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Discussion » Questions » Education » Why does a mirror appear to reverse things from left to right, but not top to bottom?

Why does a mirror appear to reverse things from left to right, but not top to bottom?

It's an old riddle, with a subtle answer. Richard Feynman gave an account of his days at Princeton, where freshman were often accosted by sophomores with such questions. Part of Feynman's genius was figuring things out in advance, so that he seemed to have the answer to impossible questions almost instantly. 

Hint to the answer - when you look at your image in the mirror, what is hidden from view?

Update August 15, 2016: Mathologer (a YT channel that I just discovered and to which you should all subscribe, if you love math) has a detailed video on this

Posted - July 28, 2016

Responses


  • I finally looked it up, and I still don't understand. Maybe I'll just smash the mirror.

      July 28, 2016 1:53 PM MDT
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  • 1113

    Aha, that's getting warmer. But if you made a copy of yourself, turned it around, so that your right aligns with its right, you'd be looking at its back. So you need one more step to create the mirror image we're familiar with. You reverse the back and front.

      July 28, 2016 1:56 PM MDT
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  • 17261
    True this. And it's not just a fantasy in the head of a little man who cries for attention!
      July 28, 2016 2:10 PM MDT
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  • 1113

    LMAO

      July 28, 2016 2:12 PM MDT
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  • 3191

    But I indeed am seeing myself as a person facing me would. If I face you and raise my right hand, I am raising the hand that is on your left.

    I never said it was "an exact copy of myself", only that I am seeing myself as someone facing me would see me.
      July 28, 2016 2:28 PM MDT
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  • 691

    It does if you turn it sideways.

      July 28, 2016 2:43 PM MDT
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  • 1113

    I don't think mirrors work that way... D:

      July 28, 2016 2:54 PM MDT
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  • 34270

    The image is exactly what is on the tshirt.  The shirt is printed from the wearers right to left (backwards).  So that when a person coming up in front of them can read the from their left to right. (Like normal)

    Look at your shirt (assuming it has writing) the writing will begin on your right side and end on your left.  The mirror is reflecting that.

      July 28, 2016 3:05 PM MDT
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  • 17596

    I mean the side not facing the mirror, usually  the butt side. 

      July 28, 2016 8:36 PM MDT
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  • Ah c'mon you're cute :-)

      July 28, 2016 11:33 PM MDT
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  • LOL aww :-)

      July 28, 2016 11:40 PM MDT
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  • 1113
    Maybe so, but even still. :D
      July 28, 2016 11:43 PM MDT
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  • xo

      July 29, 2016 12:01 AM MDT
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  • 17261
    Aww. WW, you're not a little man who cries for attention. ;-)
      July 29, 2016 2:02 AM MDT
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  • 1113

    Very nice. So, what accounts for the difference in the way the mirror image appears to differ from what we intuitively expect to see?

      August 15, 2016 3:33 PM MDT
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