Mirror why left right

And the same goes for L. Trimotio: Okay, but what about your reflection, the guy in the mirror? He is now holding the R in his left hand, not his right. Fineas: But he's not a real person. To say that he's holding it in his left hand means that you have mentally placed yourself in his position.

Fineas: You can do that, but in so doing you have uncovered the basic truth: you had to turn around. Imagine holding an arrow in your hand as you look in the mirror. If you point it up, it will point up in the mirror. If you point it to the left, it will point to the left in the mirror. But if you point it toward the mirror, it will point right back at you. Mirrors do reverse in and out—or to be more precise, they reverse the direction perpendicular to the plane of the mirror.

Now face north and look into the mirror. Point your hand east. Your image also points his hand east—not west! But point your hand north and your image points his hand south. Trimotio: Okay, but if they don't reverse any directions in the plane of the glass, but they do reverse in and out, why does the guy in the mirror hold up his left hand when I hold up my right? Fineas: That's due to the different ways the directions are defined. It is simply representable by an arrow pointing in some chosen direction, such as away from the earth's center.

Or if we are floating far from Earth, we might take "up" to be the direction from our feet to our head. If you wanted to tell a Martian which way is "up" and which way is "front", you could do it easily. Trimotio: But "right" is also simply a direction that can be represented by an arrow pointing into the right direction. Fineas: No it's not. That's because "left" and "right" are relative: they depend on our deciding on an "up" and a "front" first. So comparing "right" with "up" is not a fair comparison.

Ask two people facing each other to point "up"—they'll both point in the same direction. Now ask them where "right" is. But that is a result of you turning your head, and not of the mirror. If you hold up a word to a mirror so that you can see both the word and its image in the mirror at the same time, you will see that they both read the same direction and there is therefore no right-left flipping.

This effect is captured in the image below. If you now hold the word behind you without turning the word, and then turn your head to look directly at the word, it now does appear flipped. This shows that it is the act of turning your head and not the mirror's reflection that makes the word "ambulance" seem backwards. Can you look at the word without turning your head?

If so, the word would not appear backwards. In theory, yes. All you have to do is get behind the word and then you can look at the word and the mirror without turning your head. In practice, the word is often painted in a place such that if you get behind it, you can't see anything anymore. What if the word "Ambulance" was painted across the top of the transparent windshield such that it shows up correctly in someone's rear-view mirror.

Now the driver of the ambulance is sitting behind the word. As he looks out his windshield, he can see the word without turning his head.

As a result, he can read the word correctly. The word does not seem flipped left to right to him because he has not turned his head. This counter-intuitive notion arises from the fact that when we turn our head, we unconsciously rotate a word so that it reads correctly.

For instance, consider that you are standing in a long, narrow garage in between two vehicles. A car is parked on your left with its front grill facing you and a van is parked on your right, also with its front grill facing you. In order to have some fixed reference frame, let's call the wall right in front of you the main wall. In fact this assumption is wrong.

Your reflection didn't do a degree turn. It was reversed front to back with no rotation at all. Your brain mentally subtracts the degree turn that you assume must have happened from the observed front to back reversal and what do you get? An apparent left to right reversal!

Mike Burton, Twickenham UK The mirror does not reverse images from left to right, it reverses them from front to back relative to the front of the mirror. Stand facing a mirror. Point to one side.

You and your mirror image are pointing in the same direction. Point to the front. Your mirror image is pointing in the opposite direction to you.

Point upwards. You both point in the same direction. Now stand sideways on to the mirror and repeat. You are now pointing in opposite directions when you point sideways. Place the mirror on the floor and stand on it. This time you point in opposite directions when you point upwards and your upside down image points downwards.

In all cases the direction reverses only when you point towards or away from the mirror. The answer stems from the fact that a reflection is not the same as a rotation. Our bodies have a strong left-right symmetry, and we try to interpret the reflection as a rotation about a central vertical axis. Such a rotation would put the head and feet where we expect them, but leaves the left and right sides of the body on opposite sides to where they appear in the reflection. But if instead we imagine the world to have been rotated about a horizontal axis running across the mirror, this would leave you standing on your head, but would keep the left and right sides of your body in the expected positions.

So whether you see the image as left-right inverted or top-bottom inverted, or for that matter inverted about any other axis, depends upon which axis you unconsciously and erroneously imagine the world has been rotated about. If you lie on the floor in front of a mirror you can observe both effects at once. The room appears left-right reflected about its vertical axis, while you interpret your body as being left-right reflected about a horizontal axis running from head to foot.

My mirrors don't reverse anything, each section of mirror simply reflects what is directly in front of it. Hence whatever is on my right as I look into the mirror will be on the right in the mirror. Nothing's been reversed it's just a reflection, that's all. Seth, Edinburgh UK Lie on your side and look in a mirror. Now what sort of reversal is it? A mirror image is not left-right reversal, it is simply a mirror image.

David Pearce, Birmingham UK If you want to understand mirrors then it's helpful to read a fascinating article in the February edition of Scientific American page The subject is not mirrors, it doesn't even mention them, but it explains the confusion.

How can mirrors reverse the horizontal axes but not the vertical? It is not just in England that they appear to perform this remarkable trick; the same happens in almost all countries. Almost all. There is a small part of Australia where the reversal does not occur. The article I mentioned is about the peculiarities of languages and their influence on perception. For example some have no words for past or future, others have no words for large numbers.

The native language in that part of Australia has no words for left or right - that is, it has no local axes. Instead all references are global: North, South, East or West.

So you have to say things like "The cup is South of the plate". Now travel there and look in a mirror. Raise your North hand.