When we’re little (and in some strange cases, into adult hood), the story of Father Christmas, the fat old man adorned in red and white robes, pervades our lives, (hopefully) making us think about our actions due to the threat of being branded a “naughty child” and getting coal as a present instead of that new PlayStation game you really wanted. However, there comes a time in every child’s life where they learn the truth of Christmas. The truth that an old man doesn’t break into you’re house, leaving gifts, but that instead your parents quietly hide presents in the loft until you’ve gone to sleep on Christmas eve.

And for those of you that still believe, sorry, but the truth hurts.

But, as a bit of an annoying child, one thing always puzzled me, if this legendary man DID exist, how would he get around the world, and all its good children, in only one night? would it even be possible?

Well lets start with the children. There are roughly 2 billion under 15’s on earth at any one time (lets assume this is the point you stop believing in farther Christmas and start buying people gifts instead, you cheapskate). However, since St Nick does’t visit children of Muslim, Hindu, Jewish or Buddhist (except maybe in Japan) religions, this reduces the workload for Christmas night to about 33% of the total, around 660 million children, and with a global average fertillity rate of around 2.5 children per woman (and therefore household) this amounts to about 250 million households, assuming there is at least one good child in each.

Now, farther Christmas has circa 31 hours (if we include things like the rotation of the earth and differing time zones) to make his round trip of the world and its homes, this works out as 2240 visits per second. That is to say, St Nick has around 1/2500 th’s of a second to park up on your roof, break into your house, fill your stockings, place your presents, eat any food left for him, get out again and reach the next house.

Assuming these 250 million homes are evenly distributed around the world (which, of course, they wouldn’t be), we’re now talking 0.23 miles per household, a minimum trip length of 131.1 million miles, without diversions around storms, aeroplanes or mountains.

This means our dear old Father Christmas has to be travelling at a speed of around 1175 miles per second (4,226,000 miles per hour) this is about 5500 times the speed of sound. In comparison, the fastest ever man made object is the Helios space probes, which orbit the sun with an average speed of 44 miles per second, your run of the mill reindeer can run at about 0.00416 miles  per second (15 miles per hour).

The payload of the sleigh adds another interesting element. Assuming that each child gets nothing more than a medium sized LEGO set (two kilograms), the sleigh is carrying over 500 thousand tons, not counting Father Christmas himself. While on land, a conventional reindeer can pull around 150 kilogrmas. Even granted that flying reindeer can pull 100 times this, St Nick would need more than 8 or 9, he would need 33,000 of them. This increases the payload even further, adding another 5000 tonnes to the sleigh. This makes it similar in weight to the Seawise Giant, the longest ship ever built, and by many standards, the largest man made, self-propelling object ever.

500,000 tonnes moving at 1175 miles per second is going to produce a lot of air resistance. It would be equivalent to a spacecraft re-entering the earth’s atmosphere 168 times faster than its supposed to. As a result, the reindeer would almost instantly evaporate into a superheated cloud of atoms and molecules.

Not that it matters much, since St Nick, as a result of accelerating from a dead stop to 1175 miles per second in 0.0004 seconds, would be subjected to acceleration forces of 22 million g’s. A 115 kilogram Father Christmas (which seems ludicrously slim) would be pinned to the back of the sleigh by 217 million newtons of force, instantly crushing his bones and organs and reducing him to a quivering blob of pink goo.

Therefore, if Father Christmas did exist, he doesnt now.

Hope you had a good Christmas, and happy new year!

Alex Davis





New Eyes on the Sun: A Guide to Satellite Images and Amateur Observation by John Wilkinson