FASTER than a speeding bullet! Big deal. Leaps tall buildings with a single bound. No sweat. But X-ray vision? Now you're talking bad physics, and Jack Weyland, a professor of physics at the South Dakota School of Mines and Technology, thinks that sometimes bad physics from the movies can be a wonderful teaching tool.
Mr. Weyland, who gave a paper at a recent meeting of the American Physical Society pointing out impossible physics in motion pictures, suggests that physics teachers take full advantage of these errors. In his experience, he said in an interview with the Monitor, it works.
Take ``Superman.'' In the 1978 film, Superman rescues Lois Lane, who has fallen from the top of a tall office building. He zooms up and grabs her in midair, stopping her fall suddenly. ``The stop is as quick as if she hit the pavement,'' Weyland says. ``He has to slow her down gradually.''
Later in the film, an engine falls off Air Force One and Superman flies to the rescue, placing himself under the wing to act as the missing engine.
``The problem with that is he is developing thrust as a jet engine does, without ejecting material backwards the way jet engines do,'' Weyland points out, thereby violating Newton's Third Law of Motion.
Then there is X-ray vision. X-rays do not work the way Superman uses them. His eyes would not perceive X-ray radiation from an object or a person unless something was emitting the radiation from behind.
Spaceships in George Lucas's ``Star Wars'' trilogy have no need to bank in turns the way the fighters do in the battle scenes.
Indeed, there is no way they could in the vacuum of space, Weyland points out; banking is required only when flying through the air. In addition, explosions make no sound in space. But showing this accurately in the films would take some of the fun out of them, Weyland concedes.
How about that big lug King Kong? This is the problem of ``scaling up,'' Weyland says. ``If you increase the height of something, the weight increases more rapidly than the bone strength, and the bones cannot carry the weight.''
Nature knows this, Weyland says, and that is why elephant legs are designed differently from insect legs. A 50-foot gorilla cannot stand on the scaled-up legs of a five-foot gorilla.
Weyland even attacks that favorite of the young, the Road Runner. Road Runner and his coyote foil perpetually violate the laws of projectile motion, ignoring Newton and his famous falling-apple experiment.