In much of the animal world, night is the time set aside for sleep.

在许多动物世界里，夜晚是用来睡觉的。

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When they sleep, they seldom lie down and sleep for minutes at a time, since it's difficult for them to get up again and it's dangerous in the wild.

当它们睡觉的时候，它们很少躺下来一次睡上几分钟，因为它们很难再起来，在野外这是很危险的。

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If you go to a sleep away camp for the first time, you'll feel excited and maybe a little nervous.

如果你是第一次露营，你会感到兴奋，也许还会有点紧张。

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Studies have shown that over time, most humans need eight to eight and a half hours of sleep for the best health.

VOA: special.2009.08.26

The next time you think about going without sleep, consider this: Laboratory animals that are kept awake for long periods of time ...die.

VOA: special.2009.08.26

Sometimes people sleep for a short time during the day.

VOA: special.2009.09.27

For Betty White, finding the time to sleep is the challenge.

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It would allow machines to "sleep" for much of the time to conserve their batteries for up to 10 years.

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By the time you arrive back in your room, the futon mattresses have been carefully laid out for a good night's sleep.

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