Moral Twin Earth cases involve humans meeting aliens and disagreeing with them about moral questions. The causal theory of reference often used by naturalistic moral realists entails that such disagreement is impossible. To avoid this bad result, I invoke the experientialist analysis of moral concepts, on which they apply to objective properties represented by feelings like guilt, horror, and admiration. Combined with a new theory of reference based on empathy, the experientialist analysis accounts for interplanetary disagreement and entails ethical hedonism.