It's often possible to sidestep the difficulty of communicating evidence by focusing on explaining relevant concepts, which usually doesn't require evidence (or references), except as clarifying further reading. Evidence may be useful as motivation, when it's easier to communicate in the outline than the concepts, but not otherwise. And after the concepts are clear, evidence may become easier to communicate.

(Imagine trying to convince a denizen of Ancient Greece that there is a supermassive black hole at the center of our galaxy. You won't get to presenting actual astronomical observations for quite some time, and might start with the entirely theoretical geometry and mechanics. Even the mechanics doesn't have to be motivated by experimental verification, as it's interesting as mathematics on its own. And mentioning black holes may be ill-advised at that stage.)