all 10 comments

[–]Derpeh 1 point2 points ago

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How?

[–]johadalin 0 points1 point ago

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wikipedia

[–]packerbacker1221 1 point2 points ago

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[–]TrollinU 1 point2 points ago

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It's the shadow of the 4th dimension... basically.

[–]Harley017 0 points1 point ago

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I've never got how this is 4th dimension. Wouldn't it just be a 3d shape being stretched?

[–]Cullly 3 points4 points ago

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No. When it comes to 4 dimensions, rotating gets complicated. There's a few types types.. OPs picture is a simple rotation.

Think about it this way.....


ROTATIONS IN 3D

In 3D, think about the X, Y, and Z planes. Here is a pic explaining them. There are 3 different ways it can rotate.

The thing is... the XY rotation looks 2D because it uses only the 2 axes that make up 2D (X and Y).

Does this make sense?


ROTATIONS IN 4D

The exact same applies to 4D. Because we can only see in 3D, we can't see this extra dimension (abstract as it is), so all the rotations that use only the X, Y and Z axis look the same as the 3D version. This counts for 3 out of the 6 possible rotations (XY, XZ, and YZ).

The other 3 rotations use the 4th dimension which is marked as W. The rotations along the W planes are XW, YW, and ZW. They look like they are turning inside-out because there is no way to show 4D on a 3D animation. It's not actually turning inside out... This is merely an artifact of projecting from 4D to 3D. The cube is staying the same shape throughout the whole thing.


TL;DR: Our eyes can't see in 4D so we have to imagine a 4th dimension. OPs picture is rotating (not stretching) because it's staying the same shape throughout the cycle.

[–]Harley017 2 points3 points ago

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My brain hurts...but I kinda get it. Its just hard to visualise a 4th dimension. I'll stick to doing 3d engineering and leave all the 4D stuff for you physicists.

[–]Cullly 1 point2 points ago

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Well the good news is that it doesn't exist (that we can prove) so you don't have to get it. The fourth dimension is only an abstract concept of stuff we don't know or can't see yet. It's kind of assumed that there is one because theres 1, 2 and 3... Surely there's a 4th right?

Anyway... 4D theories help solve a lot of Mathematical and Physics problems, so that's good right. It's best to let a computer think about them.

[–]Harley017 1 point2 points ago

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True. The best I an do to visualise a 4th dimension is that mobius strip thing. It appears to be flat if your perspective was on the strip but when looking at it as a whole it is quite clearly curved.

[–]Cullly 1 point2 points ago

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Like the world was flat... until we proved otherwise. Some people had theories that it was round.