silent arc

例句：

1. 1. The arc ofthe moon casts a long shadow acrossthe deserted town.
   月亮的弧线在空旷的小镇上投下长长的影子。
2. 2. The scientist made an observation about thesilent arc of the planet'srotation.
   科学家对行星旋转的无声弧线进行了观察。
3. 3. The team followed the silentarc of the river as it flowed through the forest.
   队伍沿着河流的无声弧线行进，穿过森林。