Why does the shape of the moon change regularly?

为什么月亮的形状会有规律地变化？

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The changing position and shape of the moon was easier for them to observe.

改变位置和形状，月亮是他们较容易观察。

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Of course we call that shape of moon a crescent moon and of course the words crescent and croissant are really two flavors of the same word;

当然，呈现出这个形状的月亮常常被我们称为一轮crescent moon。而单词crescent与croissant的确是同一个单词的两种表现形式；

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Then they dissolve into nothing, only to form as if by stealth on a different horizon, dancing across the sky in the shape of a sea horse or crescent moon.

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The consortium tested the practicalities of using a printer on the Moon by setting up a D-shape 3D printer, which are used to print very large house-sized structures, in a vacuum chamber with simulated lunar material.

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