A man stands before a crowd holding a styrofoam cup. He pours the water in the cup. Maybe he smirks. Then he turns the cup upside down and . . . nothing comes out. The crowd gasps. But wait: He's not done. Poke a pencil in the bottom of the cup, he tells an audience member. Someone pokes. Still no water on the floor.
The man with the magical powers has a doctorate, and he's the dean of engineering at Dartmouth College. And there's a simple scientific explanation behind his sorcery: He slipped some slush powder into the cup.
"It's a simple polymer," said Lewis M. Duncan. "It's the same stuff they put in diapers to prevent them from leaking."
As long as there have been magic tricks -- for the better part of 5,000 years -- there have been scientific explanations for the things we see, or think we see, or see and then not see and then see again.
And now Boston's Museum of Science is helping reveal those underpinnings with "Magic: The Science of Illusion," which opened over the weekend. The show, curated by the California Science Center in Los Angeles, aims to preserve magic's magic but at the same time give museum goers at least a partial peep behind the curtain.
Famous illusions explained include: Penn & Teller's bodiless head; Goldfinger & Dove's levitating chair; Max Maven's mindreading; and Jean-Eugene Robert-Houdin's "light and heavy chest," in which someone is invited to pick up a box and then, after a few magic words are incanted, the person who had no trouble lifting it the first time, suddenly finds it too heavy to budge.
Behind these and other illusions lie cables, levers, magnets, mirrors, more mirrors, some simple math, and an iron plate. The theater of the trick disguises the science and heightens the mystery.
"Magic combines -- and has almost always combined -- very sophisticated mechanical, electrical, and material technology with very straightforward techniques in deception and misdirection," said Duncan, who has not seen the exhibit.
The engineering professor, whose official specialty is in experimental space plasma physics, said it's our natural interest in science that has made magic so universally appealing for millennia.
"It's part of human curiosity," he said. "Nature often does things we don't expect. Why do the leaves change? What's the source of an aurora?"
Or: How can a body be made to disappear, leaving only its head behind? That goes back to the psychology of misdirection.
"If I'm staring at you, looking at you intently and speaking intently, the pressure you'll feel to raise your head and look directly at me is enormous," said Larry Haas, a professor of philosophy at Muhlenberg College in Pennsylvania and director of the school's Theory of Art and Magic program.
"Magicians know how to make that happen so you don't even feel a suspicion about what's going on," he said. "Then you don't see the elephant being dragged in."
Penn, who has made a career of dragging in unseen elephants and other objects, said it's hard to beat the "ah-ha" feeling of suddenly being able to see through an illusion. That feeling is "to me, one of the most powerful feelings any one can ever have."
Although he and his silent partner (and frequent victim) Teller, reveal the mystery of their bodiless head trick in the museum exhibit, their magic goes further than their explanation. That's because understanding the math, chemistry, or physics of a trick is ultimately unsatisfying, Penn said.
"Sometimes people come up to me after a show and ask how we did something," Penn said. "Once in a while, I tell them. And there's no look of satisfaction at all. I don't think they really want to know how we did it.
"They want to look into themselves and see the whole process of how they got false information from the world. Telling them I shifted something from my right hand to my left isn't what they really want to hear. There's more to it."
Michael Rosenwald can be reached at email@example.com