The Aurora Borealis, better known as the northern lights, has amazed humans for millennia, but do you know its history or how it happens?

Before we understood how the northern lights worked, people around the world created myths about how it happens. People sometimes interpret the lights as celestial fires, spirits of dead people or divine warriors.

In actuality, the northern lights work something like this.

The sun is always emitting a stream of charged electrons and protons, this is called a solar wind. When the sun emits a burst of these charged particles, it is called a solar flare. The solar flare travels to Earth’s magnetic field. Most of the particles get bounced off, but in polar regions, where the magnetic field is weaker, the particles of charged electrons and protons can escape into the atmosphere. There, those charged particles transfer their energy to oxygen and nitrogen. The oxygen and nitrogen then release this energy, often in the way of light. That released light is the northern lights.

Norwegian physicist Kristian Birkeland first found out how and why the Aurora Borealis happens. In 1899, he built the first northern lights observatory on top of Mount Halde in Norway. The observatory closed after a couple decades because living there meant having to endure the cold weather and snowstorms. The researchers decided to move to Tromso in 1926 and began a new research lab there. Still, the original observatory remained on Mount Halde until it was destroyed by the Nazis during World War 2. In the 1980s, the lab was rebuilt and still stands today.

“History lives on our premises,” said Hakon Haldorsen, the founder of Friends of Haldetoppen, a historical society. “If we don’t take care of the building, no one will find the story.”

While Kristian Birkeland and his helpers were in Tromso and Mount Halde, they learned about how different colors occur; The different colors in the northern lights depend on which gas the protons and electrons hit and how high up it is in the atmosphere. Green is the most common color to happen. It is produced by oxygen about 100–250 km above Earth. Red is created at around 200km to 500km above the earth. Blue light is rare and it is created by electrons and protons bumping in oxygen at around 100km above the air. Combinations of these colors can create yellow and purple, which are much rarer than the other colors.

The northern lights are fascinating, but few people understand it. Dr. Magnar Gellikstad Johnsen said, “To understand the physical nature of things is to understand what happens on the very basic levels.”

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