Scientists pinpoint just how 急速な／放蕩な Santa would have to travel to visit every child on the 惑星... and 明らかにする／漏らす why, at this 速度(を上げる）, Rudolf's nose wouldn't be red
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As Christmas approaches, children around the world will be 熱望して を待つing a visit from Santa and his reindeer.
But with around two billion children on the 惑星, Santa really has his work 削減（する） out for him tonight.
Scientists have calculated that Santa would need to travel 89 million miles (144 million kilometres) to 配達する 現在のs to all the good girls and boys around the world.
That is the 同等（の） of 飛行機で行くing his sleigh all the way from Earth to the sun in a 選び出す／独身 night.
ーするために leave some time for 配達するing 現在のs, this means Santa would need to travel at 5.1 million miles per hour (8.2 million kmph), or 0.8 per cent of the 速度(を上げる） of light.
That incredible 速度(を上げる） might also explain why Joly Saint Nick is able to fit his belly 負かす／撃墜する a 狭くする chimney.
によれば Albert Einstein's theory of special 相対性, 反対するs travelling with Santa's sleigh will become compressed in size as they 近づく the 速度(を上げる） of light.
But most strange of all, scientists say that, at this 速度(を上げる）, Rudolf's famous nose wouldn't appear red at all.
Scientists have calculated that Santa would need to cover?89 million miles (144 million kilometres) to 配達する 現在のs to all the children who celebrate Christmas. This is the 同等（の） of travelling almost all the way to the sun in a 選び出す／独身 night (在庫／株 image)?
Dr Laura Nicole Driessen, a 無線で通信する 天文学者 from the University of Sydney, made these festive 計算／見積りs based on a 決まり文句／製法 created by 粒子 physicists from Fermilab in the 1980s.
First Dr Driessen 概算の the number of children that Santa would need to 配達する 現在のs to.
There are だいたい two billion children on Earth, but Christmas is only celebrated in some way in 93 per cent of countries we can assume that seven per cent of children don’t need 現在のs.
But, of course, even の中で those who celebrate Christmas not every child is good enough to 令状 a visit from the man himself.
令状ing for the Conversation, Dr Driessen says: 'We know Father Christmas only 配達するs 現在のs to those who truly believe.
'If we assume the same 百分率 of 信奉者s by age as 設立する in the 部隊d 明言する／公表するs, that leaves us with だいたい 690 million children.'
And with about 2.3 children per 世帯 世界的な, Santa will need to stop at a 最小限 of 300 million homes tonight.
'Spreading those 世帯s 平等に across 69 million square kilometres of habitable land area on Earth,' says Dr Driessen.
ーするために make that 旅行, Santa would need to travel at a 最小限 速度(を上げる） of?5.1 million miles per hour (8.2 million kmph), or 0.8 per cent of the 速度(を上げる） of light. Pictured: The NORAD Santa Tracker?
'Father Christmas has to travel 144 million kilometres on Christmas Eve. That’s nearly the same as the distance from Earth to the Sun.'
That would be a very tall order if Father Christmas only had the 10 hours between 20:00 and 06:00 the next day when children in the UK are sleeping.
Thankfully, he gets a few extra hours thanks to Earth’s rotation.
If the children are 平等に 分配するd around the globe, then Sata has at least 24 hours to travel from the make his way all around the 惑星.
And, with the 11-hour difference in time zones between one 味方する of the world and the other, Santa has a total of 35 hours from the first child 落ちるing asleep to the last waking up.
Dr Driessen says: 'Let’s say Father Christmas uses half his time to zip in and out of each 世帯, which gives him 17.5 hours total or 0.2 milliseconds per 世帯. He uses the other 17.5 hours for travelling between 世帯s.
'My hypothesis is that he needs to travel at a whopping 8.2 million kilometres per hour, or 0.8 per cent of the 速度(を上げる） of light, to 減少（する） off all the 現在のs.'
But if Santa wants some time to eat a mince pie and put his feet up and the end of the evening, Dr Driessen 示唆するs he might have to travel 意味ありげに faster.
Some of the strangest 影響s would occur when looking at the 有望な nose of Rudolf the reindeer. At this 速度(を上げる）, scientists say it might not appear red at all (在庫／株 image)?
