# Riddle

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• #593866
popa_bar_abba
Participant

Why when you look in a mirror, is the right and left inverted, but not the up and down?

#723428
Gabboim
Member

How should I answer this if my date asks me?

#723429
oomis
Participant

Popa, that’s not really true. The up and down IS inverted, but only from right to left. However, if you look into certain types of cameras, the image IS inverted up and down (the eye does this also, but the brain “rights” the image we see).

#723430

nothing is inverted

its a matter of nomenclature

up and down is the same however you rotate yourself through an axis going from your head to toes

right to left only “changes” because we imagine the perspective of the person in the image, and change the nomenclature accordingly.

#723431
popa_bar_abba
Participant

Yes, but why is there only an axis going down, isn’t there also an axis going across?

#723432

you can put an axis anywhere you want

but when you compare your position to the “position” of the virtual person im the mirror there has been a virtual rotation along the up down axis. of course there was no rotation at all just we pretend there is another person in the mirror and according to his perspective, his right is our left.

forget the mirror, stand facing another person. you have the same perspective as far as up-down. also east west. north south, but right left are called depending on whos perspective. this is just a convention of nomenclature but does not represent any reality

#723433

im very glad to see you back

“remind me if i forget” wonderful.

#723434
2qwerty
Participant

Pba,

Maybe you have the wrong kind of mirrors. Try looking at the inside of a reflective spoon, you should see yourself upside down but right/left will remain as is.

#723435
Sam l Am
Member

I am responding to popa, taking up his offer to respond to the 100k/90k riddle on the Age Gap thread thereafter:

Why when you look in a mirror, is the right and left inverted but not the up and down?

When the plane of the mirror is horizontal, the mirror does reverse up and down. Just think of the upside down landscape you can see in the surface of a lake.

Left and right are the only directions which are described relative to the observer. Up and down (and north, south, etc) are independent of whichever way you’re facing. When you look in the mirror, up, down, east and west are still in the same place. But you read printed text from left to right – not east to west – hence the problem with ‘mirror writing’.

A mirror doesn’t reverse left to right either as you will see with an asymmetric object. Imagine the mirror is one of those impression taking toys that had a dense number of pins in which are pushed back on contact and retain the 3D shape. Now imagine pressing your body into it and step back. The illusion is, because we are roughly symmetrical, that there has been a left/right inversion. The reality is your right side is on the right side of the image.

One way to start to get a handle on this is to take a piece of paper with your name written on it. Look at it in the mirror and it will be reversed. Now turn it vertically. You will find that the lettering is reversed, but it is not upside down. That should start to give you a clue as to what is going on. Now take your finger and point to the first letter in your name, both on the paper and on the mirror. Notice that there is a one-to-one correspondence — if the letter appears on the left hand side of the paper from your perspective, it appears on the left hand side of the mirror.

Take a piece of thin, translucent paper and write your name on it. Stand in front of a mirror and hold the paper up so that you can read the paper normally. Now look in the mirror. You are seeing the back of the translucent sheet in the mirror, and the word is not reversed — it looks completely normal. Now turn the paper over and look at it in the mirror. It is reversed, but so are the letters on the back of the translucent sheet. Note that you turned the paper over — you reversed it!

In other words, the reason why letters look reversed in a mirror is because you are presenting them to the mirror reversed. The reason why someone coming toward you can read the message on your T-shirt is because the letters on your T-shirt are reversed (from your perspective) when you wear it. If you printed the words on the T-shirt so that you could read them (from the inside of the shirt), the words would look reversed to an approaching person but they would look great in a mirror.

#723437
RuffRuff
Member

Sam,

Your East and West Shtickle doesn’t really come in, and neither does the river example. If you lie down or you turn around the paper to read it up down, it won’t reverse to be read upward.

What you lead up to is the actual answer, though. In short, you are looking at a front view from the back. I wrote another example earlier, but the mods deleted it. I guess they found it offensive, somehow. Yeah, it’s hard to tell…

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