After the Sun sets on a summer evening and the sky fades to black, you may be lucky enough to see thin, wavy clouds illuminating the night, such as these seen over Billund, Denmark, on July 15, 2010.

2010年7月15日，丹麦比隆市上空，夏日晚上太阳已经落山，天空渐渐黑下来，人们幸运地看到薄薄的波状云层照亮了夜空。

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In a statement, Copenhagen police said a large group of protesters had organised themselves in a so-called "black bloc", in which they put on masks - an illegal action at a demonstration in Denmark.

BBC: Climate activists condemn Copenhagen police tactics