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| possibility that visitors can, by themselves, achieve a very satisfying understanding through abstraction from multiple and contextually different examples. Many museums fail to provide this possibility because they show only a single representative example of each effect or process. A Different Drum to Demonstrate Resonance The basic problems of exhibit design are not solved by the general considerations that I have outlined. Each effect, each idea, each way of conceiving some aspect of nature requires a topic-specific design. One sees the need for an exhibit - that is, one is aware of a crucial link that is missing at the beginning or middle or end of some topical chain. The need may become apparent while teaching our aides or in conducting some of the formal classes here. Frequently this need festers for a year or more before someone on the staff or a visitor suggests a reasonable way of forging the link. In the meantime one continues to fabricate less crucial links in the chain. For example, we have been developing many exhibits on optical and acoustical resonance, but we have not figured out how to show, clearly and convincingly, what goes on when a non-resonant device, like a bow, excites a resonant violin string. We are getting closer. We increased the weight of the rope that is stretched across the 120 feet of the museum so that when the visitors jerk the rope they can feel the reflected pulse pull on their hand a moment later. We have a series of different length glass pipes, each of which responds, like a seashell held to the ear, by selecting and resounding a characteristic note out of the ambient noise of the museum. We have a 400-pound pendulum that visitors can put in motion only by pulling repeatedly and at the proper time on a cord that is very weakly attached to the pendulum by a small magnet. We are building an Aeolian harp. All of these exhibits work around the edge of the basic phenomena, but we still do not have anything to show how the rubbing of a bow or the hissing of a stream | of air is converted into a sustained tone in a musical instrument. We are planning other links in this resonance chain. We know roughly how to demonstrate the resonance absorption of yellow light by sodium vapor, but we have not yet managed to develop this important exhibit. On the other hand, we have not yet decided how to convey what is going on in a resonant electrical circuit. Perhaps, after we have built more links in an electrical phenomena chain, a method for this particular demonstration will occur to us. There are no general prescriptions for exhibit design that will solve this problem. Yet it is precisely on the success in finding such solutions that the quality of science museums depends. Addiction to Individual Discovery A museum's logistics force its staff to have flexible teaching strategies. Conducting a group tour is impossible. It is also impossible, even if one wished, to insist that visitors work with the exhibits in a prescribed order. In a crowded museum, the visitor may not be able to progress to the "next step" because other people are in the way. Even people who come together take separate paths and0 then call to each other, "Hey, come look at this!" When staff members are frustrated by our visitors' tendency to this kind of "Brownian motion," I urge them to look back and remember how many different kinds of patterns and circumstances in their own learning were wonderful like the variety of my mountain walks. The character of our visitors' exploration of the museum is the main reason for our having aides - we call them Explainers - moving around the floor, stopping to play with or fix one of the exhibits. (Any attempt to repair an exhibit invariably draws an eager group.) The difficult problem for the staff is how to show our visitors the path leading to the broader vistas and the sense of unity and coherence that one would like them to perceive and which, to a large extent, they would like to find. | ||