Why do letters appear backwards in mirrors? Just curious.
Hmm. I thought everything appeared backwards in mirrors. Except for vampires who may not appear at all. 
It’s not so much that they appear backwards as it is you’re looking at them from the other side.
I thought it was our eyes and brains can’t comprehend the whole reflected light thing properly, but I could be wrong (and probably am.)
Stuff in mirrors is reversed front-to-back, not left-to-right. That is, perpendicular to the plane of the mirror. However, to view something in the mirror, you have to rotate to paper or book 180[sup]o[/sup] to get it to face the mirror. This rotation is where the left-to-right reversal comes from.
I’m sure we’ve had threads on mirrors before, but I’ll leave it to the interested reader to search for them.
The column doesn’t appear to be online, but Cecil answered this one on p. 81 of More of the Straight Dope
What was the answer?
Ok, it’s been a while since I’ve done any of this, and I don’t know how much I can explain what I know on a Messageboard, but here goes:
Letters aren’t the only things that appear “inverted”. So do you (go look in a mirror and you’ll see!)
The reason for this is that light is reflected directly back at you from the point which it comes from. By that I mean that the light bouncing off you, making you able to see you, hits a mirror and bounces back at the same angle that it hits the mirror. So when you’re standing in front of a mirror, the reflection of your right arm hits the mirror and comes back more or less at the same place. Thats why it looks like your right arm is in the place where a persons left arm would be if they were facing you IRL. (I can’t do this without a diagram!!!).
Does this make sense?
I think linking to a webpage about mirrors and how they work would be appropriate now, because I’m clearly making a fool of myself here:
http://www.glenbrook.k12.il.us/gbssci/phys/Class/refln/u13l1c.html
Hope this helps. (proably more than I did!)
When I was young I noticed that things seemed to appear reversed side to side but not top to bottom (looking at yourself, for example, your left was your right, but your ‘top’ was still your top). I always assumed this was because your eyes were side by side not ‘stacked’.
Imagine it this way. Imagine that an image in a mirror could be seen from both sides. If you are standing next to a person and you’re both looking in the mirror, you are seeing a “reversed” image. But if you were to leave your friend and walk around behind the mirror, you would see a “normal” image of your friend. The image in a mirror isn’t reversed, you’re just looking at it from the wrong side.
The problem is in thinking of things in terms of left-right, rather than absolute directions. My bathroom mirror, for instance, is on a west wall, so if I stand in front of it, my right arm is to the north. If I raise my north arm, my image also raises its north arm. In other words, there is no reversal of sides in the mirror. There is, however, a front-back reversal: My nose is pointing west, but my image’s nose is pointing east.
The reason we interpret this as a left-right reversal is that we’re used to seeing other people. If there’s someone in front of me, and they turn around to face me, they’ll almost always do so by turning horizontally, rather than doing a somersault. Hence, when I see my image in the mirror, my brain processes it as “That person on the other side of the glass has turned around horizontally to face me”, so it looks like its north arm should be its left arm.
Look in a mirror. Wave your left hand. If what you were really looking at was your twin (and not your reflection) they’d appear to be waving their right hand. Here’s where the confusion lies - you imagine the image to be ‘reversed’ because you are thinking in terms of left and right, and mistaking the image as being another human being.
But it’s not, it is merely a direct reflection.
If it was in reverse, then the hand diagonally opposite to your left would be waving. And your head would be facing an image of your feet.
It is not a reversed image, it is a reflected image.