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Comment by sethbannon | Hacker News Reader

Incredible. Is there still no solution to the Newton's cradle like problem with magnets?

I'm really curious about this as well. The lecture is from 2008, so it's entirely possible that he or someone else has solved it by now, and I'd really be curious to know what the answer is. It's such a simple system of marbles and magnets, so it's pretty incredible that such an unintuitive thing would happen. You'd also expect that, given the simplicity of the system, any weird behavior would have some elementary explanation (elementary to trained physicists and mathematicians, anyway), but apparently not.

Stick around for the end of the video where he demonstrates an equally incredible and (at the time of the lecture) unexplained phenomenon with "chiral tippe tops".

Is it just me or does someone else also thinks that the comments section is incredibly enlightening to read! :-)

He said there is no solution for the chiral tippy-top as well.

Isnt it related to that rotating widget demo on the space station? Terry Tao had a good explanation of it.

Would you have a link? If you're thinking of the Tennis Racket theorem, I don't think it's the same thing as chirality, is it? The special tippy-top would erect itself only when spun in one direction but not the other.

> The tennis racket theorem asserts that when rotating a rigid body with three distinct moments of inertia, the rotation around the axes with the largest or smallest moments of inertia is stable, but the rotation around the axis with the intermediate moment of inertia is unstable.

src: https://plus.google.com/+TerenceTao27/posts/e3GLg4Ki4dj

Yes, https://news.ycombinator.com/item?id=14125097

Does not explain chirality... I didn't watch the original video so closely, sorry.

Reply on news.ycombinator.com