When you tackle a new problem the hardest part is often just figuring out what you don't know, but need in order to solve the problem. You might find a paper or

When you tackle a new problem the hardest part is often just figuring out what you don't know, but need in order to solve the problem. You might find a paper or book that solves a very similar problem (if you're lucky) but find you just can't understand what you're reading. This is probably because the author assumed his audience would know things you've never even been exposed to. It would be rather hard to write much of anything if authors didn't do this! However, it makes life rather difficult for "foreigners" to the discipline who don't have a good idea of the discipline's city layout and what neighborhoods they need to hang out in to find help. The ideal solution is to get a local guide to help you, but a map of knowledge covering as much of the city as possible would be almost as helpful if it were any good. Unfortunately, mapping cities of knowledge is harder than mapping real cities! It would be utterly fantastic if math (or physics, economics, etc.) books and publications came with associated meta-data that would tell you what dependencies are associated with what you're reading. Ideally, it should be possible to trace the map from string theory right back to counting. This map would be your guide to all the rabbit holes you dive into! It wouldn't perform magic and explain quantum physics to you in a paragraph, but it would give you an idea of how much you don't know and where you need to start.