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7 Wonders of the Natural World

Aurora Borealis (Northern Lights)

The aurora borealis (also called the northern lights) consists of awe-inspiring twirls of light in the sky, caused by "solar wind" -- electrically charged particles interacting with Earth's magnetic field. The aurora borealis can be up to 2,000 miles wide, but it fluctuates in size, shape, and color, with green being the most common color close to the horizon while purples and reds appear higher. Named after Aurora, Roman goddess of dawn, and Boreas, Greek god of the north wind, these ribbons of color are best viewed in northern climates like Alaska but have been seen as far south as Arizona.