It seems that famed scientist Albert Einstein had more trouble finding his way home from work than he did finding the key to atomic power. One evening as Einstein sat deep in thought aboard the train that brought him home each night, the porter approached to collect his ticket. Einstein rummaged around in his coat, through his pockets, in his shirt, and everywhere else he could think of, growing alarmed at his inability to find the ticket.
"That's okay, Dr. Einstein," said the porter. "I know you ride this train every day. I can collect tomorrow."
"That's fine for you, young man," Einstein replied, "but how am I supposed to know where to get off the train without my ticket?"