But if you go to outer space nowadays,

但如今要是你到了外太空
you can find truly inertial frames of reference.

你可以找到真正的惯性参考系
That's the first law.

这就是牛顿第一定律
The first law, if you want to say,

关于牛顿第一定律如果你要问
"What's the summary of all of this?"

"它该如何概括呢"
The summary is that constant velocity doesn't require anything.

概括起来就是匀速运动并不需要任何外力
The reason it looks like a tautology,

其原因听起来像是绕圈子
because you look around,

因为你看看四周
nothing seems to have its velocity forever.

似乎一切都不可能永远运动下去
Then you say, "Oh, that's because there's a force acting on it."

然后你就说 "那是因为有力作用在上面"
It looks like a tautology because you're never able to

这听上去像个死循环因为你不可能
show me something that moves forever at a constant velocity,

找到永远匀速运动下去的物体