Waves in the Sky

The mysterious night-shining clouds known as the Noctilucent clouds or NLCs appear in this late summer evening of Sweden. They lie near the edge of space, reflecting sunlight from about 80 kilometers above Earth’s surface. They are usually spotted above the Polar Regions in summer. Click on the second photo to see a closer telephoto view of the NLCs wave-like pattern. © P-M Heden