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/sci/ - Science & Math

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12007368 No.12007368 [Reply] [Original]

This doesn't look like it "should" be possible, but it also looks like it's the case.
Why?
Why is it that it looks like it shouldn't be possible, and why is it possible?

>> No.12007371

Because it is.

>> No.12007441

>>12007368
The rotation group is fucked up

>> No.12007444
File: 3.48 MB, 256x256, Atomic_spin_2.gif [View same] [iqdb] [saucenao] [google]
12007444

>> No.12007448

>>12007368
Because rotation by 4pi is equivalent to no rotation

>> No.12007462

>>12007448
But rotation by 2pi isn't?

>> No.12007463

>>12007368
I mean why not? if it works it works right

>> No.12007467

>>12007463
this

>> No.12007689

>>12007368
because [math]\pi_1(SO(3)) \cong \mathbb{Z}/{2\mathbb{Z}}[/math]

>> No.12007702

>>12007368
As Ike Chuang once said, we must show reverence for the majesty of SU(2).

>> No.12007837

Another thread about spin groups? Is this a new meme?

>> No.12008281

>>12007368
I think it only "feels impossible" because one imagines a rubber that in reality can't be turned around and axis forever

>> No.12008286

>>12008281

But it isn't. If you look closely (easiest on the ribbon coming from right) it loops over the cube for one rotation and then under for the alternating rotations. The net effect is no twisting over time.

>> No.12008338

>>12007368
this has been used to allow fluid flow between rotating components
>>12008281
it works IRL, you can test this out with some ribbon and a disk

>> No.12008351

>>12007837
Its just iq gating and its effects in action

>> No.12009495

It becomes very obvious/intuitive how it works when you focus on only two rods at once.

>> No.12009575

>>12007462
Lrn2spinstructure

>> No.12009617

>>12007368
you can try it irl
take a cup upright in the palm of one of your hands, rotate it once over your head so your arm is a bit twisted, then the second time under your armpit so that the arm is untwisted again. all while holding the cup upright.
result: the cup made 2 full rotations and your arm is still attached.

>> No.12009629

>>12009617
Is that at all related to why quaternions have "double cover" of rotations?

>> No.12009639

>>12007368
looking at the bottom-screen-to-top-of-cube ribbon makes me want to call bullshit on this.
The bottom should carry on getting twisted.
And yet, all I see is just the purple side facing me, completely fucking with my brain, raw and with no lube, in the process
Fuck, I'm a simpleton.

>> No.12009649

>>12009617
Can you provide a visual because I'm way too retarded to understand what you mean

>> No.12009652

>>12007368

it looks possible to me.
try looking at it.

>> No.12009765
File: 705 KB, 920x1345, rotating_cup.png [View same] [iqdb] [saucenao] [google]
12009765

>>12009629
ye
>>12009649
see pic, taken from Bredon's "Topology and Geometry"

>> No.12009898

>>12009765
This is kung fu

>> No.12009900

>>12007368
>>12007444
NONE OF THE LINE CROSS

>> No.12009904

topologists are dark wizards

>> No.12009938

Is all rotation in higher dimensions a combination of some planes? For example you can rotate square in its only plane. If you rotate a cube, you choose a certain plane with an axis going through it and rotate the cube with it, but not "three-dimensionally". If you have a 4D tesseract, you can independently rotate it in planes fully orthogonal to each other. But does it stay all the same in the higher dimensions? Like if the number is even, you have dimension/2 independent rotations and if odd, one dimension is unused. Or is there something more complex up there?

>> No.12010041

>>12009765
yoooo
i learned about this when i first got into quaternions because of gimbal lock. it freaks me out. so cool.

>> No.12011598

quit posting this weinstein shit.
give it a fucking rest.
the guy is a fraud.

>> No.12011611

>>12009765
This is anatomically impossible. I just tried it and hurt my shoulder.

>> No.12011623 [DELETED] 

>>12007368
You nailed gravitoelectromagnetism.
>Join us
https://www.thunderbolts.info/wp/

>> No.12011671

>>12011611
>This is anatomically impossible.
For you.

>> No.12013645

>>12007368
Are there any videos of a working physical model?

>> No.12013661

>>12011611
https://youtu.be/rC0jAICfNwc?t=25

>> No.12013709

>>12013661
this shit genuinely feels like forbidden knowledge to me

>> No.12013739
File: 278 KB, 800x600, d1388161.jpg [View same] [iqdb] [saucenao] [google]
12013739

Stretch your arm out in front of you with the palm out of your hand down.
Now try and turn the palm upwards using only elbow movements.

>> No.12013746

>>12013661
Thank you for giving me something new today!

>> No.12014972

>>12013739
well I guess it's a Sieg Heil to you my friend

>> No.12015549

>>12007462
not for electrons & other spin-1/2 particles

>> No.12016398

>>12009617
I tried doing this and now my arm is all fucked up. And I broke the cup, which was a priceless family heirloom. Thanks a lot!

>> No.12016431

>>12016398
try it with your neck