If you could move at the speed of light, your time would stand still, if you could move faster than light, your time would move backward.
如果你能以光速运动，你的时间就会静止不动；如果你能以快于光速的速度运动，你的时间就会倒退。
The final step came when steam was introduced into the cylinder to drive the piston backward as well as forward, thereby increasing the speed of the engine and cutting its fuel consumption.
最后一步是将蒸汽引入气缸，使得活塞前后推动，从而提高了发动机的速度，降低了燃料消耗。
Hummingbirds are well known for their wing speed and ability to hover and fly forward and backward with more precision than a helicopter.
众所周知，蜂鸟的翅膀拍打速度极快，它即可以凌空悬停，也可以快速向前飞行和向后飞行，其飞行的精准度甚至超过了直升机。
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