Why is the sky dark at night?

夜空为什么是黑的？

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Keep your bedroom dark at night and free of all distractions.

晚上让房间保持黑暗、清除所有干扰。

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Havana's once elegant seafront promenade, the Malecon, is now often dark at night because of lack of street lighting.

而由于路灯关闭，哈瓦那一度繁华的海滨大道马雷贡夜间也经常漆黑一片。

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She is easily frightened. For example, she is too chicken-livered to walk down a dark street alone at night.

VOA: special.2010.06.13

First,they don't meet in the daytime; they meet either early before light,at dawn, or after dark,at night.

首先，他们不在白天聚会;,要么在天亮前的黎明，要么在天黑后的夜晚。

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They have meetings at night,in the dark.

他们在夜晚集会。

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"There are still way too many areas in the city that are dark at night, " the mayor said.

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London's smarter streets are dark at night, with the lights on only in the basements where the housekeepers live.

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In Pyongyang, the rhythms of life hark back to a previous century: the city goes dark at night, and the most common way of getting around town is by foot.

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