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 | truncated rubber highway marker mounted on top of it. The air stream supports a light-weight volley ball. The Bernoulli effect is strong enough so that one can feel an appreciable inward force if one tries to pull the ball out of the stream. People tap the ball and watch it oscillate in the stream; they partially cover the orifice with a hand or direct the stream to one side; they remove the ball and try to throw it so that it is caught by the stream. But they also do completely irrelevant things. Girls let their long hair stream up in the air current; kids hold their Tshirts over the orifice and let the air stream cool their bellies. Some people play catch with the ball either through or around the air stream. We lose about 25 balls a year - one per 20,000 visitors. If the ball is missing, people tear up bits of paper and see how these behave in the air stream. It is a pretty good exhibit, but we should build more links in this particular chain. I cannot really say that I have noticed any difference in the way visitors to the Exploratorium behave on sunny and cloudy days. But for the staff and especially for me, and my feeling for you when you come to visit, whether the sun is turned on or not makes an incredible difference. This is because of the Sun Painting. I think it crucially important to have an exhibit of such scale and beauty. A beam of sunlight comes through a skylight from a sunfollowing mirror to illuminate the dusty gloom at the north end of the building. It strikes an angled flat mirror which sends it parallel to the floor into an array of vertical prisms; a multitude of vertical strips of mirror then pick up each individual spectral color, directing each color first behind and then onto an eight-by-fifteen-foot frosted screen. The exhibit demonstrates light scattering, prisms and mirrors and color, and sunlight. It is a brilliant abstract painting that shimmers and changes as people move in the light path and brush against the mylar mirrors behind the frosted screen. We have other exhibits of beauty, and without them the museum would be sterile and incomplete; but none are so fine as the Sun Painting. Not all the exhibits in the museum need to be of great beauty, but surely some must be, or the place would be for nobody. | ||||
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| because a loose collection would have gone every which way and become tangled on the polefaces. We were too timid (or not clever enough) to use such a messy array of wires. We used a permanent magnet rather than a variable electromagnet because we thought the exhibit would thereby be conceptually more obvious. Thus, one by one, we designed out any and all the features that might have made the exhibit worth spending some time with. We converted the tree into a telephone pole. Although the best exhibits commonly link several intersecting chains of ideas, this property is not essential. The Bernoulli Blower is a case in point. Here, a large blower has a | |||||