On cloudy days or at night it was impossible to tell the time with a sun clock or a sundial.

在阴天或晚上，无法用太阳钟或日晷看出时间。

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About 5,500 years ago, the Egyptians invented the sun clock.

约5500年前，埃及人发明了太阳钟。

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For instance, if a homing pigeon is to navigate with its Sun compass, its clock must be properly set by cues provided by the daylight/darkness cycle.

例如，如果一只信鸽要用它的太阳罗盘进行导航，它必须根据日光/黑暗的循环所提供的线索正确设置时间。

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And some designs provide power round the clock, not just when the sun is shining, by storing energy in the form of molten salt.

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With an accurate clock, you could take a reading from the sun at noon and figure out your longitude.

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"You wake up in the morning at about 5 o'clock ... and then you watch the sun rise and this extremely peaceful and serene atmosphere and then you just look at the sun coming like a ball of fire, rising from the sand and then coming up, " recalls Jibunoh.

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