It's a physics toy that demonstrates angular momentum, potential energy, and kinetic energy.

是个物理学家玩具可以演示还有能和势能。

As it did, angular momentum became important.

随着它坍缩，得重要起来。

That's called conservation of angular momentum.

这称为「守恒定律」。

What's neat is that they can maintain angular momentum indefinitely.

最酷是它可以永久性地保持。

Since the angular momentum doesn't change, when the distance increases the velocity has to decrease.

由于，当距离增加时，速度就会小。

More angular momentum means she can make more turns before needing to replenish what was lost to friction.

更多意味着 她可转更多圈 ──在因摩擦力损失，需再补充之前。

Take quantum vortices, which are basically whirlpools of angular momentum in materials like superconductors and superfluids, giving them strange properties.

以子涡旋为例，它基本上是超导体和超流体等材料中漩涡，使它们具有奇特性质。

Well, as a planet orbits the Sun it may not keep a constant speed but it does maintain its angular momentum.

当行星绕太阳运行时，它可能会保持恒定速度，但它会保持。

By bending in the middle and using fast twitch muscle fibers, they can whip around without ever changing their net angular momentum.

透过在身体中断弯曲并使用快肌纤维，它们可以在改其净情况下摆。

But the original star's angular momentum is preserved.

但原星体得以保留。

That's called the conservation of angular momentum.

- 这就是所谓守恒。

It has lots of angular momentum  which causes it to spin.

它具有大，这使其旋转。

This is because of a principle called conservation of angular momentum.

这是因为称为守恒原理。

Basically, an object’s angular momentum describes its tendency to stay rotating.

基本上， 物体描述了它保持旋转趋势。

And we could use photo gates to measure its change in angular momentum.

我们可以使用光电门来测其化。

So their rotation speed slows down to compensate and keep their angular momentum the same.

因此它们旋转速度慢以补偿并保持它们相同。

In other words, when did the moon acquire the exact angular momentum that it has now?

换句话说，月球是什么时候获得了它现在所具有精确？

Because angular momentum must be conserved.

因为必须守恒。

And, like linear momentum, angular momentum is always conserved.

和线性、一样 一直得救。

Yeah, you have to get more angular momentum, like more orbital inner momentum to not fall in.

是，你需要更多，就像更多轨道内能，这样才会掉进去。