When you are reading a book written by an expert in a given field and you are not an expert in that field, you will eventually come across something which the author has taken it for granted that you will understand. Or else, you will find something that the author has not explained sufficiently for you to understand. Even if the book has been written for an inerested layperson like you, it will happen. At that point, it is very helpful to visit the internet and seek out a plain language explanation of the concept that is giving you trouble.
This has always served me well in the past. I am not an advanced scientist, but I enjoy reading about advanced science. And I like to think I have a pretty keen understanding of things precisely because I am willing to research a topic instead of tossing a book away as incomprehensible. However, it appears that I have now come to an impasse.
It seems that, if you keep reading more and more advanced topics, you will eventually find that there are no plain language explanations of any of the concepts you don't understand because, quite frankly, if you need a plain language explanation of, say, the "Ricci Curvature Tensor" without a lot of advanced math and a passing grade in a 300-level prerequisite course, you probably aren't advanced enough to even know that the thing exists. This is a shame because I am lead to believe that it is very important for getting through the rest of the chapter.
What truly bothers me about this whole thing is that I am 353 pages into this book which is now more than 20 years out of date and I am only reading it because (a) several years ago, a philosophy professor accused me of plagiarizing it and (b) I want to read the much more current sequel which looks far more interesting and has a much nicer picture on the cover.