12 questions of Christmas

When exactly is Christmas Day? Was there a Star of Bethlehem? Could Santa deliver gifts to all the world's children? What are the chances of a White Christmas? How far has your Christmas dinner travelled? And do reindeer ever have red noses?

When exactly is Christmas Day?

By Robert Verkaik

No one knows when Jesus was born. Early Christians tried to calculate the date of Christ's birth based on the Annunciation, 25 March, the Bible's first account of when Mary was told she was pregnant. If this is taken as the conception of Christ, nine months later it is 25 December.

But Jewish tradition has it that Jesus was born during Hanuk-kah, 25 Kislev into the beginning of Tevet. In the Julian calendar, 25 Kislev would be 25 November.

Others say Jesus and Mohammed shared the same birthday. Mohammed was born on the 12th of the Muslim month of Rabi-ul-awal in the 7th century which this year was celebrated in April. Muslims use a lunar calendar, so Mohammed's birthday will eventually fall in December. Most Eastern Orthodox churches celebrate Christmas on 7 January.

Christmas was first celebrated on 25 December in the 5th century in the time of the Constantine, the first Christian Roman emperor. This date was probably chosen because the winter solstice and the ancient pagan Roman midwinter festival called Saturnalia was in December. The winter solstice is the day with the shortest time between the sun rising and setting. It falls between 22 and 25 December.

Was there a Star of Bethlehem?

By Cahal Milmo

Opinion is split on just what the Magi were looking at when, according to gospel of Matthew, they saw the star of the king of the Jews in the eastern sky and set off for Bethlehem.

Some historians argue that the light is entirely mythical - part of a series of "stars" that legends of the time described as heralding a royal birth.

Astronomers have pored over the question for centuries, exploring theories that the star was a comet or a supernova.

This week a British astronomer, Professor Mike Bode suggested that what the Three Kings saw was not a star at all but a "conjunction", the passing of two planets so close to each other that they appear as a single light source. Professor Bode calculated that, in June of 2BC, Jupiter and Venus passed close together and would have created a bright object.

Some scholars argue that the date of Christ's birth is actually June, based on references to his conception. But even with the conventional December date, Jupiter appears a strong candidate for the Star of Bethlehem.

But believers in a second coming may struggle for a new celestial signal of salvation. Light pollution, caused by the upward glare of electric lights, is making it increasingly difficult for earthbound telescopes to penetrate the heavens. A modern Magi would probably have to rely on satellites rather than the firmament to locate an infant saviour. During the 1990s, the area of countryside in the developed world with completely dark skies reduced by 27 per cent.

Scientists estimate that less than half of the population of Europe and parts of the Middle East, including Israel and the West Bank, will ever see the Milky Way.

As a result, most observatories in the Western world have had to relocate to the much darker southern hemisphere or what is left of the dark countryside.

Is a Virgin Birth possible?

By Jeremy Laurance

The Christian doctrine of the Virgin Birth is that Jesus was conceived in his mother's womb without a human father. The Immaculate Conception took place when the Holy Spirit "overshadowed" Mary. However, Christ was not created from nothing, as the church says he "took his flesh from Mary". The doctrine's importance to Christianity is that it shows Jesus's divine and human natures united, paving the way for all humanity to be united with God.

In scientific terms, a virgin birth is classed as parthogenesis - when an embryo grows and develops without fertilisation by a male. Parthogenesis occurs in some plants, insects, fish and vertebrate animals such as lizards. The resulting organism is a clone of the original because it has an identical genetic make-up. Parthogenesis does not occur naturally in humans or other mammals. However, modern scientific techniques have made it possible to create clones of mammals, beginning with Dolly the sheep in 1996. It would in theory be possible to create a child from a virgin mother whose sole genetic inheritance was from her.

Was Jesus black?

By Robert Verkaik

This question has preoccupied theologians since at least the end of the 19th century. What most concede is that he could not have been a white Caucasian as depicted in Western iconography. In Revelation he is said to have hair "like wool" which is used as evidence to show he was of African descent. The indigenous people of the Middle East at the time of Jesus's birth were mostly of African birth. The existence of Black Madonnas, dark-skinned images of Jesus's mother, Mary, have also strengthened the case for Jesus being of non-Caucasian descent. Jesus' male ancestors trace a line from Shem, the eldest son of Noah. Anthropologists believe they would have been of mixed race because of their time spent in captivity in Egypt and Babylon. The "black/white" argument is easily settled if one follows the American test of whether someone is racially "black". Under the "one-drop rule" if any person has any black ancestors he or she is considered "black" even if they have pale skin colour. Under this rule, Mariah Carey, LaToya Jackson and Jesus would all be classified as "black".

