You can't comb a tan egg flat without creating a cowlick

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en.m.wikipedia.org/wiki/Hairy_ball_theorem

cross-posted from: https://lemmy.world/post/28431423

The theorem has been expressed colloquially as "you can't comb a hairy ball flat without creating a cowlick" or "you can't comb the hair on a coconut".

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Good thing they're actually tori, topologically.

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By moving the entire comb parallel, sure. But you can move one end slower than the other (i.e. as if you planted one end and pivoted it around, just with some speed, not stationary) and you can comb it without it.

Thanks, I expected it would figure itself out. But I guess it only works in the desktop -> mobile direction, not the reverse.

Totally, I don't understand why it doesn't work that way.

Why does Wikipedia do this?

Whoever posted the link was on mobile at the time and didn't feel like deleting the m. after copy pasting.

Yeah ik. Just confused why Wikipedia itself does it

Does what? Have a separate site for mobile viewing? There's many good reasons..

It would be better to handle it by detecting what device youโ€™re on rather than having encoded into the url. That way it wouldnโ€™t matter what device the page was shared from.

usually it is just a redirection. One of the reasons wiki does this is that their stack is more older device friendly (for the most part, you can use wikipedia perfectly fine without any js), and having adaptive view usually requires js (there are some other ways too), but wiki is constrained. So when browser recieves a request from a mobile user agent, they just redirect to mobile site.

That's a terrible idea. Because many users change their user agent for security.

No, you can't expect to detect what devices someone has. That's the thought process of an inexperienced dev.

A hairy doughnut โ€ฆ on the other hand, is quite easily combable.

What gives someone the right to speak like this. You think this is the kind of factoid I can just forget?? No, this meme is going to jockey my brain until the day I die.

Like a chicken?

"CHICKEN JOCKEY!"

throws popcorn at phone screen

My nephews have been screaming this. I thought they were just insane, but apparently I've missed a meme!

I want to know more. Does this only work for donuts with 1 hole? Odd numbers of holes?

For mathematicians in Germany, this is known as the "Hedgehog Theorem" ("Satz vom Igel", as in "you can't fully comb a hedgehog")

I think it would be hard to find a hedgehog that would allow itself to be combed.

I remember first hearing about the Hairy Ball Theorum when watching some of the extended features on our Monster's Inc DVD. One of the animators was talking about how they had to constantly be re-combing Sully's hair to make sure the cowlick was in an unseen location

I'll have to poke around at some point because there was a really neat video on that DVD as well that was talking about the origin of the Monsters Inc universe, and how the monsters both discovered the power of screams and built the doors/portals for reaching the human world and I remember it being super interesting and extremely fleshed out for something that literally never happen on screen and probably doesn't influence anything on-screen at all

Shave 'em. I don't want no cowlick near my balls

You haven't lived until a cow licks your balls.

I guess the closest I've gotten to that is to have a cow lick the "T" off of the "Passat" lettering on my trunk a couple years ago.

...where were your balls when that happened?

nowhere near the trunk of the car, thankfully. :-)