At 11, Alan Alda was fascinated by the colorful, translucent undulations of a burning flame.

So he asked his teacher, “What is a flame?”

“It’s oxidation,” she said.

The answer dumbfounded him. A flame is indeed oxidation, a type of chemical reaction that occurs when something burns. But the word did not capture why a flame burns orange or why it produces heat, or anything else that the young Mr. Alda really wanted to know about it.

“It’s just giving it another name,” he said by telephone last week. “It’s like saying, ‘Well, a flame is Fred.’ And that really doesn’t get you anywhere.”

Mr. Alda, now 76, pursued acting rather than science — many people still think of him as Hawkeye Pierce from the television series “M*A*S*H” — but his fascination with the universe persisted.

In the 1990s, he led the collaboration that created “QED,” a play about the brilliant, irascible, bongo-playing physicist Richard Feynman, with Mr. Alda playing Dr. Feynman. Also, for 11 years, he hosted the PBS television show “Scientific American Frontiers.”

In talking to so many scientists, Mr. Alda wondered how they might do better at explaining their work, and suggested to universities that communication skills should be taught to science majors and graduate students. He made that pitch to officials at Stony Brook University on Long Island, who liked it so much that they founded the Center for Communicating Science in 2009.

The center, part of the university’s journalism school, offers courses and workshops including improvisation sessions for scientists; Mr. Alda sometimes shows up to help teach. The goal is not to turn the participants into Second City troupe members, but to help them interact with an audience without using jargon — “to connect better,” said Elizabeth Bass, the center’s director.

The old question about the flame came back when the journal Science asked Mr. Alda to write an editorial about communicating science. His article began with the anecdote.

Then he thought, why not also create a contest where anyone — including scientists — could offer an explanation of a flame, and recruit 11-year-olds to judge which one is the best?

That is what he and Stony Brook did, setting up a Web site, http://flamechallenge.org, to collect entries, which can be video, graphics or just words.

The deadline is April 2.

“We’re really hoping this will bring attention from a different direction to the question of communicating science,” Mr. Alda said. “And it will be fun. What scientists entering this contest will realize is it isn’t that easy.”

The winner will receive a V.I.P. pass to the World Science Festival, from May 30 to June 3 in New York City. At the festival, Mr. Alda plans to host a live version of the contest, perhaps asking about flames again, perhaps posing a different question.

“I hope what we will have is 11-year-olds saying, ‘I don’t get it,’ ” he said. “We might see some interesting techniques evolve during that event.”

Sixty-five years after he asked his teacher, how would Mr. Alda answer today? What is a flame?

“It’s oxidation, actually,” he said, laughing.