To 配達する everything nice and 急速な／放蕩な, Santa could travel 10 per cent of the 速度(を上げる） of light - or 66.5 million miles per hour (107 million kmph).
However, at these 速度(を上げる）s, things would start to get very weird for Father Christmas.
Thanks to the theory of special 相対性, from our 視野 Santa and anything travelling with him would appear to be much skinnier than usual.
Even though Einstein 予報するs that Santa would 伸び（る） more 集まり as he gets faster, as he 近づくs the 速度(を上げる） of light he would get compressed in the direction he’s travelling ? letting him slip 負かす／撃墜する a chimney with 緩和する.
Dr Katy Sheen, a physicist in the 地理学 department at the University of Exeter, has 以前 示唆するd this could also be why Santa always looks the same age.
As 反対するs 近づく the 速度(を上げる） of light, time moves slower from their でっちあげる，人を罪に陥れる of 言及／関連 than in ours which means that Santa would age slower while travelling.
Yet, thanks to something called the?Dopler 影響, the strangest 影響s would occur if we were to look out for the 有望な light of Rudolf's nose.
This is the same 影響 which means that an oncoming 救急車’s サイレン／魅惑的な sounds higher pitched than it does once it has passed.
The Dopler 影響 means that 動議 changes the frequency of the sound wave based on the direction of 動議 of its source. This is why 救急車 サイレン／魅惑的なs sound lower after they've passed us
予定 to the Dopler 影響, Rudolf would appear to have a 有望な orange nose as he 飛行機で行くs に向かって you and a dark 黒人／ボイコット nose as he 飛行機で行くs away
As the 反対する races に向かって us, the waves are compressed making the pitch higher and as it moves away the waves stretch out to produce a lower トン.
The faster something is moving the more pronounced this 影響 becomes which means that Rudolf’s breakneck flight will create an extraordinarily strong Dopler 影響.
Red-coloured light has a wavelength, the distance between one 頂点（に達する） to the next, of 694.3 nanometres when its source is at 残り／休憩（する）.
飛行機で行くing at 10 per cent of the 速度(を上げる） of light, we would see this light 転換 radically in either direction.
Dr Driessen says: 'At this 速度(を上げる）, Rudolph’s nose would be blueshifted to 有望な orange (624 nanometres) as he was 飛行機で行くing に向かって your home.
'And it would be redshifted to a very dark red (763 nanometres) as he was moving away.
'The darkest red human 注目する，もくろむs can see is around 780 nanometres. At these 速度(を上げる）s, Rudolph’s nose would be almost 黒人／ボイコット.'
That means no one on Earth would ever really get to see Rudolf's famous red nose.
WHAT IS THE DOPPLER EFFECT???
The Doppler 影響 is a 井戸／弁護士席-understood physical 現象 which is also seen in astrophysics as the universe 拡大するs and creates 'redshifting' but is more 一般的に seen in サイレン／魅惑的なs.
For example, when a blaring 救急車 or police car shoots past with its サイレン／魅惑的なs on, they seem high-pitched as they approach you and then lower-pitched as they 速度(を上げる） past.
This is 予定 to the compression of sound waves as they come closer, and they then stretch out as they grow more distant.
A stretched-out sound wave has a greater wavelength, and therefore a lower frequency, resulting in an ますます lower pitch.
In astronomy, scientists use this 影響 to 手段 the 速度(を上げる） of distant 星／主役にするs and 惑星s.
When light sources in space move away from us, their wavelengths are stretched out into the red end of the spectrum.
Likewise, when something is moving に向かって us the light wave is compressed and the light 転換s に向かって the blue part of the spectrum.
By looking at this red and blue 転換, we are able to work out how something is moving 親族 to Earth.
For example, by 手段ing the red-転換 of distant supernovae the Hubble Space Telescope and James Webb Space Telescope have helped to calculate how 急速な／放蕩な the universe is 拡大するing.
天文学者s have also used this 影響 to work out whether a 星／主役にする is 軌道ing another.
The Doppler 影響, or Doppler 転換, 述べるs the changes in frequency of any 肉親，親類d of sound or light wave produced by a moving source with 尊敬（する）・点 to an 観察者／傍聴者
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