Christmas is a time for magic and miracles, not to mention the mulled wine and mice pies but, according to one man, it's also a time for science. Christen Pears reports.

RUDOLPH is female, Santa has diabetes and you need the telescope of the WM Keck Observatory in Hawaii to get the best out of your turkey.

These are just some of the theories put forward by Roger Highfield in his bestselling book Can Reindeer Fly? The Science of Christmas.

From the optimum amount of gravy on your dinner plate and why children hate sprouts, to cloning Christmas trees and the Virgin Birth, it explores and examines Christmas myths and traditions from a scientific point of view.

While most of us are content just to eat our turkey, thermodynamics experts have come up with equations to help us cook it to perfection. We all hope for a white Christmas but meteorologists have analysed the snow cycle in such detail they can predict the phenomenon years in advance. And there are plenty of biologists and geneticists, who, according to their religious outlook, are working to prove or disprove the Virgin Birth.

"I have been investigating the science of Christmas for more than a decade. When I started to become interested in the subject, I was unprepared for the range of insights that would eventually emerge," says Highfield.

"Take, for example, those flying reindeer, Santa's red and white colour scheme and his jolly disposition, they all have a scientific basis, being linked to the use of a hallucinogenic toadstool in ancient rituals."

Yes, it's true, the kindly old man who pops down the chimney every year has his origins in the widespread use in northern Europe of a type of magic mushroom known as fly agaric.

According to Patrick Harding, a fungi expert at Sheffield University, the mind-altering drug was taken by shamen in Lapp villages, who believed their souls left the body, took the form of an animal and flew to other worlds to communicate with spirits. They returned bearing gifts of knowledge which would help villagers solve their problems.

The idea of Santa coming down the chimney also has its origins in the shamans, he claims. The door and chimney in the tent-like dwellings were one and the same so there is a clear parallel between the shaman entering someone's home and Santa squeezing down the flue. Santa's distinctive robes are a tribute to the mushroom's red cap and white dots and it's not beyond the realms of possibility that his trademark 'ho, ho, ho' is the euphoric laugh of someone who's been indulging in a bit of fly agaric.

And the reindeer, where do they come into it? Apparently they were rather fond of drinking shaman urine, containing the diluted hallucinogenic - as were the villagers. Under the circumstances it's not hard to imagine how a gang of flying deer found their way into the legend.

And if you like to believe that Santa's portly appearance is the result of all those mince pies and sherry left out for him by children (and use it as an excuse for your own over-indulgence), you're in for a shock. According to Highfield, it's more likely to be due to a defective gene that causes him to pile on the pounds and what's more, he's probably diabetic.

The book answers that age-old question of how Santa manages to circle the globe on Christmas Eve, making his way down millions of chimneys and handing out millions of presents. "The answer lies in his unprecedented research resources and expertise across a range of fields, spanning genetic engineering, computing, quantum electronics and quantum gravity," says Highfield. And here's me thinking it was all done by magic.

Rudolph also comes in for a debunking. Although reindeer are the only species of deer in which both sexes have antlers, the males lose theirs around Christmas time, following the mating season. To have antlers, as he is usually portrayed on Christmas cards, everyone's favourite reindeer would have to have been castrated - or be a female. The author suggests Rosie is a more appropriate name.

It's not just the Christmas myths that come under the spotlight. Can Reindeer Fly? examines the psychology of giving cards and presents, the formation of snowflakes and the reasons behind the Christmas blues and the science of cooking.

The best way to prepare your turkey, for example, is not to slam it in the oven but to use a laser, preferably a powerful one like that in the telescope of the WM Keck Observatory in Hawaii. This ensures the right amount of heat is applied to each part of the bird by constantly adjusting the beams as they are scanned over the surface.

Once the turkey's cooked you have to consider the best way of serving it and scientists have discovered that a depth of 3mm, approximately three large tablespoons, is the optimal amount of gravy. This replaces the amount of moisture lost during the cooking of the standard Christmas roast.

There's an optimum eating strategy too. Different parts of the meal absorb gravy at different rates so to make the most of your Christmas dinner, start with the turkey, parsnips and green vegetables, followed by the roast potatoes.

No doubt that's advice most of us will ignore but even the Luddites among us have to admit that science could play more of a role in Christmas future. In the last chapter, Highfield takes a light-hearted look at Christmas 2020 when atmospheric engineers guarantee snow on December 25 and GM Christmas trees keep their needles. If you dread the thought of dozens of relatives descending for the big day, then a virtual family reunion could be just what you're looking for and, if the festive film choice is less than appealing, why not custom make your own movie using digitally-created versions of your favourite actors? It's not as far-fetched as it sounds. Most of this technology already exists in one form or another.

Can Reindeer Fly is more than a collection of bizarre and interesting facts and theories. Highfield has a more serious purpose than merely to entertain and hopes the book will encourage more people to think about science and the way it affects our lives every day.

"Christmas and associated celebrations offer a wonderful excuse to explore a broad range of fields, from biotechnology and fractals to neuropharmacology and nanotechnology," he says. "If appetites are whetted for science, or at the very least curiosity about the subject is stimulated, I will be pleased."

But doesn't all this take the magic and mystery out of Christmas? "No," says Highfield. "My experience of writing this book undermines the idea that the materialist insights of science destroy our capacity to wonder, leaving the world a more boring and predictable place," he says. "For me, the very reverse is true. I can still remember the day when I first became convinced that Santa did not exist. Now, when the Santa myth is refracted through the prism of science, he seems more real than ever."

l Can Reindeer Fly? The Science Of Christmas by Roger Highfield (Weidenfeld and Nicolson £9.99).