What are good ways to insult a mathematician? 

A group of unethical psychologists want to find out who is smarter – engineers, physicists, or mathematicians. They design an experiment where they leave a group of engineers, a group of physicists and a group of mathematicians in separate rooms with enough food to last them all for two months, all in cans but with no can opener, and sets of writing utensils and no paper. The doors are locked and they cannot escape.

When the psychologists check on the engineers, they are all well-fed. It turns out that working together, they figured out how to use their pens to open the cans.

When they check on the physicists, they are still alive and they see that calculations cover the walls, but they have only eaten about half the food. The calculations detailed a method for throwing the can such that it would break open, complete with theoretical probability that the can will open.

When they check on the mathematicians, they are all dead, and the walls, ceiling and floor are completely covered in calculations. At the end of the calculations is written "it is possible to open the cans."