Could Santa deliver gifts to all the world's children in one night?

By Cahal Milmo

Of course he can, with help from Nasa, Einstein and 360,000 reindeer. Scientists have been wrestling with the feasibility of Santa's job description since the 1850s. The latest thinking is that delivering one kilogram of presents to the world's 2.1 billion children (regardless of religious denomination) is entirely realistic, with a little lateral thinking.

Scientists at the American space agency, Nasa, reckon the man from Lapland relies on an antenna that picks up electromagnetic signals from children's brains to know what presents they want. Assuming an average of 2.5 children per house Mr Claus must make 842 million stops tonight to fill his orders.

By allowing a quarter of a mile between each stop, he must travel 218 million miles with about a thousandth of a second to squeeze down each chimney, unload a stocking, eat a mince pie, swig cooking sherry and get his sleigh airborne again. To achieve this he must travel at 1,280 miles per second. Travelling east to west, he can stretch Christmas Day to 31 hours.

To have enough presents, Santa's sleigh must carry 400,000 ton of gifts. With the average non-turbocharged reindeer capable of pulling only 150kg, Father Christmas would need 360,000 reindeer to heave his vehicle skyward.

The cavalcade would have a mass of about 500,000 tons which, at the required speed, would cause each reindeer to vaporise in a sonic boom flattening every tree and building within 30 miles. Father Christmas would have a mass of two million kilograms, causing him to combust when his reindeer come to their sudden halt. Piffle.

First, Einstein's theory of relativity dictates that the faster an object travels, the slower time appears to pass. So at the speed he is travelling, .0001 of a second allows Santa to perform his tasks at leisure pace. Second, as an expert in quantum physics, Mr Claus knows wormholes in the fabric of universe allow him to move instantly from one dimension and place to another. His sleigh is a time-machine powered by an unknown fuel which any economy on the world would have on its Christmas list.

Is this the season of goodwill?

By Maxine Frith

The common perception is that the suicide rate always goes up over Christmas. But in fact, the number of people who kill themselves drops by around 7 per cent during December - although it then rises to its highest monthly rate in January.

Despite the reduction in suicides, calls to the Samaritans increase by 10 per cent between Christmas and New Year.

The murder rate also goes up by 4.2 per cent, partly due to the increase in domestic violence that is widely reported by police forces.

More than 8,000 children called the NSPCC or ChildLine phone lines between Christmas Eve and 4 January last year to talk about emotional problems and abuse. One in five people says that the festive period causes them stress, according to the mental health charity Mind.

And of the five million elderly people who live alone in the UK, one million will spend Christmas Day on their own.

A poll by Reader's Digest found that people's greatest irritation over the Christmas period is the plague of family grievances that the holiday season engenders.

More than a third said that they had to deal with arguments between relatives every year.

Even events out of the family home are not much better - half of office parties feature a punch-up and one in three with an incident of sexual harassment.

Do you ever get a Silent Night?

By Cahal Milmo

Only on the pages of a carol sheet and in the depths of galaxies.

The silence to which the hymn refers can only be found in a vacuum and, since human existence is difficult inside a Hoover, the only place where true silence can be found is space.

The result is the strange paradox that silence has no sound. For example, when sci-fi films excite their audiences with the familiar roar of a rocket blasting between the planets, they are lying - there is nothing to be heard between the stars and planets. The impossibility of silence is all the more perplexing because humanity is in increasingly dire need of it, or at least a bit more peace and quiet.

Experts believe that the high sound levels of modern society not only damage the human ear but also contribute to stress.

The European Environmental Agency calculated earlier this year that 450 million people, some 65 per cent of the population in Europe, are regularly exposed to noise levels of 55 decibels and above - the level shown to generate annoyance.

About 115 million experience 65dB and above, suffering an increased risk of high blood pressure, and 10 million are exposed to 75dB or more - a level known to generate high levels of stress.

The Health and Safety Executive says that a third of workers in noisy jobs will permanently damage their hearing.

What are the chances of a White Christmas?

By Cahal Milmo

Bookies yesterday put the odds of London receiving the requisite single flake of snow on the roof of a weather bureau in the capital that would make it a white Christmas at 5/2.

