that if you took the mass of the Earth and mass of the Moon and the apple

如果把地球月球和苹果的质量
and divided by the radius,

代入公式除以半径
you'll get a number

你得到的值
that won't agree with the force of gravity near the Earth as we know it.

和我们所知近地引力的大小是不同的
So the point is,

所以这说明
when a function is proportional to all these things,

如果公式和这些量是成比例的
there is always a proportionality constant.

那就需要一个比例常数
And the constants--

这个常数
One of the purposes of a constant is

常数的作用之一就是
to make the dimensions come out right;

保持量纲一致
the other is to make the values come out right.

另一作用就是使数值正确
Because I got to make sure that

因为我要确定近地条件下