Seen as scintillating curtains and swaths of light in the night sky, the aurora borealis ("or northern lights") are most readily visible in the far northern regions of the Earth. (The "southern lights" are called the aurora australis.) Occasionally, a space weather event will cause the aurora borealis to be visible as far south as the continental U.S. Dr. Shane Larson
, research associate professor of astronomy at Northwestern University and associate director of CIERA
, returns to discuss what causes these fantastic displays of lights, what the colors mean, and why they are always changing.