Like many science instructors, George Mason University physics Professor Robert Ehrlich likes to perform tricks to engage students in the classroom. One of his favorites involves a drinking glass, water, and some cardboard. Traditionally, a teacher partially fills the glass with water, places a piece of cardboard across its mouth, and turns the contraption upside down. Thanks to the miracle of air pressure, the cardboard holds tight and the water remains in the glass. But Ehrlich’s variant takes the demonstration one step further: Placing the glass strategically above a cowering student’s head, he actually removes the cardboard—and the water stays put. His secret: Before going to class, Ehrlich places a nearly invisible wire mesh across the mouth of the glass. That mesh supplies enough surface tension to hold the water in place.

Ehrlich, 63, earned his Ph.D. at Columbia and taught at the University of Pennsylvania, at Rutgers, and in the State University of New York system before settling at George Mason. Though he has distinguished himself as a cutting-edge researcher in particle physics, he’s perhaps become best known for making science more accessible to laymen. A few years ago, he wrote Why Toast Lands Jelly-Side Down, and this month, Princeton University Press released Nine Crazy Ideas in Science: A Few Might Even Be True. In it, Ehrlich offers scientifically rigorous assessments of nine unconventional theories, concluding each analysis with a rating of zero to four “cuckoos”—zero meaning the idea might one day be proved correct and four asserting that it’s most certainly false. Roughly half the chapters—including “More Guns Mean Less Crime,” “AIDS Is Not Caused by HIV,” and “Sun Exposure Is Beneficial”—address health and public policy issues; the others—including “The Solar System Has Two Suns,” “Time Travel Is Possible,” and “There Was No Big Bang”—cover physics.

Ehrlich isn’t against outlandish ideas; many scientific explanations that are now considered beyond reproach, he notes, were initially thought by mainstream scientists to be “crazy”—everything from relativity and black holes to continental drift and the notion that an asteroid impact killed off the dinosaurs. Many crazy ideas, he says, are dispatched because statistics don’t add up, because promoters are too zealous to appreciate their ideas’ pitfalls, or because theories are too all-encompassing to be functional.

But experienced scientific mavericks, Ehrlich says, know they must be firm in the face of opposition. Ehrlich knows this charge firsthand: He’s advocated the plausibility of particles that travel faster than light—a theory rejected by many of his physics peers. Though he’s still a member in good standing of his community of colleagues, posing unconventional theories “requires a lot of self-confidence,” he says.

Ehrlich is already working on a sequel to Nine Crazy Ideas, which will feature such topics as “Media Violence Does Not Contribute to Real-Life Violence” and “The Moon Affects the Behavior of People and Animals.” Other chapters may emerge as readers answer Ehrlich’s call to send him their own crazy ideas. Already, he’s steeling himself for a flood of e-mails. “I hope I didn’t make a mistake by including that request in the book,” he says. —Louis Jacobson