Photo of the Day 186

Aurora Borealis, Acadia National Park, Maine, 2005

Photograph by Michael Medford

Nature's light show—aurora borealis—bathes Maine's Acadia National Park in a pink glow. These dazzling patterns in nature, called aurora australis in the Southern Hemisphere, are created when charged particles outside the Earth's atmosphere collide with atoms in the upper atmosphere, producing a glowing display of curtains, arcs, and bands stretching across the sky.

(Photo shot on assignment for, but not published in, "Autumn in Acadia National Park," November 2005, National Geographic magazine)