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  • The Aurora Borealis, otherwise known as The Northern Lights are one of nature’s most

  • beautiful displays of omnipotence. Despite what its name suggests, The Northern Lights

  • can be seen almost anywhere in the world, even as far south as the equator. The phenomenon

  • has been witnessed in Honolulu and Singapore. However, sightings that far south are extremely

  • rare, it’s most commonly witnessed within the Arctic Circle. The South Pole also has

  • its own version of the Aurora Borealis, called the Aurora Australis. And Earth isn’t the

  • only planet with aurora, you would witness a similar phenomenon if you were to stand

  • on Jupiter or Saturn. Uranus has aurora too, but unlike the other planets with their wave-like

  • aurora, the aurora on Uranus would look like glowing dotsand yes, I am talking about

  • the planet. But what exactly causes these mysterious light shows? Let’s find out.

  • Some Inuit believe that the spirits of their ancestors can be seen dancing within the lights

  • of the Aurora. The Vikings believed that the Aurora was a bridge of fire to the sky, forged

  • by the gods. Well, spoiler alert, according to modern science, the northern and southern

  • lights are not dancing spirits or a bridge of fire. They are actually caused by something

  • much more tangible, the Sun.

  • Our Sun is a 4.57 billion-year-old ball of hydrogen and other gasses fusing away in space,

  • 150 million kilometres away from planet Earth. And every once in a while it kicks up a bit

  • of a storm, a Solar Storm to be precise. The Sun produces energy by smashing hydrogen atoms

  • together in its core, under such immense temperatures and pressures, to cause the hydrogen atoms

  • to fuse, to form helium atoms. This process is known as nuclear fusion. When atoms are

  • under these kinds of pressures they turn into a mushy soup of freely moving particles, which

  • is a fourth state of matter known as plasma. The Sun is essentially a gigantic ball of

  • swirling plasma.

  • Using the process of nuclear fusion, the Sun is able to turn small amounts of matter into

  • enormous quantities of energy. It’s how the Sun has managed to keep producing energy

  • for billions of years without running out of fuel. If human-kind were able to consistently

  • replicate nuclear-fusion here on Earth, we would be able to make almost infinite amounts

  • of energy, using relatively little resources. In fact, if you could convert the mass of

  • one bag of sugar into energy it would be enough to drive a car, non-stop, for 100,000 years.

  • All this plasma swirling around within the Sun generates huge magnetic fields. These

  • magnetic fields are under such immense pressures within the Sun, that sometimes the lines of

  • force of theses magnetic fields meet. When this happens, the magnetic field is forced

  • outwards, towards the surface of the Sun. Once it reaches the Sun’s surface it ejects

  • outwards into space at great speeds, taking extremely hot gasses and charged particles,

  • also known as plasma, with it. This is known as a solar flare and they can be witnessed

  • on the Sun’s surface as a very bright spot followed by a cloud of gas. When a very large

  • solar flare occurs containing a significantly huge amount of energy, it is referred to as

  • a Coronal Mass Ejection or CME for short. The gas clouds produced by a CME can sometimes

  • be larger than the Sun itself.

  • CME’s and solar flares don’t stop just outside the Sun’s surface. Charged particles

  • ejected from the Sun continue to travel outwards through space over enormous distances. After

  • travelling through space for around two days they will reach planet Earth. This is known

  • as the solar wind and it can be extremely dangerous. If the magnetic field released

  • from a solar flare or CME were to hit planet Earth it could cause the extinction of the

  • human race. So why hasn’t it? After all solar flares are taking place regularly on

  • the Sun’s surface.

  • Well the solar wind does actually hit Earth, often, but our trusty planet is well-prepared.

  • We have a defence system to protect us from the huge amounts of energy the Sun bombards

  • us with on a daily basis. Just like the Sun, the Earth produces its own magnetic field.

  • At the Earth’s core is a ball of solid iron, the heat of this iron turns the surrounding

  • outer core into flowing liquid iron. The movement of this outer liquid core produces a magnetic

  • field, that, luckily for us, encompasses the Earth.

  • The Earth’s magnetic field protects us from all sorts of harsh destructive forces that

  • come from far away in space, including solar flares. This protective barrier is called

  • the Earth’s magnetosphere and it extends thousands of kilometres into space. That sounds

  • large, but it’s actually rather modest, Jupiter’s magnetosphere extends over seven

  • million kilometres into space on each side of the planet. In fact, on Jupiter’s nightside,

  • the side facing away from the Sun, the magnetic field which is emitted is so large, that it

  • reaches Saturn.

  • Anyway, back to Earth. Most of the Sun’s solar winds simply bounce off the Earth’s

  • magnetosphere when it reaches us. However, the magnetosphere has two weak spots, at the

  • north and south poles. At these two locations the magnetic fields which protect planet Earth

  • are much less prevalent than nearer the equator.

  • This means that a very small percentage of the charged particles that come from the Sun

  • do make their way into the Earth’s atmosphere via the two weak spots at the poles. When

  • this happens the electrons in the solar wind collide with oxygen and nitrogen atoms in

  • the Earth’s atmosphere. During this interaction energy is transferred from the atoms in the

  • solar wind to the Earth’s oxygen and nitrogen atoms. Raising these atom’s energy states

  • and exciting them. When an atom gets excited its electrons move into an orbit further away

  • from the nucleus.

  • These newly excited atoms need to release this new found energy tocalm themselves

  • downand return to their baseline energy state. The oxygen and nitrogen atoms release

  • this energy in the form of particles of light or photons. The light they give out is what

  • we call the aurora. This process of exciting atoms to cause them to release energy in the

  • form of light is the exact same way that neon lights work. The aurora are simply mother

  • nature’s neon lights, executed on a far grander scale. The only difference is that

  • nature uses this phenomenon in a far subtler way than to advertise strip bars.

  • The aurora typically appears in vast curtains or waves of light following a distinct line

  • across the sky. They appear this way because they are following lines of force in the Earth’s

  • magnetic field. Yep, that’s right, the aurora uses the force.

  • The different colours of the aurora are caused by different gases in the atmosphere. Each

  • gas emits a unique colour when it is excited. For example, oxygen gives off a green light

  • when it’s excited, which is the most common colour seen in the aurora. Nitrogen on the

  • other hand, gives of blue and red colours when excited.

  • So to summarise, when charged particles released from the solar flares on the Sun’s surface

  • hit our planet at either the north or south pole, they interact with atoms in the Earth’s

  • atmostphere. Causing their electrons to move to a higher energy state. When the electrons

  • drop back down to a lower energy state they release photons, tiny little particles of

  • light, which light up the night’s sky in a spectacular display of painted waves, following

  • the natural magnetic field lines of planet Earth.

  • Knowing how the aurora are formed may spoil the beauty for you, but I believe there’s

  • an even greater beauty in understanding the science behind one of nature’s most breathtaking

  • performances. So if youre ever lucky enough to experience the aurora for yourself, just

  • take a moment to contemplate on how truly marvellous and magnificent the universe really

  • isand then take selfies.

The Aurora Borealis, otherwise known as The Northern Lights are one of nature’s most

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オーロラの原因は? (What Causes the Northern Lights?)

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    Pucca Shen に公開 2021 年 01 月 14 日
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