thousands of machines working together - so that's why most children tend to get just one large present each year.

OK, but wouldn't there be some kind of sonic boom generated by Santa and his sleigh travelling at six times the speed of sound?

Yes, but Santa has fitted a specialised speaker to the side of his sleigh to counteract this.

Instead of the peaks and troughs of a sound shock wave, he offsets it with troughs and peaks of 'antisound' generated by the speaker.

This 'anti-sound' device is similar to some of the technology used in hearing aids, or the special headphones now commercially available which block out all outside noise, allowing wearers on planes to watch on-board movies without the constant thrum of the aircraft engines.

This is beginning to make sense. But one thing still baffles me: how does he get to all those houses in just one evening? I appreciate he travels at supersonic speeds, but it's not just a question of circumnavigating the globe - he has to stop at every house with children, shimmy down the chimney and drop off presents before continuing on his merry way.

It is a formidable task. There are 2.1 billion children in the world, and assuming there are an average of 2.5 children per household, that amounts to 842 million houses for Santa to stop off at. Multiply that by the average spacing between households, and you're looking at 221 million miles for Santa to travel. In a single night.

Of course, he has 24 hours from the moment the first place on the international date line turns midnight on Christmas Eve until the last.

If he travels backwards against the direction of rotation of the earth, he gains almost another 24 hours. That gives him two ten-thousandths of a second to get between each of the 842 million homes. He is travelling, therefore, at 1,279 miles per second, or just over 6,000 times the speed of sound.

We've already explained that he is inside a relativity cloud, which means he can move much faster than the rest of the universe. He therefore sees the rest of the world as virtually frozen in time, so he can in fact deliver his presents at leisure, with no need to hurry.

So, what can you tell me about fairies?

Er, isn't it past your bedtime yet?