PURPOSE: Demonstrate the dark axle illusion.
DESCRIPTION: A loop of metal rod is illuminated as it is rotated rapidly about a diameter. The vertical diameter of the loop appears to be darker than the rest of the area, which appears as a dimly lighted disc.
REFERENCES: (PIRA unknown.) See Demonstration Reference File for information about this illusion.
EQUIPMENT: White metal rod with loop, rotator, and goose neck lamp.
SETUP TIME: None.
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