There are some things Jearl Walker won't do to prove his point. He won't walk across a bed of hot coals; the last time he tried that, he burned himself so badly he almost lost a foot. And he won't dive off a three-story building onto a pile of cardboard boxes, though he believes it would be an arresting way to study impact. "Ultimately," he explains, "I decided it would be a foolish way to die."

Still, Walker doesn't hesitate to dip his fingers in molten lead, or gargle supercold liquid nitrogen, or even lie on a bed of nails while someone smashes a brick on his chest with a sledgehammer. His message is that physics doesn't have to be dreary. "Kids dread the subject," explains Walker, 36, a full professor at Ohio's Cleveland State University. "They have been taught that physics is very mathematical, and that it has nothing to do with their lives. That's just crappy," he adds impatiently. "I try to make it real, to make them care about the things I find fascinating, like the beginnings of the universe. Sure, some of my tricks are childish and silly, but they don't interfere with the physics."

Clearly they don't interfere with his popularity either. Every year some 800 undergraduates vie for the 250 seats in Walker's lecture course, though he is a demanding instructor who flunks five percent of his students. The author of a lively textbook entitled The Flying Circus of Physics, he is a regular contributor to Scientific American, scripts a weekly radio show on science for the Canadian Broadcasting Corporation, and recently finished a pilot for a local public-TV series. How does he feel about his fellow scientist-showman Carl (Cosmos) Sagan? "The best thing since Einstein," says Walker. A native Texan, born in Fort Worth, Jearl went to MIT as an undergraduate intending to study chemistry, but switched to physics after he flunked the first test. Bored with the way the subject was taught—"like witchcraft," he recalls—he stuck it out, and began his teaching career as a graduate student at the University of Maryland. "The students were going to sleep and so was I," he says. "A lovely girl in one of my classes asked me to give some examples of how physics would affect her life, and I couldn't think of even one. Now I'm trying to get kids interested in things around them, like bathrooms. Most of us never even understand how the toilet flushes."

To penetrate his students' apathy ("Most of them are thinking about drugs and sex"), Walker realized he had to turn to histrionics. Now when he talks about gravity, he starts with a pratfall. Before his injury, he walked on hot coals to show how perspiration could provide insulation; unfortunately, he neglected to sweat. To illustrate the properties of sound, he dresses up in drag as a cheerleader.

Divorced in 1977 after 10 years of marriage and three children, of whom he has custody three days a week, he encourages students to call him with questions at his suburban Tudor home. It's there that he dreams up his blatant attention-grabbers, like a multimedia show on nuclear weapons featuring slides and a laser display to music by Pink Floyd, the Rolling Stones, Aerosmith and the Beatles. "My job isn't to moralize," he says, "but these kids don't have the faintest idea what kind of destruction went on at Hiroshima and Nagasaki." To jolt them into understanding, he shows pictures of the two cities' destruction, then switches abruptly to a shot of his 11-year-old son Chris wearing a silly hat. As nuclear explosions burst around him, the little boy's smiling face slowly fades. "It's a wallop to the stomach," says Walker, "but it makes them remember. I am determined that kids see the Greek tragedy in the stuff we call physics, the laughter and the sadness. After all, physics not only runs the everyday world, it may be the end of it."