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Friday, August 19, 2011

Magical Mirrors

Sometimes it's fun to set aside trivial questions like evolution vs. creationism and address the really important questions in life. The last time we did this was when we discussed the proper way to hang toilet paper [Gil Dodgen Explains the Salem Conjecture].

Chad Orzel of Uncertain Principles has posted a link to Rhett Allain at DOT.PHYSICS who asks one of those big questions that we've all pondered obsessively ...
Why do mirrors reverse left and right, but they don’t reverse up and down?.
Please proceed with caution because Rhett comes about as close as one can to answering the question—thus removing it from the top ten list of mysteries. If you want to preserve your childhood fantasies about the magical properties of mirrors then I advise you to ignore this posting.


  1. I think that one comment posted in reply is particularly interesting. A mirror on the ceiling (or on the floor, btw) will reverse up and down. And that got me to thinking: A mirror to your right (or left) will reverse left and right, just as a mirror in front of you (or behind you) reverses front and back.

  2. FWIW I don't think Rhett nailed the central issue. I've added my own explanation to that thread.

  3. @Anonymous

    I think it gets very confusing if you talk about "up" and "down", because then you have to think about the viewpoint to which these are relative. The question is easier to address if you stick to talking about the top, bottom, left and right of the object being reflected.