Juilliard-trained. Schooled in Shakespeare, Strindberg, Oscar Wilde. Dedicated to her art, and to the idea of art.

But in "Interstellar," the widescreen sci-fi epic from Christopher Nolan, opening Friday, Jessica Chastain plays a scientist with a head full of equations and questions about time, relativity, quantum mechanics. She's an astrophysicist.

"Actually, I am an astrophysicist," insists the twice Oscar-nominated actress, on the phone from Los Angeles the other day. "I've been paying the bills through acting. And now I'm finally able to combine both of my pursuits."

Which, of course, is a joke.

"It was really a stretch for me," Chastain confesses. "A lot of the parts I play are. Maya in 'Zero Dark Thirty' " — her CIA officer, bent on hunting down Al-Qaida mastermind Osama bin Laden — "was opposite anything that I had known of, or thought of. She was so different from the world that I inhabit — my everyday life.

"And this character, she's wrestling with an agricultural crisis on Earth. She's also wrestling with her own crisis. … She's trying to learn how to feel love again."

It's tricky for Chastain — or for anyone who has seen the film and doesn't want to be a jerk and spoil it for others — to discuss her role in depth. "Interstellar," nearly three hours long and made for $150 million, is a grand-scale endeavor that literally bends the physical universe (think that Paris cafe scene in "Inception") as it mulls matters of science and the soul. It's ambitious. It's Kubrickian. It will wow Nolan's ardent fans.

Suffice it to say that Chastain plays the daughter of Matthew McConaughey's NASA test pilot-turned-farmer, Cooper. In real life, he's 44, she's 37. In "Interstellar," however, they are separated by considerably more years than that — with no old-age makeup in use. Clearly, there's some temporal monkey business going on.

"I definitely had to understand anything that I'm saying in the film," Chastain said. "You have to know where it comes from, why your character would say it. But other than that, I was very gentle with myself. I didn't force my brain to go, 'Well, I have to understand all about astrophysics in order to play this character.' It was more like, 'What am I directly involved with, and how can I learn as much as I can about that?'

"But even though I felt hugely inadequate playing this incredible woman, it made me feel better thinking that, in a way, there's no big answer, because every question leads to another question. If you expect an answer, you're doing it wrong."

Chastain — who had a mere seven films released in 2011, including "The Help" (her supporting actress Academy Award nomination) and Terrence Malick's "The Tree of Life," opposite Brad Pitt — did have questions she wanted answered by her co-star, Michael Caine. She plays Caine's protégé — a whiz kid learning from the wise scientist overseeing a secret NASA project to save humankind.

"I always try to work on films where I get to hang out with an acting legend," Chastain says with another laugh. "I've recently worked with Liv Ullmann, which was a dream come true, and I've worked with Al Pacino. I love movies, I love the films of the past, I understand how art can shape us … and I definitely want to get as much out of it as I can when I'm hanging out with someone who's had such an incredible career.

"And so, when I was working with Michael Caine, I was trying not to be completely like a journalist, asking him questions every five minutes. I was trying to play it cool and not seem like I was interviewing him. But we got to talk about his films. I love 'Hannah and Her Sisters.' The character he plays is so incredible, so we talked about that. We talked about him starting in theater, and what brought him to the film world, and why he hasn't gone back."

For Chastain, "it was an incredible day. … You understand, working with him, why he is such an important figure in cinema."

During a break, Chastain went over to Nolan, who has cast Caine in "The Dark Knight" trilogy, in "The Prestige," in "Inception," to thank the director.

"I turned to Chris and I said, 'Oh my God, this day is so great. … I'm going to remember every minute of this.' "