Hello, My name is Joe and I am a junior in high school. I am taking AP Calculus right now along with a basic physics class. I am very, very interested in the special and general theories of relativity, but I want to know the exact logic behind it. Right now, I don't really understand any of it. I am looking for a source that will start from scratch and explain everything. I have done a lot of research on my own so I know what the theories are but I can't find an explanation that starts at my level of understanding. I know the special theory of relativity is a way that the principle of relativity and the fact that the speed of light is a constant velocity no matter the velocity of the observer do not contradict eachother. But in order to truly understand this I need to start by understanding why the speed of light is constant no matter the velocity of the observer. I read somewhere that no one really knows why this is but I would at least like to know where this idea came about and what evidence there is that supports this. There is obviously logic behind this fact. I don't want to assume anything without fully understanding it. If my level of mathematical background is not sufficient then I want to know what the next step is in truly understanding relativity. I am in the middle of a calculus course right now, and I understand all math up to this level extremely well. If someone has any suggestions for me I really appreciate any advice at all. Thanks in advance!