Previous in Forum: Charging 24v batteries   Next in Forum: Energy Conservation Through Dryer Exhaust Air Recirculation
Close
Close
Close
31 comments
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 663

The old mirror question!

06/10/2007 9:48 AM

I know it's an old one... just thought it may still tease a few of our readers!

If you look in a mirror your reflestion is inverted left to right...yes?

E.G You wave your right hand....Mirror man waves his left!

How come the mirror doesn't invert up and down?

(Martin Gardner wrote a hugely witty piece on this topic in his 'Matematical Puzzles & Diversions' many years ago)

__________________
health warning: These posts may contain traces of nut.
Register to Reply
Pathfinder Tags: reflection riddle
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Guru
Popular Science - Biology - New Member Hobbies - Musician - New Member APIX Pilot Plant Design Project - Member - New Member Hobbies - CNC - New Member Fans of Old Computers - ZX-81 - New Member

Join Date: Jan 2007
Location: Centurion, South Africa
Posts: 3921
Good Answers: 97
#1

Re: The old mirror question!

06/10/2007 5:08 PM

This question was done not so long ago.

I want you to do a little experiment first.

Take a piece of clear plastic film (± 100mm x 1000 mm)

Now write with a marking pen a L on the left HELP in the centre and a R on the right.

Now take the strip with the writing facing you. The L close to the left and the R close to the right hand. Now face the mirror and look at the image.

The writing is correct. The L is on your left and the R on your right.

If you wiggle your left thumb the thumb wit he hand marked as L Will wiggle.

Did the mirror flip the image left to right or top to bottom? The answer must be NO.

What is really happening? The piece of film in your hand provides the clue. There are an apparent flip from front to back. Consider yourselves looking at an opaque version of your features from the back.

If you take a web cam and put it below or above your screen.

What do you see now?

The writing is the wrong way around.

But the picture is correct.

Movements are opposite {but correct)

Do your face look familiar?

__________________
Never do today what you can put of until tomorrow - Student motto
Register to Reply
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 663
#2
In reply to #1

Re: The old mirror question!

06/10/2007 5:39 PM

I got a shock one day when I was a kid, walking past a large shipping container made of alluminium like half a vertical cylinder standing on end ( think of a giant beer can sliced in two vertically).

As I walked past one way...mirror man walked by in the opposite dirercion!!...it stopped me dead in my tracks!

__________________
health warning: These posts may contain traces of nut.
Register to Reply
Associate

Join Date: Dec 2005
Posts: 41
#3

Re: The old mirror question!

06/11/2007 12:27 AM

Its a matter of definition.

Up is still up, so left / right must still be left / right.

Its still the same relative to us

Mirror man's definition of left / right must also be reversed.

Turn your head side ways and you still have the problem.

up is still up.

__________________
alzie
Register to Reply
Guru

Join Date: Jul 2006
Location: Silicon Valley
Posts: 5356
Good Answers: 49
#4
In reply to #3

Re: The old mirror question!

06/11/2007 12:59 AM

How come when I take a picture of a mirror with my camera, the mirror in the picture doesn't work anymore?

__________________
"Perplexity is the beginning of dementia" - Professor Coriolus
Register to Reply
Participant

Join Date: Jun 2007
Location: Doorwerth, Netherlands
Posts: 3
#5

Re: The old mirror question!

06/11/2007 2:25 AM

Because your eyes are positioned horizontally

Register to Reply
Active Contributor

Join Date: Aug 2006
Posts: 16
#6
In reply to #5

Re: The old mirror question!

06/11/2007 3:09 AM

Bugger, beat me to it

Register to Reply
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 6039
Good Answers: 245
#11
In reply to #5

Re: The old mirror question!

06/11/2007 1:13 PM

That was my first knee-jerk too, but take a look: there is no difference with only one eye. It is simply the definition of left and right.

__________________
Teaching is a great experience, but there is no better teacher than experience.
Register to Reply
Participant

Join Date: Jun 2007
Location: Doorwerth, Netherlands
Posts: 3
#26
In reply to #11

Re: The old mirror question!

06/15/2007 2:52 AM

Please define left / right when you have one eye.

(What is so special about a horizon?)

So my conclusion with only one eye up/down is the same as left/right!

So, further, up/down is also reversed for the person in the mirror.

So, going on, left/right is linked to the position of our eyes.

And therefore, and because things are defined by us humans related to our body, the position of our eyes was/is important.

Register to Reply
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 6039
Good Answers: 245
#27
In reply to #26

Re: The old mirror question!

06/15/2007 9:03 AM

1. If you are looking straight north, anything west of north is left, and anything east of north is right. The person in the mirror is looking south, so for him/her anything east of south is left, and anything west of south is right.

2. Imagine yourself as a (12-hour) clock viewed from above your head (above as defined by your body position). Straight ahead is 12:00. any earlier time is left (up to about 15 minutes earlier, depending on your peripheral vision), and any later time is right (similar caveat). This one works without modification no matter what direction you are facing (even hanging upside-down).

Neither of these definitions has anything to do with the number of eyes, as long as the eye or eyes face (point) toward the front of the person.

__________________
Teaching is a great experience, but there is no better teacher than experience.
Register to Reply
Participant

Join Date: Jun 2007
Location: Doorwerth, Netherlands
Posts: 3
#28
In reply to #27

Re: The old mirror question!

06/15/2007 9:33 AM

clear answer.

But, there is always a but

In your answer you introduced the 'body position'. Perhaps this fulfills the same purpose as my 'second eye'. With one eye there is no difference between left right up down etc.


I'm sorry for the short and perhaps unclear answers. Perhaps unclear in my mind also. I will try to get a more elaborate answer after my holidays

My gut feeling is, like already argued in this forum, that it's a matter of definition.

Register to Reply
Guru

Join Date: May 2006
Location: Placerville, CA (38° 45N, 120° 47'W)
Posts: 6039
Good Answers: 245
#29
In reply to #28

Re: The old mirror question!

06/15/2007 9:53 AM

Left and right by definition MUST refer to your body position- its YOUR left and YOUR right! If I'm facing you, or even if I'm standing beside you facing the same direction, MY left is unrelated to YOUR left. Since I have no idea what direction you are facing right now, I can't possibly know where your left is located.

You do have a left and a right, even if you have no eyes at all! A blind person knows what to do when you tell them to face toward the left, or reach toward the left, etc. They do require a body to have a left and right; they do NOT require eyes!

Dick

__________________
Teaching is a great experience, but there is no better teacher than experience.
Register to Reply
Guru

Join Date: Jul 2006
Location: Silicon Valley
Posts: 5356
Good Answers: 49
#30
In reply to #29

Re: The old mirror question!

06/15/2007 11:08 PM

Maybe that's why my blind driver is costing me a bundle in car insurance.

__________________
"Perplexity is the beginning of dementia" - Professor Coriolus
Register to Reply
Anonymous Poster
#7

Re: The old mirror question!

06/11/2007 3:39 AM

This is a pretty dumb Thread....

No one is at all intrigued or confused....Del should have done a check searched for 'mirror'.

Rorrim Nam

(Led Eht Tac)

Register to Reply
Guru
Popular Science - Biology - New Member Hobbies - Musician - New Member APIX Pilot Plant Design Project - Member - New Member Hobbies - CNC - New Member Fans of Old Computers - ZX-81 - New Member

Join Date: Jan 2007
Location: Centurion, South Africa
Posts: 3921
Good Answers: 97
#8
In reply to #7

Re: The old mirror question!

06/11/2007 5:23 AM

It might be a repetition but it is not all that dumb.

The face I see in the mirror every morning is not really what I look like (except on the morning after the night before).

Many great minds have thought about it and even wrote in reverse to enable Reading in a mirror. Not so long ago it formed a large part of our knowledge.

Mirrors was also believed to have magical powers.

Commenter's on the previous thread may have thought about it and may put additional info on the table.

For example: Do the horizontal placing of our eyes have any relevance?

__________________
Never do today what you can put of until tomorrow - Student motto
Register to Reply
Guru
Hobbies - Musician - New Member Greece - Member - New Member

Join Date: Mar 2007
Location: Greece / Athens
Posts: 722
Good Answers: 28
#10
In reply to #8

Re: The old mirror question!

06/11/2007 8:44 AM

The image of the mirror (say the image of me) is an "one to one" reprentation of the original image (say me)... This means that any object which is at the right side of me will produce an image on the mirror that is still at the right side of me (it is, of course, at the left side of the "mirror-man" but the "mirror-man" is not a real man...ha, ha...)

Because of this, a written word (say the word "TO") is shown "reversed" in its image on the mirror (say "OT")... The same happen not only if the word is oriented horizontaly (right-left) but, also, if it is oriented verticaly (up-down)... The oriantation doesn't matter...

