Like magic out of a Harry Potter novel, such a metal could contract on command, or swing back and forth like a pendulum.

像这种仿佛出自《哈利·波特》小说中的魔法一般的金属可以按照指令收缩，或者像钟摆那样前后摇摆。

youdao

I am like a pendulum that does not swing.

我仿佛一只已不再动的钟摆。

youdao

The concept had been deemed too hard to control: the rover would swing like a pendulum as it flew, and its radar was too inaccurate to find safe anchorage.

NEWYORKER: The Martian Chroniclers