# The mirror.

ivanhoe
Posers and Puzzles 26 Aug '03 00:31
1. 26 Aug '03 00:31

Look in a mirror.Your left hand seems to have become your right
and your right is now apparently your left. You have been laterally
reversed! Why does the mirror not reverse you vertically as well ?

Have fun !

IvanH.
2. richjohnson
TANSTAAFL
26 Aug '03 01:06
Originally posted by ivanhoe

Look in a mirror.Your left hand seems to have become your right
and your right is now apparently your left. You have been laterally
reversed! Why does the mirror not reverse you vertically as well ?

Have fun !

IvanH.
because the body has a vertically oriented plane of symmetry.
3. TheMaster37
Kupikupopo!
26 Aug '03 13:21
Originally posted by ivanhoe

Look in a mirror.Your left hand seems to have become your right
and your right is now apparently your left. You have been laterally
reversed! Why does the mirror not reverse you vertically as well ?

Have fun !

IvanH.
First a general explenation on how we see;

Light comes from a source, reflects on an object and makes it's way into our eye. Once that has happened we 'see' the object.

Now in this case we have one object we see, namely our body, and a second reflection in the mirror.

Light comes into the room (or where ever you may be) and hits the mirror, reflects onto your hand, bounces back to the mirror, and reflects into your eye eventually. When looking in the mirror, we see our left thumb closest to us in the reflection (light comes from the left, on your hand, and bounces back, but it stays on the left when it hits the mirror. When we notice what happens with our left pink, it's further of then the thumb, so also in the mirror, but there it's a right hand.

Now when we look on what happens with up and down, light coming from up reflects higher in the mirror, and thus comes from above our eyes. Same for down. Up stays up and down stays down.

Draw it out for yourself (but imagine light-sources on the parts of your body).

Uh, i hope this was clear ðŸ˜µ
4. Fiathahel
Artist in Drawing
26 Aug '03 13:48
ðŸ˜•
5. 26 Aug '03 14:18
A mirror doesn't swap left with right or up with down, it swaps in with out.

If I have a wedding ring on my left hand, when I wave my left hand at myself in the mirror, my image waves the hand with the ring on. But, because of the vertical oriented plane of symmetry mentioned by richjohnson, I interpret that as if someone who looks like me is waving his right hand. As well as wearing his wedding ring on the wrong hand, this strange person seems to part his hair on the other side to me and to be wearing a shirt that buttons the wrong way, but these are all artefacts of my interpretation of what I see.

Another way to think of it is to imagine you are facing North, with a mirror in front of you. Move your East hand upward and your image moves its East hand upward, but if you move your hand North, your image moves its hand South, that is, towards you.
6. Phlabibit
Mystic Meg
26 Aug '03 15:01
Originally posted by ivanhoe

Look in a mirror.Your left hand seems to have become your right
and your right is now apparently your left. You have been laterally
reversed! Why does the mirror not reverse you vertically as well ?

Have fun !

IvanH.
It's good to see we think alike... I have spent many hours thinking about this. Most people don't even bother to answer me about it since they don't realize the implications.

Phla-
7. 26 Aug '03 23:441 edit
Originally posted by Phlabibit
It's good to see we think alike... I have spent many hours thinking about this. Most people don't even bother to answer me about it since they don't realize the implications.

Phla-
... and the implications are ....... ?

IvanH.
8. Phlabibit
Mystic Meg
27 Aug '03 03:33
Originally posted by ivanhoe
... and the implications are ....... ?

IvanH.
That our perceptions of things go beyond normal physics... a mirror should switch left for right, up for down...

but it does not...

It should... but does not.

I don't care what you say... it should.

ðŸ˜‰
9. TheMaster37
Kupikupopo!
27 Aug '03 07:59
If you don't care what we say, then you have no right to invoke physics at all ðŸ˜›
10. 27 Aug '03 08:301 edit
Originally posted by ivanhoe

Look in a mirror.Your left hand seems to have become your right
and your right is now apparently your left. You have been laterally
reversed! Why does the mirror not reverse you vertically as well ?

