Career path

I just read Career advice for engineers, and there’s one piece very impressed me:

I don’t do any career goals or anything like that. I try and do things that are a) interesting to me and b) that the world needs.

To me a) is easy, but b) is not. What do we need actually? Is it another IM, a faster browser, or a nuclear fusion reactor? I guess it is the reactor, it’s something not every people think about but we humanity are going to need to move further.