In our last post we took a deep dive into the ocean to find the black dragonfish – an animal that can glow bright red – in the search for the secret behind Rudolph’s red nose. That post was the first of four festive questions posed to us this Christmas. The second is this: Why would Rudolph being a red nosed reindeer actually help Santa?

The story we all know

The story goes that Santa had eight reindeer to help pull his sleigh through the air. You know the ones – Comet, Cupid, Donner, Blitzen, and then the last reindeer was apparently called Etcetera. They helped Santa pull his sleigh on Christmas Eve year after year with no problems until one night… one foggy night… Santa couldn’t see where to go.

When you have as many deliveries to make as Father Christmas does in one night, not being able to see is a massive problem! We’ve calculated all those stops in a Boom Advent post all about Santa’s diet on Chrismtas Eve – you can read that here.

Santa standing next to famous world buildings - the Eiffel tower, the Shard, and the Empire State building.
In our Boom Advent article we worked out how much weight Santa would gain by eating all the mince pies left out at all the stops he has to make to deliver presents for Christmas. It was a lot!

To help get through the foggy night and still deliver the presents to all the kids on the nice list, Santa needed the extra help of a special red nosed reindeer – Rudolph. After that, apparently, all the reindeer loved him and shouted out with glee (yipee). So what about this glowing red nose is so helpful?

view of cityscape
Photo by Aleksandar Pasaric on

Seeing through fog

Normally the furthest we would be able to see is limited by the curvature of the Earth. We keep looking out in one direction in a straight line but the Earth ‘drops’ away from that line as it curves around in a gigantic ball, so soon enough we can only see things that are really tall (since they can poke up above the horizon still) and nothing on the ground.

Those would be perfect conditions – with light easily being able to get through the air and reaching our eyes. That might be light from the sun bouncing off an object and then reaching our eyes or a lightbulb shining directly towards us.

ozone layer protect from uv sunlight
Light from the Sun illuminates a lot of things around us but it has to get here first. You can read more about this in our Ozone article.

But the air around us can change – by smoke, extremely hot temperatures, sand from a desert or ash from a volcano, or by lots of tiny water droplets being whipped up into the air like clouds that have fallen to the ground. These ground clouds – blankets of tiny water droplets in the air – are what we call fog. Now light that tries to travel through the air bounces off these droplets and gets scattered. The light finds it difficult to get through and that makes it hard for us to see things through the fog.

An erupting volcano
An erupting volcano kicks lots of ash into the air and this can cause problems for pilots.

We can’t rely on just being able to see things based on light from the sun reaching the object, bouncing off, and then reaching out eyes in these conditions. Another problem for Santa is that he flies the sleigh at night, so there isn’t any light from the sun to rely on in the first place!

Drivers on the road can switch on their fog lights to help other drivers see them. This way, instead of waiting for light to get to a car from the sun, bounce, and reach the driver, light is coming directly from the car itself. That makes it far easier to spot the car through the clouds and avoid it.

A driver who can’t see through the fog may be tempted to turn on a brighter light to help them see further. This can actually make things worse though – since the light can bounce back from the fog droplets and into the driver’s eyes. We call this glare. What you need to be able to see is the road right in front of you – not necessarily two miles down the road!

street lamp over street at night
Photo by Green_grey Darya on

Fog lights are cleverly designed to shine the light downwards towards the ground in a thin strip. Imagine taking a torch and putting a piece of thick black tape over the top and bottom of the torch light – leaving only a rectangular strip in the middle. Now you’ll get a rectangular beam of light shining out. Instead of lighting up absolutely everything and spreading the light out everywhere – for it to potentially bounce back off all the droplets – you have a focused beam that you can direct just where you need it. This is exactly what fog lights are designed to do.

Santa’s Sleigh

But Santa flies through the night with Rudolph the red nosed reindeer on Christmas Eve when surely no one else is around… So why does he need the big red light? Well, it’s probably less about warning other drivers of magical sleighs that he is there and avoiding a crash, and more about finding his way to all the houses in the world.

If you wanted a light to help brighten up the night sky and help you spot things through the snow, you need to pick the right light. There are lots of wavelengths of light, all of them do slightly different things. You can check out another Boom Advent post that asks the question ‘What is Colour?’ to find our more about that. Within the colours that our human eyes can see – blue through to red – red light shines through the fog the best. Blue light can get scattered and spread out slightly more than red light does!

The spectrum of visible light.

This means that if Rudolph’s job is to light up the ground in front of the sleigh so that Santa can see where to go, he needs the perfect light. If it’s too bright it will reflect back off the fog and cause glare. If it’s the wrong colour, it might get scattered by the fog and not help Santa see.

Luckily, Rudolph the red nosed reindeer has the perfect beacon out in front to guide the sleigh’s way.

A reindeer with a big shiny nose!



2 Responses

Leave a Reply

%d bloggers like this: