Sphere Eversion: Hacon's Half Torus

This method was discovered by Derek Hacon in mid-1970s(?).
A sphere, when "folded", can be viewed as a half torus with two half spheres.
References:
Circle Deformation in Hacon’s Sphere Eversion by Yongheng Zhang: archive.bridgesmathart.org/20...
Mathologer's video: • Smale's inside out par...
Hacon's notes: www.math.utah.edu/~hacon/spher...

[@cosmnik472]

Remember, you mustn't tear it or crease it

[@Poyni]

this one i can somewhat understand unlike the de neve/hills method

[@JohnPaulBuce]

everywhere i go i see it

[@sharkfang802]

I can just barely wrap my head around what’s going on. It’s basically the torus inverse just applies repeatedly to the walls of the sphere after extending it into a cylinder.

[@francogonz]

This is gorgeous

[@narcissesmith9466]

In a way, if a sphere can be inversed, its "already inversed". Idk if that makes sense

[@Ykulvaarlck]

i'm sorry but this is utterly incomprehensible

[@amazingfireboy1848]

Okay, but that thumbnail...

[@mstech-gamingandmore1827]

i like the music

[@KarleonBR]

Easy step

[@user-VKL34674]

0:17

[@Tyn4tyk]

what? how?

[@tultrapfighter]

Geometry is basically like doing drugs

[@alex.g7317]

Am I real?

[@cheedozer7391]

This is probably the easiest eversion to visualize!