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It's a concern that's boggled the minds of Titanic fans for 20 years: in the final moments of the 1997 classic, the shipwrecked Jack and Rose find a door among other flotsam to keep them afloat in the open sea. Rose climbs up on the door while Jack doesn't. Eventually he succumbs to the freezing water and drowns. Diehard Jack fans have long argued that "Jack could totally fit on that door".

In his latest interview with Vanity Fair, director James Cameron has broken his silence on that contentious scene.

When asked why both Jack and Rose couldn't fit on the door, he says, "And the answer is very simple because it says on page 147 [of the script] that Jack dies. Very simple. . . . Obviously it was an artistic choice, the thing was just big enough to hold her, and not big enough to hold him . . ."

His takeaway from the reactions to the scene is this: "But it does show that the film was effective in making Jack so endearing to the audience that it hurts them to see him die. Had he lived, the ending of the film would have been meaningless. . . . The film is about death and separation; he had to die. So whether it was that, or whether a smoke stack fell on him, he was going down. It’s called art, things happen for artistic reasons, not for physics reasons."

But he made sure that physicists wouldn't object to the scene.

Cameron shares, "I was in the water with the piece of wood putting people on it for about two days getting it exactly buoyant enough so that it would support one person with full free-board, meaning that she wasn’t immersed at all in the 28 degree water so that she could survive the three hours it took until the rescue ship got there.

"[Jack] didn’t know that she was gonna get picked up by a lifeboat an hour later; he was dead anyway. And we very, very finely tuned it to be exactly what you see in the movie because I believed at the time, and still do, that that’s what it would have taken for one person to survive."

There you have it, Titanic fans! Jack had to die for artistic reasons and it was the physics of Rose's survival, not Jack's death, that mattered the most to Cameron.