July 30, 2016
When you were born, the Sun rose on a world that had never seen you before. Since then, every dawn has arrived in a universe subtly altered...
Ripples Through a Dark Sky
Birthday · July 30, 2016
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APOD published July 30, 2016. Credit: Clear Skies. A publication-date match, not a photo taken on your date. Independent of NASA.
Sunlight ripples through a dark sky on this Swedish summer midnight as noctilucent or night shining clouds seem to imitate the river below. In fact, the seasonal clouds often appear at high latitudes in corresponding summer months. Also known as polar mesospheric clouds, they form as water vapor is driven into the cold upper atmosphere. Fine dust supplied by disintegrating meteors or volcanic ash provides sites where water vapor can condense, turning to ice at the cold temperatures in the mesosphere. Poised at the edge of space some 80 kilometers above, these icy clouds really do reflect sunlight toward the ground. They are visible here even though the Sun itself was below the horizon, as seen on July 16 from Sweden's Färnebofjärdens National Park.
Image credit: Clear Skies