Why does a mirror appear to reverse left and right but not up or down?
Add your possible solutions in a comment, I will put the one which will convience me here
Comments: Flat Nested Threaded Embedded Oldest First Newest First Reflections By psyang on Tuesday, August 29, 2006 (UMST) It has to do with gravity. When we face someone, the difference in orientation between them and us is that they have rotated 180 degrees along the z-axis (where I define the z-axis to be the direction of gravity - straight through the top of their head into the ground). As such, their left is on the same side as our right, and their right is on the same side as our left. But their top and bottom are identically oriented to our top and bottom. When we view ourselves in the mirror, the thought that left and right are reversed is because we expect the reflection to imitate how we view others in real life - their left to our right, etc. But in a mirror, our image's left is produced by light travelling from our eye, to the mirror, reflected back to our right side. So what we expect to be our left is really our right. Suppose there was no gravity. Then we may meet people oriented 180 degrees along the x-axis (where the x-axis is defined as from left-to right, straight through their right and left sides). Thus, their feet are where our head is, and their head is where our feet are. But their left is on our left, and their right is on our right. If this were the norm, then our view in a mirror would seem to reverse top and bottom, but not left and right. Reply to this Comment Every one should remember law of reflection! By richa on Saturday, October 14, 2006 (UMST) I wonder what newtons law of gravity has to do with law of reflection. We in reality see upside down images which is then converted to the normal image.When we look at an object in a mirror (or through a lens) we are looking at an image of the object. When an object is illuminated with light (or when it merely gives off light), light rays from the object are moving in a variety of directions. Some of these light rays from the object ultimately strike the mirror. These light rays reflect off the mirror, following the law of reflection. Some of them reflect towards the eye of an obsever, recreating the image on the back of our retina, which in turn our brain perceives and interprets. The image of the object in the mirror is the result of reflected rays. The actual image location is the location where reflected rays from the mirror intersect. This location can be either behind the mirror (if reflected rays diverge) or in front of the mirror (if reflected rays converge) But regardless of which side of the mirror the image is formed on, the image location is formed where the reflected rays intersect. To identify the image location, reflected rays must be traced forward or backwards until they intersect cheers, Richa Upadhyay Reply to this Comment An addition to my previous answer By richa on Saturday, October 14, 2006 (UMST) It is true that the images formed on your retina are upside-down. It is also true that most people have two eyes, and therefore two retinas. Why, then, don't you see two distinct images? For the same reason that you don't see everything upside-down. One of our most remarkable tools - the brain - is hard at work for us at this task. Processing visual information is a complex task - it takes up a relatively large portion of the brain compared to other senses. This is because your brain performs several tasks to make images 'easier' to see. One, of course, is combining the two images, which is helped by the corpus callosum, the tiny part of your brain which joins the two big hemispheres. The other part is handled in the optic part of your brain itself, and part of its job is to make images right-side-up. It does this because your brain is so USED to seeing things upside-down that it eventually adjusts to it. After all, it's a lot easier to flip the image over than it is to try and coordinate your hands and legs with an upside-down world! As a result, though, it is believed that for the first few days, babies see everything upside-down. This is because they have not become used to vision. cheers, Richa Upadhya Reply to this Comment Might have something to do with eyes relative position By roryjoon on Saturday, December 09, 2006 (UMST) I am thinking it might have something to do with the eyes in respect to each other. Assume an alien whose two eyes are lined up vertically instead of horizontally( human case). How they would observe themselves in mirror in this case? Reply to this Comment The difference is in the frames of reference. By msnicki on Wednesday, December 13, 2006 (UMST) Right and left are defined relative to the person either looking at or in the mirror. Up and down are defined by an outside frame of reference, namely, the world around us. Reply to this Comment It doesn't By wahmeya on Monday, February 19, 2007 (UMST) A mirror doesn't reflect left and right, it reflects into and out of the mirror. If you point an arrow towards a mirror it seems to be pointing out of it. A more elaborate explanation of this (and many other puzzles) is available in the book How Would You Move Mount Fuji. Reply to this Comment Reflection By Ames_88 on Wednesday, March 07, 2007 (UMST) Does our image appear larger when we step back from a mirror or is this just a misconception, if so why do we think it is?Ames. Reply to this Comment Not Bad, but ... By IsoMorphium on Friday, March 16, 2007 (UMST) ...the full answer is: The mirror doesn't reverse left and right, but front and back. And if we try to look in the same direction as the person in the mirror, we usually turn 180° around and then left is what was right before and so on. Reply to this Comment Simply because God created it that way! By AMusallami on Wednesday, September 26, 2007 (UMST) Human eyes are placed horizontally next to each other: (=) (=) That makes the reflection of the light comes from right side into the mirror reflect into left eye and vise versa, as in the lows of reflection... Ahmad Reply to this Comment Convex Mirror By supersonic on Thursday, November 01, 2007 (UMST) Nobody thought about convex mirrors. They DO show images upside down. Reply to this Comment another solution By siddharthsk on Saturday, December 08, 2007 (UMST) I think it is because the mirror is considered "in front" of the person. So by the law of reflection and mirroing co-ordinate system it show left-right inversion. To see top-bottom inversion one can consider mirror is either at top or at the bottom. Thanks Siddharth Reply to this Comment The mirror DOES flip top to bottom! By MikeH on Monday, January 07, 2008 (UMST) I agree