The unbreakable cypher

Abstract

Abstract Otto Frisch [20], the German physicist, was in Birmingham, England, at the beginning of the Second world war, preoccupied with the possibilities of achieving a nuclear fission bomb and denying the German side access to the Norwegian stocks of heavy water (deuterium oxide), which would be required for building such a weapon. A committee was set up to study the prospects, and this anecdote of Frisch’s illustrates the ovenvrought temper of the time. The report which Peierls [another emigre physicist in Birmingham] [42] and I had sent to (Sir) Henry Tizard on Oliphant’s advice had triggered the formation of a committee, with (Sir) George Thomson [son of J. J., the discoverer of the electron] as chairman, which was given the code name ‘Maud Committee’. The reason for that name was a telegram which had arrived from Niels Bohr [79], ending with the mysterious words ‘AND TELL MAUD RAY KENT’. We were all convinced that this was a code, possibly an anagram, warning us of something or other. We tried to arrange the letters in different ways and came out with mis-spelt solutions like ‘Radium taken’, presumably by the Nazis, and ‘U and D may react’, meant to point out that one could get a chain reaction by using uranium in combination with heavy water, a compound of oxygen and the heavy hydrogen isotope called deuterium, abbreviated D. [Frisch does not mention that a cryptographer was enlisted to study the problem and came up with ‘Make Ur day nt’.] The mystery was not cleared up until after the war when we learned that Maud Ray used to be a governess in Bohr’s house and lived in Kent.