WASHINGTON (WASHINGTON POST) - It's the emotional climax of the film - Neil Armstrong in his spacesuit standing on the lip of a crater on the moon, holding a bracelet spelling out the name of daughter Karen, who had died seven years earlier, before her third birthday.

Played by Ryan Gosling, Armstrong tosses the bracelet into the depths of the dark crater, as tears stream down his face, a stirring farewell scene that comes toward the end of First Man, the Armstrong biopic directed by Damien Chazelle that opened nationwide last Friday (Oct 12).

There's just one problem: There is no evidence that it ever happened. Historians say it is likely another example of Hollywood injecting a bit of dramatic fiction to heighten the movie's emotional punch.

At a rally in Ohio last Friday night, President Donald Trump attacked the movie not for what's in it but for what isn't: A scene showing the moment when the American flag is planted on the surface of the moon.

"He's the man that planted the flag on the face of the moon," Mr Trump said. "There was no kneeling."

It was a reference to NFL athletes kneeling in protest during the national anthem.

The film was inspired by the authorised biography of Neil Armstrong by author James Hansen.

In the authorised biography that inspired the film, author James Hansen wrote that the mementos Armstrong took to the moon were limited: Some medallions commemorating the Apollo 11 lunar mission, jewellery for his wife, a piece of the Wright Brothers' airplane and his college fraternity pin.

"I didn't bring anything else for myself," Hansen quotes Armstrong as saying.

His then wife Janet Armstrong was apparently distressed that "Armstrong took nothing else for family members - not even for his two boys", Hansen wrote.

"Another loved one that Neil apparently did not remember by taking anything of hers to the moon was his daughter Karen," Hansen added.

Nasa's chief historian Bill Barry said questions about the scene came up recently during an event for the movie at the Kennedy Space Centre.

The conclusion, he wrote in an e-mail to the Washington Post: "The scene was created for the movie, and there is no specific evidence that Neil Armstrong left any 'memorial items' on the moon."

Former Nasa chief historian Roger Launius, who is also a former senior curator at the National Air and Space Museum, agreed.

"There is no evidence to support the assertion that he left a bracelet of his daughter on the moon," he said.

Though apparently fiction, the moment is a critical one. Throughout the film, Armstrong, who died in 2012, is portrayed as a stolid and steely pilot who keeps his cool in all sorts of stressing situations, from when his spacecraft started tumbling during the Gemini 8 mission to the tense landing on the surface of the moon during Apollo 11.

He is understated and cool throughout the film - even when told he has been selected to command the Apollo 11 mission, he replies with not much more than a nod.

The death of his daughter from a brain tumour, however, serves as an emotional undertow, a recurring theme in the film that reveals Armstrong's humanity.

After her death, he has a vision of her playing at a party, and at one point he slips her bracelet into a drawer.

Honouring her memory on the lunar surface would have been poetic. Hansen wrote: "What could have made the first moon landing more meaningful 'for all mankind' than a father honouring the cherished memory of his beloved little girl (she would have been a 10-year-old), one of her toys, an article of her clothing, a lock of hair?"

Other Apollo astronauts paid tribute to their families on the moon.

Eugene Cernan, the last man to walk on the moon in 1972, wrote his daughter's initials in the lunar dust before he departed. Buzz Aldrin carried photos of his children, and Charlie Duke left a photo of his family on the lunar surface.

While there is no evidence of it, it is possible Armstrong did something, as well - and that is why Hansen said he is OK with it in the film.

"We don't know for sure what Neil did," he said in an interview. "Maybe that's a rationalisation."

Still, he said that the scene takes "dramatic licence, for sure, and it's a fairly big one". But he said that the moment "plays really well in the movie, and that's maybe the bottom line for the filmmaker".

Hansen added: " Sometimes the power of poetry prevails over the uncertainty of fact."

A previous screenwriter also had a similar scene in his version of the script, he said. But instead of a bracelet, Armstrong brought one of Karen's shoes to the moon.

Such a display of emotion, especially during an operational mission, also might have been out of character for a man who Janet Armstrong said in the book, "can be thoughtful, but he does not give much time to being thoughtful, or at least to expressing it".

During the film, Armstrong on a few occasions gazes longingly at the moon.

But during a 2001 interview, when historian Douglas Brinkley asked if he ever would "just go out quietly and look at the moon", Armstrong answered: "No, I never did that."

Former Apollo astronaut Al Worden, who served as a consultant on the film, said in an interview that Chazelle, the director, was rigorous in making sure he got all the technical details right, from how the astronauts entered the spacecraft, to the locations of the switches and buttons inside.

"He went to great lengths to make it accurate," Worden said. "There's just no question about that. He did a superb job."

He said Armstrong "would probably like" the film, even if he is portrayed "as a little bit more aloof than he really was". He added: "I always found him to be very friendly, very cool and calm most of the time."

Then again, Armstrong was an engineer, dispassionate and fact-oriented.

During the 2001 interview, Brinkley asked Armstrong what he thought of the movie The Right Stuff, adapted from Tom Wolfe's book. Armstrong responded that he thought "it was very good filmmaking". But he was critical of the freedoms that Hollywood took documenting the early days of the Space Age.

While it may have been entertaining, it was, he said, "terrible history".

"The wrong people working on the wrong projects at the wrong times. It bears no resemblance to what was actually going on".