水平如镜。

The water was as smooth as glass.

《牛津词典》

为了测量两极之间的高程差，测量员在两极中间的一个水平基座上使用了光学水准望远镜。

To measure the difference in elevation between poles, surveyors used an optical level—a telescope on a level base—placed halfway between the poles.

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这些炙热、年轻的恒星构成了这幅NASA斯皮策太空望远镜所摄宇宙图像中的风景。 年轻的恒星看上去忽明忽暗，这是由于恒星表面冷点、热点的转换所造成的亮度水平的改变。

The young stars dip and peak inbrightness; shifting cold and hot spots on the stars' surfaces cause brightnesslevels to change.

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