The "Mountain Or Valley?" Illusion ─ minutephysics

Thanks to Skillshare for supporting this video: http://skl.sh/MinutePhysics for 2 free months!

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.

Support MinutePhysics on Patreon! http://www.patreon.com/minutephysics
Link to Patreon Supporters: http://www.minutephysics.com/supporters/

MinutePhysics is on twitter - @minutephysics
And facebook - http://facebook.com/minutephysics
And Google+ (does anyone use this any more?) - http://bit.ly/qzEwc6

REFERENCES
Twitter posts:
https://twitter.com/Astro2fish/status...
https://twitter.com/BadAstronomer/sta...

Bad Astronomy Blog post: http://blogs.discovermagazine.com/bad...

Multistable perception http://en.m.wikipedia.org/wiki/Multis...

Top-left Lighting http://en.m.wikipedia.org/wiki/Top-le...

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

Created by Henry Reich


<style>.embed-container { position: relative; padding-bottom: 56.25%; height: 0; overflow: hidden; max-width: 100%; } .embed-container iframe, .embed-container object, .embed-container embed { position: absolute; top: 0; left: 0; width: 100%; height: 100%; }</style><div class="embed-container"><iframe src="http://www.youtube.com/embed/V7C318DGB38" frameborder="0" allowfullscreen></iframe></div>

Watch Video on YouTube Watch Full-Window Video