[philomathdan]

Becoming an expert in one thing takes a lot of time and effort, and this must be maintained even after reaching the goal. But getting a reasonable understanding of many things is not too bad. E.g. working through a freshman level physics text will give you a pretty good (or above average, at least) understanding of the field of physics, and this could be done in a span of months. Maybe try something like this for one subject after another. It could be that this amount of knowledge satisfies you for a given subject and you don't need to go further. But if it doesn't satisfy you, move on to more material. If there really are things you want to spend the time and energy on to reach expert level, you will naturally find them this way. And I suspect that list of things will be a lot smaller than when you started.