Officially, meteorologists put the chances of snow nationwide on Christmas Day at "very unlikely", although, by the middle of next week, there is a 60 per cent chance that southern England will be under several centimetres of the fluffy stuff.

The long-term outlook is somewhat different. Enjoy any December snow while you can for the white Christmas bonanza for turf accountants, who tend to profit to the tune of £1m from the lack of snow, is likely to be a quirk of history.

London has only had six white Christmases since 1957 and thanks to humanity's talent for producing carbon dioxide, the Dickensian festive scene will remain only on greetings cards.

Climatologists this week predicted that global warming would make snow in December a thing of the past for all of Britain apart from its highest mountains and more northerly climes.

Scientists at the Met Office calculate that winters will be up to 30 per cent wetter within a generation, with an average rise in temperature of up to 3.5C by 2080. A Met Office spokeswoman said: "We won't see the effects immediately but the trend is that snow levels will drastically fall over the next century."

Is Christmas bad for the environment?

Martin Hickman

Yes. People consume far more at Christmas than at other times of the year.

Gifts are made at factories that use lots of energy and contribute to global warming. Finite and diminishing natural resources such as metals go into them. In particular, plastics use a high amount of oil, yet these goods are often poor quality and disposable, something especially so for toys at Christmas.

Transporting these products to the shops results in more energy use and pollution.

Intensive food production to sate our festive appetite discourages wildlife and allows pesticides to leach into streams and rivers.

About three million tons of rubbish will build up in our homes, yet barely a quarter will be recycled. The remainder will be incinerated or dumped in landfill, both of which cast out pollutants. Friends of the Earth believe that this Christmas is likely to generate a record amount of waste because each year we buy more and more presents and food.

The only bright spot environmentally is that while we are stuffing our mouths with food or ripping open our presents (wrapped with disposable paper), we are not jumping into our cars and spewing pollution from the exhaust pipes. Or working in factories to supply goods for the next Christmas.

How far has your Christmas dinner travelled?

By Maxine Frith

According to the Soil Association, most of the meat and vegetables on the average Christmas dinner plate will be cheap imports. The turkey may have come from Norfolk, but your carrots are likely to have come from Morocco, the crackers from China and the Brussels sprouts from the Netherlands. When you add in cabernet sauvignon from Chile, cranberries from the US and runner beans from Guatemala and assorted goods, the total "food miles" bill comes to 43,674. The Soil Association estimates that 12 British farmers are going out of business every day because they cannot compete with cut-price foreign goods.

The transportation by air of 200g of Chilean grapes will generate 1.5kg (3.3lb) of greenhouse gas - equivalent to leaving a lightbulb on all weekend. But, while buying locally sourced food could save Britain £2.1bn in environmental and congestion costs, it could double the average bill because of the higher prices charged by small and organic producers.

Is Christmas unhealthy?

By Jeremy Laurance

Christmas lunch of turkey, roast potatoes, stuffing, bacon, bread sauce, cranberry sauce, brussels sprouts and gravy adds up to 620 calories. Follow it with Christmas pudding and cream and the calorie counter zooms up to 1,306.

With a glass of champagne, (100 calories) a couple of glasses of burgundy (90 cals each) and a glass of port (185 cals), the total leaps to 1,771 calories. Once a year, a blow out on this scale - a day's worth of calories at a single sitting - is unlikely to do any lasting harm. But if you keep it up over the holiday period you will inevitably put on weight.

There are some health benefits too though. The sprouts and carrots contribute to the five-a-day target for fruit and vegetables, the cranberries may help to ward off infections and alcohol in moderation cuts the risk of heart disease. But the greatest health benefit of Christmas is - or should be - the good cheer it generates.

Do reindeer ever have red noses?

By Cahal Milmo

The notion of reindeer and red noses - or more to the point the infernal tune that assails Christmas shoppers - can be blamed on Robert May, an advertising copy-writer in 1930s Chicago.

Mr May was commissioned by his company to invent a seasonal tale to give away to customers of a department store chain and the resulting yarn of Rudolph, the disfigured ruminant, sold six million copies. Mr May never made a penny from his invention because the copyright belonged to his employer.

But recently researchers discovered that there is in fact such a thing as a red-nosed reindeer. Scientists in America found that reindeer were susceptible to a particular type of mite which irritates the nasal passages and causes the animals to rub their noses raw.