* There is a little uncertainy about the use of the word uncertainty in regard to Heisenberg’s principle. Michael Frayn, in an afterword to his play Copenhagen, notes that several words in German – Unsicherheit, Unscharfe, Unbestimmtheit – have been used by various translators, but none that quite equates to the English uncertainty. Frayn suggests that indeterminacy would be a better word for the principle and indeterminability would be better still.