[In answer to question: why does a mirror reflect things left-for-right and yet not top-for-bottom? SEE LETTERS]
The mirror thing ? Well, yes, this comes up now and again in nice thinking people !
My answer is this. A mirror doesn’t actually reverse laterally OR vertically. But it DOES reverse front to back – as you’d expect.
Which means you are looking at the image from a different direction, and have swapped YOUR definitions of left and right.
If you set up the mirror along an East-West line, and stand facing it, you’ll see that both the object (you) and the image of you have the same side facing West. And the same side facing East. It’s the the fact that you’ve been turned inside out from North to South that’s made you into a left-handed creature ! And it’s true no matter how you stand, sit, or turn upside down. The mirror actually does turn around the ‘handed-ness’ of an object in that virtual space it creates. In the case of molecules, and fundamental particles with ’spin’, it’s very significant.
A small note … I broke my right hand just before taking my ‘O’ Level exams. So I did write them with my left hand … which was … tricky ! But for fun, outside the exams, I allowed myself to ‘do what came naturally’ , and found that it was easy to write in ‘mirror writing’ … working from right to left, but using exactly the same movements, mirrored that my right hand knew so well. I can still do that. And if you put a mirror at the side of what I’m writing, you can read it easily. Did you know Leonardo da Vinci did this ? I only found this out later … but I have no idea WHY he did this.