"It was a little bit like Shakespeare's 'Julius Caesar.' That's not to be critical," Graham said. "Shakespeare wasn't less of a playwright because he didn't get all the history correct."

The movie shows that Feynman reluctantly joined the presidential commission after being recruited by Graham. Although weakened by cancer, the outspoken Feynman fully committed to the investigation after arriving in Washington eight days after the ill-fated launch.

The scientist known for his unruly gray hair, nerdy glasses and keen intellect refused to accept the notion that the explosion's cause would never be determined, even though the shuttle was one of the most complex machines ever built and many of its 2.5 million parts were submerged in the Atlantic Ocean.

"An explanation can be found," Feynman asserted before beginning an independent probe. Most of the managers and engineers he encountered were closemouthed, worried about their careers. But as Feynman said, if no one was allowed to determine the explosion's cause, everyone would lose their job.

At first, Feynman believed the main shuttle engines were at fault, after discovering cracks in turbine blades and witnessing extreme vibrations during a test firing. That theory proved false, however, when telemetry data indicated the engines fired perfectly during the 73 seconds prior to the deadly blast.

A breakthrough came when NASA released photos showing a plume of flame spurting from the side of a solid rocket booster. Flame was a symptom of the failure, Feynman realized. But what was the cause? What was different about this launch compared to all the previous missions?

A call to the National Weather Service provided the answer. Cape Canaveral, Fla., experienced freezing temperatures that winter morning, while on prior launches it had never been colder than 53 degrees.

"That's the variable," said Feynman.

Engineers warned NASA about this critical, weather-related issue. But the space agency was under intense pressure from Congress and the military to maintain unreasonably ambitious flight schedules. The risky decision to launch not only claimed the lives of the Challenger crew members but also grounded the shuttle fleet for nearly three years.

Ultimately, Feynman's detective work arrived at this: Rocket booster design flaw + management failure + cold weather = disaster.

Feynman didn't live to see the next shuttle launch. He died in February 1988 at age 69 of cancer possibly caused by radiation exposure more than four decades earlier at Los Alamos, N.M.

In his appendix to the commission report, Feynman urged NASA to always be frank, honest and informative with the public so its tax dollars could be spent wisely.

"For a successful technology, reality must take precedence over public relations," Feynman wrote, "for nature cannot be fooled."