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This video is about why words flip left & right (aka horizontally) in a mirror but not up & down (aka vertically). The answer has to do with specular reflection, mirrors being like windows into another world (alternate universes, just with in and out flipped!), and transparency of the things we write on.

REFERENCES
Specular Reflection
https://en.wikipedia.org/wiki/Specula...

PhysicsGirl video about mirrors
   • Why do mirrors flip horizontally (but...  

Fermat’s principle

http://electron6.phys.utk.edu/optics4...

Thomas-Fermi screening
https://en.wikipedia.org/wiki/Thomas%...

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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