On Thursday, February 13, 2003, at 04:30 PM, Henning Makholm wrote:
Just a random thought: There used to be an informal rule saying, "never write a false statement on the blackboard". Some student is bound to mindlessly copy it down and take it for truth.
I used to insert well-placed coefficients ("2", usually) into equations on the blackboard in physics. So much fun. Once it actually got half of the class....