It's so simple...

__________________
George
Register to Reply
Anonymous Poster
#18
In reply to #8

Re: The old mirror question!

06/12/2007 4:45 AM

This thread is prejudicial . I manage fine without the theory.

Register to Reply
Active Contributor

Join Date: Jun 2006
Location: Mexico City
Posts: 16
#9

Re: The old mirror question!

06/11/2007 8:41 AM

The answer is: the mirror does not really invert our image, it´s just the fact that trough the mirror we look at ourselves as a third person looking at us, so if we move our right hand to some one looking at us (ourselves in this case) the hand we are moving will be percieved as our left one. It´s just symetry and the change in the point of view (when we look at the mirror) what causes this confusion.

Register to Reply
Guru
Engineering Fields - Electromechanical Engineering - Technical Services Manager Canada - Member - Army brat Popular Science - Cosmology - What is Time and what is Energy? Technical Fields - Architecture - Draftsperson Hobbies - RC Aircraft - New Member

Join Date: Sep 2006
Location: Clive, Alberta, Canada
Posts: 5907
Good Answers: 204
#13
In reply to #9

Re: The old mirror question!

06/11/2007 3:35 PM

You are correct..Left and Right are just names. If you take a large clock with you in front of the mirror, then every position of an arm on the clock will be symetrically represented in the mirror from its actual position. The mirror does not invert right and left, but produces a reflected image only. When you move your right hand, you will look at the right hand side of the image in the mirror, relative to you...

Chris

Register to Reply
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 663
#14
In reply to #13

Re: The old mirror question!

06/11/2007 3:38 PM

And that's why the clock in the mirror reads the right time!

__________________
health warning: These posts may contain traces of nut.
Register to Reply
Guru
Engineering Fields - Electromechanical Engineering - Technical Services Manager Canada - Member - Army brat Popular Science - Cosmology - What is Time and what is Energy? Technical Fields - Architecture - Draftsperson Hobbies - RC Aircraft - New Member

Join Date: Sep 2006
Location: Clive, Alberta, Canada
Posts: 5907
Good Answers: 204
#15
In reply to #14

Re: The old mirror question!

06/11/2007 5:02 PM

So if all of a sudden... a cat with a machine gun on your left shoots a dog on your right, and the mirror is concave, did the bullet in the mirror travel in a straight line, at uniform velocity, from left to right, or did it, as the curved mirror would show, travel along a curved path, from left to right again, at varying velocity.... ?

:)

Register to Reply
Guru
Popular Science - Weaponology - New Member United Kingdom - Member - New Member

Join Date: May 2007
Location: Harlow England
Posts: 16499
Good Answers: 663
#17
In reply to #15

Re: The old mirror question!

06/12/2007 2:50 AM

It would go from right to left and... shoot myself in the foot I guess!

__________________
health warning: These posts may contain traces of nut.
Register to Reply
Guru
Engineering Fields - Electromechanical Engineering - Technical Services Manager Canada - Member - Army brat Popular Science - Cosmology - What is Time and what is Energy? Technical Fields - Architecture - Draftsperson Hobbies - RC Aircraft - New Member

Join Date: Sep 2006
Location: Clive, Alberta, Canada
Posts: 5907
Good Answers: 204
#22
In reply to #17

Re: The old mirror question!

06/12/2007 1:28 PM

uh uh.. it would go from left to right because the curved mirror would invert it back to the original orientation... I think....lol

Register to Reply
Guru
Popular Science - Biology - New Member Hobbies - Musician - New Member APIX Pilot Plant Design Project - Member - New Member Hobbies - CNC - New Member Fans of Old Computers - ZX-81 - New Member

Join Date: Jan 2007
Location: Centurion, South Africa
Posts: 3921
Good Answers: 97
#24
In reply to #22

Re: The old mirror question!

06/14/2007 2:17 PM

It would be very much the same as looking into a prism from the long side perpendicular to the surface.

Or 2 mirrors at 90deg and 45deg to the viewer..

Path of light, Hit left mirror and reflect to 2nd mirror and is reflected to the right parallel to incoming beam.

The curved mirror will enlarge the image or depending on the curve the image may be perceived to be in front of the mirror.

