The physics of Santa

Much scientific ink has been spilled on the thorny subject of how it is possible for Santa to deliver presents to millions of eager children in the hours between dusk on Christmas eve and dawn on Christmas day. Mikkelson (Snopes, 2003) for example, has calculated that in order to deliver presents to the nearly 100 million households in the Christmas-marking parts of the world, Santa would need to deliver to approaching 1,000 households, and travel at some 650 miles, every second of his long night, starting in New Zealand and working his way westwards towards Hawaii.

Each present, once at its destination, is of course stationary (i.e. not moving). It must therefore, whether on the sleigh or in the process of delivery, decelerate from a velocity of 650 miles per second to zero in either less than 1 thousandth of a second (if it is hand-delivered), or at the very least as it travels the distance between the sleigh (on the roof) and the stocking or tree, some 3 metres away (if it is jettisoned while the sleigh remains in flight). Either way, the g-force experienced by the present would reduce it to a heap of smouldering mush. This may afford the explanation for the Figgy Pudding that was so often delivered to households in Victorian times.

However, science (and with it the quality and variety of presents) has moved on since then, and Santa has availed himself of a more up-to-date, if abstract, branch of physics.

Heisenberg’s well-known Uncertainty Principle – often invoked by drunken physicists as they struggle to find their way from one Christmas party to another (in the days before Covid 19, of course) – states that the position and velocity of any object cannot both be known at the same time (we shall leave aside, for the purposes of this note, what Einstein said about ‘the same time’ because it only complicates matters). Thus, if Santa and the team of reindeer stick to a strict speed limit, so that the velocity of any given present is a known constant, its position is indeterminate, lying somewhere within a ‘probability cloud’ of possibilities. The present can, in a way, be said to be wherever one wishes it to be, just as Schrodinger’s cat can be said to be both dead and alive. The exact mechanism linking this essentially thought-driven process to a solid object such as a present, via quantum mechanics, is not yet fully understood but was first explored towards the close of last century (Penrose, 1989).

The ‘wave function’ (if you like, the ‘shape’ of the probability cloud), determined by boundary conditions such as answers to the questions ‘what am I getting for Christmas?’, ‘Does Santa exist?’ and ‘Did my letter really get to the North Pole?’, will ‘collapse’ into a singular position as soon as the present’s velocity is changed (for example by lobbing it off the constant-speed sledge) And lo! It appears, delivered by Quantum Santa.

One final warning: exhortations to ‘look for Santa in the night sky’, if they were to result in a genuine sighting, would result in the collapse of the delicately-maintained wave function, denying the observer, and everyone else, their Christmas present.

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