Einstein's thought experiments

Einstein's thought experiments are a way for him to explore ideas about the universe without actually doing any real experiments. He would imagine a situation in his mind and then think more deeply about what might happen in that situation. For example, in one famous thought experiment, he imagined a man in a train going at the speed of light. He then thought about what would happen if the man stepped outside of the train while it was still moving at the speed of light. This thought experiment helped him to develop some of the ideas behind his famous theory of relativity.