ELI5: How do mirrors work?

Mirrors work by bouncing light straight back at your eyes like a super-smooth wall bounces a ball.

Think about playing with a bouncy ball. If you throw it against a bumpy, rocky wall, the ball will bounce off in a crazy, unpredictable direction. But if you throw it against a totally flat, hard gym floor, it bounces right back up into your hands.

Light does the exact same thing:

• Rough surfaces scatter light: Most things in your bedroom, like your wooden door or soft blanket, look smooth to your fingers, but they are actually full of microscopic bumps. When light hits them, it bounces off in every single direction. This lets you see the object, but it can't show you your face.
• Mirrors keep light neat: A mirror is made of super-smooth glass with a very shiny layer of metal—usually silver or aluminum—painted on the back. Because the metal is completely flat and shiny, the light rays bounce off it without getting mixed up.

Because the light rays bounce back in the exact same pattern they left your face, your brain is tricked into thinking there is another identical twin standing right behind the glass, copying every move you make.