Like Christmas approaching, children around the world will be eagerly awaiting a visit from Santa and his reindeer.
But with nearly two billion children in the world, Santa has his work cut out for him tonight.
Scientists have calculated that Santa would have to travel 89 million kilometers (144 million miles) to deliver presents to good girls and boys around the world.
That is equivalent to flying his leg from the Earth to the Sun in one night.
In order to find time to deliver the presents, this means that Santa would have to travel at a speed of 8.2 million kilometers per hour or 0.8 percent of the speed of light.
This incredible speed may also explain why Joly Saint Nick can fit his stomach down a narrow chimney.
According to Albert Einstein’s theory of relativity, objects moving in Santa’s sleigh are compressed as they approach the speed of light.
But most surprising of all, scientists say that, at this speed, Rudolf’s famous nose would not have appeared red at all.
Scientists have calculated that Santa would need to travel 89 million kilometers (144 million miles) to deliver gifts to all the children celebrating Christmas. This is equivalent to traveling almost all the way to the sun in one night (stock photo)
Dr Laura Nicole Driessen, a radio astronomer at the University of Sydney, calculated the celebrations based on a system developed by physicists from Fermilab in the 1980s.
First Dr Driessen estimated the number of children that Santa would like to give presents to.
There are about two billion children on Earth, but Christmas is celebrated in some way in 93 out of 100 countries, which means that 7 percent of children do not need presents.
But, of course, even among those who celebrate Christmas, not every child is good enough to go to the man.
Writing in the Discussion, Dr Driessen said: ‘We know that Father Christmas gives gifts to people who really believe.
‘If we compare the number of believers at the same age as those found in the United States, we have about 690 million children.’
And with an average of 2.3 children per family worldwide, Santa will need to visit at least 300 million homes tonight.
‘Spread those families around 69 million square kilometers of habitable land on Earth,’ says Dr Driessen.
To make this trip, Santa needed to travel at a speed of 8.2 million kilometers per hour, or 0.8 percent of the speed of light. Photo: NORAD Santa Tracker
‘Father Christmas has to travel 144 million kilometers on Christmas Day. This is equal to the distance from the Earth to the Sun.’
This would be a very tall order if Father Christmas only had 10 hours between 20:00 and 06:00 the next day when the children of the UK are sleeping.
Luckily, they get extra hours because of the rotation of the Earth.
If the children are evenly distributed around the world, then Sata has at least 24 hours to travel from his journey around the world.
And, with an 11-hour time difference between one side of the world and the other, Santa has a total of 35 hours from when the first child goes to sleep until the last one wakes up.
Dr Driessen says: ‘Let’s say Father Christmas spends half his time going in and out of each house, which gives him a total of 17.5 hours or 0.2 milliseconds per house. They spend another 17.5 hours commuting between families.
‘My guess is that they would have to travel at a maximum speed of 8.2 million kilometers per hour, or 0.8 percent of the speed of light, to leave all the gifts.’
But if Santa wants time to eat a mince pie and kick his feet up into the evening, Dr Driessen says he needs to move very quickly.
Some of the most amazing things can happen when you look at the glowing nose of Rudolf the reindeer. At this speed, scientists say it may not appear red at all (stock photo)
To deliver everything nice and fast, Santa can travel 10 percent of the speed of light – or 66.5 million miles per hour (107 million kmph).
However, at this rate, things would start to get strange for Father Christmas.
Thanks to the theory of special relativity, from Santa’s point of view everything that goes with him looks even better than usual.
Although Einstein predicted that Santa would become more dense as he ran, when he approached the speed of light he would compress his destination – allowing him to easily slide down the chimney.
Dr Katy Sheen, a scientist in the Department of Geography at the University of Exeter, has previously suggested that this could be the reason why Santa is only seen at the same age.
As things are close to the speed of light, time moves slower from their perspective than from ours which means that Santa ages slowly as he travels.
However, thanks to something called the Doppler Effect, a very surprising result could be achieved if we looked at the light from Rudolf’s nose.
This is the same thing that means the siren of an approaching ambulance will sound louder than it would when it is passing.
Doppler effect means that motion changes the frequency of sound waves depending on the direction of motion. This is why the sirens of the ambulances are heard on the ground after they pass us
Thanks to the Doppler Effect, Rudolf appears to have a bright orange nose when he flies towards you and a black nose when he flies away.
As the object moves towards us, the waves are compressed to make the sound louder and as it moves the waves are stretched to make a smaller sound.
The fastest moving objects are the most visible which means that Rudolf’s flight creates a wonderful Doppler effect.
Red light has a wavelength, the distance between one peak and the other, of 694.3 nanometers when the source is at rest.
Flying at 10 percent of the speed of light, we see the light moving in both directions.
Dr Driessen says: ‘At this speed, Rudolph’s nose would have turned bright orange (624 nanometres) as he flew past your house.
And it is redshifted (763 nanometers) as it leaves.
The deepest red eye can see is about 780 nanometers. At this speed, Rudolph’s nose would be black.’
This means that no one in the world can see Rudolf’s red nose.
WHAT IS THE DOPPLER EFFECT?
The Doppler Effect is a well-known physical phenomenon that also appears in astrophysics as the universe expands and ‘redshifts’ but is often seen in sirens.
For example, when a screeching ambulance or a police car zooms by with its sirens on, they appear louder as they approach you and then lower as they pass.
This is due to the compression of the sound waves as they get closer, and they expand as they get bigger.
A stretched sound has a longer wavelength, so it has a lower frequency, which makes the sound louder.
In astronomy, scientists use this to measure the speed of distant stars and planets.
When light sources in space move away from us, their wavelengths are stretched to the red end of the spectrum.
Similarly, when something moves towards us the light is compressed and the light moves to the blue side of the spectrum.
By looking at this red and blue transition, we can tell how something is going on in the world.
For example, by measuring the redshift of the most distant sky, the Hubble Space Telescope and the James Webb Space Telescope have helped to determine how the sky is expanding.
Astronomers have also used this to determine if a star is orbiting another star.
The Doppler effect, or Doppler shift, refers to the change in frequency of any type of sound or light produced by a moving source with respect to the observer.
