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The mirror doesn't flip anything at all. As humans we normally keep our feet on the floor and turn around by rotating around the vertical axis, thus when we fac
by jstanley 6y ago
The mirror doesn't flip anything at all. As humans we normally keep our feet on the floor and turn around by rotating around the vertical axis, thus when we face another human they've normally rotated around the vertical axis relative to us.
We're just not used to seeing the fronts of humans who have not rotated relative to us, so the mirror appears to have flipped the image horizontally.
If we customarily rotated around a horizontal axis, i.e. every time you look "behind" you're upside down (note this won't actually work very well given that you'd normally want to rotate around the axis perpendicular to the surface of the Earth, but just for sake of argument...), then we might believe that the mirror has flipped things vertically. It still hasn't actually flipped anything, it's just that we are viewing the front of a person who has not rotated.
- lordnacho 6y agoFussball players do the horizontal flip. You're still right of course.
- jstanley 6y agoHa, perfect example, I'll use that in future! A table football player looking at himself in the mirror would wonder why he was upside down.
- rixed 6y agoExactly. And it is even easier to convince oneself that that's actually what is going on if instead of trying to explain why the mirror "flips" the image of a person, one try to explain why the mirror "flips" a written word. Take a piece of paper, write a word onto it, and turn it towards the mirror. Now observe the word. Is it flipped left to right? If so, it's because when turning it towards the mirror _you_ turned it around the vertical axis. Do this again, this time rotating the paper around the horizontal axis and voilà, the word is now flipped upside down. IIRC that's Feynman who have written somewhere that mirrors do not flip things right to left, nor top to bottom. They flip things front to back.
- unkulunkulu 6y agoI once got into a bar fight trying to explain this. I somehow got the idea that people who are used to write top-to-bottom might see it as flipping upside down. At the time I thought of Chinese letters being used that way, so while I was trying to tell about this to my friends a guy at the near table got really offended and went “you talking to me? You calling me chinese? Lets go outside!” It ended well :)
- jwatte 6y agoThe mirror DOES flip one coordinate, the "hither" versus "yon" coordinate. If you hold a paper of text up against the mirror, and it looks mirrored, then you can notice that the original text ALSO looks inverted to you, if the paper is translucent. Right is right. Up is up. However, "hither" becomes "yon." Exactly like we would expect by looking at the math for reflection in a plane.
- rrobukef 6y agoThe plastic foils for overhead projectors are transparent. Just imagining it messes with my mind. It is a great science experiment to try!
- davrosthedalek 6y agoMirrors flip front and back.