It is the change to darkness in the sky.

天空这变化意味着要进入黑暗。

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In humans melatonin levels rise at night, in response to darkness and cues from the circadian clock.

人类的褪黑激素水平在夜晚上升，以响应黑暗和昼夜节律钟发出的信号。

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As dusk turns to darkness, álvares snaps on an infrared headlamp and we continue hiking into the hills.

夜幕低垂，黑暗即将来临。阿尔瓦雷斯打开红外探照灯，继续我们山中的远足。

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Deep into that darkness peering, long I stood there wondering, fearing,Doubting, dreaming dreams no mortal ever dared to dream before;

VOA: special.2010.10.31

They're not bidden to be cast out in to utter darkness where there's weeping and gnashing of teeth.

没有因为无所事事而受惩罚,他们没有被罚去充满哭泣声和牙齿的无尽的黑暗里。

耶鲁公开课 - 弥尔顿课程节选

He dug deep into the darkness, hitting the steel so hard that his body began to fail him.

VOA: special.2009.02.21

Due to darkness, eight golfers were unable to finish their first rounds, and will complete them on Friday.

BBC: SPORT | Golf | Rose shares lead at Nissan Open

But the effort was called off Friday due to darkness, and the team will try again on Saturday, Guerrero said.

CNN: STORY HIGHLIGHTS

"The overall effect is not going to be turning a light switch off" and banishing the entire US to darkness come the stroke of midnight, says Memo Diriker, director of the European-American Business Institute at Salisbury University.

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