If you have ever visited anywhere with high latitudes near the North or South Pole, you may have seen the sky lit up by magical, beautiful lights. At the North Pole, this is referred to as the ‘Northern Lights’ or the ‘Aurora Borealis’, which means ‘northern dawn’.
In Inuit cultures, it was originally believed that these lights were caused by spirits of ancestors that were dancing through the glistening lights in the night sky. In Norse mythology, the Aurora Borealis was believed to be a fiery bridge that was built across the sky by the Norse gods. With modern science, however, we have a much better understanding of the Aurora Borealis today. So what exactly causes the Northern Lights?
The Northern Lights are caused by activity from the sun. While most people think of the sun as just emitting light or heat, there is actually a lot more happening on the surface. As gasses burn at millions of degrees within the sun, there are huge storms that emit charged particles—such as electrons—through space. Some of these particles fly directly from the sun to Earth.
When these highly charged particles from the sun hit molecules in the Earth’s atmosphere, such as oxygen or nitrogen, it causes the particles to become filled with energy. When this happens, the particles quickly try to return to a state that isn’t highly energized. To do this, the energy is released from the molecules as a photon of light. When millions of photons of light are emitted at the same time, it causes the sky to light up and creates the Aurora Borealis.
The Earth acts as a giant magnet. It also has a magnetic field. This field has two poles just like a magnet: north and south. When electrons fly through space, two things can happen: they are reflected away by the Earth’s magnetic field, or they follow it to the poles.
Because the magnetic field is weaker at the poles, the electrons are able to freely enter the atmosphere without being reflected away. The strong magnetic field covering the rest of the Earth is what prevents similar effects from happening elsewhere.
If you have ever seen the Aurora Borealis, you have likely seen it displaying a rainbow of colors ranging from green, yellow, blue, purple and red. The colors of the Northern Lights are determined by the types of molecules in the atmosphere.
The most common molecule to become energized is oxygen that hovers about 60 miles above the Earth’s surface. When these oxygen molecules release photons, the light appears green. This is why most of the time the Aurora Borealis is mostly green. Oxygen that is much higher up in the atmosphere, around 200 miles above the Earth’s surface, causes red light to be emitted. When nitrogen molecules emit photons, it causes a blue or purple Aurora Borealis.
The Aurora Borealis is one of nature’s most splendid and wonderful spectacles to see. When planning your next vacation destination, consider taking a trip out to Alaska, Iceland, or Norway to experience the Aurora Borealis in all its glory. The best time to catch a glimpse of this light show is between 10PM and 2AM. Just make sure there are no clouds and don’t forget to bring your down jacket, because it can get quite cold, especially at night!