Popular Science References in Statement of Purpose for Ph.D
From my experience, telling the tale why you became so fascinated with one particular topic is to be kept to a minimum. It does not add any weight or edge to your SoP, other people will have their more or less interesting story. You can use maybe one or two sentences and I don't see any need to have a "not a specifically small" paragraph on why you became fascinated with a topic. It might sound harsh, but they will not care. You have to use the limited space in your SoP for other things. But that's another question/answer.

In short, I would avoid citing pop science to a very bare minimum, especially in a field as rigorous as physics. Unless you use this reference to show something you have achieved. For example, I read pop science X which inspired me to run experiment Y which has produced Z.