Mr. Wizard's World

Density Gradient, Paper plates, Thirsty Plants, Slime, Shark Movement and Vacuum Fountain and more (5x13)

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Sarah is not sure of the meaning of the word density, but has referred to someone as dense meaning thick-headed. Mr. Wizard shows Density Gradient, Microscopic Vorticella, Paper Plate Tops, Sound of Thirsty Plants, Greenhouse Effect, Fractal Geometry, Slime & Disappearing Cup, Shark Movement, and Vacuum Fountain.