(The Hill) – With the Friday release of the critically acclaimed film “Oppenheimer,” audiences are getting a fresh look at the physicist dubbed the “father of the atomic bomb.”

Cillian Murphy stars as the title role in the Christopher Nolan-directed biopic based on the 2005 Pulitzer Prize-winning biography by Kai Bird and Martin Sherwin, “American Prometheus: The Triumph and Tragedy of J. Robert Oppenheimer.”

Gregg Herken, author of “Brotherhood of the Bomb: The Tangled Lives and Loyalties of Robert Oppenheimer, Ernest Lawrence, and Edward Teller,” described Oppenheimer as “complicated and contradictory.”

“He could be needlessly cruel, but he could also be very generous,” Herken told The Hill this week.

Here are five little-known facts about the real-life Oppenheimer, who before dying of throat cancer at 62 in 1967, changed the course of history:

Intelligence evident at an early age

The New York Times, in a 1963 profile of Oppenheimer, described how when the budding scientist was in the third or fourth grade, he “made an infrequent trip to the playground.”

“A child threw a ball out of the playground and the director criticized the throw,” the Times reported. “But young Robert calculated the force with which the ball struck the sidewalk and demonstrated that it could not have hurt anyone.”

As a third grader, Oppenheimer was also already conducting laboratory experiments, Sherwin and Bird wrote in their book.

At 10-years-old, he studied physics and chemistry.

And according to “American Prometheus’s” authors, Oppenheimer’s intellect sometimes came across as “too precious.”

“When he was nine, he was once overheard telling an older girl cousin, ‘Ask me a question in Latin and I will answer you in Greek.’”

Mystery surrounds the ‘J’ in his name

Oppenheimer’s birth certificate indicates that the “J” in his name was in honor of his father, Julius.

The scientist’s father, Bird and Sherwin wrote, “had already settled on naming his firstborn Robert, but at the last moment, according to family lore, he decided to add a first initial, ‘J,’ in front of ‘Robert.’”

But, the Los Alamos National Laboratory noted in an article that in a 1946 letter to the U.S. Patent Office, Oppenheimer wrote, “This is to certify that I have no first name other than the letter J, and that my full and correct name is J Robert Oppenheimer.”

Whatever the case was, Oppenheimer would “always be called Robert,” according to Bird and Sherwin.

He took private lessons to learn Sanskrit

After meeting a professor of Sanskrit at the University of California, Berkeley, Oppenheimer sought out private tutorials to learn the ancient language.

“He liked things that were difficult,” Oppenheimer’s friend, Harold Cherniss said, Bird and Sherwin wrote in their book.

“And since almost everything was easy for him,” Cherniss said, “the things that really would attract his attention were essentially the difficult.”

Soon after the lessons began, Oppenheimer was reading the Hindu scripture the Bhagavad-Gita.

“He had a facility for language,” Herken said, recounting how Oppenheimer gave lectures in Dutch while teaching a course at the University of Leiden in the Netherlands.

When Oppenheimer tapped one of his graduate students to take over a class for him, the student responded, “But Robert, I don’t speak Dutch.”

But, Oppenheimer allegedly retorted to the student, “It’s such easy Dutch.”

Einstein urged him to avoid Red Scare witchhunt

Oppenheimer’s security clearance became the focus of a four-week hearing in 1954 by the U.S. Atomic Energy Commission.

While Herken acknowledged that Oppenheimer had some ties to the Communist Party — calling it a “casual relationship” — the commission ultimately pulled his security clearance following the hearing in a move that critics said wreaked of McCarthy-era Red Scare fears.

Ahead of the hearing, Albert Einstein attempted to persuade fellow scientist Oppenheimer to resign from the commission and potentially avoid the public battle.

“Einstein argued that Oppenheimer ‘had no obligation to subject himself to the witchhunt, that he had served his country well, and that if this was the reward she [America] offered he should turn his back on her,” Bird and Sherwin wrote in their book.

After Oppenheimer rebuffed the advice, Einstein “walked to his office in Fuld Hall, and nodding in Oppenheimer’s direction, told his assistant, ‘There goes a narr [fool].”

He later felt guilt about his role in the Manhattan Project

“When the bomb went off, there was no question that Oppenheimer effectively celebrated,” said Herken, a historian and former University of California, Santa Cruz and Merced professor.

But after tens of thousands of people died in 1945 when the United States dropped two of the bombs that Oppenheimer helped create on the Japanese cities of Hiroshima and Nagasaki, the physicist “had these doubts.”

“He certainly had reservations and some feeling I think of guilt after the fact, after the casualty figures came in,” Herken said.

In a 1945 letter addressed to Secretary of War Henry Stimson, Oppenheimer wrote, “We believe that the safety of this nation — as opposed to its ability to inflict damage on an enemy power — cannot lie wholly or even primarily in its scientific or technical prowess.”

“It can be based only on making future wars impossible,” he said.

“He never apologized for the bomb,” Herken said. “He never said, ‘I regret that the bomb was used.’ I think his argument was — maybe he didn’t express it in so many words — but that it was necessary.”