with Psyang. If we try to map the real object onto its image, we seem to want to rotate it around the vertical axis stating that the mirror has then flipped left to right. However, we could equally well rotate the real object around the horizontal axis (in the plane of the mirror) and state that the mirror has flipped top to bottom. So why do we choose to rotate around the vertical axis? I suspect this is because we have a instinctive preference to preserve 'up-ness', or 'top- and bottom-ness' throughout the rotation and/or we consider the vertical direction rather 'special'. Reply to this Comment what about cameras? By insidi0us on Monday, May 19, 2008 (UMST) I originally thought it had to do with our brains making sure the top stayed on top, bottom on bottom, as some have stated above... it only looks appropriate if my right arm moving shows my mirrored body's left arm moving, because it's on the same side, as perceived by me. same goes for my head being on top, or if i jump. so in essence, the mirror is physically doing the same thing to all the light rays that hit it. a light ray coming in from the bottom left will exit towards the top right, at equal but opposite angles on the other side of the horizontal and vertical axes crossing the point where the light hit the surface. our brain just figured out what looks right, much like it does when we are newborns trying to make sense of our view of the world. that's all well and good, but what about when you take a picture of a mirror... why is everything still flipped in the same exact fashion that we perceive it with our eyes? does this imply that something is physically different with the up/down portion of a light ray's direction? what if i tilt my head 90 degrees to the side? why does it all still work the same way? by the way, i think it's funny when someone says it has to do with our two eyes being positioned horizontally to each other. try closing one eye... NOTHING CHANGES. Reply to this Comment
It has to do with gravity. When we face someone, the difference in orientation between them and us is that they have rotated 180 degrees along the z-axis (where I define the z-axis to be the direction of gravity - straight through the top of their head into the ground). As such, their left is on the same side as our right, and their right is on the same side as our left. But their top and bottom are identically oriented to our top and bottom.
When we view ourselves in the mirror, the thought that left and right are reversed is because we expect the reflection to imitate how we view others in real life - their left to our right, etc. But in a mirror, our image's left is produced by light travelling from our eye, to the mirror, reflected back to our right side. So what we expect to be our left is really our right.
Suppose there was no gravity. Then we may meet people oriented 180 degrees along the x-axis (where the x-axis is defined as from left-to right, straight through their right and left sides). Thus, their feet are where our head is, and their head is where our feet are. But their left is on our left, and their right is on our right. If this were the norm, then our view in a mirror would seem to reverse top and bottom, but not left and right.
Reply to this Comment
I wonder what newtons law of gravity has to do with law of reflection.
We in reality see upside down images which is then converted to the normal image.When we look at an object in a mirror (or through a lens) we are looking at an image of the object. When an object is illuminated with light (or when it merely gives off light), light rays from the object are moving in a variety of directions. Some of these light rays from the object ultimately strike the mirror. These light rays reflect off the mirror, following the law of reflection. Some of them reflect towards the eye of an obsever, recreating the image on the back of our retina, which in turn our brain perceives and interprets. The image of the object in the mirror is the result of reflected rays. The actual image location is the location where reflected rays from the mirror intersect. This location can be either behind the mirror (if reflected rays diverge) or in front of the mirror (if reflected rays converge) But regardless of which side of the mirror the image is formed on, the image location is formed where the reflected rays intersect. To identify the image location, reflected rays must be traced forward or backwards until they intersect
cheers,
Richa Upadhyay
It is true that the images formed on your retina are upside-down. It is also true that most people have two eyes, and therefore two retinas. Why, then, don't you see two distinct images? For the same reason that you don't see everything upside-down. One of our most remarkable tools - the brain - is hard at work for us at this task.
Processing visual information is a complex task - it takes up a relatively large portion of the brain compared to other senses. This is because your brain performs several tasks to make images 'easier' to see. One, of course, is combining the two images, which is helped by the corpus callosum, the tiny part of your brain which joins the two big hemispheres. The other part is handled in the optic part of your brain itself, and part of its job is to make images right-side-up. It does this because your brain is so USED to seeing things upside-down that it eventually adjusts to it. After all, it's a lot easier to flip the image over than it is to try and coordinate your hands and legs with an upside-down world! As a result, though, it is believed that for the first few days, babies see everything upside-down. This is because they have not become used to vision.
Richa Upadhya
I am thinking it might have something to do with the eyes in respect to each other.
Assume an alien whose two eyes are lined up vertically instead of horizontally( human case). How they would observe themselves in mirror in this case?
A mirror doesn't reflect left and right, it reflects into and out of the mirror. If you point an arrow towards a mirror it seems to be pointing out of it.
A more elaborate explanation of this (and many other puzzles) is available in the book How Would You Move Mount Fuji.
Human eyes are placed horizontally next to each other: (=) (=)
That makes the reflection of the light comes from right side into the mirror reflect into left eye and vise versa, as in the lows of reflection...
Ahmad
I think it is because the mirror is considered "in front" of the person. So by the law of reflection and mirroing co-ordinate system it show left-right inversion. To see top-bottom inversion one can consider mirror is either at top or at the bottom.
Thanks
Siddharth
