The motor drives a gear at the top of the tail, causing the tail to swing back and forth, which propels the robot upward.

发动机带动机器人尾巴顶部的齿轮，引导尾巴前后摇摆，推动其上升。

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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。

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When the lamp-lighter knocked against them, or the wind blew through the cathedral, they would swing back and forth like pendulums.

当掌灯人碰到那些油灯，或者风吹进教堂的时候，油灯就会像钟摆似的来回摇摆。

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And so it goes, cycle after cycle, as conditions swing back and forth from one extreme to the other.

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The double doors seemed to swing back and forth in the breeze.

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"I've seen the pendulum swing back and forth, and I hope that the successful mission will push it back in the direction of Mars exploration, " Hubbard said.

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