But we all know

但我们都知道
that the reason things come to a halt when you push them is,

推完之后会停下来的原因就是
there eventually is some friction or drag

最后还是有某种摩擦或者拖拽
or something bringing them to rest.

或者别的什么使得物体静止下来
Somehow, if you could manufacture a really smooth frictionless surface,

如果你制造一个绝对光滑无摩擦的表面
that if you took a hockey puck or something

然后在上面放个冰球或者别的什么
and an air cushion and you give it a push,

或者气垫然后推它一下
in some idealized world,

在理想条件下
it'll travel forever.

它会永远运动下去
So it's hard to realize that in the terrestrial situation.

这在现实世界很难实现
But Galileo already managed to find examples

但伽利略已经成功找到了
where things would roll on for a very, very long time.

物体可以运动很长很长时间的例子