"Do You Know Everything?"

Er... yes, I have been asked that by high school students and even undergraduate students. What they wanted to know by asking that is whether a physics know everything that was taught in an undergraduate curriculum, and that that information and knowledge is something that a physics can simply dial up whenever he/she wants to.

It's an interesting question, and something that can have a range of answers, depending on the nature of that physicist job. I suppose if you are a university instructor, you will have a very well-honed knowledge of the subjects that you regularly teach. If you are a practicing physicist/research physicist and you don't teach, you probably are well-versed in the subject area that you deal with everyday, but not so much on the other areas. If you are a physicist that has left the field, or don't often make use of the topics that you came across while in college, then you may not be able to dial in such topic.

But the thing I always stress when I try to answer such a question here is that, as physicists, we all share the same basic knowledge. All of us know what Maxwell equations are and had done countless problems in E&M. All of us know what a "Hamiltonian/Lagrangian" are and have equally done numerous problems in classical mechanics. We certainly know what Schrodinger equation is and have an idea of what it can do. Now, we all may not be able to look at an advanced undergraduate mechanics problem and solve it immediately the way we did when we were taking such a class, but given enough time and some refresher activity through our old notes or text, we should be able to solve such a problem again. The point here is that we may not be able to immediately tackle such a problem, but we have that ability and knowledge to solve it if we have to.

So in a sense, we do know everything (almost) that we came across while in college. We may not recall how to tackle them, or what they are right away,  but we have that ability to recall such things given time and effort. As physicists, we share that common knowledge and skill. And one of such skill is the ability to learn, which I consider to be THE most important thing that I learned in being a physicist.

Zz.