Scientists have determined exactly how fast Santa would have to travel to visit every child on the planet… and reveal why Rudolf’s nose wouldn’t be red at this speed
As Christmas approaches, children around the world eagerly await the visit of Santa Claus and his reindeer.
But with approximately two billion children on the planet, Santa really has his work cut out for him tonight.
Scientists have calculated that Santa Claus would have to travel 90 million miles to deliver presents to all the good girls and boys around the world.
That’s the equivalent of flying his sled all the way from Earth to the sun in one night.
To save some time for delivering presents, this means Santa will have to travel at a speed of 5.2 million miles per hour (8.2 million km per hour), or 0.8 percent of the speed of light.
That incredible speed could also explain why Joly Saint Nick can stick his belly through a narrow chimney.
According to Albert Einstein’s special theory of relativity, objects traveling in Santa’s sleigh will become smaller as they approach the speed of light.
But strangest of all, scientists say Rudolf’s famous nose wouldn’t appear red at all at this speed.
Scientists have calculated that Santa Claus would have to travel 144 million kilometers to deliver presents to all the children who celebrate Christmas. This is equivalent to traveling almost all the way to the sun in one night (stock image)
Dr. Laura Nicole Driessen, a radio astronomer from the University of Sydney, made these festive calculations based on a formula devised by particle physicists at Fermilab in the 1980s.
First, Dr. Driessen estimated the number of children to whom Santa Claus should deliver presents.
There are approximately two billion children on earth, but Christmas is only celebrated in some way in 93 percent of countries. We can assume that seven percent of children do not need presents.
But of course, even among those who celebrate Christmas, not every child is well enough to warrant a visit from the man himself.
Dr. Driessen writes for the conversation: ‘We know that Santa Claus only delivers presents to those who really believe.
“If we assume the same percentage of believers by age as in the United States, we arrive at approximately 690 million children.”
And with about 2.3 children per household worldwide, Santa will have to visit at least 300 million homes tonight.
“Distribute those households evenly over 69 million square kilometers of habitable land surface on Earth,” says Dr. Driessen.
To make that trip, Santa would have to travel at a minimum speed of 8.2 million km/h (5.1 million miles per hour), or 0.8 percent of the speed of light. In the photo: the NORAD Santa Tracker
‘Santa Claus has to travel 144 million kilometers on Christmas Eve. That is almost the same as the distance from the earth to the sun.’
That would be a tall order if Santa only had 10 hours between 8pm and 6am the next day when the children in Britain were asleep.
Luckily, he gets a few extra hours thanks to the Earth’s rotation.
Once the children are evenly distributed around the world, Sata has at least 24 hours to travel around the entire planet from there.
And with an 11-hour difference in time zones between one side of the world and the other, Santa has a total of 35 hours from the first child to fall asleep to the last to wake up.
Dr. Driessen says: ‘Suppose Santa uses half his time rushing in and out of each household, giving him a total of 17.5 hours or 0.2 milliseconds per household. He uses the remaining 17.5 hours for traveling between households.
“My hypothesis is that he would have to travel as fast as 8.2 million kilometers per hour, or 0.8 percent of the speed of light, to deliver all the presents.”
But if Santa wants some time to eat a mince pie and put his feet up at the end of the evening, Dr Driessen suggests he may have to travel considerably faster.
Some of the strangest effects would occur if you look at the bright nose of Rudolf the reindeer. At this speed, scientists say it may not appear red at all (stock image)
To deliver everything nice and quickly, Santa Claus could travel 10 percent the speed of light – or 66.5 million miles per hour (107 million km/h).
However, at these speeds, things would get very strange for Santa.
Thanks to the special theory of relativity, Santa Claus and everything traveling with him appear much thinner than usual from our perspective.
Although Einstein predicts that Santa Claus would gain more mass as he gets faster, as he approaches the speed of light he would become compressed in the direction he is traveling – making it easy for him to slide down a chimney.
Dr. Katy Sheen, a physicist in the geography department at the University of Exeter, has previously suggested that this could also be the reason why Santa Claus always looks the same age.
Because they are objects approaching the speed of light, time moves more slowly from their frame of reference than it does in ours, meaning Santa ages more slowly as he travels.
But thanks to something called the Dopler effect, the strangest effects would occur if we were to look out for the bright light from Rudolf’s nose.
This is the same effect, meaning the siren of an oncoming ambulance sounds louder than once it has passed.
The Dopler effect means that motion changes the frequency of the sound wave based on the direction of motion of the source. This is why ambulance sirens sound lower after they pass us
The Dopler effect makes it look like Rudolf has a bright orange nose when he flies towards you and a dark black nose when he flies away
As the object rushes towards us, the waves are compressed, causing the pitch to rise. As the object moves further away, the waves extend to produce a lower pitch.
The faster something moves, the more pronounced this effect becomes, meaning Rudolf’s breakneck flight will create an extremely strong Dopler effect.
Red-colored light has a wavelength, the distance between one peak and the next, of 694.3 nanometers when the source is at rest.
If we fly at 10 percent of the speed of light, we see this light shift radically in both directions.
Dr. Driessen says: ‘At this speed, Rudolph’s nose would have shifted blue to bright orange (624 nanometers) as he flew towards your house.
“And it would redshift to a very dark red (763 nanometers) as he walked away.
‘The darkest red human eye we can see is about 780 nanometers. At these speeds, Rudolph’s nose would be almost black.”
That means no one on earth would ever see Rudolf’s famous red nose.
WHAT IS THE DOPPLER EFFECT?
The Doppler effect is a well-understood physical phenomenon that is also observed in astrophysics when the universe expands and causes ‘redshift’, but is more commonly seen in sirens.
For example, when a blaring ambulance or police car speeds past with its sirens on, they appear high as they approach you and then lower as they speed past.
This is due to the compression of sound waves as they get closer, and they expand as they get further away.
An extended sound wave has a longer wavelength and therefore a lower frequency, resulting in an increasingly lower pitch.
In astronomy, scientists use this effect to measure the speed of distant stars and planets.
When light sources move away from us in space, their wavelengths are stretched into the red end of the spectrum.
Likewise, when something moves towards us, the light wave is compressed and the light shifts to the blue part of the spectrum.
By looking at this red and blue shift we can figure out how something is moving relative to the Earth.
For example, by measuring the redshift of distant supernovae, the Hubble Space Telescope and the James Webb Space Telescope have helped calculate how fast the universe is expanding.
Astronomers have also used this effect to find out whether a star is orbiting another star.
The Doppler effect, or Doppler shift, describes the changes in frequency of any form of sound or light wave produced by a moving source relative to an observer.