Nick
Lv 4
Nick asked in Science & MathematicsPhysics · 2 months ago

# Why does a mirror reverse things horizontally but not vertically?

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• marty
Lv 7
2 months ago

The reason you think it’s reversed horizontally is that you’re used to looking at the front of people who turned to face you. This is the same reason they can read your shirt; the words were written so that if you turn to face someone, the words will be oriented appropriately to their viewing. You’re so used to this, in fact, that you automatically (and largely unconsciously) re-flip the sight of people facing you in order to get a “proper” orientation: when your friend faces you and raises the hand on your left, you immediately interpret that as being their right hand.

But the mirror image isn’t a rotation, it’s a reflection, so your visuospatial autocorrect gets confused, and anything that was designed with the assumption that your front and back would switch places only by turning (e.g., text on a shirt) ends up displaying “backward”.

You can check this by just looking down at your shirt while wearing it: the text will be in the same horizontal orientation (i.e., the last letter on your left) as displayed in the mirror. Of course, when you do this, the text will also appear flipped vertically (provided you can see past a second autocorrect), but that’s because you are looking at it via a rotation (about a horizontal axis rather than the usual vertical axis), which produces a vertical flip that the shirt’s designer didn’t account for (because people don’t normally turn around by rolling forward to stand on their heads)

• 2 months ago

Mirrors don't reverse things horizontally.  Lift your left hand while looking at a mirror.  The hand that goes up in the reflection will also be on your left.

They do reverse things forwards and backwards though.  Point your finger at the mirror and your reflection will point back at you in the opposite direction.

• 2 months ago

It doesn't reverse anything! What your brain wants is odd!

Maybe you prefer your left side on the right?? Need a camera for that.

• Anonymous
2 months ago

Or better still, reject the world.