The Different Levels of Knowledge

There are different levels. So the crudest level is you learn there's a thing called a piano and there are notes. And in principle that gives you the ability to play anything. But the ability to do it fluently and integrate a lot of information and real time, that's different. The same way in physics. There are different levels you can understand basic things about the physical world. You can understand them from different perspectives. If you want yourself to make a contribution to pushing the frontiers, that's a different thing. Then you really have to command the subject and have confidence that you can do calculations  and understand how things will work if you change them.