"Why do mirrors flip text to be right-to-left, and not top-to-bottom?"
A lot of people give the correct (but nonsequitur) answer "mirrors don't flip text horizontally or vertically, the flip it through the plane of the mirror". But it is still the case that if you hold a book up to the mirror almost certainly you'll be reading right-to-left, but still top-to-bottom! That needs an explanation!And the answer is this: you broke symmetry when you decided to hold the book up to the mirror – you probably rotated the book about the vertical axis, not its horizontal axis. I first heard this from @shachaf. If you have a book in your hand and you simply tilt it forward then you'll be reading the text left-to-right bottom-to-top in the mirror, but that's a much less natural motion, and is not usually how you present text to the mirror.
It's crazy to me how often folks get this one wrong. Like, they hear "mirrors actually mirror through the plane of the mirror" and nod sagely, and forget to explain the original phenomenon that almost all text I see in mirrors requires me to read right-to-left+top-to-bottom.
https://x.com/ptrschmdtnlsn/status/1837960441152295154
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Rick Korzekwa
in reply to Ben Weinstein-Raun • •Ben Weinstein-Raun likes this.
Daniel Filan
in reply to Rick Korzekwa • •like this
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Daniel Filan
in reply to Daniel Filan • •Ben Weinstein-Raun
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Ben Millwood
in reply to Daniel Filan • •is that what they're calling it these days
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in reply to Ben Weinstein-Raun • •kip likes this.
Ben Weinstein-Raun
in reply to Ben Weinstein-Raun • •Like, if I think it through all the way, I can see why I am actually mentally privileging the vertical axis, but it's hard to get my system 1 to understand this.
Ultimately I think the biggest thing is that humans are roughly bilaterally symmetrical but not top-bottom symmetrical, and my guess is that this is sufficient to do the symmetry breaking. Like, if you parity-flip me, I still visually "make sense" as a left-right-swapped person, but I don't "make sense" as a top-bottom-swapped person; people don't have their heads on the bottom.
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Ben Weinstein-Raun
in reply to Ben Weinstein-Raun • •So there are at least two interesting thought experiments about putative zero-g humans:
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Ben Millwood
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Rick Korzekwa
in reply to Ben Weinstein-Raun • •Yeah, I was about to say the same thing about bilateral symmetry.
Another thing I just realized is that if I look at a mirror on a ceiling it intuitively feels like it's reflecting across the mirror and not switching left/right.
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