The equation-filled blackboard is one of the most reliable props of academia, not just in cartoons and movies, but in real life. You know a scientific discussion is taking a turn for the serious when the protagonists head to the board. Walking into a colleague's office, a glance at the scrawled notes on their board gives you a taste of their current research preoccupations and teaching commitments; wobbly chalk drawings along the bottom edge are a pretty good sign that the office's owner has a small child in their life.