Good films, bad physics. South Dakota professor takes Hollywood to task to help teach high school science

By , Special to The Christian Science Monitor

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.''

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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.

Wile E. Coyote dashes off a cliff. He keeps going horizontally until he loses momentum in that direction, then he begins to fall. That is impossible: An object falls at the same rate whether you drop it straight down or fire it as a projectile.

If you simultaneously dropped a stone and fired a pop gun aimed levelly, both pop-gun cork and stone would hit the ground at the same time.

Weyland says that the American Journal of Physics recently polled college students, and 57 percent of them got that fact wrong. ``A large share of even college-educated people don't have a good perception of trajectory motion,'' he says. One point of that survey is obvious and hardly unknown: American students are frequently poorly educated in science.

But Weyland believes all the bad science in the films could go a long way to fixing that. He has put together a videotape of some of these scenes and takes them around to high school classes with interesting results, he told the physics meeting.

``Normally, physics professors go to the blackboard and ask questions,'' he says. ``There is usually deadly silence. But when I show teen-agers those clips, we're talking about their turf, the movies, and it lowers some barriers.''

Weyland says he has taken his tapes into high school classes containing students that were thrown out of regular classes for attitude problems.

``But by the time I was through, they were really interested and asking good questions.''

Two weeks ago, 90 students showed up for Weyland's lecture at the Lead, S.D., high school. According to librarian Crystal Cameron, the students, who were on their own time, enjoyed the videotape that Weyland used ``because they've seen these movies a hundred times.''

After his lecture, the students asked Weyland why they couldn't just go to a movie to enjoy it. ``He told them that it was something else to do with their minds,'' Mrs. Cameron said. ``You know how kids take these things literally. They tend to believe what they see on the screen.''

And almost no aspect of physics is ignored by the movies. When Indiana Jones steals the golden idol in ``Raiders of the Lost Ark,'' he substitutes a handful of sand to compensate for the weight of the idol and fool the alarm system.

``The density of gold is extremely high,'' Weyland says. ``I estimate the idol probably weighed 60 to 100 pounds. He would have needed a whole wheelbarrow of sand.'' A physics teacher would not need a vivid imagination to have a good time with that, he told the physics convention.

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