[thedoc (OP)]

Ocsi Veres asked the Naked Scientists:
   
How come the image of roadsigns, number plates etc appear the wrong way around in my rear view mirror, yet the countryside I have just passed trough appears the right way around?

What do you think?

[syhprum]

It is because you have turned your head around relative to what you are viewing what you are seeing with your right eye is what you should be seeing with your left and visa versa.

[percepts]

It is because you have turned your head around relative to what you are viewing what you are seeing with your right eye is what you should be seeing with your left and visa versa.

If that were correct then when you looked at yourself in a mirror you wouldn't find that your left side becomes your right side and your rightside your left, so it has nothing to do with rotating your head.

[syhprum]

The image in the mirror is looking out whereas you are looking in that is where the reversal has occurred

[David Cooper]

It doesn't reverse them left to right, but front to back. The letter or digit that is on the left is still seen on the left in the reflection.

[burning]

To expand on David Cooper's point and address the question central to the OP, there isn't a difference in how the mirror reflects words and how it reflects road side objects.  The difference is in how you think about what you are seeing.  Right and left are concepts that are defined relative to the observer.  As David Cooper points out, any object that is on your left will always appear to your left in a mirror, and any object to your right likewise appears to your right in the mirror.  If you are looking at, for example, a barn on the left side of the road, you see it on your left as you approach, and then you look in the mirror and it is still on the left.  That seems correct to your mind.  The barn is where you expect it to be and thats all you care about.  However, keep in mind that someone driving the opposite way down the road would have the barn on their right.  When they are seeing right in front of them the same side of the barn that you see in your rear view mirror, they are seeing it differently than how you see it.

However, some things we look at we attribute an intrinsic handedness to: other people, text, physical objects (like cars) that have an assymetry that reduces to a left-right difference as they are commonly used.  When we look at those objects in the mirror, we try to impose that intrinsic handedness on what we see and they look wrong.  So consider a road sign that is facing drivers going the other way.  The first letter on the sign is on the right hand side <i>from your point of view</i>, while the last letter is on the left side.  When the sign appears in your rearview mirror, the first letter is still on the right and the last letter is still on the left.  It is no different than the barn, its just that you notice that the image in your mirror is arranged differently than how you expect.  Nonetheless, what is on your personal right in reality is on your personal right in the mirror.