The Ball and Table Illusion
What to see and do: The ball is moving along the line during the first clip, right? But during the second and third clips it is going upwards. Not really,the ball is actually moving along the same path it did in the first clip.
What's happening: This illusion shows that your eyes use shadows to tell how close or far away an object is from the ground.
Credit: This illusion was discovered in 1990 by Daniel Kersten, Pascal Mamassian, and David Knill at the University of Minnesota. Kersten, D. J., Mamassian, P., & Knill, D. (1991) "Moving cast shadows generate illusory object trajectories," Investigative Ophthalmology and Visual Science, 32, 1179.
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