You don’t need to know anything about early-20th-century German physicist Werner Heisenberg’s “uncertainty principle” to understand British playwright Simon Stephens’ “Heisenberg,” now at American Conservatory Theater.
But Stephens purposefully conceived his boy-meets-girl (or rather septuagenarian-meets-42-year-old) two-hander in relation to Heisenberg’s theory: In observing a phenomenon, the observer affects the phenomenon, making accurate measurement impossible — and therefore unpredictability inevitable.
In “Heisenberg,” which premiered at the Manhattan Theatre Club in 2015, by the end of a six-week relationship, both characters have behaved in at least somewhat surprising ways.
When the play begins, cheerful force-of-nature Georgie, an American ex-pat in London, has just slipped up behind a complete stranger, Alex, a quiet, 75-year-old Irish butcher, at a train station and kissed him on the back of the neck. It was apparently an impulse on her part.
“Do you find me exhausting but captivating?” she asks him merrily at one point early on.
He doesn’t know quite what to think — she likes to “make things up,” she says, so it’s hard for Alex, who’s honest and plainspoken, to know when she’s lying and when she’s telling the truth.
But soon enough it doesn’t really matter: The two lonely opposites need each other and the relationship takes a course that, while unusual because of the age gap, is actually rather predictable.
In fact, it’s a fairly familiar trope of plays and movies — the buttoned-down, repressed man (“I don’t feel. I think,” Alex tells Georgie sternly) and the zany, free-spirited young woman who seduces him and loosens him up.
The hour-and-a-half-long play is directed here by Hal Brooks on a clean, spare stage (sets and lights by Alexander V. Nichols) with nifty pop-up furniture to suggest the various indoor and outdoor settings, and that’s all that’s needed.
Because Georgie propels the action, she’s the main character. So it’s unfortunate that Sarah Grace Wilson overacts and lacks the quirky charm that the role requires in order for stolid Alex fall in love with her. She is in fact way more exhausting than captivating.
As Alex, James Carpenter’s deep listening, bemused reactions and innate sense of Alex’s profound dignity and decency make his character, in the end, the more interesting one.
Scientific theories notwithstanding, “Heisenberg” is ultimately a romantic comedy that doesn’t necessarily put a new spin on May-December affairs but at moments is insightful about the vagaries of love, whatever your age.
Presented by American Conservatory Theater
Where: 415 Geary St., S.F.
When: 8 p.m. most Tuesdays and Fridays, 2 and 8 p.m. Wednesdays and Saturdays, 2 p.m. Sundays; closes April 8
Tickets: $15 to $110
Contact: (415) 749-2228, act-sf.org