Consider the rate of change of the object. Consider the rate of change relative to one’s own position. An airplane flies at a specific altitude. The melting of ice cubes on a tabletop at room temperature. How much molecular alteration must occur before the state change is noticeable? How much time passes before one notices? What is the slowest perceptible change? Ice floes on the tidal Hudson River, viewed from the waterfront adjacent to the Poughkeepsie rail station, one morning and one afternoon. The ice floats one direction the first day and the other the next. See the ice floating south and imagine the ice floating north. See the ice floating north and remember the ice floating south. The patterns and texture of ice on Himalayan mountaintops, as viewed from a NASA satellite camera. The course of the Catskill Aqueduct was plotted on a Shawangunk Trails map. The closest public access to this underground aqueduct, which delivers drinking water to New York City, is located in Minnewaska State Park Preserve. When the park’s roads became impassible by car, I walked. Based on the perceptual abilities of one’s eyes, choose the fallen leaves with the highest color saturation.