In most dramas in which the characters are based on real people, there is a point at which the character deviates from the real person. However, playwright Michael Frayn worked to keep that distinction as small as possible. Having studied memoirs and letters and other historical records of the two physicists, Frayn felt confident in claiming that "The actual words spoken by [the] characters are entirely their own." With that in mind, the character descriptions apply to both the representative characters as well as the physicists themselves. There is a great amount known about all of the primary characters presented in Copenhagen ; the following includes those bits of information which are directly relevant and referenced in the work itself.