A captain notices a light in the distance, on a collision course with his ship. He turns on his signal lamp and sends, “Change your course, 10 degrees west.” The light signals back, “Change yours, 10 degrees east.” The captain gets a little annoyed. He signals, “I’m a US Navy captain. You must change your course, sir.” The light signals back, “I’m a Seaman First Class. You must change your course, sir.” Now the captain is mad. He signals, “I’m an aircraft carrier. I’m not changing my course.” The light signals back a final message: “I’m a lighthouse. Your call.”