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Magic Mirror on the Wall, How Do You Even Work at All?

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Keith Sabine
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The magic of mirrors
Keith Sabine   12/2/2014 10:11:52 AM
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Another oddity about mirrors is apparent if you stand in front of them. Raise your left arm. The image in the mirror raises its right arm. So horizontally, mirrors transpose left and right. But nod your head, and the mirror nods back without transposing up and down.

Max The Magnificent
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Re: The magic of mirrors
Max The Magnificent   12/2/2014 11:09:04 AM
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@Keith: Another oddity about mirrors is apparent if...

This is because we have two eyes separated horizontally -- also the way in which the brain's right hemisphere processes info from th eleft eye and vice versa -- if we had one eye located in the center of our forehead and the other on our chin and so forth, then the transposition effect woudl be in the vertical plane instead of the horizontal.

Max The Magnificent
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Still Confused
Max The Magnificent   12/2/2014 11:26:34 AM
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Hi Bernard -- thanks for this explanation, but I'm still confused.

As I mentioned before, I've read Richard Feynman's book QED: The Strange Theory of Light and Matter, and I follow the idea that the photons can (and do) take every possible path (even though this makes my mind throw a bit of a wobbly); also that phase changes between the various paths result in a peak such that the angle of incidence = the angle of reflection.

I've also read The Quantum Universe: (And Why Anything That Can Happen, Does) by Brian Cox and Jeff Forshaw, which covers the same thing is a slightly different way.

But even accepting all of this -- the surface of the mirror is composed of atoms -- and although it looks smooth at our macroscopic level, when we "zoom in" it would look like the surface of the moon at the atomic/photonic level with all sorts of "bumps" and suchlike, which you would think would scatter the light in all directions.

And then we have the fact that the electron shells surrounding an atom aren;t spherical -- they come in all sorts of weird and wonderful shapes (yes, I know they aren't hard shells -- rather probabilities and stuff).

And then we have the fact that -- as far as I understand it -- a photon doesn't "bounce" off the electron shell an atom like one billiard ball bouncing off another -- instead it raises an electron to a higher energy level -- then at some time in the future that electron falls back to its original energy level and emits a new photon -- but what's to say that this photon won't head off in any direction...

My noggin hurts...

Keith Sabine
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Re: The magic of mirrors
Keith Sabine   12/2/2014 11:36:07 AM
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Indeed Max, we are horizontally symmetrical but not vertically symmetrical... but it's our brain which is doing the processing of what is left and what is right. And our brain is conditioned to thinking (for millions of years) that the mirror is not really there, so it inverts right and left.

anon0735652
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Re: The magic of mirrors
anon0735652   12/2/2014 12:08:20 PM
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We see our left side on the left side of the mirror, our hair at the top, etc. The 'transposition' is simply us trying to turn ourselves around in our mind to imagine what we look like based on the image in the mirror. We could just as easily imagine ourselves upside-down instead but that is not the way our minds work since our pre-processing based on evolutionary usefulness with most external arrangement and movement occuring in the horizontal plane (that also being the reason why our eyes are horizontally spaced, i.e. the eye arrangement is a result of the same cause but is not the cause).

Regarding the core question about the paths, it seems that the discussion falls into the common trap of asserting the particle-wave duality while dwelling on the discrepancies that arise when considering the photon as one or the other or both in a conventional sense, which it is not! Just think about the definition of 'path'. What are those lines that were drawn? What is moving along them? The answer is that nothing is moving along those paths specifically. The photon is only localized at emission and detection. However, those paths can be considered as building blocks to the complete 'path' in a similar fashion to how a line segment is an approximation of part of a curve.

RichQ
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Re: The magic of mirrors
RichQ   12/2/2014 12:33:58 PM
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It seems to me that the problem is our use of the terms "left" and "right" which are relative to the observer. If we are facing east, looking at ourselves in a mirror that is "facing" west, the hand on the north is the same for both the person and the image. There is no reversal occurring in the plane of the mirror. As you say, our brains insist on perceiving the reflection as though it were an object and assigning left and right attributes based on that mental model, then mentally rotating the model about the vertical axis to form the model for the object facing us. It's the mental rotation that reverses the right and left-handedness of things. But the reflection isn't a rotation, it's a reversal in the direction normal to the plane of the mirror, and that is different. The world we percieve in the mirror has a coordinate system that is left-handed where ours is right-handed, because only the z-axis (the one into the mirror) has been reversed. X and Y in the plane of the mirror are not reversed.

Another way of thinking about it is that the object in the mirror has been reversed in the z-axis only. If it were a physical transformation, it would be like having every atom in our body reverse its front-to-back position. Left and right, top and bottom remain the same. But if we were to do that in real life, what we called our right hand would now be our left.

By the way, if you want a reflected image that looks like you facing yourself, put two mirrors together at right angles to one another and look at the reflection occurring at the seam. It is the result of a double reflection from you to one mirror then to the other mirror before returning to you. That does reverse right and left, but not top and bottom because that is the axis of symmetry for the reflection. The image you see will look like your clone looking back at you (except for the seam line).

 

DougInRB
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Re: The magic of mirrors
DougInRB   12/2/2014 12:36:51 PM
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Hang on a minute.  If we blame our brain on the transposition, why does it still look transposed when we take a photo of a mirror image and look at the photo later?  This is especially obvious when there are letters being reflected.

This all seemed so simple before I read this article.  Why did you have to mess with my brain???

 

DougInRB
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Re: The magic of mirrors
DougInRB   12/2/2014 12:40:21 PM
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@RichQ: Great (and simple) explanation.  Thank you!  I feel better now.

Duane Benson
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Re: The magic of mirrors
Duane Benson   12/2/2014 1:19:51 PM
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The mirror image isn't really reversed. When you look into a mirror, you're  essentially standing behind yourself and looking at your back side.

Except that you've removed your back skin and everything up to such a thin layer of your front side that it has all of the color and shape of your actual front side. You're looking at your back side with the imagery from your front side layered on top. So, when you move your right arm, the mirror image is also moving its right arm.

Or something like that

Duane Benson
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Re: Still Confused
Duane Benson   12/2/2014 1:25:05 PM
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'the surface of the mirror is composed of atoms -- and although it looks smooth at our macroscopic level, when we "zoom in" it would look like the surface of the moon at the atomic/photonic level with all sorts of "bumps" and suchlike, which you would think would scatter the light in all directions.'

Given that there is so much space between the electrons and the nucleus, zoom in enough and rather than a bumpy surface, it would look more like empty space. Light should simply pass through all of that space and we shouldn't be able to see anything at all.

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