Why do we see ourselves in the mirror being left and right upside down?

The first to see this problem has been around for several years, although a bit curious but has not carefully thought about the reason. A few days before work in the road when suddenly thought of this problem, so focus on the spirit of serious thinking, after a few hours of thinking and finishing, the problem has a clearer understanding. So here's a note.

Before I wrote this article, I took some time to search the Internet and found the answer was so varied. Some say that because the eyes are symmetrical, some say that our body is symmetrical, and some say that the definition of the problem, but also from the optical principle of analysis, and even the use of this "advanced" knowledge of the true and false vector analysis (but unfortunately such a high-force lattice of the answer is also wrong).

In my opinion, none of these answers can persuade me and make me satisfied. In fact, after thinking about it, the question is quite simple, the mirror does not reverse us, the reverse is our thought, or because our fixed thinking makes us think that the left and right are reversed. To figure this out, you need to figure out what the mirror is upside down in this question.

What's upside down? Recall how we saw each other when we were talking to each other in person. No one can doubt that when we face a person his or her side should be opposite to ours, his left hand is on our right, and his right hand is on our left. This is because the body structure of the other side is the same as ours, but he rotated 180 degrees to our level, so everything in the horizontal direction was reversed. And that, in our opinion, is natural and "positive". In other words, what we intuitively think of as "positive" should be in accordance with the physical law: After horizontal flipping, the left and right should be completely reversed. Let's see what happens when you look in the mirror. When we stand in front of a mirror, we see ourselves in the mirror as if it were true, his left hand is on our right and his right hand is on our left. But think about it as if there is a problem: his heart is on our left (his right hand) you comb to the right hair, he is to the left comb your left face of a mole on his right face ... So it seems that all the things in the mirror are upside-down--the one that ran to the left on the right, and the one on the left to the right. In other words:The mirror of all the things we have in contrast to the mirror outside of us is not even upside down, originally on our left, incredibly still on our left, originally on our right side incredibly still on our right. This is not exactly what should happen after a horizontal flip. This is the real reason why we feel the mirror is turning our left and right upside down. It does not flip around like we do with others, just flips the original symmetrical part (hands, eyes, etc.), while asymmetric ones are all "mistaken" (heart, button, hair, mole on the face, etc.). actually, it's not upside down.It says that the mirror has made all the things that are asymmetric in US wrong, only to flip the original symmetrical ones. In fact, this is not true, the mirror does not reverse anything in our body, the reason we feel our right and left hand in the mirror upside down, just because our hands are symmetrical, we mistakenly put their own hand in the mirror as the left hand of the person in the mirror. To illustrate this, now close your eyes, imagine in your mind, or if you have the conditions, you can actually do the experiment. Suppose you stand in front of a mirror and hold a piece of paper in your hand, the paper is translucent and there is a word on the paper. Now flip it horizontally so that the word is in the mirror, and because the paper is translucent, you can see the same word from the back of the paper. Now, please answer, is the word you see from the back of the paper the same as the word you see from the mirror? It's not hard to think about it, but it's the same from the back of the paper and the words you see from the mirror, all in turn. such as: Remember when you just learned optics, the exam often encountered to give you a clock in the mirror into the image, and then asked you are the points of the topic. The teacher taught us a "cheat" method, encountered such a question to turn over the test, this time you see is the answer, than you want in the brain faster than the error. The word from the back of the paper was reversed because we flipped the paper horizontally, so the word turned upside down. And the word we see in the mirror is reversed because it's like it was originally based on a word that had been flipped. In other words, the image of the mirror does not flip the object horizontally, it simply renders an object faithfully. Now assume that a person standing in front of you, at this time his left and right with you is the exact opposite, then let him turn back, at this time because he level turned 180 degrees, so his left and right with you, at this time to take a mirror in front of him, then the mirror he and the real his left and right? Of course it was the same, and at this time he was the equivalent of the previous word, and the mirror was only faithful to show him out. This is actually the case when we look in the mirror, but the observer happens to be ourselves. What the hell happened?What about the upside-down feeling when I look in the mirror? In fact, it is because when we face ourselves in the mirror, we instinctively assume that we are facing ourselves in the mirror, as we usually face other people, according to the situation we see in our eyes. But in fact, when we look in the mirror, the mirror is based on the image of someone who is in the same direction as we are. (referring to the thought experiment above) since the direction is the same, so the left and right is not reversed, but this happens with our experience in the face of others contrary, so we think the mirror turned us upside down. Reference: The first three one is the original me, one is from the back to see me, one is the mirror of me. The three are the same. The last one is what I think you should see when you really face yourself, and this is just the opposite of the actual situation. The "Jade" in the figure, the middle of a vertical equivalent to our body, three horizontal equivalent to our eyes, hands, feet and other symmetrical parts, and that point is equivalent to our heart and other asymmetrical parts. The only point that looks upside down is that some parts of our body are inherently symmetrical, so it looks like these parts of the mirror are consistent with experience. But in fact we see the whole person and the situation in our experience is completely reversed, at this time if we destroy its symmetry, such as raising the left hand, you can find the opposite lifted is the right hand. Why is there no upside down ?The reason why there is no upside down is because our experience makes us think that when facing a person, his or her side should be flipped, because he rotated 180 degrees horizontally. However, since both the normal and the face of the mirror, our body in the vertical direction is not flipped, so give us the feeling is consistent, will not let us appear upside-down feeling.

Why do we see ourselves in the mirror being left and right upside down?