Mystery of how Santa fits down chimneys, can deliver presents without being seen 'solved' by relativity theory

December 14, 2016, University of Exeter
Christmas Tree

The mystery of how Father Christmas can deliver presents to 700 million children in one night, fit down the chimney and arrive without being seen or heard has been 'solved' by a physicist at the University of Exeter.

Santa and his reindeer zoom around the world at such speed that - according to relativity theory - they would shrink, enabling Father Christmas and a huge sack of presents to fit down chimneys.

Dr Katy Sheen, a physicist in the Geography department at the University of Exeter, has also found a scientific explanation for why Santa is not heard arriving by children, and why they rarely catch a glimpse of him on Christmas eve.

She will explain to children at the University of Exeter (Wednesday 14th December), that Santa's stealth delivery is partly explained by special devised by Albert Einstein, whom Dr Sheen thinks bares a passing resemblance to Santa.

Relativity theory explains how Father Christmas can fit down the chimney. At the speeds he needs to travel to deliver presents to every child, Father Christmas shrinks - or gets thinner - in the direction he is travelling. And he has to be careful not to stop for a mince pie in a chimney, or he could grow back to full size!

Dr Sheen will tell children at the University of Exeter's Science of Christmas Festival on Wednesday 14th December that relativity also explains why Father Christmas appears not to have aged throughout the ages, because relativity can slow down clocks.

When Dr Sheen was seven years old she wrote a letter to Father Christmas asking why he never got any older (letter attached). She received a response in shaky handwriting telling her it was 'all magic'. But the budding physicist was not convinced and wanted a rational explanation - which 26 years later she has now found.

As evidence of how Father Christmas's enormously fast delivery round has kept the years off him, she will present a picture of St Nicholas from 1901 and a photo from this year to the children at her talk.

The physicist has calculated that Santa and his reindeer would have to travel at about 10 million kilometres per hour to deliver presents to every child expected to celebrate Christmas in 31 hours (taking into account world time zones).

If millions of children have been good, and deserve bigger stockings, he may need to travel even faster. Such speed would make him change from red to green and, at greater speeds, he would disappear! Children would not be able to recognise him as he would appear as a rainbow-coloured blur, eventually disappearing to the human eye.

Travelling at more than 200,000 times faster than Usain Bolt, the world's fastest man, the laws of physics explain why Father Christmas is rarely seen by children while delivering presents.

The Doppler effect would make Santa change colour because the light waves he releases would get squashed at such a high speed.

The Doppler effect also explains why children cannot hear Father Christmas arrive. As Santa and his sleigh approach, the sound of bells and his deep 'ho, ho, ho' would get higher and higher (like when an ambulance siren whizzes by) and then become completely silent, because he would move beyond human hearing range. Even the sound of Santa urging on Rudolph would become unrecognisable, and then inaudible to the human ear.

If children hear a bang on Christmas night, it may not be the sound of Santa dropping his presents, landing on their roof in his sleigh, or sliding down the chimney with a plop. Santa's reindeer could have broken the speed of sound, resulting in a 'sonic boom.'

Dr Sheen, a physicist working in the University of Exeter's Geography department, is not planning to present her research to a peer-reviewed journal (it's prepared with the festive spirit in mind), and has done the calculations in her own time to interest children in science and physics.

Sheen will demonstrate the impact of the Doppler effect - which would make Santa able to deliver his presents without detection - by letting the children listen to the sound of a speeding ambulance, even though it is much slower than Father Christmas and his sleigh.

The Doppler effect is responsible for making a siren, such as on an ambulance or a police car, increase in pitch as it comes towards you and lower pitched as it drives away. This is because the wave length changes when it moves towards and away from you.

Dr Sheen calculated how fast Father Christmas would have to travel by working out the number of households likely to be celebrating Christmas around the world, along with the number of children likely to be in them. She hopes her explanation for Santa's stealth delivery system - and therefore his very existence - will inspire children to take a greater interest in physics, and put a science kit on the list of presents they want in their stockings.

"Visiting around 700 million in 31 hours would mean he would have to travel at 10 million kilometres an hour if he is to deliver presents to every child," Dr Sheen said. "How does Santa manage to reach these phenomenal speeds? Well that's magic! However, he would certainly need a lot of fuel - so don't forget his glass of sherry, a mince pie or two and some carrots for the reindeer!"

Explore further: Should parents lie to children about Santa?

Related Stories

Should parents lie to children about Santa?

November 23, 2016

Shops are bursting with toys, mince pies are on the menu and radios are blasting out Christmas tunes—so it's time for another festive favourite: lying to children.

Researcher explains how Santa delivers presents in one night

December 7, 2011

Don’t believe in Santa Claus? Magic, you say? In fact, science and technology explain how Santa is able to deliver toys to good girls and boys around the world in one night, according to a North Carolina State University ...

Engineer Explains How Santa Can Deliver Gifts in One Night

December 8, 2006

If you’re skeptical of Santa’s abilities to deliver presents to millions of homes and children in just one night, North Carolina State University’s Dr. Larry Silverberg, professor of mechanical and aerospace engineering, ...

Recommended for you

A phonon laser operating at an exceptional point

July 20, 2018

The basic quanta of light (photon) and sound (phonon) are bosonic particles that largely obey similar rules and are in general very good analogs of one another. Physicists have explored this analogy in recent experimental ...

