Reorganizing the Theory of Relativity

"Huan'er! Look, these are two parallel lines that will never intersect! Do you know?" Yan Moran drew two lines on the paper, and then wrote these few sentences. Ruan Tiantian smiled, reached out and took two pieces of paper that had been cut and placed them on the table in parallel, and then said, "These are also two parallel lines! But..." As she spoke, she quickly twisted the two pieces of paper together and then placed them in front of Yan Moran, "Isn't it just one piece now?" Yan Moran was in a daze, not realizing that Ruan Tiantian had already walked to him. "Yan Moran! Think clearly!"