What are the implications of the phrase, “I don't know what you mean when you say 'the whole world' or 'generations before him! I thought there was only
us. I thought there was only now."

well if u read the book you would know that she meant to

the direction of the magnetic field produced by an electric current will change when the direction of the electric current changes. for example : if a current is flowing in a straight length of wire, the magnetic field is described by a concentric circle (using right-hand rule).