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> Meanwhile, in 3D, there is no global coordinate system for the space of rotations There are plenty, it's just that you can't have a 3-dimensional one without
by Grustaf 9y ago
> Meanwhile, in 3D, there is no global coordinate system for the space of rotations
There are plenty, it's just that you can't have a 3-dimensional one without singularities.
https://en.wikipedia.org/wiki/Hairy_ball_theorem https://en.wikipedia.org/wiki/Hairy_ball_theorem
- tgb 9y agoThe term "coordinate system" isn't well-defined without context. I was taking non-singular implicitly as part of that - actually, not so implicit since that's sort of the point of the digression. Of course, other contexts are happy to say that, say, polar coordinates are a coordinate system even including the singular point at radius 0, so I probably should have been more careful and said a "coordinate chart."