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## Question

When my daughter was about 4 or 5 years old, I saw her doing

odd looking calisthetics in front of a full-length mirror.

Then she asked me the question, "Why does the mirror switch

left and right, but not up and down?" I had no idea how to

answer her in a way she could understand. In fact, I'm not

even sure I understand. Does anyone have a clear and concise

answer to my daughter's question that a child of that age

could understand?

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Hmm an answer a 5 year old can understand.....

You are trying to explain axis of symmetry to a five year old, I guess I would give them credit for being pretty smart and start out like this.

"The mirror rotates the image along a vertical axis"

I would then use a prop to demonstrate what I am talking about. It could be a picture that I stand up and place my finger on the top middle and spin it 180 degrees to show her what I mean by "rotating on a vertical axis"

If you can see through the back of the picture to at least make out some of the real picture on the other side you will see the mirror image through the back. A better choice may be to use a drawing or a picture printed on regular paper (so it is semi see through, or if you have a transparency that would be even better). Tell her that is what the mirror is doing.

If that didn't work, I would say "The mirror doesn't switch left and right, it switches front and back" This is a worse explanation in my opinion, and is harder to understand in my opinion. But if the first one didn't work, this one might, you never know how people will perceive things.

And if both of those don't work, I would just tell her she is not seeing a mirror image, but instead looking into a portal into bizzaro world, where they do everything backwards than us. And she is just seeing her double from that world through this portal.

That last one is obviously a joke, so don't be mad at me when your daughter needs years of therapy because she keeps seeing her evil twin spying on her.....

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Here's an approach (your mileage may vary)

"It doesn't switch left and right. AND it doesn't switch up and down. Here, I'll show you.

(1) Your feet are on the floor out here and, in the mirror, your feet are on the floor. Your head and the mirror-head are nearer to the ceiling. So, you're right, it doesn't switch up and down. (If it did, your mirror-feet would be near the real ceiling.)

(2) Let's put a ring, bracelet, or wristwatch on your arm. Put it on the arm that's nearer to the window at your left [Ed note: or some landmark that is visible in the room]. Now, your ring is closer to the window, and the mirror-ring is closer to the window. So it doesn't switch left and right. (If it did, your mirror-ring would be farther from the real window)

What it ACTUALLY does is switch front and back!

(3) Stand facing the mirror, with one arm pointing to the mirror. Your body is further away from the mirror than your hand is. But the hand in the mirror looks closer to you than the body in the mirror is. So it is switching front to back".

Edited by CaptainEd
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the mirror does not reverse anything, you just percive it to be a different person turned around facing you. when you raise you left hand, the hand in the mirror on the left side goes up (left as you perspective). however, if the image on the mirror was a different person, then it is its right hand. Basically the mirror reflects in same direction the light appears.

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Switching of left and right (but not up and down) by the mirror is an illusion.

The source of this illusion lies in vertical symmetry of human body.

Imagine a creature with no such symmetry looking at its own reflection in the mirror.

Will this creature experience this illusion?

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Switching of left and right (but not up and down) by the mirror is an illusion.

The source of this illusion lies in vertical symmetry of human body.

Imagine a creature with no such symmetry looking at its own reflection in the mirror.

Will this creature experience this illusion?

Yes, it will. =/

From CaptainEd:

(2) Let's put a ring, bracelet, or wristwatch on your arm. Put it on the arm that's nearer to the window at your left [Ed note: or some landmark that is visible in the room]. Now, your ring is closer to the window, and the mirror-ring is closer to the window. So it doesn't switch left and right. (If it did, your mirror-ring would be farther from the real window)

Maybe it is also switching the window's position, as well. =P

I don't think I would tell her this, but I've seen kids use the L method with the index finger and thumb to determine which hand is their left. Standing in front of a mirror, you would have to hold up your right hand in order for your mirror image self to see the L (which would normally indicate your left hand). Bad stuff there. Bizzarro world is likely the best answer.

Perhaps using sticks or some solid straight object to show that the reflection an object follows a straight line. Perhaps showing her how light reflects off of a mirror will help, especially if you can represent the path of reflection of an object. I hope that makes sense. If not, I'll make a video this weekend.

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<p>It's simply the placement of the mirror.</p>

<p>A mirror in front of you reflects the x axis (right to left).</p>

<p>A mirror to your left reflects the z axis (front to back).</p>

<p>A mirror below you reflects the y axis (top to bottom).</p>

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<p>It's simply the placement of the mirror.</p>

<p>A mirror in front of you reflects the x axis (right to left).</p>

<p>A mirror to your left reflects the z axis (front to back).</p>

<p>A mirror below you reflects the y axis (top to bottom).</p>

I like that.

I was looking for some Bill Nye demos that could help explain it (he's got a strange way of explaining things to children that usually seems to work).

I found this, but it's not really a reasoning as much as a demonstration of observing the reflection.

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I say just have her look into a spoon (or concave mirror in general) and tell her, "There, it flips up and down as well!" and call it a day...

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The reflected image is just like another person standing in front of us. And we do not see the person upside down.

btw... look at the mirror with head tilted by 90 degree or while lying down, and the mirror switches up and down.

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