The "Mountain Or Valley?" Illusion
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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! Its 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
Twitter posts:
twitter.com/Astro2fish/status/859799730565414912
twitter.com/BadAstronomer/status/859800278358528001
Bad Astronomy Blog post: blogs.discovermagazine.com/badastronomy/2010/05/19/a-lunar-illusion-youll-flip-over/
Multistable perception en.m.wikipedia.org/wiki/Multistable_perception
Top-left Lighting en.m.wikipedia.org/wiki/Top-left_lighting
Minute Physics provides an energetic and entertaining view of old and new problems in physics — all in a minute!
Created by Henry Reich