如果太阳只发出很小一点的光，并且地球周围不存在大气层，那么在春分这天，昼夜等长，都是12个小时。
If the sun were just a tiny point of light and Earth had no atmosphere, then day and night would each be exactly 12 hours long on a spring equinox day.
一般文献所给出的四点吊桩的吊点布设是以吊索等长为前提的。
The arrangement of four lift points to hoisting a pile, as given in general technical literature, is on the premise of slings with equal length.
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