爸爸你真酷，虽然你很笨，但是当我需要你时，你总能照顾我。

Dad you're cool, because although you are silly, you always look after me when I need you.

youdao

在我最需要你时，却哪儿都找不到你。

When I needed you the most, I could not find you anywhere.

youdao

就当我最需要你时，你却离开了我。

You left me just when I needed you most.

youdao

It is true mathematically, you can add two numbers, but you've got to ask yourself,"What am I doing as a physicist when I add these two numbers?"

在数学上它是正确的,你可以引入这两个常数,但是你需要问问自己,当我引入这两个常数时,这么做有什么物理意义

耶鲁公开课 - 基础物理课程节选