If your eyes were stacked one above the other, then the mirror would flip up and down.
A mirror flips left and right, but not up and down
61–70 of 84 posts
Re: A mirror flips left and right, but not up and down
#62If your eyes were stacked one above the other, then the mirror would flip up and down.
try shutting one eye and see if you still believe that
Re: A mirror flips left and right, but not up and down
#63Mirror's don't flip left and right. We implicitly compare a mirror image to the original by rotating the object, and naturally we maintain top/bottom orientation, this gives the appearance of "flipping" the object left to right. However, if you use vertical rotation to super-impose the object on its mirror image you'll see that it seems to have been flipped top-to-bottom instead.
The little players on a foosball table probably think mirrors flip up and down, since that is their normal method of turning around.
Is that true or does their mind explode because they see a figure that can only exist wearing the other color shirt?
Re: A mirror flips left and right, but not up and down
#64Mirrors don't flip anything. Oversimplification (ignores angle of light from object observed to eye), but here: Imagine standing in front of a mirror, both arms straight out. A photon leaves your left index finger, travels straight to the mirror, and is reflected straight back. Now imagine photons leaving all your parts, traveling to the mirror, and reflecting straight back. That's all.
That doesn't answer the question, though. You have to explain why that means my right hand appears to be on my left side.
The question is "Why is it that when you look in the mirror left and right are flipped, but not the up and down?"
When I look in the mirror I see my right hand exactly where it should be, on the right side of the mirror. If I approach the mirror and then touch it, my right hand touches the right hand image in the mirror, as do my forehead and toes respectively.
Someone who asks this question, after understanding what's happening with the light, appears to expect that the left hand with the watch (for example) in the mirror should be on the same side of the mirror as the real left hand with the watch if the observer turned himself 180 deg (away from the mirror). That's a psychological phenomenon, not a physical one, and I don't know why we do that.
One way to answer, then, is that mirrors don't flip anything, our brains do it, and erroneously.
Re: A mirror flips left and right, but not up and down
#65Mirrors don't flip left and right, or up and down. They flip front and back.
This is the first part of the answer. The second part is that, since we define the left and right on an object relatively to its front and back, flipping the front and back also swaps how left and right are defined. There is no confusion with top and bottom as they are not defined relative to front and back.
Re: A mirror flips left and right, but not up and down
#66Assuming a mirror's face is its front: Photons bounce off the right side of you, strike the left side of the mirror, and then reach your eyes. Similarly for the left side. Photons bounce off the top side of you, strike the top side of the mirror, and then reach your eyes. Similarly for the bottom side.
I think this explanation is based on the (erroneous) tendency of people to think of what they see in the mirror as themselves turned around.
Look at the desk in front of you. The right hand drawer is near your right hand. The left hand drawer is near you left hand. Now why did you just call the right side of the mirror, which is near your right hand, as the left side?
Re: A mirror flips left and right, but not up and down
#67My high school history teacher asked this same question (yes, it is that old) and my answer at the time was: Left and right are assigned relative to where you are facing, while up and down are not regardless where you're facing. The same part of your body is reflected at the same side in the mirror (paint your cheeks with different colors; the mirrored cheeks have the same color on the same side as the normal). Howev…
You know, that was exactly my answer as a teenager as well, and the answer I thought I knew when I clicked on this thread, but I don't think it's a sufficient explanation. Even if you assigned up and down as relative, no vertical flipping appears to take place. I believe InclinedPlane's answer [1] is much better. We implicitly perceive the reflection as having rotated as a human would, by turning around on his or her…
Left and right has one frame of reference - facing. Up and down has another frame of reference - room ceiling/floor. Mirror inverses the facing frame of reference but not the room frame of reference.
Left and right, up and down are just convention in our mind. We human use facing to assign left and right, and use ceiling and floor to assign up and down. There is no switching sides in the mirror in reality. You red hand (if you color it) is on the same side inside or outside of the mirror, just as your head and feet are on the same side inside or outside of mirror.
We just assign a new left/right to the mirrored image because we see where the facing in the mirror is; however, our head is near the ceiling and feet are still on the floor so the room frame of reference hasn't changed, and thus up/down are labeled the same in the mirror.
The point my history teacher trying to make via this exercise was to say most stuffs (in history particular) were relative in a frame of reference. It's the same event but through a different angle would be called different thing, when moved to a different frame of reference. The mirror exercise is the terrorist/freedom fighter argument in physical illustration.
Re: A mirror flips left and right, but not up and down
#68When looking at a mirror a human will imagine a clone has gone over to the other side, rotated around the vertical axis, then inverted along the horizontal axis parallel to the mirror. That last part is the perceived "flip" but it is a direct consequence of the imagined axis of rotation. If you imagine a being who is accustomed to a horizontal axis of rotation in their movement, you can see how they would imagine their clone going to the other side of the mirror, rotating around the horizontal axis, then inverting along the vertical axis parallel to the mirror. They would then ask why a mirror flips up and down, but not left and right, for they are accustomed to up and down switching after a rotation, where we are accustomed to left switching with right. (In fact I suspect we identify "up and down" as strongly with this invariant as we do with gravity.)
Any being with freedom of action along some plane, who is accustomed to rotation around an axis perpendicular to that plane, will experience much the same thing: a rotation around some axis parallel to the mirror, followed by an inversion around the axis parallel to the mirror and perpendicular to the rotation. They will then perceive a "flip" along that axis of inversion.
The question reveals a lot about the biases of the the person doing the asking.
Re: A mirror flips left and right, but not up and down
#69It's too bad the question, repeated in the title, is phrased in such a way that it will perpetuate the myth that mirrors flip left and right. I wouldn't mind some editorializing so the title no longer claims the switch as fact.
Re: A mirror flips left and right, but not up and down
#70actually it does flip up and down, you just have to put the mirror on the ceiling. or on the floor.
so to conclude; by definition of this question the result is fixed, you are allowed to fix y- axis but not x-axis when you are translating mirror image to real world image.