__________________
Never do today what you can put of until tomorrow - Student motto
Register to Reply
Guru

Join Date: Jul 2006
Location: Silicon Valley
Posts: 5356
Good Answers: 49
#25
In reply to #24

Re: The old mirror question!

06/14/2007 11:51 PM

So that explains why when you yell into a canyon your words come back backwards.

__________________
"Perplexity is the beginning of dementia" - Professor Coriolus
Register to Reply
Guru

Join Date: Mar 2007
Location: Etherville
Posts: 12334
Good Answers: 115
#12

Re: The old mirror question!

06/11/2007 2:15 PM

Dunno , but I just search.

__________________
For sale - Signature space. Apply on self addressed postcard..
Register to Reply
Anonymous Poster
#16

Re: The old mirror question!

06/11/2007 8:40 PM

Stand in front of the mirror. Look at the image. Put out your left hand. Then notice that the hand to the left of the image has also moved out. Note it is the hand on the same side. Note also that your head's image is still to the top. There is no vertical or side-to-side reversal.

Now look at where your nose is. In the image the nose is closer to you, whereas if you stepped forward to the place where your image is it would be the back of the head that would be there.

What is really happening is that the reversal in direction is in the direction of the noirmal to the mirror surface.

It is also interesting to look at a right handed screw thread in a mirror. It looks like a left-handed screw.

Greg

Register to Reply
Guru
Popular Science - Biology - New Member Hobbies - Musician - New Member APIX Pilot Plant Design Project - Member - New Member Hobbies - CNC - New Member Fans of Old Computers - ZX-81 - New Member

Join Date: Jan 2007
Location: Centurion, South Africa
Posts: 3921
Good Answers: 97
#19
In reply to #16

Re: The old mirror question!

06/12/2007 7:03 AM

"It looks like a left-handed screw."

Oh I always wondered why these screws are made -It must be made for DIY mirror-man.

He drilled the hole with a (left-handed, south paw, CCW ) CMI (counter mirror image) drill and bit.

__________________
Never do today what you can put of until tomorrow - Student motto
Register to Reply
Anonymous Poster
#20
In reply to #19

Re: The old mirror question!

06/12/2007 7:16 AM

The screws are fine. You'd have to have to use a posi-drive/Phillips screw driver though.

F Spencer.

Register to Reply
Guru
Popular Science - Biology - New Member Hobbies - Musician - New Member APIX Pilot Plant Design Project - Member - New Member Hobbies - CNC - New Member Fans of Old Computers - ZX-81 - New Member

Join Date: Jan 2007
Location: Centurion, South Africa
Posts: 3921
Good Answers: 97
#21

Re: The old mirror question!

06/12/2007 7:39 AM

The fascination thing with mirrors start when we are young.

The image formed in our eye is actually upside down and flipped left to right.

It is said that a baby sees upside down and only after some time the brain reverses the image.

The reason why the image seems logical to us is the left right symmetry.

A web cam and pc monitor would make a better "mirror" because it is correct but it does not feel comfortable. Try it!

My Son bought a camera (nice photos of my grandchild is a must)

The camera has a auto correct feature. That is if a photo is viewed the top is always at the top (irrespective of the orientation of the camera) (90 deg steps)

My son was boasting about the camera and I told him how to fool the camera.

You take a picture of the child lying in the arms of somebody from the head side (at an angle). on an older camera the head would have been at the bottom.

The camera won because the photo came out heads up.

Spooky?

__________________
Never do today what you can put of until tomorrow - Student motto
Register to Reply
Anonymous Poster
#23

Re: The old mirror question!

06/12/2007 5:40 PM

It reverses neither up and down, nor left and right. It reverses front and back.

Register to Reply
Anonymous Poster
#31

Re: The old mirror question!

06/30/2007 2:24 AM

So that it doesn't appear to be coming closer and frighten Del out of what wits he has.

Register to Reply
Register to Reply 31 comments
Interested in this topic? By joining CR4 you can "subscribe" to
this discussion and receive notification when new comments are added.
Copy to Clipboard

Users who posted comments:

alzie (1); Anonymous Poster (6); chrisg288 (3); dbarends (3); Del the cat (3); dkwarner (3); G.K. (1); Hendrik (5); Kris (1); Mario Gasca (1); mysticgohan (1); vermin (3)

Previous in Forum: Charging 24v batteries   Next in Forum: Energy Conservation Through Dryer Exhaust Air Recirculation
You might be interested in: Microplate Readers, ID Card Readers and Encoders

Advertisement