Physic makes it into some of Shakespeare’s plays, but physics has never been, like sex and slamming doors, a staple of the stage. So the immense success of Copenhagen, which applies the rules of quantum mechanics to human motivation as it explores the still-mysterious 1941 meeting between physicists Werner Heisenberg and Niels Bohr in the city of the title, came as a surprise to Michael Frayn. Already a proven master of sex and slamming doors (in the delirious farce Noises Off), the British playwright here applies Heisenberg’s Uncertainty Principle — which asserts that the more accurately you pinpoint the position of a particle, the less accurately you’ll be able to measure its velocity, and vice versa — to human interaction and memory.

But what could be more uncertain than the commercial fate of a play that moves its characters about like particles in an atom while they rehash their scientific collaboration and re-enact a mutable encounter on which hinged the fate of the world? Yet as ingeniously staged by Michael Blakemore (who won a Tony), Copenhagen proves stimulating entertainment. Moreover, in the national-touring production that’s making its final stop at the Colonial Theatre, it’s ably acted by the trio of Len Cariou, Mariette Hartley, and Hank Stratton, whose boyish Heisenberg is so slick that his tearful commemoration of his " ruined and dishonored and beloved homeland " is the more moving.

That the heady 1998 play won London’s Evening Standard Award as well as the 2000 Tony is less surprising than you might think. Indeed, the work has so engaged the public that it has rekindled the controversy over the reasons for the visit of Heisenberg, then head of Hitler’s atomic-research team, to his Danish mentor in the midst of World War II. The known facts are these. In September of 1941, Heisenberg, a German nationalist but not a Nazi, went to Copenhagen, where in the 1920s he and Bohr had brainstormed what became known as the Copenhagen Interpretation of quantum mechanics. He was to deliver a lecture, but the real purpose of his visit seems to have been to speak with the older Nobel-winning physicist, who had been like a father to him.

The meeting was strained; Bohr was a half-Jew in a Nazi-occupied nation. In Frayn’s hypothetical re-creation, the ghosts of Heisenberg, Bohr, and Bohr’s wife, Margrethe, run through the encounter over and over, trying to isolate Heisenberg’s goal. Bohr and Heisenberg went for a stroll, probably to escape microphones secreted in the house. Heisenberg apparently asked Bohr the question " Does one as a physicist have the moral right to work on the practical exploitation of atomic energy? " And the evening ended abruptly and angrily, with the two men never resuming their friendship or, indeed, agreeing on what had taken place.

So why did Heisenberg go to Copenhagen? To seek absolution for his work toward an atom bomb from Bohr, his " father confessor? " To fish for information regarding Allied assessment of the feasibility of a bomb? Or, as he later claimed, to forge a tacit agreement, which blew up when Bohr did, that physicists on both sides agree not to turn their brains to mass destruction? Was he trying to make a bomb or ensure that no one would? Did his subsequent failure stem from bad science or moral reluctance? Eloquently Frayn explores the possibilities, applying Heisenberg’s Uncertainty and Bohr’s Complementarity to a " quantum ethics " that does not ignore the irony that Bohr played a part at Los Alamos while Heisenberg wound up without blood on his hands.

The play is talky but elegantly constructed, culminating in a coda in which the three ghosts consider that, just possibly, the downward trajectory of the world was diverted by " that one short moment in Copenhagen. " What Blakemore and designer Peter J. Davison contribute is the concept by which the trio circle and collide like particles on a round, near-empty stage that’s as suggestive of a courtroom as of an atom. We, the audience, are the observers who (according to Heisenberg’s theory) influence the experiment, a small number of spectators placed in an on-stage arc behind the action to complete the circle.

But such an intellectually vigorous work needs to be put across by its actors, whose task is prodigious: even if we don’t understand all of the science, they must, or how would they learn the lines? Moreover, Frayn has created characters who are passionate, whereas by most accounts the real Heisenberg was unemotional except about music. Cariou is a less avuncular than explosive Bohr (though both he and Stratton’s Heisenberg can bend double over their Schrödinger’s-cat jokes). Hartley softens the skeptical Margrethe; yet she rises to dignified fury. These actors may not illustrate Bohr’s Complementarity, but they complement one another well enough.