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Comment by dhimes | Hacker News Reader

They don't. They keep the right on the right, the left on the left, the top on the top and the bottom on the bottom.

I never quite got why this was a paradox tbh.

The paradox exists because when you ask a person "why it flips horizontally but not vertically" most people can not respond. Usually they can not even begin discussing the premise of the question. Notice how even in your comment you did not really attack the premise, just gave a parallel explanation that skips talking about the premise. This does not really help, because as with most paradoxes, the issue is exactly with the premise. The linked video by Physics Girl does a great job at explaining the paradox away.

I've found that explanation to be pretty good, as a matter of fact. The paradox seems to arise because from a psychological effect of "projecting" the directions with respect to the image "looking" back at you. Once you get people to stay in their reference frame (left, right, top, bottom above) they see their mistake.

Prob the best comment here

Yup. Mirrors reflect front to back. It's the struggle between accepting as literal what you've always been told, and the data being reported by your own senses, mitigated by language and cliché.

Agree. I don't mean to belittle people that get confused by this (many other things perplex me), but this always seemed very intuitive to me.

Intuitively, why does a mirror-image appear to be flipped left-to-right compared to a photograph?

Isn't it the photograph that is flipped? After all if I'm in front of a mirror my left hand appears to the left and the right hand appears to the right. But on a photograph it's the opposite.

Intuitively just consider the difference between the two:

What DO you see? In case of the mirror, you see what's BEHIND you, because the stuff in front of you is blocked by the mirror, no? And just to be clear, by "you" I mean your eyes, and in particular the direction your eyes are looking at.

Now in contrast a photograph never shows what's BEHIND the camera (now that would be kind of funky, don't you think?), but - just like your eyes - only captures what's in front of the lens.

And there's your difference.

I don't know how to "explain" intuition, but usually I imagine not myself but some kind of geometric shape in front of a mirror (say a square with the edges labelled). If I try to visualize how light bounces, it is intuitive that in a mirror I'm seeing the light bouncing from mirror -> me in the proper way and in a photo, I'm looking at the shape directly with a camera (I'm where the mirror was).

They mirror things forward-to-back.

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