# Theory of relativity explains how Santa gets down your chimney

15 Dec 2016

Santa giving a thumbs up. Image: Subbotina Anna/Shutterstock

Naysayers of the magic of Santa have pooh-poohed his ability to travel down chimneys to deliver presents, but now researchers looking into the theory of relativity have found ‘proof’ that he can.

One of the fundamental aspects of Christmas – for many children around the world – is leaving out a treat for Santa and his reindeer at the foot of the chimney, as a thank you for delivering presents to them each year.

But when we start to think about how a large man can travel down a chimney, become invisible and leave back up the chimney, some questions start to be asked.

## Fastest sleigh in the galaxy

Researchers at the University of Exeter in the UK, however, have come to Santa’s defence with a new scientific answer for how he is able to achieve such impressive feats every year – using the theory of relativity.

According to Dr Katy Sheen, a physicist in the geography department at the university, the existing scientific theory would mean that as Santa and his reindeer travel across the globe at such a speed that they would actually shrink.

This would allow Santa to travel down the chimneys with ease and, more importantly, remain undetected from any children who can’t resist trying to catch him in the act.

Based on previous calculations, to deliver the necessary amount of presents to children, Santa’s sleigh moves at more than 1,000km per second, or 3,000 times the speed of sound.

## A way to teach kids about physics

However, if you’ve noticed that some of those mince pies have gone uneaten by the fireplace, don’t take it personally – they could reverse the relativity effects and bring him back to full size.

Science even explains why Santa goes undetected from children and adults alike, thanks to the Doppler effect.

As Santa approaches on his sleigh, the sound of bells and his deep “Ho ho ho” would get higher and higher and then become completely silent, because he would move beyond human hearing range.

But if a sound is heard, Sheen said, then it is likely one of Rudolph and co breaking the sound barrier with a ‘sonic boom’.

With plans to present these findings to a group of schoolchildren, Sheen hopes to encourage them to take a greater interest in physics for their own careers in the future.

Colm Gorey was a senior journalist with Silicon Republic

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