Why do words appear backwards in a mirror?

A very interesting question. I think you also noticed that the words and letters in a mirror’s reflection while backwards are not upside down. Looks like very strange behavior, so why does this happen?

Very profound questions you’re asking and the answer illustrates a very advanced concept variously called mirror-symmetry, inversion symmetry or P-symmetry (the P stands for the word parity). Understanding symmetries turns out to be one of the key or fundamental ingredients needed to understand the Universe we live in.

The complete answer to your questions is somewhat complicated so let’s try to understand what’s going on in small simple steps. Just try to understand each step before going on to the next step and when we’re done you’ll have a complete understanding of the answer. You may have to ask your dad or mom to help you understand some of these concepts.

To start let’s do a little experiment. Get a piece of cardboard and cut it into a rectangle. You can also use poster board or even plain paper but it works best if you use something that is a little stiff.

Next write your name on the rectangle in big bold letters that are easy to read. A crayon is a good choice for this. Then get a pencil and tape it to the back of the rectangle so that the sharp writing end points to the ceiling when you hold the rectangle in front of you to read your name. When you’re done you should have something that looks like this:

The pencil lies along an imaginary line called an axis (understanding science requires a lot of pretending or imagining. For me, this works best when I try to think about things with imaginary pictures). Since the pencil points up towards the ceiling when you read your name this is called a vertical axis.

Take your rectangle over to a mirror and hold it in front of you so that you can read your name. Now, while keeping the sharp end of the pencil pointed towards the ceiling, turn the pencil (called rotation) so that your name is visible in the mirror. What you see in the mirror will look something like this:

As you previously observed your name appears backward in the mirror but the letters while backward are right side up. Since you rotated (turned) the rectangle while keeping the pencil axis always pointed in the same direction then the pencil axis is also called an axis of rotation or, in short, a rotation axis. Thus the complete name for the pencil axis is a “vertical rotation axis”.

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Tags: Physics, Science

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