Have fun !

IvanH.
I think of it as an fallacy caused by us liking to stay on our feet when we turn. You have elected to place yourself into the front/back orientation of your reflection by making a half turn while staying on your feet, but then your left and right don't match your reflection's left and right. The mistake you have made is that for no particular reason you decided to turn about your vertical axis. Other selections you could have made are:

To rotate about the axis passing towards the mirror through your stomach, this makes everything wrong: Your left and right are swapped compared to the reflection but your top and bottom are also wrong, and you are still back to front.

To rotate about the axis parallel to the mirror going through your left and right side, this sorts out your back/front orientation AND your left right orientation, but it swaps your top and bottom.

To rotate about an infinite number of other axes parallel or not parallel to the mirror, achieving a slightly different effect with each one but never getting the reflection that you want.

The rule is that any number of rotations cannot achieve a reflection. Any rotation in a plane parallel to the reflection required will still leave another reflection required, but in a different plane. Rotations NOT parallel to the original reflection will leave a reflection and a further rotation required to get the desired reflection.

The psychology is that we only usually consider one of those infinite number of possible rotations, and then we worry about why its effects don't seem balanced.
11. Fiathahel
Artist in Drawing
27 Aug '03 10:39
Originally posted by iamatiger
I think of it as an fallacy caused by us liking to stay on our feet when we turn. You have elected to place yourself into the front/back orientation of your reflection by making a half turn while staying on your feet, but then your left and right don't match your reflection's left and right. The mistake you have made is that for no particular reason you ...[text shortened]... nite number of possible rotations, and then we worry about why its effects don't seem balanced.
I couldn't have said it better myself.
due to my poor english ðŸ˜‰
12. Acolyte
27 Aug '03 16:34
Originally posted by iamatiger
I think of it as an fallacy caused by us liking to stay on our feet when we turn. You have elected to place yourself into the front/back orientation of your reflection by making a half turn while staying on your feet, but then your left and right don't match your reflection's left and right. The mistake you have made is that for no particular reason you ...[text shortened]... nite number of possible rotations, and then we worry about why its effects don't seem balanced.
Someone needs to invent a device for reflecting macroscopic objects:

If you put a record through it and then played the record, it would play backwards.

You could make a left-handed version of anything.

There'd be the potential for numerous practical jokes, such as reflecting one of someone's shoes.

I'm sure there'd be more interesting consequences...
13. Fiathahel
Artist in Drawing
28 Aug '03 09:12
Originally posted by Acolyte
Someone needs to invent a device for reflecting macroscopic objects:

If you put a record through it and then played the record, it would play backwards.

You could make a left-handed version of anything.

There'd be the potential for numerous practical jokes, such as reflecting one of someone's shoes.

I'm sure there'd be more interesting consequences...
The easiest way for doing that is by teleporting. Only you don't teleport the original, but a reversed copy. Only then, you don't have the original any more. Is that a problem?
14. 02 Sep '03 15:09
Originally posted by ivanhoe

Look in a mirror.Your left hand seems to have become your right
and your right is now apparently your left. You have been laterally
reversed! Why does the mirror not reverse you vertically as well ?

Have fun !

IvanH.

Very interesting posts indeed !

The answer is: The mirror actually reverses you back to front.

That's all for now folks.

Joe.
15. 20 Sep '03 14:29
[i]Originally posted by RolandYoung

Another way to think of it is to imagine you are facing North, with a mirror in front of you. Move your East hand upward and your image moves its East hand upward, but if you move your hand North, your image moves its hand South, that is, towards you.[/b]

I guess you, Roland Young, came closest.
Maybe a jury ought to decide in this matter.

The North-South example convinced me to give my vote to you !

IvanH.