I never get this Lena thing. Back when I was in college (that is 20 years ago in China), nobody knew it was a picture from some Playboy magazine. It was taught in the first class that there is this Lena picture as one of the standard testing images in image processing area. I'd say many of my "ignorant female classmates" actually felt encouraged that a photo of a pretty woman is important in this academic area.

(And I guess it also helped to remind some "ignorant male classmates" that their female classmates are Girls, not some "abstract nerdy polyhedra".) ... And now someone dug out some "secret dark history" and Lena suddenly becomes "offensive" and discouraging to All girls? (But hey I do acknowledge that Some girls could be offended!)

I think in general human (or should I say hu-people?💡) history is dark and bloody, and all human languages come out of it. There might be dishonorable stories behind many of our digital figures, alphabets, characters, math symbols, formulae, ... But I think most of them has been abstracted out with time. For me it feels a grave regression to add those waste dump back into extracted essential.

(Just my 2 cents.)

Think about it: Euclidean geometry could be very offensive to the ocean of Solaris, whose natural language is spherical geometry. It might even understand manifold only but not integers/rational numbers.

Anyone familiar with how a square wheel rolls? The site's users seemed confused. Even the OP, who gave two answers, one correct and one incorrect, has accepted their own incorrect answer and defended it. Maybe I'm wrong. But then so would be Stan Wagon.

@MichaelE2 None of the answers is correct when you want a "bicycle with square wheels".

This is simply showing the trajectory of a circle but you only see the inscribed square

Especially in the last frame you see that no bike would hover in the air.

This is also not correct.

Why would the wheel of a bike hover over the ground as shown there?

@halirutan The curve is the ground so it’s not hovering, look here.

@C.E. Ahh.. that clears it up. It's definitely not what I thought when reading the question.

@Silvia For everyone here I have no doubt that the use of Lena as a good example for image manipulation functions is completely innocent of any ill will. The issue (in my mind) is the prevalent disbelief that anyone else could be offended by it and therefore they shouldn’t be offended. That is what is disconcerting.

@JimB This is something I would never question. For most things in the world, there is someone who is offended by it and this is OK. But growing up is about learning how to deal with your emotions and that you being offended doesn't mean your offender has to deal with it. Especially, as long as we have freedom of speech and the offender didn't do something unlawful.

So would bullying need to involve some unlawful act to be inappropriate on the part of the bully?

@JimB I wasn't referring to you in the slightest, and I can't make the connection between bullying and someone feeling offended, because you don't agree with them.

Sorry, my "growing up" comment was meant to be a joke. I did not take offense at anything that you said.

@JimB My main concern nowadays is that I see too many people who cannot cope with that being offended doesn't mean you are entitled to something. The Lena example struck home for me, because at our university, it was the other way around as far as I can tell. We were happy that our CS course had female students because it was really nice to see that women have an interest in technology.

If anything, we helped them more because we felt it's a good thing to have a diverse class. And now people jump on some arbitrary thing that in my opinion has, if any, only a tiny influence on bringing women to tech.

I think we're in complete agreement. I'm only suggesting that one recognize that someone (and actually I really mean large groups of folks) could be legitimately offended and that some reconsideration of one's views should occur. The end result could very well mean that no change of one's view is necessary.

@JimB Yes. I just wished many very large groups of people would feel more offended by important things (none of which are a concern to me where I live). Brexit, Iran, US gov and their health-system, ... just to name a few.

@halirutan @C.E. We solved this problem in my physics class in '81/82. Our professor had constructed an inverted catenary road out of wood, a couple of meters in length, for two square wheels on an axle. He affixed a chain to the side of the road so that when the roadway was turned over the chain hung and matched the curvature of the road. Perhaps the coolest thing is that if you placed the wheel on the road and tilted the road slightly, the wheel rolled under the force of its own weight.

@b3m2a1 "Why not firewomen too?" -- "Woman" is derived from "wife" + "man" so you should get into an infinite recursion. (The meaning of "wife" here is female person; the word for male person was "were." There was also "wapman" to go with "woman." Many centuries ago, circa 13th c, "man" came to be the dominant way to refer to adult males.)

In 1960s/70s, when I was growing up, you might hear an adult throw it in the face of a woman, "if a woman were supposed to be charge, they wouldn't have called it a chair-MAN." It was to undermine the power of idiots like that the movement to get rid of words describing occupation as X-men got some traction.