# The Physics of Santa

By Shaun Hendy 24/12/2013 1

At this time of year, many parents worry about the risks posed to their children from exposure to Santa Claus. We know very little about the science of Santa because the government refuses to fund research into Christmas,as it cannot be linked to direct economic benefit.

Yet, as Colin Craig has been at pains to remind us this year, unless we know the facts, how can we be sure that Santa’s reindeer are chemical free or whether he even exists? Luckily, Radio New Zealand commissioned a small study this year to answer some of New Zealanders most pressing concerns about Santa*.

Many New Zealanders want to know how fast Santa has to travel to deliver all his gifts.

We estimate that Santa has a bit over 30 hours to do this, assuming that he starts around midnight on New Zealand’s side of the international date line, and finishes before people wake up on the other side.

We are less sure about how many children he has to visit: there are about 2 billion children in the world, and when you ask them whether they have been naughty or nice, they inevitably claim they have been nice. As scientists – and some of us were once children ourselves – we just don’t buy this. We think that it is more likely that only about half the children in the world, roughly one billion, have managed to be nice all year.

To deliver presents to these children, Santa has to visit about 5000 homes per second, assuming that there are 2.2 nice kids per household.

When Santa visits New Zealand, however, he has to deal with the fact that Kiwi kids are generally regarded as pretty nice, and this means he has to visit almost all of them**. If he is to reach the children on his list, Santa only three minutes to deliver his presents to the 800,000 Kiwi kids who were not naughty this year.

To fly from Cape Reinga to Rakiura, Santa and his reindeer must travel about 1600km in that three minutes. This works out to be a speed of around 32,000 km/h – 320 times the open road speed limit or about the same speed the space shuttle travels when it orbits the Earth. This is pretty fast.

But how does he power his reindeer? We think that Santa must be sharing the Xmas mince pies and glasses of sherry that are left out for him with his reindeer to keep their energy levels up.

While he travels over New Zealand, his reindeer have to pull him, his sleigh and about 400 metric tonnes of gifts. To achieve their need for speed, the reindeer must supply kinetic energy of about 13 gigajoules. If each child in New Zealand leaves Santa one Xmas mince pie (say, 400 kilojoules) to share with his reindeer, this will only supply around 5% of their energy needs.

Santa’s energy shortfall works out to be roughly the amount of chemical potential energy is stored in two barrels of oil. Hmmm.

More research is clearly needed. We would recommend however that Santa give consideration to delivering his presents in the day time so that he can take advantage of recent advances in solar cell technologies. This would also make life easier for scientists who currently have to write lengthy applications for permission to stay up past their bed time in order to study this mysterious phenomenon.

Declaration of interests: I have been informed that I was bad this year for wasting taxpayers’ money, so Santa is unlikely to be leaving a present for me under the tree. You can rest assured that this has in no way influenced the conclusions drawn in this blog post.

* Radio NZ apparently has no editorial policy on whether the gentleman in question should be referred to as Santa, Santa Claus or Father Christmas. We’ll stick to Santa.

** Anecdotally, my younger sister reports that her two older brothers, despite being Kiwis, were not always nice. This just goes to show how unwise it is to rely on hearsay evidence.

### One Response to “The Physics of Santa”

• ross says:

There was obviously a need to sleigh a few hoary myths. This (nearly) did it.

But the deceleration and acceleration from chimney to chimney must take a toll on the brains of both reindeer and Santa. Shaun only mentioned the overall trip. Mega giga joules? 1000 mellow puffs per household should do it,

You are right Shaun, we are all a total waste of taxpayers money and what have we produced?

To quote from the editorial:

“Ideally, all commercially valuable science would be financed in the private sector and public funds would be strictly for the pursuit of knowledge for its own sake. But that hope faded long ago. Without public subsidies not much science would be done.”

Here’s my riposte from John Polanyi:

“It is folly to use as one’s guide in the selection of fundamental science the criterion of utility. Not because (scientists)… despise utility. But because. .. useful outcomes are best identified after the making of discoveries, rather than before.”

[ Concerning the allocation of research funds. Speech to the Canadian Society for the Weizmann Institute of Science, Toronto (2 Jun 1996) ]

And what did the Romans (scientists of the day?)do for us!!!