You're not dumb. It's a subtle point, otherwise special relativity wouldn't have been necessary to invent. (You may find it worthwhile to read a more normal art

You're not dumb. It's a subtle point, otherwise special relativity wouldn't have been necessary to invent. (You may find it worthwhile to read a more normal article on special relativity -- it's much easier to understand than general relativity.) The two rocks land just as Bert and Dana are closest to each other. The two rocks are equally distant from that point. But as the light propagates towards them, Bert continues to move towards the light from the impact ahead of him, and away from the impact behind him. Thus he will see the light from the former impact before the latter. (The traditional thought experiment is described in terms of trains and lightning, instead of buses and moon rocks. If you do a web search for that plus "special relativity", you should find plenty of descriptions that are closer to the original.)