... The Australian National University] [Department of Physics] [Paul Francis] [Main Roleplay Page] . These exercises are my attempt to adapt the technique of Problem Based Learning to the context of introductory astronomy and astrophysics classes. ... As students grapple with the puzzle, they are forced to learn the subject matter of the course. ... This exercise is designed for 1st year University students with a reasonable high-school background in Maths and Physics. ...