Scottish Country Dance of the Day

​Finally, 'Tis the night before Christmas when Santa loads his sleigh with presents and travels by reindeer to deliver gifts, often by going up and down chimneys!

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Christmas Eve in some parts of Scotland is also called "Sowans Nicht" from "sowans" - a gelatinous gruel-like dish made from oat husks and fine meal steeped in water.   Branches of a rowan tree have also been traditionally burnt on Christmas Eve to signify that any bad feeling between friends or relatives has been put aside for Yuletide.

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Santa, as is well known, is a special person because if he were ordinary folk, he would certainly have trouble with the physics and logistics of his mission this night.

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From the physics of Christmas, originally published by Spy Magazine in 1990, here are some interesting facts:

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Christmas scientists and mathematicians have conservatively estimated that  by those who generally celebrate Christmas, Santa will have about 378 million children to deliver to in a fairly short time frame.

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Thankfully, due to the rotation of Earth he’ll have a good 31 hours to deliver presents - rather than just 24 - assuming he’s flying East to West to match Earth’s rotation.

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With a further assumption of 3.5 children in each household, based on a recent average census rate, that leaves him with 91.8 million homes to visit, or 822.6 visits per second, requiring a stay of about one thousandth of a second to deliver presents to each home.

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All in all, Santa’s sleigh will need to move about 650 miles (1,050km) per second, which is 3,000 times the speed of sound or 0.35 per cent the speed of light.

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At such a speed it's possible Santa may start to feel the effects of relatiivity, particularly time dilation, causing him to age very slightly slower than the rest of the people on Earth - perhaps partially explaining his perpetual ability to deliver presents at Christmas.

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The sleigh will also have a sizable number of presents on board, further complicating matters.

If each child were to receive a present no more than 2lbs (0.9kg) in weight, the sleigh would still weigh more than 320,000 tons - just shy of the weight of the Empire State Building, 370,000 tons.

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An average reindeer on Earth can pull only 300 pounds (135kg), so in this scenario 214,200 reindeer would be needed.

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Of course, considering these are special flying reindeer, they may well be able to handle heavier loads.

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But with the weight and speed of the sleigh, it appears that the front two reindeer - Dasher and Dancer, until Rudolph’s inclusion - will be subjected to 13.4 quintillion joules of energy per second.

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Normally, this should cause them to burst into flames almost immediately after taking flight. The entire reindeer team, assuming only eight are used, would be vapourised in 4.26 thousandths of a second!

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To keep up with this mad pace, Santa may well need a snack of the cookies and milk and mince pies set out for him in various homes.

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A team of scientists from The Big Bang UK Young Scientists and Engineers Fair calculated that  Santa would consume150 billion calories in milk and cookies and mince pies during his journey, if he accepted all the snacks on offer at various homes.  

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Santa may appreciate some more wholesome sowans while on his journey if you care to set some out. 

And like other log burnings, be sure that your rowan fire has died down in the fireplace so that Santa has a clear path down the chimney. 

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Fortunately, every year, through the magic of Christmas Santa easily overcomes these mundane logistics in order to accomplish his Christmas Eve mission.   

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Happy Christmas!   Merry Christmas!