Do teachers fall for such stuff?

Editor's Introduction -- Some schoolbook-writers evidently assume that teachers are stupid enough to believe almost anything. Just look at how some Prentice Hall writers have purported to "explain" a famous scene in a film.
from The Textbook Letter, May-June 1993

Elegant Illusion and Shabby Fakery

William J. Bennetta

The film Royal Wedding, issued in 1951 by Metro-Goldwyn-Mayer, includes a delightful, four-minute sequence in which Fred Astaire, animated by his love for Sarah Churchill, dances in a hotel room. His passion is so powerful that it evidently frees him from gravity, for he is seen to dance not only on the floor but also on the room's walls and ceiling. The illusion is elegant, and the sequence is deservedly famous.

I was reminded of both Astaire and Royal Wedding recently, because they have been used in some shabby fakery that appears in Prentice Hall's Motion, Forces, and Energy, a middle-school book in the Prentice Hall Science series. This case illustrates, with exceptional clarity, what can happen when the writing of schoolbooks is left to charlatans.

On page 13 of Prentice Hall's book, the student sees a single frame from Royal Wedding. It shows Astaire dancing upside-down, and it carries this caption: "No need to turn this photograph right-side-up. Fred Astaire is dancing on the ceiling, or so it seems. How is this effect achieved in the movies?" In the teacher's edition, Prentice Hall's writers give this "answer" in a note: "The actor stays in one place, but the background is slowly rotated. When the film is shown, it is turned upside down so that the actor appears to be on the ceiling."

What rubbish! The writers, who obviously don't know how the scene was filmed, have simply taken two wild guesses -- one involving rotation of a background, the other involving inversion of the film. Both guesses are wrong, and they combine to produce an "explanation" that isn't even plausible, but the writers evidently don't care. They seem to assume that teachers are stupid enough to believe almost anything.

What would happen if you set up a camera and filmed a dancer who stayed "in one place" while a background was "slowly rotated" behind him? What would your film show? It would show a man dancing in front of a background that was moving with respect to both the man and your camera. And no matter how you projected such a film, it could not yield the illusion that M-G-M has achieved -- the illusion that the room is stationary with respect to the camera while Astaire moves with respect to both, traveling from floor to wall, wall to ceiling, and so forth.

The writers' second guess -- "When the film is shown, it is turned upside-down" -- is just idiotic. If the film were turned upside-down, the entire sequence would be seen backward, because a film that runs through a projector upside-down must also run reversed; the sequence would also be silent, because turning the film upside-down would make the sound-track useless. And even if inversion of the film could make Astaire seem to dance on the ceiling, it could scarcely account for his dancing on the walls. How would that effect be achieved? Perhaps teachers are supposed to imagine that the film is also turned sideways.

Now, how was the scene really done? I thought I knew the answer, but I checked by sending an inquiry to Turner Entertainment Company, in Los Angeles. Turner is the current owner of Royal Wedding, having acquired the M-G-M film archive about seven years ago. Turner's vice-president for worldwide film services, Richard P. May, sent me a short letter that confirmed my understanding.

For the scene in question, M-G-M built a full-scale room (comprising a floor, a ceiling and three walls) that could rotate around a horizontal axis. While Astaire danced inside it, the whole room turned; and the camera turned with it, because the camera was firmly attached to the room's floor. One aspect of M-G-M's elegant illusion, then, was not an illusion at all. The room really was stationary with respect to the camera, because -- with respect to the rest of the world -- the room and the camera were rotating together. The result was an effect that never could have been obtained by simply putting Astaire near a rotating "background."

In my inquiry to Turner Entertainment, I quoted Prentice Hall's nonsense about turning the film upside-down, and I said that I knew it to be wrong. In his letter to me, Richard P. May commented: "You are absolutely correct, of course, in that the film could not be turned upside down in the projector to make it appear that Fred Astaire is dancing on the ceiling. . . ."

For a full-length review of Prentice Hall's Motion, Forces, and Energy, see The Textbook Letter, November-December 1992.

William J. Bennetta is a professional editor, a fellow of the California Academy of Sciences, the president of The Textbook League, and the editor of The Textbook Letter. He writes frequently about the propagation of quackery, false "science" and false "history" in schoolbooks.


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