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By Tristan Lejeune

The theatre is a great place to talk about physics. The lights, the X-and-Y grid of the stage, the nearly unlimited props, the trapped audience who already paid their money — film and TV can lie to you, but plays are made of physics.

Theater J, where scripts are either an intellectual workout or not worth doing, is an even better place to talk about atoms, quantum mechanics and wave theory. Michael Frayn’s Copenhagen, running until January 29, is about a moment where theoretical and nuclear studies and morality converged into history. It’s the best play about physics since Tom Stoppard’s Arcadia, and I wholeheartedly recommend it for any theatergoer who craves cerebral recreation.

In late September of 1941, Werner Heisenberg — renowned physicist, author of the uncertainty principle, and inspiration to Albuquerque meth kingpins — traveled from his native Germany to German-occupied Denmark. He spoke at a conference, glad-handed a few dignitaries. And he met with Niels Bohr, his half-Jewish former mentor and partner. The matter of their meeting became the subject of intense debate among intelligence agencies, universities and historians as Bohr and Heisenberg would go on to play roles in the Allied and Axis nuclear programs.

Actors Tim Getman, Michael Russotto and Sherri Edelen don’t so much play, respectively, Heisenberg, Bohr and Bohr’s wife, Margrethe, as much as they play self-examining echoes of them, now “long dead.” Even as they go through the motions of Heisenberg’s visit to a Copenhagen home, surrounded by invisible Nazis, they’re watching themselves do it, observing (like keen scientists) their own facial expressions, tone and word choices as they search for meaning and motive. A key characteristic of any good experiment is that it can be repeated under controlled conditions (like actors in rehearsal), so they try again and again to sift through the past and get to the whats and the whys.

Was Heisenberg hoping for absolution through confession to his old instructor? Did he come to give some hint of Berlin’s nuclear ambitions that he hoped would reach the other side? Or was he feeling Bohr out, trying to gleam how close Britain and America were to their own A-bomb?

For this examination, you’re in good hands with director Eleanor Holdridge. Her Copenhagen has excellent pacing and a healthy blend of appeal to the mind and the heart. And she’s coached worthy performances out of her three actors — even when they briefly forget their lines, you don’t want to stop watching.

I’m less sold on the technical aspects. The set, Danish modern (by way of a doctor’s waiting room? in a dream, maybe?) is fine, insofar as it goes, but the gentlemen’s suits could fit them better. And a note on the music: Beethoven’s “Moonlight Sonata” is lovely, but it does not make a subtle entrance. Either leave it on or turn it off, please — having it come in and out of a monologue is highly distracting.

But these are minor quibbles. When the three actors are sparring and cajoling around the stage, reliving the discoveries of much of modern physics, the audience has so much fun they quickly forget jackets too long for the shirt sleeves underneath.

Edelen rises above her role’s limits — she’s rather written as a dutiful female listener type — to find strong moments of influence; her character is the only one without a Nobel Prize, but in terms of memory, she has as much to say as anyone. Russotto and Getman have a crisp repartee, the former sweeping and broad, the latter always looking inward. All three performers deserve applause.

Light on plot and heavy on theme, Copenhagen is catnip for science fans, history fans, and especially fans of brainy theatre.

Copenhagen runs at Theater J through January 29.