Mirrors reverse images left to right because they reflect light straight back at you.

The longer version

Mirrors puzzle people because the reversal they perform runs along the depth axis, not sideways. It reflects light straight back, so the front of an object stays at the front and the back stays at the back. What actually changes is the front-to-back direction, and the brain interprets that reversal by imagining itself turned around like a person facing the other way.

That mental rotation is what produces the impression of a sideways flip. Text looks backwards for the same reason, because the page has been turned to face the glass. Front-to-back reversal also explains why a mirror image of a clock runs the wrong way around.

Where this entry sits

Everyday physics and chemistry hide small wonders in plain sight, from kitchen reactions to the light in the sky. These short facts explain matter, energy, electricity, magnets, sound, and the simple units we use to measure the world. The full list sits on the Science and Physics page, where every entry is listed in order.