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

是个物理学家的玩具可以演示角动还有动能和势能。

As it did, angular momentum became important.

随着它的坍缩，角动变得重要起来。

That's called conservation of angular momentum.

这称为「角动守恒定律」。

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

最酷的是它可以永久性地保持角动。

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

由于角动不变，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.

更的角动意味着 她可转更 ──因摩擦力损失动，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角动的漩涡，使它们具有奇特的性质。

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，它可能不会保持恒定的速度，但它的角动会保持不变。

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

透过身体中断弯曲并使用快肌纤维，它们可以不改变其净角动的情况下摆动。

But the original star's angular momentum is preserved.

但原星体的角动得以保留。

That's called the conservation of angular momentum.

- 这就是所谓的角动守恒。

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

它具有的角动，这使其旋转。

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

这是因为称为角动守恒的原理。

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

基本上， 物体的角动描述了它保持旋转的趋势。

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角动的变化。

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

因此它们的旋转速度慢以补偿并保持它们的角动相同。

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所具有的精确角动的？

Because angular momentum must be conserved.

因为角动必须守恒。

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

和线性动、角动一样 一直得救。

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

是的，你需要更的角动，就像更的轨道内动能，这样才不会掉进去。