Heidegger's brush

Looking with one eye through a Polaroid filter at a bright patch of sky for 10 to 15 seconds, and then suddenly rotating the filter 90°, produces a faint yellow patch with faint magenta lobes at right angles (like a double ended shaving brush). The orientation of the yellow brush (vertical above) is the orientation of the electric vector and depends on the orientation of the Polaroid. The effect appears to have something to do with fatigue in the retina.

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