Bats have an engineering problem: how to find their way and find their prey in the absence of light.

蝙蝠们遇到了一个技术上的难题：如何在没有光线的条件下认路和捕食。

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Darkness is the absence of light.

黑暗就是没有光亮。

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Black is an absence of light, so it is not in the rainbow.

黑色是光所缺乏的颜色，因此它不在彩虹里面。

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Face it, it's difficult to use light to display the absence of light!

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In the absence of light, life in dark waters can also depend on organic substances dead or alive reaching the depths of the ocean.

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That's a murkiness of purpose, not an absence of light.

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