11.7M views · Apr 23, 2011 · 21:25 · 0 HN recommenders · 3 mentions · discussed 2021–2025
A 21-minute animation showing how a sphere can be turned inside out without creases or tears, known as sphere eversion.
Why Hacker News points people here: Linked as a classic visualization when sphere eversion or counterintuitive mathematics comes up.
“Here are two classic youtube videos on the topic of sphere eversion”HN comment, 2022
“you can completely turn that sphere inside out without creating any holes or creases[1].”
Sphere eversion without creases
> 19. Given a solid ball in 3‑dimensional space, there exists a decomposition of the ball into a finite number of disjoint subsets, which can then be put back together in a different way to yield two identical copies of the original ball. While you're at it, you can completely turn that sphere inside out without creating any holes or creases[1]. [1] this video
“Here are two classic youtube videos on the topic of sphere eversion”
Classic sphere eversion video
Here are two classic youtube videos on the topic of sphere eversion; they mostly overlap, but I am posting both for double the hilarity in the comment sections :) (the full 21 minute one) this video (the first 10 minutes) link If I remember correctly, I think the 10 minute one has the more hilarious comment section.
“here's a 20m video explaining how to invert a sphere without tearing it”
Explains turning a sphere inside out
Sort of a tangent, but here's a 20m video explaining how to invert a sphere without tearing it: this video
