Why do mirrors switch left-right and not top-bottom?

Question

Why do mirrors switch left-right and not top-bottom? Why do ambulances write "Ambulance" backwards rather than upside-down?

Answer 1

I won "Best Answer" for answering this kind of question about a month ago. Here is a slightly modified part of that answer:

I confronted myself in my bathroom mirror; as a result, I offer the following analysis.

Looking in the mirror with my recognizable bathroom and bedroom beyond "in its depths," I imagined myself being the person in the mirror examining how all things were treated as they appeared in or were "transformed" in the "mirror world." Walls, floor, ceiling all continued into the mirror world, but the things furthest behind me in my world were now the furthest in, in mirror world.

It's like holding out an infinitely thin sweater by the sleeves, front upwards, and then turning it iside out, away from you. The right sleeve becomes the "left" one and vice-versa --- try it! And yet the front of the sweater, held flat, upwards, remains upwards during this process. So, the left-rightness of this "mirror inversion" appears to "switch left and right," but doesn't affect "up" and "down," in this EXPLICIT, practical example.

I think this is the nub of the answer, but there are further implications found by examining mirror world a bit more carefully.

If you now start looking around in mirror world, you notice a remarkable thing: the left-right interchange is not just for your own mirror image, it's true for EVERYTHING. Looking straight into the mirror, this is hardly surprising: the edge of a picture I could just see through the door, behind my real world left hand, was now behind the "right-hand" of mirror man (MM).

I then turned, to look to the side, parallel to the mirror. In the real world, there was my toilet, just beyond and below the far edge of the mirror. (You may not wish to know that.) A corner shelf was to my right.

Mirror man disagreed, and pointed out in rather strong and critical language that I had it all wrong. He asked me to look at the situation from his point of view. I had to reluctantly agree. His toilet was to the right; his corner shelf was to the left!

This meant that no matter in what direction mirror man looked, while standing on the projection of my floor, EVERYTHING had a left-right switch, no matter in which direction he turned.

I confess that I found this remarkable. It meant that the "sweater-like inside-outness" applied to everything, to depth in the mirror, sideways, in fact turning around and looking in any direction. It's an INTRINSIC property of mirror world, without altering the way gravity operates --- that still pulled mirror man to the floor.

I decided to take what mirror man had told me lying down, on my right side, parallel to the mirror. Gravity pulled me to my "right"; but it pulled mirror man to HIS left, though physically it was still downwards.

What did all this mean, mathematically?

It meant that if a set of coordinate axes (O, x, y, z) in my world had their origin O in the silver reflecting surface of the glass mirror, with Ox horizontal to the left, Oy straight out at me, and Oz vertical, then in mirror man's world those same axes, for him, would be Ox', - Oy', and Oz'. The - Oy' is the mathematical consequence of the "sweater inside out effect" perpendicularly to the mirror surface. It's the ONLY one that's changed.

In my world, my axes form a "right-hand screw set (RHSS)." It's responsible for advanced physics students screwing up their hands and faces as they try to imagine which way a vector cross-product points, the direction of the Coriolis effect, in which direction a tipped-over gyroscope will precess, or which way a moving particle will be deviated in a magnetic field.

But mirror man lives in a world governed by a "left-hand screw rule." When I stand, doing my physics student thing in front of the mirror, my right-hand screw rule demonstration becomes mirror man's left-hand screw rule demo. I do it with my right-hand; he does it with his "left-hand."

So: ALL of the strange effects described come about from just one simple transformation, the "flipping" of all the coordinates normal to the mirror so that y ---> - y'. This DOESN'T change the direction of the x- and z- axes, but it does imply a change from an RHSS world into an LHSS world, or an "everything horizontally inside-out" world.

And THAT'S finally WHY: When you look in the mirror ... left becomes right and right becomes left ... but the top and bottom aren't reversed as well.

It's also why ambulances write "Ambulance" backwards rather than upside-down.

Live long and prosper.

Answer 2

Vasek, you can bend backward before an vertical mirror with your lettered Tshirt (or put a book in front of it) and still the text will be flipped horizontally. Have you considered why in a concave (spherical )mirror (such as a spoon) up is down, right is left and left is right. Edit: Dear Vasec, Trak's answer inspired me and has made me laugh, "so much for conservation or vertical axis". But I am sure that Scythian meant well by pointing that you should try to forget all preconcieved knowledge of "labeled directions" and think out of the box. Although the manner in which he has expressed it might sound a little harsh. Use your imagination, make your mirror slowly become concave, and flat again, and concave again..... take it in outer space if you want to, there are no limits in imaginary land! Imagine that you are one single asymetrical letter in space looking at the mirror, rotate the mirror about its center in an x,y and z axis while the mirror is still in a never ending "circular mutation transition" from flat to spherical to flat... Oops, I meant rotate yourself (as an asymetrical letter) in front of the ever changing mirror. Imagine that you can see the mirror image from every angle in which you rotate. Good luck! Have fun=) Sleep well xx

Answer 3

Liner view reflections from mirrors do make top and bottom switched left-right. Light reflected through two mirrors lets you see yourself as others really see you! Top-bottom switches like lens held at arms length are due to prism or z path of light passing through because of shape. Flat windows change things very little! Look at the curved rear glass of a old aerostar van sitting in the drivers seat at night with the rear light switched on Manuel. bright objects on the floor are magnified greatly! Also switched left-right.

Answer 4

Thats a intelligent question ! (PIG IRONY)
and the answer is that mirrors DONT switch left to right
WE SEE the change of sides because we see it from the facing side of the mirrors.
see it from behind then the switch leftright wont be there

And only for the sake of answering your actual question
Ill tell how to make the mirror switch from top to bottom
turn around 90 degree your object
WHOALA ! it has turned upside down

Answer 5

Because the light from the right side comes back to your right side, same for left and top and bottom.
The mirror is not actually switching left right, it reflects whatever comes to it directly back, our eye interprets that as "switching"