The “Mountain Or Valley?” Illusion04:33

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Published on June 29, 2017

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This video is about a multistable perceptual illusion, similar to the hollow face illusion, whereby maps or aerial or satellite photos look upside down/inside out, ie, concave (valley) parts look convex and convex (mountainous) parts look concave. Just flip the images around and things will make a lot more sense! It’s just because our eyes gauge depth based on the location of shadows, and the sun always casts shadows on the bottoms of things.

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REFERENCES
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Bad Astronomy Blog post:

Multistable perception

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Minute Physics provides an energetic and entertaining view of old and new problems in physics — all in a minute!

Created by Henry Reich

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