spaceSpace and Physics

Santa Claus Mysteries Explained With Theory Of Relativity, Sort Of


Stephen Luntz

Stephen has a science degree with a major in physics, an arts degree with majors in English Literature and History and Philosophy of Science and a Graduate Diploma in Science Communication.

Freelance Writer

flying reindeer

We're still not convinced on the whole flying reindeer bit, but physics has explained a few bits of the Father Christmas story. KOVTUN DARIA/Shutterstock

The theory of relativity can explain how Santa and his reindeer can fit down chimneys and not be seen or heard while spanning the world in a single night, according to a physicist. She has acknowledged some holes in her work, but that just leaves more room for future scientists to figure out the rest.

Some scientists have recently argued that lying to children about the source of their presents can have negative psychological effects, but others prefer to embrace myth as a learning opportunity. Every year at this time scientists attempt to explain aspects of the Father Christmas story using actual science. Despite always finding parts of the story beyond even the most optimistic explanation, the efforts do provide an opportunity to reveal some of the magic of science.


This year, Dr Katy Sheen of the University of Exeter has decided that many of the more curious components of the myth make sense when you take special relativity into account. Sheen presented her ideas at an event for children held by the university this week.

"Visiting around 700 million children in 31 hours would mean he would have to travel at 10 million kilometers (6 million miles) an hour if he is to deliver presents to every child," she explained in a statement. Delays to consume sherry, mince pies and carrots would increase this speed further.

At this significant portion of the speed of light, special relativity would come into play. One consequence is that all the crew – reindeer and rider alike – would shrink in the direction in which they are traveling.

Sheen noted that such shrinkage would be very helpful for squeezing down chimneys, or in fact any other unsealed entrances now that chimneys are no longer standard issue in houses.


Relativistic speeds would also make the present-bearing crew look bluer as they approach and red as they recede, and the color confusion might explain why there have been no confirmed sightings. "Ho Ho Hos" would be Doppler shifted beyond the range of human hearing, although Sheen skipped over why sonic booms from breaking the sound barrier are not a regular feature of Christmas Eve.

Approaching the speed of light would also increase the mass of the reindeer and their burden, and Sheen admits there were some things she can't explain. "How does Santa manage to reach these phenomenal speeds? Well, that's magic!” she said. Or perhaps, as Arthur C. Clarke would put it, sufficiently advanced technology.

Last year an effort in a similar vein explained that the story of Rudolph's red nose makes much more sense in light of what we have recently learned about how reindeer vision adapts to changing seasonal conditions.


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