The Mirror does Lie
Imagine, you are standing in front of a mirror, facing it. Raise your left hand. Raise your right hand. Look at your reflection.
When you raise your left hand your reflection raises what appears to be his right hand. But when you tilt your head up, your reflection does too, and does not appear to tilt his/her head down.
Why is it that the mirror appears to reverse left and right, but not up and down?
When you raise your left hand your reflection raises what appears to be his right hand. But when you tilt your head up, your reflection does too, and does not appear to tilt his/her head down.
Why is it that the mirror appears to reverse left and right, but not up and down?
posted by Rajesh Lal at
8:01 AM
16 Comments:
It show everything it sees on the side that it sees it. It doesnt reverse your image it reflects it. If it showed you upside down it wouldnt be a reflection.
Mirrors reflect light in a straight line that is perpendicular to the surface that the light strikes. So a flat mirror reflects images straight back, but a concave mirror flips the reflection vertically also, so that up is down as well.
Chirality is the term used to describe something having "handedness", & chiral pairs are defined as mirror images of each other.
Because your eyes are side by side and not stacked on top of each other.
because of the way light reflects it will flip an object horizontally not vertically as light. imagine its not a mirror its another person you raise you left hand to them it will look like the right hand but not vertically different
a mirror is a flat object which reflects in 2D, there is no 3D in a mirror, thats an optical illusion.
silly, it is not a concave mirror. The mirror is producing a reflection, nothing magical. Geeze, what a lame question
What's more is that when you tilt your head up or down, that is relative to the body, and whatever you do, the mirror doesn't change, just reflects it, so the image in the mirror will also go up or down relative TO THE BODY. That would be a completely different motion.
Such as if you had someone just standing opposite of you, facing you. If you raised your left hand and they raised their right, it would be as if you're looking at a mirror (appearances disregarded), but if you tilt your head up and they tilt their head down, that's a completely different movement relative to your own bodies. It becomes asymmetrical.
But that really doesn't matter since.. a standard flat mirror reflects all light from the same direction at the exact same angle, no rays cross each other and the image does not flip. Simply, you are viewing the rays of light from the opposite side.
This has nothing to do with reflectivity or optics.
This is simple reference coordinate systems.
Thus up always appears up, down always appears down.
Conversely, left appears right, and right appears left.
Left and right cannot be used as references. Substitute east and west, for instance, and see if they hold.
You will find they do!
Stupid question really, simple answer, can't blame Rajesh though, he's pulled out some beauties in the past weeks
Stupid question really, simple answer, can't blame Rajesh though, he's pulled out some beauties in the past weeks
EJ is right, the answer to this question is that the mirror image does not change left right top or bottom. When something is on the left side of you, you will see it on the left side in the mirror.
However, for the guy in the mirror things have changed. What you see on the left is on his right side.
This is caused by the fact that the coordinate system of the mirror guy has transformed. It is mirrored with respect to the mirror plane. When we have an orthogonal coordinate system x,y,z and x, y are parallel to the mirror plane or actually in the mirror plane, meaning that the mirror is in z==0. Than the guy in the mirror has his reference coordinate system that is transformed by x,y,-z.
Now this guy has his face pointed towards the mirror, it seems that it is a normal guy who turned around. That's why we like to identify ourselves with this guy and think how he would think left and right is. Than it seems that our left is his right. However this guy is built up in the negative z direction and it is not a rotation symmetric person. This is where the confusion comes from.
I would like to see how Rajesh can explain this in a more elegant way.
it's the same when looking at another person....u right is his left...n he is not upside down or wat...
As Bas has pointed out, right and left don’t [i]really[/i] get swapped. If something is to the right of you, it will still be to the right of you when looking at it through a mirror – you will have to turn your eyes or head slightly to the right to look at its reflection. Bas’s theory of psychologically placing yourself into your mirror image gets close to the point, but it doesn’t explain why, when looking at a written word through a mirror, you need to read it from right to left rather than from left to right. Here’s my attempt:
A mirror doesn’t actually invert left and right, it inverts front and back. If you write something on a piece of paper and then [i]turn it around[/i] so that it is facing [i]in the same direction[/i] as you, then hold it against the light and look at its back, you will see the writing is left/right-inverted, just as you would see it in a mirror. This is simply because you’ve turned it around. To look at something through a mirror, you must also have it facing the same direction as you, so you get the same effect, except instead of seeing it “through the back” (like the writing on paper), you’re seeing it “from the front” because front and back are inverted.
So why do we think [i]left and right[/i] are swapped? As Bas said, it's psychology, but more than just putting oursevles into our images position. When we see a mirror reflection, our mind creates a 3D model of the environment we see (otherwise we would just see moving forms on the mirror surface). Our mind wants this model to be a 1:1 copy of what is really there, but would rather do so by “turning” (rotating) what we see than “inverting” (reflecting) it, because that involves less brain work. Unfortunately for our mind, it is mathematically not possible resemble a reflection through rotation alone. So instead of biting the bullet and going for the front/back-inversion, most of the time our lazy minds just pretend what we see is a rotation around the vertical axis, only noticing the fraud when left and right become relevant, which isn’t too often. Whenever they do become relevant, we tend to hang on to the rotation and combine it with a reflection on the vertical/depth plane (swapping left and right), which ends out as the same transformation.
In theory we could also choose to see the mirror reflection as a combination of rotation around the horizontal axis and reflection on the horizontal plane, but that’s a pretty mind-boggling way of looking at it. We’re much less flexible when choosing what is up and what is down than we are when choosing left and right. We typically choose the person in question as reference when deciding what left and right are (a person looks right when (s)he turns his/her eyes or head clockwise), but choose the outer world as reference when defining up/down (a person looks up if (s)he is looking towards the sky – even if (s)he is lying down or doing a handstand).
it's called a mirror not an opposite.
because of the way light reflects it will flip an object horizontally not vertically as light. imagine its not a mirror its another person you raise you left hand to them it will look like the right hand but not vertically different
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