The Science of Christmas


By Luke Farnish and David Winlo

It’s that time of year again. Secret Santas are being set up, house Christmas dinners being planned, and many a slightly frozen student is heading to Unio for a seasonal hot drink. In other words, it is December, and Christmas will soon be upon us. Here at The Broad we celebrate Christmas in various ways, and we scientists are no different. So here is a scientific explanation of some, if not all things Christmas.

1. Santa is on his way, and what a way it is!

Even if we discount the children of parents from non-Christmas-celebrating backgrounds, Santa is going to have to deliver to around 700,000,000 children in a single night. Then we need to divide those children by household and assume even distribution of those households around the world, otherwise we’ll still be calculating by New Year’s. Now with 1.47 km between each house, Santa has a journey of 342,510,000 km on his hands, and we haven’t finished yet.

If Santa travels so as to maximise the length of the night of Christmas Eve, he has 32 hours. To travel over 342,000,000 km in that time will require him to really push his reindeer, as they’ll need to pull him along at 6,650,808 mph, or 10,703,438 kph, about 167 times faster than the fastest-moving machine ever made, the Voyager 1 space probe. So spare a thought for the poor guy and his reindeer, and leave them a mince pie and some cherry.

2. Christmas has its origins in religion.

For Christians, this time of year is about the birth of Jesus, and now, this is true for many physicists and astronomers. The bible writes that Jesus’ birth was accompanied by a new star in the sky and, what’s more, it’s not the only source from the time (5BC, a date even many high ranking church members agree with) to mention such an event. We call three of the visitors of Jesus the ‘three wise men’ but their true name is the Magi, followers of an ancient religion whose beliefs are focused on a single God and that contact may be made through the stars. They were astronomers! Texts of the time record the stars in fantastic detail and most scientists believe that there truly was a temporary ‘star’. But what was it? There are some strong contenders.

In 1614, Johannes Kepler, one of the most famous astronomers of all time, suggested a conjunction (overlapping from the perspective of Earth) of planets. It can be calculated that were a number around this time. However, they are not always very bright and many occurred in the wrong place for the Magi to follow. A supernova, an exploding star, can be VERY bright, even brighter than the moon. But, supernovae leave a trace, that being a nebula, a huge cloud of gas. No nebula of the correct age and position has been found, but, the Andromeda galaxy, our own galaxy’s neighbour has many nebulae and could have been in the correct place.

Another big contender is a comet, a large ball of ice that circles the sun in a huge orbit, meaning they can only be seen every few hundred years or so. Chinese astronomers noted one in 5BC that remained stationary in the sky for 70 days. What’s more, comets have huge tails of ice that could easily ‘point’ to the ground, much as in the Christmas card depiction of the star. The only major issue with this theory is human nature of the time, where comets were seen as bad omens. Perhaps we will be trying to work out what the ‘star’ was for many years to come, and perhaps that, to an astronomer, is the best sort of Christmas present.

3. The Nativity story.

Another Christmassy source of scientific intrigue is the Nativity story, in particular, the birth of Jesus to the Virgin Mary. What by many is held to be a highly significant miracle can be interpreted very differently by looking back through the translations of the Bible. The New Testament was written in Koine Greek, a form of the language no longer spoken natively. The writer of Matthew, the book which contains the Nativity story, referred to a passage from the Old Testament, saying ‘a parthenos shall conceive and bear a child’. ‘Parthenos’ is the word which translates to ‘virgin’ in the English translations of the New Testament, but can also simply mean ‘young woman’, which was the meaning of the Hebrew word ‘almah’ used in the passage the Greek author refers to.

Whilst Mary giving birth to Jesus may not have been an example of parthenogenesis, the scientific word for a virgin birth, there are plenty of animals which are. Among them is an animal likely to be seen on dinner tables across the nation this 25th of December – the turkey. In most cases the egg either doesn’t develop at all, or doesn’t develop normally. But some other animals, including various sharks, lizards and invertebrates, have been documented as being capable of parthenogenesis as a successful method of reproduction, though not a sole one.

4. On a rock band’s Christmas wish…

In 1973 Wizard told the world that they ‘Wish it could be Christmas every day’. Well, it can be, but only in one place, Christmas Island! Technically a part of Australia, despite being over 2,600 km (about 1,600 miles) from Perth near West Java. It’s not a big place, just 19 by 14 km with a population of about 2,000, the majority of the island’s inhabitants being of Chinese descent. Much of the island is made up of protected wildlife areas with the mining of guano (hardened bird faeces) for use in fertilisers being a well-known trade on the island since its initial colonisation.

It’s interesting, however, that Wizard mentions ‘every day’ because there is, in fact, a second Christmas island whose days are rather special. Kiritimati (pronounced ‘Christmas’ and previously spelt ‘Christmas’) is about 10,000 km (about 6,200 miles) east from Christmas Island and part of the Republic of Kiribati. It’s a fascinating place. The whole island is now a nature reserve (although much of its internal area is taken up by a lake), but in the 1950s the area was used for nuclear tests by the UK, leading to still detectable damage (many locals have suffered as the people of the island were not removed during tests). The towns of Kiritimati have rather unimaginative names including London, Paris (now abandoned), Poland and Banana, sometimes called Banana wells. But perhaps the most interesting fact about Kiritimati is its days. Christmas comes early here as Kiritimati is the only country in the UTC+14 time zone, meaning that a day starts for them 14 hours before it does in London (that’s the London in the UK, not their London!). This enabled the islands to trade more easily with other Pacific nations. So, not only is it Christmas every day, but for some, Christmas comes early.

We wish you all a wonderful Christmas from the both of us (and everyone at The Broad), and hope you enjoy all the science articles in 2017. ¡Feliz Navidad!

ImageRed Crabby David Stanley is licensed under CC BY 2.0

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