Ring Around
Two dark discs, one in a tight ring and one in a wide one.
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Two dark discs, one in a tight ring and one in a wide one.
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Comment ça marche — à lire plutôt après avoir essayé
Pulled out, pushed in
The discs are the same size. A ring close to a disc tends to be merged with it, so the disc borrows some of the ring’s size and looks larger; a ring far away is compared with it instead, and next to something big the disc looks smaller.
The Belgian philosopher and mathematician Joseph Delboeuf described it in 1865. It is a close relative of the Ebbinghaus circles, and it has been suggested that the same thing makes a portion of food look smaller on a large plate.