Oklahoma brood riveting in 'Osage County'

Albert Einstein jokingly explained the theory of relativity this way: When a guy sits on a hot stove, a minute feels like an hour. When his girl sits on his lap, an hour passes like a minute. This explains why badly written one-act plays seem to last longer than the Hundred Years' War, and the 3 1/2 hours of "August: Osage County" can blow over us like a summer thunderstorm.

That total includes two intermissions, and you will need them to process everything that goes on in this dense, fascinating drama. As the extended Weston clan coos, quarrels, harangues, wrangles and blusters, Tracy Letts' Pulitzer-winning characters deliver revelations to each other and epiphanies to us until the end.

Carolina Actors Studio Theatre gambled that this expensive, expansive production should open its new home in NoDa, and the gamble has paid off. The 13-person cast, led by harrowing performances by Polly Adkins and Paula Baldwin as a mother and daughter locked in potentially mortal combat, is as fine as any I've seen in local theater.

Modern America usually absorbs culture in sound bites, condensed ideas and emotions that can be gulped down and (too often) just as quickly forgotten. But this "August" reminds us of the pleasures of a four-course meal eaten, digested and remembered at leisure.

Eugene O'Neill is Letts' inspiration in this case, both for duration and sensibility. He, too, wrote three-act dramas about the ways people interact when they're connected by blood but disconnected by bitterness, anger, narcissism and the inability to empathize.

Even O'Neill might not have introduced us to a gruffly genial narrator who sets the emotional stage for us in the opening scene, then vanishes for good. He's Beverly Weston (George Gray in a memorable extended cameo), who was acclaimed for a first book of poetry 40 years ago and has long since sunk into a sardonic, alcohol-fueled state of peace.

His disappearance provokes his extended clan to gather around Violet (Adkins), his pill-addled wife. Soon we meet their three daughters: clinging Ivy (Jennifer Hubbard), rage-filled Barbara (Baldwin) and feckless Karen (Frances Bendert). With them come unsuitable spouses, bickering in-laws, and children growing up too fast or not at all.

Like O'Neill, Letts can be symbolic: The Native American caretaker in the Weston attic (Karina Roberts-Caporino) could be the reminder of the genocide that pricks our conscience, and one monologue implies that this household - crumbling physically, as well as psychologically - is a metaphor for America. Even the family name suggests the westward march of the pioneers.

Yet unlike O'Neill, Letts can often be intentionally funny. For all its heft, "August" has darkly comic moments where least expected. The line "Karen, he killed himself!" is delivered for laughs and gets them.

Michael Simmons has directed in a way that makes the lives onstage not only vibrant but believably messy: Conversations overlap, asides seem improvised, action keeps going away from the main conversations on the three levels of Dee Blackburn's sprawling set.

Simmons has cast against type - Anne Lambert as a mean-spirited aunt, Brett Gentile as a mild-mannered (if philandering) husband - and used actors we've seen rarely (Peter Smeal as a fumbling cousin) or not at all (high school junior Madeleine Moore, pitch-perfect as a pot-smoking teen).

Their skill can't prevent the play from seeming a bit long, as the fireworks die down and characters disperse. Yet their commitment never wavers: When an actor slammed a screen door so hard that it came unhinged near the end, I wondered for a moment if that damage was intentional. So vivid is this production that every gesture in it seems real.