17 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

cantdrive85
1 / 5 (4) Dec 14, 2016
"How does Santa manage to reach these phenomenal speeds? Well that's magic! ....Santa's stealth delivery is partly explained by special relativity theory

Yep, magical pseudoscience.
TheGhostofOtto1923
3.7 / 5 (6) Dec 14, 2016
This is also how xian apologists work their magic but they are entirely serious about it-
xinhangshen
1 / 5 (9) Dec 14, 2016
It seems that many people still don't know that Einstein's relativity theory has already been disproved both theoretically and experimentally (see "Challenge to the special theory of relativity" March 1, 2016 Physics Essays). The most obvious evidence is the absolute time shown by the universally synchronized clocks on the GPS satellites which move at high velocities relative to each other while special relativity claims that time is relative (i.e. the time on each reference frame is different) and can never be synchronized on clocks moving with relative velocities. We should abandon all the wrong relativistic spacetime based physics theories to open our mind for new theories.

As this is such an extremely important message that can prevent billions of taxpayer's dollars from being wasted on the wrong physics theories, all people, especially science news reporters, are obliged to deliver this message to the entire community of the physicists in the word.
Merrit
5 / 5 (1) Dec 14, 2016
Even if this article you mentioned is correct we wouldn't abandon relativity. Newton physics can be considered wrong and it is still used when the extra precision of relativity is not needed. GR relativity is likely incomplete and/or right for the wrong reasons, but there is currently no better theory. Even if there was it would likely be more complicated and only used when additional precision was required. Whether Einstein is technically correct or not does not change the usefulness of his equations or the fact that they predict results that are scientifically proven. Proven Einstein wrong would only prove that there is a better theory yet to be discovered.
Mimath224
5 / 5 (4) Dec 14, 2016
I should warn to the uninformed reader, that this article is not scientific: Santa is only flattened on one axis, but in the normal plane to that axis he still is fat enough to not being able to fit across the chimney.

Also, each gift being thrown at that speed has enough kinetic energy to explode with the force of a nuclear bomb, so only bad child get gifts.

Sorry for pricking your balloons...

Is that a case for Santa does not exist? (tears in my eyes) Right, well how about all those homes that don't have a chimney? How does Santa manage that one eh? But of course Santa is magical anyway so he can just wish it and it happens. Why do you think he never gets caught...he doesn't want to be bothered about all those thousands of questions we'd ask.
Seeker2
not rated yet Dec 14, 2016
@rimefoyi
...Santa is only flattened on one axis, but in the normal plane to that axis he still is fat enough to not being able to fit across the chimney.
I thought he wound be spaghettified along his axis of motion - up or down the chimney.
Captain Stumpy
3.8 / 5 (5) Dec 14, 2016
Why do you think he never gets caught...he doesn't want to be bothered about all those thousands of questions we'd ask.
@Mimath224
well... he got caught at least once: http://www.chillo...e-21.jpg

LMFAO

.

I should warn to the uninformed reader, that this article is not scientific:
@rimifoyi

surely you can't be serious!

LOL

the funny thing about the article... and pretty much the same thing that Otto said:
it's how some people think and justify their beliefs

gkam
2.1 / 5 (7) Dec 14, 2016
He appears in each place by the Laws of Probability.
Mimath224
5 / 5 (4) Dec 15, 2016
@Captain Stumpy, No you got it wrong, That was one of Santa's elves getting caught for posing as Santa...if you think I'm going to stop hanging up my socks...you'll have to do better than that, Ha!
TheGhostofOtto1923
3.5 / 5 (6) Dec 15, 2016
Also, each gift being thrown at that speed has enough kinetic energy to explode with the force of a nuclear bomb, so only bad child get gifts
Except that I am sure Santa has inertial dampers first proposed by heinlein in his Lazarus Long stories. He got the idea from santa I'm sure.
h20dr
Dec 15, 2016
This comment has been removed by a moderator.
ddaye
5 / 5 (3) Dec 15, 2016
He appears in each place by the Laws of Probability.

Schroedinger's Santa. Since nobody observes him, he's in every house at the same time.
Seeker2
5 / 5 (1) Dec 16, 2016
He appears in each place by the Laws of Probability.
Schroedinger's Santa. Since nobody observes him, he's in every house at the same time.
Maybe quantum entanglement?
onesimplepath
5 / 5 (2) Dec 21, 2016
Forget relativity, quantum mechanics can solve this. The superposition principle allows santa to be in every house simultaneously as long as no curious children try to stay up to see him. Otherwise, his position would be fixed and the other kids wouldn't get their presents.
Mimath224
5 / 5 (1) Dec 21, 2016
Forget relativity, quantum mechanics can solve this. The superposition principle allows santa to be in every house simultaneously as long as no curious children try to stay up to see him. Otherwise, his position would be fixed and the other kids wouldn't get their presents.

If Santa used a quantum cloak maybe no one would see him but I don't know if that cloak would interfere with superposition....would it?
randomcyborg
3.7 / 5 (3) Dec 21, 2016
Santa compresses in the direction of motion, and spaghettification removes Santa's visibility in all other spatial dimensions. By using a chrono-synclastic infundibulum, Santa inverts time compression, giving him all the time he needs; this uses a dark energy tap made by the Elf Corps of Engineers.

Using trans-dodge values, Santa modifies his local QPO (quantum probability overlay) to remove himself from the global QPO; an "infinitely often standing wave" effect puts him in all children's houses simultaneously. Because of the Shevek effect, no sonic booms are created, Santa's reindeer are silent, and Santa's boots make no sound. Finally, because of Clarke's Third Law, one sound only is heard, and that only in children's dreams: "Ho! Ho! Ho! Merry Christmas!"
dlethe
Dec 31, 2016
This comment has been removed by a moderator.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.