Exeter, Devon UK • Jul 13, 2024 • VOL XII

Exeter, Devon UK • [date-today] • VOL XII
Home Science The Truth Behind The Aurora Borealis

The Truth Behind The Aurora Borealis

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Anyone who has ever seen the Aurora Borealis (the northern lights) or even their star crossed lover the Aurora Australis (the southern lights) will tell you just how magnificent they are. They can stretch across the entire horizon and illuminate the night’s sky from up to 650km up. These wonderful displays are one of the few exceptional sights mother nature lets us in on. But possibly since the first recorded sighting of the lights in China, all the way back in 2600 B.C. we haven’t simply content with watching, we have sought to understand them.

Throughout history the lights have been marvelled at and people have tried to explain them in countless ways. They are sited in ancient folk tales and legends as signs that foretell the coming of this that or the other, my favourite being that they are said to simply be a good babysitter, used to this day to scare poor Norwegian children into not staying out too late for fear of the Aurora. I cannot speak for divine intervention or even ancient cosmic babysitters but I can offer an explanation of the lights that is accepted by the scientific comminuty and by philosophers alike.

perhaps the closest thing we might get to stardust

It all starts hundreds of millions of miles away, at the sun. The sun’s outermost layer, called the corona (not named after the beer unfortunately) as you can imagine gets extremely hot, reaching on average two million degrees Celsius. At this temperature the particles in the corona layer, mostly ionised hydrogen, have so much energy that the sun’s gravity can’t hold them in and they break out of large holes in the sun’s atmosphere known as corona holes or sunspots.

In giant clusters the cumulative energy of these charged particles is astronomical and they fly uncontested through space in all directions at speeds of around five hundred miles per second as what is known as solar winds or more dramatically a solar storm. When these charged particles reach the earth they encounter its magnetic field, a shield around the planet which tirelessly protects it from cosmic events such as this.

Should the charged particles ever reach the earth’s surface the radiation would do severe damage to all life on earth. It wouldn’t even make a good disaster movie because if the magnetic field failed or these particles found a way through, it would be completely irreversible, once we lose that shield we’d lose. So thankfully the charged particles are mostly deflected from the earth by the magnetic field.

However, the field is weak at the north and south poles and so at the poles some particles do get through. From there they are accelerated along the magnetic field lines toward the poles and are funnelled into the earth’s atmosphere. Once they are inside the charged particles collide with the gasses that have accumulated in the atmosphere, mostly oxygen and nitrogen molecules.

Aurora Borealis at a Pole. Source: wikimedia.org

The wealth of energy released from these collisions is what you see when you look at the auroras, energy in the form of visible electromagnetic waves, light. Different molecules and varying heights create different colours, colliding with low oxygen molecules creates the vibrant and most common green, higher oxygen molecules create the deep and exciting reds while nitrogen is responsible for the more mystical and enchanting blues and purples.

So, the Aurora Borealis we’ve all seen or heard about somewhere is simply millions upon millions of charged particles, perhaps the closest thing we might get to stardust, colliding with molecules in the atmosphere to release energy in the form of electromagnetic waves that paint the sky with ecstatic colour. Creating possibly the greatest light show on earth.

There is little more to learn about the Auroras; the science is sound and the results exciting. The only thing we don’t know is how to pin point and predict them. The light itself is created by the release of energy and you can’t exactly track an energy as common as visible light.

the first recorded sighting of the lights was in China, 2600 B.C.

So if you’re thinking of booking a holiday, go for the destination and not just for the lights. There are places where sightings are common, reindeer herders in Norway have said that it’s just like the snow or the rain, it’s a normal occurrence. Yet no one knows exactly when it will happen. I’d advise you to go very far north or very far south, away from any light pollution at a time where the sun is very active.

The sun goes through an activity cycle every 11 years where it’s activity is at high or low points, where it exhibits larger or smaller amount of solar activity). We know that it’s on a come down at the moment so the next best time to try and see it at ists best will happen in 2024. Just make sure that’s the first thing you put into your IPhone 16S. And do see it at some point. Its a wonder of the world that simply can’t be put into words.

If you would like to read more about space type things then try this article where Holly Belcher discusses a TED talk about the possibility of future generations living on Mars.

Or this one where Rhys Davies talks about the developing tech for a manned mission to Mars.



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