[twhb]

Why is it that mirrors flip your image left to right, but not top to bottom?

That’s a question that Richard Feynman supposedly asked his grad students. Once you answer it, I think you’ll realize that #1 is anything but trivial.

Answer below, stop reading this comment if you want to figure it out on your own.

It’s because you’re comparing the mirror image to what you’d look like if you walked around the mirror, instead of to what you’d look like if you floated over the top. This assumption of horizontal travel is incredibly deeply engrained in humans, to the point that the English language doesn’t even have up/down equivalents to the words “left” and “right”, i.e. a word that means the direction closer to your head than to your feet regardless of your orientation.

[Ao7bei3s]

A mirror doesn't swap left and right, it swaps front and back.

The realizations that people expect yaw rotation because that's what they are used to, or that normal day language isn't always precise (my left? your left?), seem extremely trivial to me and doesn't require any deep philosophical "insights".

In the hard sciences, you often don't even need the handwavey "swap a and b" explanation when it is much more useful to just model its behavior (ingress ray/plane intersection, normalize ingress ray, subtract twice normal vector of plane from ray to get egress ray direction).

I'm sure Feynman was a great physicist and teacher, but he's also great at just wowing people by using lots of words without saying much. Like in his famous why-is-ice-slippery video where he goes onto a completely unnecessary discourse on the nature of questions instead of just answering the dang question.

I always felt that is the perfect way to showcase the difference between education and edutainment, and I assume his lectures were a bit more substantial.

[twhb]

I think you’re certainly correct, but remember that the question wasn’t just about understanding mirrors, but using mirrors to make a point about bias. “A mirror image is swapped left to right” doesn’t appear to be biased at all, and yet it is.

Also, just for fun: what makes calling it swapped front to back more valid than left to right? One could recover the (translated, rotated) original image through any of a front to back swap, left to right swap, or top to bottom swap. They’re all lenses, and equally valid.

[Kim_Bruning]

https://en.wikipedia.org/wiki/Anatomical_terms_of_location

I guess technically correct, because they're mostly latin loan words.

[twhb]

I didn’t know that terminology, thank you.

But reading the article, are those not applicable only to body parts? Would an astronaut ever say to another astronaut, while floating in different orientations, “Hit the button to your superior”?

Either way, I think it’s at least correct to say that there are no layman words for it.

[LudwigNagasena]

I fail to see how it in any way relates to #1.