LOOKING into the middle distance as if into the caverns of time, Ansel Elgort plucks out a memory of using a telephone landline to speak to a friend.

Mr Elgort, if you have not yet twigged, is young - 20 to be precise. He is also very big among the teen set, and, courtesy of his new movie, Men, Women and Children, is about to make a name for himself among those old enough to remember party lines, never mind the dark ages before mobile phones.

We are talking all things tech because Men, Women and Children is an ensemble drama about relationships in which mobiles and the internet feature prominently. Elgort plays Tim, once a promising football player, now lost in his computer games. Other characters include a husband who tries internet dating, a mother who monitors her daughter's every move online, and a pushy parent trying to kick-start an acting career for her child via the web.

"I really never saw this as an internet movie," says director Jason Reitman (Juno, Up in the Air). "I wanted to make a movie about relationships in 2014. To be married, divorced, to be a parent, a child, falling in love in high school. You can only discuss that in 2014 by discussing our virtual relationships as well."

The cast divides between teens and the middle aged. The latter had questions about social media, says Elgort, but not Reitman. "Jason really knows his stuff. He should, he's making a movie about it."

Reitman did feel a digital divide, though. "You take the young actors in this film, I'm 15 to 20 years older than them. But I might as well be 100 years older. The life that they grew up within does not resemble my childhood at all."

With more than two million followers on Twitter, Elgort is no slouch at social media. That he should have acquired so many acolytes so quickly is testament to his short but remarkable career to date.

Before Men, Women and Children, which had its premiere at the London Film Festival in October, the young New Yorker had only been in three movies. But what a trio. He made his debut in the remake of Carrie, followed by a lead role in the science fiction adventure Divergent. Then came the big one - the adaptation of teen tragedy The Fault in our Stars. Adapted from the bestseller by John Green, Stars has been a twenty-first century Love Story. Made with a production budget of $12 million its worldwide gross now stands at $304m (Box Office Mojo).

With toasty reviews for all three, and a certain look, Elgort has even acquired the label handed out to talents before him, that of a young Brando.

"Ansel has an emotional weight to him that fills a room very quickly," says Reitman. "He is the definition of a movie star. He looks like a young Brando. He's going to go very, very far."

There was just one problem when he was called upon to play a troubled teen in Men, Women and Children, Reitman recalls. "It's hard for him to not smile, that's the only trick with him. He thinks about smiling and the luminance in the room goes up ten times. The real trick was always how do we keep him heavy. But he knew how to find that."

As coincidence would have it, Elgort is wearing a jumper with a Wild One-style motorcycle on it.

"I love those old guys," he says. "Him and Paul Newman were probably my favourite two actors growing up."

The son of an opera director and a photographer, Elgort grew up in a home were old movies were king. "My dad is 74. He was born in 1940 so he grew up watching those movies." It was a love he passed on to his son. "It was probably Brando that made me want to be an actor."

When he told his parents of his ambitions, their advice was to get some training. So off Elgort went, to dance and acting classes and singing lessons. Though his first role was on the stage, it is in film that he is now making his name. He is also a music producer, releasing his first record this year.

After the teen dramas, Men, Women and Children is a good fit for Elgort, supplying both a director to work with that he has long admired, and a subject that interests him. For him, communicating by text is just the latest variation on an old method.

"People used to write letters too. Writing words down to express feelings is a very old concept. People are still going to talk in real life or meet up. I don't think there is anything wrong with people having a lot of conversations over text."

Reactions to the movie differ with age, he says. "Old people always view this movie as, 'Oh my God it's so scary, is this really what is happening in the world right now?"

I ask him to define old people. "All you guys," he jokes to the assembled press. "Just kidding. I think like 40…"

He doesn't regard the movie as scary.

"It's just real and it's true."

Men, Women and Children opens in cinemas on December 5