Northern lights originate from the sun. During large explosions and flares, huge quantities of solar particles are thrown out of the sun and into deep space. These plasma clouds travel through space with speeds varying from 300 to 1000 kilometers per second. When they are closing in on Earth, they are captured by Earth's magnetic field and guided towards Earth's two magnetic poles.

When the atmosphere stops the solar particles, they collide with the atmospheric gases present, and the collision energy between the solar particle and the gas molecule is emitted as a photon - a light particle. And when you have many such collisions, you have an aurora - lights that may seem to move across the sky. In order for an observer to actually see the aurora with the naked eye, about a 100 million photons are required.