Have you ever removed a rubber glove and had it turn inside out in the process?

If you peel off a left hand glove and it turns inside out, what you have is no longer a left hand glove, but a right hand glove. How weird is that?

Lay the inside-out glove on a table with the fingers toward you. Put your left hand on the table with your fingers toward the glove’s fingers. Your thumb and the glove’s thumb are directly across from each other. So are the forefingers and so one. It’s like a mirror image.

Imagine doing this with a rubber mask that conforms to your face and looks exactly like you.

You pull the mask off, but it gets stuck at your nose. As you continue to pull, the mask turns inside out, the only contact being nose-to-nose.

At last the nose becomes unstuck and the mask is free. What’s staring back at you is the mask turned inside out.

When you had the mask on, your right cheek was the mask’s right cheek and your left cheek was the mask’s left cheek.

Now, your right cheek is directly across from the part of the mask that once covered your right cheek, but has become the mask’s left cheek. Likewise, your left cheek is directly across from the part of the mask that covered your left cheek, but has become the mask’s right cheek.

You are looking at your face, but it’s not exactly your face. The left and right sides have been switched.

This is what happens when you look in a mirror: the left and right halves of your face get switched. Tape a picture of yourself to a mirror. Look at the picture, then at your reflection. See the difference?

“But I thought last week you said a mirror doesn’t flip things — that we do?”

I finished last week’s column by saying a mirror flips the z axis.

There are three axises: x, y, and z. The x axis is left and right. The y axis is up and down. The z axis is front and back. (These axises are part of the Cartesian coordinate system developed by René Descartes.)

Cut out an arrow — a thick, exit-sign sort of arrow.

Point the arrow to your right. The arrow in the mirror is also pointing to your right. (Your right, not your reflection’s right.)

Point the arrow up. The arrow in the mirror points up.

Point down. The arrow in the mirror points down.

Point left. It points left.

Point the arrow straight ahead. The arrow in the mirror points straight ahead. No, wait. It doesn’t. The arrow in the mirror points back at you.

The reason the arrow points back at you is because a mirror flips the z axis, the same way you did with the glove and the mask.

Cue the eerie music.