When the Symbols Overlap

Yu Chi ransacked the already messy room before he finally found what he was looking for. It was a ping pong ball. He walked to the working table and shoved all the crap away. 

"Captain Gu, let us assume this is Earth." Yu Chi placed the yellow ping pong ball on the table and then grabbed a mirror to place it beside the ping pong ball. "There is another Earth inside the mirror." Then, he used his phone as a mirror to place on the other side of the ball. "There is another Earth here too." Yu Chi's eyes danced with excitement, "They are different even though they are reflecting the same things!" Gu Jun nodded slightly, he slowly caught up to what the man meant.