Is all of the powerful tale â€˜Unbrokenâ€™ really true?

It's so beloved that it seems almost heretical to question any aspect of "Unbroken," the best-selling book that has just been turned into a major motion picture directed by Angelina Jolie.

"Unbroken" is billed as the true story of Louis Zamperini, an Olympic runner who served in the US Air Force during World War II. While on a mission over the Pacific Ocean in 1943, his plane went down.

What follows is an account of human struggle and survival in the face of seemingly insurmountable odds.

While there's no doubt that Zamperini, who died last July at age 97, is an American hero, we wondered whether parts of his story could have possibly, maybe, unintentionally been exaggerated or mis-remembered. Random House, which published the book, would not comment on its editing or vetting process, but The Post called upon experts in endurance, survivalism and torture to weigh in on some of the book's more incredible claims.

The Panel:

Dr. Claude Piantadosi, professor of medicine at Duke University and author of "The Biology of Human Survival: Life and Death in Extreme Environments"
Thomas Coyne, chief instructor at the Survival Training School of California who has also provided training techniques to the US Marines, Navy and Air Force
Dr. Allen Keller, director of the Bellevue/NYU Program for Survivors of Torture

"Louie" should have died after prolonged sun exposure and no water for a week in the Pacific, says an expert.Photo: Universal Pictures

1. While lost at sea on a life raft, getting burned daily by the equatorial sun, Louis went six to seven days without water. Is this possible?

"This is highly unlikely, but remotely possible depending on the shade and the temperature," says Dr. Piantadosi. "If it was cool and shady, people can last perhaps up to a week; if it is very hot and sunny, as little as 48 hours." Dr. Keller agrees. "Very credible story," he says. "At the two-week mark, you perish."

2. Louis nearly drowns when his plane plummets into the ocean. According to the book, once underwater, he passes out, then comes to (no time frame is given). He begins "gulping reflexively," swallowing salt water and gasoline. He then finds canisters of carbon dioxide, which propel him to the surface of the ocean.

Dr. Piantadosi says it's possible to swallow water while drowning and survive. Dr. Keller agrees, but is more skeptical. "You have someone who was an Olympic athlete, but whether there's some dramatic license with this . . . this description is incredible."

How much water could Louis have swallowed? "Uhh . . . that's a tough question," Coyne says. "Not that much. You only have a few cubic feet in your lungs." He doesn't buy the account of the carbon dioxide canisters pushing Louis to the surface. "That sounds like a spy movie, like something out of 'Mission: Impossible.'"

"Unbroken" director Angelina Jolie talks to the actors on set.Photo: AP

3. Could one sustain, as Louis claimed, six blows to the nose with the tail end of a flashlight without the nose breaking? In this case, Louis also claimed his nose was broken weeks before, so badly that the bone stuck out — and this was after the Japanese captured him at sea.

"Far-fetched," says Dr. Piantadosi. "If the bones were exposed, and the person was badly malnourished, the infection rate would be quite high without good medical care." That first break, Coyne says, "is not just going to heal up in a couple of weeks. For it to be hit six times with a flashlight — that would probably do some severe damage." Dr. Keller thinks Louis "may have believed that, but I'm not sure he was really able to distinguish whether the site they were hitting had already suffered maximum trauma."

4. While in a Japanese concentration camp, Louis suffers from dysentery, starvation and intermittent 104-degree fevers — and then he is placed in front of 100 soldiers who have each been ordered to punch him once, in succession. (The book claims there may have been as many as 220 blows to the face.) Is this survivable? If so, what are the chances you emerge without brain damage?

"This is a bit far-fetched," says Dr. Piantadosi. "The blows would have had to have been pretty modest." "My guess is recall bias," says Dr. Keller. "I don't know that he would have known it was really 100 times."

This example gives Coyne serious pause: "With the fever, your brain's almost cooking and wanting to turn off." The bones of the eye sockets and nose, he adds, aren't very solid. "It seems that would cause severe deformation of the face," he says, adding that there are UFC fighters laid out by one punch. "One hundred punches in a row . . . I have no idea how anyone could survive that."

5. Could Louis, days later, have the strength to hold a heavy, six-foot-long wooden beam above his head for 37 minutes?

"I can't answer this intelligently," says Dr. Piantadosi. "It would depend on the weight [of the beam] and how weak he was." Dr. Keller thinks Louis may have had a distorted sense of time, but Coyne finds the scenario laughable. "What the f–k?!?" he says. "Sure. Why not while hopping on one leg and saying his ABCs backward?"