See, for a static rod,

对于静态的绳子
got an angular momentum going into the board,

有一个指向黑板里的角动量
it really means it's falling down like this.

事实就是它会这样落下来
But if a rotating gyro got an angular momentum.

但如果旋转的陀螺得到一个角动量
On top of an existing angular momentum,

在已有的角动量之上
then the new angular momentum is now just a rotated angular momentum.

新的角动量就是现在的旋转角动量
So, when seen from the top,

所以从上面看下去
the gyro will be doing what's called a "precession".

陀螺做的运动称为"进动"
If you support it,

如果你固定住它
it will just slowly go round and round with this tip here.

它就会绕着这个尖端一圈一圈地转
Now, does this remind you of anything you have seen before?

这个有没有让你想起之前遇到的情况呢
Yep.

请讲