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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. REFERENCES Bad Astronomy Blog post: http://blogs.discovermagazine.com/badastronomy/2010/05/19/a-lunar-illusion-youll-flip-over/ Multistable perception http://en.m.wikipedia.org/wiki/Multistable_perception Top-left Lighting http://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