When you watch the sunrise carefully with him, you tell him to look at the mountains and the scenery that can be seen from the same place, and talk to him casually, and then you are silent for a while, as if thinking about something, and say, "I I remember that the sun set from there last night, and it rose from here again today. How could this happen?" Don't say anything more, if he asks you, don't answer him, just say something else.Let him think for himself so that he can think.