photo #9381969

Night had already reached Lake Vesijärvi in southern Finland when Arvi Orell (Member 51,853) looked out from his summer cottage in Kangasala. But in the upper reaches of the atmosphere above him, the day was not quite over.These were noctilucent clouds, whose tiny ice crystals form at altitudes of around 50 miles (80 kilometres), high enough to catch sunlight long after the Sun has dipped below the horizon for those on the ground. The silvery-blue ripples of Arvi’s ‘night-shining’ clouds spread across the darkening sky as the last light lingered on the still lake below.