All around the Arctic, colorful lights appear to be dancing across the sky. Their bright colors attract many people from all over the world, who come to observe and admire the unique lights. This occurrence is known as the Aurora Borealis, or the Northern Lights.

For centuries, groups of people who observed the Aurora Borealis believed that the lights were the work of gods and spirits. Many scientists from the past also made observations of the phenomenon, but the scientific reasoning behind the Northern Lights remained a mystery until 1896, when a Norwegian scientist named Kristian Birkeland proposed a theory about them. He suggested that they were caused by interactions between particles from the sun and the earth’s magnetic field. This was the first accurate explanation of the Aurora Borealis.
What causes us to see these lights? The Aurora Borealis is a result of the reaction between charged particles (particles that carry electricity) from the sun and atoms in the Earth’s atmosphere. Gas particles from the sun are thrown away from the sun’s atmosphere because of its rotation, and they are blown away from the sun and towards the earth because of solar wind (a constant flow of charged particles from the sun). Most gas particles from the sun are turned away by the earth’s magnetic field, but the magnetic field is weaker at the North Pole, so some particles enter the earth’s atmosphere. When these charged particles hit atoms in the earth’s atmosphere, they cause electrons (a charged particle within an atom) to move to a higher-energy state. This happens because the electron is “excited” by an outside energy, which, in this case, is the collision of particles. Eventually, the electrons drop back to a lower-energy state. As the energy level drops, the energy is released as a photon (light). The photons these electrons release is what we see as the Aurora Borealis.

If this is the reason we see the Aurora Borealis, why are there different colors of light? The answer is actually simple: Differences in color come from the types of gas particles colliding and where they collide. For example, a yellowish-green light is produced when gas particles from the sun hit oxygen atoms 60 miles above the earth’s surface. Red light is produced by oxygen atoms around 200 miles above the earth. When gas particles hit nitrogen atoms, blue or purplish-red light is released.

The Aurora Borealis has amazed people for centuries, and they continue to be a wondrous display of vibrant lights. With our knowledge of the science behind them, we have a greater understanding of the interactions between the sun and Earth.