1 sentence

1. 想象一组嵌套的圆柱体，以不同的速度旋转。

   xiǎng​xiàng yī zǔ qiàn​tào de yuán​zhù​tǐ, yǐ bù​tóng de sù​dù xuán​zhuǎn.

   Imagine a set of nested cylinders, rotating at different speeds.

   Source: CCMatrix