I really like this demo. It is simple and surprising, yet deceptively subtle and complex.
It also draws my attention to explanations. The first time I saw Steve present this he didn’t explain it, but I was transfixed. Effective demonstrations don’t always come with explanations. Sometimes less is more.
I’m no physicist, but I’m not fully satisfied by the explanation of what’s going on here. In that sense, despite the beautiful slo-mo, I preferred the first version I saw. I find this demo intensely pleasing despite it leaving me hanging.
Don’t get me wrong, I’m not advocating that we all go around deliberately producing unsatisfying explanations or consistently refusing to give any at all, but what works for me is that I’m left wanting to get my hands on a set of these to test it out, to explore and investigate the phenomenon to try to understand it better. Surely that’s one of the indicators of a great demo?
3 thoughts on “Self-siphoning beads”
Thanks for posting this Elin! I wasn’t sure whether to try and explain it in the first video. I’m glad you see a good reason not to :).
I expect two contributing factors are that the joints have a limited range of movement and the connections between the joints are inflexible. As the momentum pulls on the wire I suspect it might aid the lifting of the stationary wire by whip-lashing it.
To see what the contributing factors are the experiment should be varied slightly. Start with a couple of metres as it is now but then part way through vary between flexible/inflexible wire and also ball joints and no ball joints. I suspect the impact of the balls initially throw the wire into the air but it is the semi-flexibility of the wire and limited movements of the joints that causes the phenomenon.
Would be interesting to see footage of the variations 🙂
It’s a beautiful demo, Elin and Steve.
My understanding (what a useful phrase that is) was that this is due to inertia and the limited range of movements of the links (as mentioned above).
Similar effect in this spinning chain demo:
and this spinning string toy