Semantic knowledge tree
Elon Musk on his reddit ama said
I do kinda feel like my head is full! My context switching penalty is high and my process isolation is not what it used to be.
Frankly, though, I think most people can learn a lot more than they think they can. They sell themselves short without trying.
One bit of advice: it is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to.
The semantic tree of Elon is where we root our basis of understanding.
For him, it is rooted in physics. It is a form of first principles thinking.