FERMI PROBLEMS. The piano tuner problem is an example of a Fermi problem, which is named after Enrico Fermi, the great nuclear physicist. Fermi was known for using the method of estimation for producing an answer to a Fermi problem and for teaching the method to his students. The problem is set in Chicago, where Fermi demonstrated the first artificial self-sustaining nuclear chain reaction in a reactor built in the squash court under the stands of the University of Chicago’s Stagg Field.

The way of thinking used in estimating answers to Fermi problems can be of great practical importance. The wikepedia entry tells how Fermi estimated the strength of the atomic bomb that detonated at the Trinity test (the first test of a nuclear weapon), based on the distance traveled by pieces of paper he dropped from his hand during the blast. Fermi’s estimate of 10 kilotons of TNT was remarkably close to the now-accepted value of around 20 kilotons.