The Chain Fountain

January 17, 2014 1:25 AM

A video showing a chain of beads behaving in a very peculiar way appeared on Youtube some time ago. Many people attempted to provide explanations, but most of them weren't quite satisfactory.

Later, two physicists published a paper (paywalled) on the phenomenon and posted a video discussing it on the Royal Society Youtube channel. They also talk about the educational value of the demonstration and the analysis in the video.

posted by tykky (30 comments total)

The video says that the physics of a chain moving along its length were known since 1850s and in standard mechanics textbooks by the 1860s, but nobody before Mould had seen chains rising up in this way.
posted by three blind mice at 1:45 AM on January 17, 2014 [2 favorites]

I saw the film but didn't think it was hard to explain. Just gravity acting on a chain with a fixed minimum arc.
posted by Thing at 1:56 AM on January 17, 2014

Thing: "I saw the film but didn't think it was hard to explain. Just gravity acting on a chain with a fixed minimum arc."

I am sure the Royal Society is awaiting your application.
posted by brokkr at 2:45 AM on January 17, 2014 [10 favorites]

Thing: "I saw the film but didn't think it was hard to explain. Just gravity acting on a chain with a fixed minimum arc."

If you watch the last link you'll see that it's actually more interesting than that, and can happen to chains without a minimum arc.
posted by Proofs and Refutations at 2:47 AM on January 17, 2014 [3 favorites]

Yeah, if nothing else then watch the video for the macaroni fountain.
posted by brokkr at 2:57 AM on January 17, 2014

I'm not very bright and no doubt I've issued something here, but it seems the Royal Society proved that the chain of beads can't behave in the way the first video shows, because the beads are round. The chain of round beads they used was very different to the ones in the first video, being separated by much longer threads. Is the point that the first one is acting like a chain and working in a completely different way to, for example, the macaroni chain?
posted by dg at 3:14 AM on January 17, 2014 [1 favorite]

Thing, the arc of the chain mid-siphon is clearly far larger than the minimum arc of the chain itself, or it wouldn't be able to coil into the beaker. Or am I misunderstanding you?
posted by Pre-Taped Call In Show at 3:15 AM on January 17, 2014 [1 favorite]

dg, the beads in the original (Mould) video are not free to rotate about their centre of mass, because the filaments connecting them are short and rigid, and those filaments have nonzero mass themselves. Thus the Mould chain acts more like the macaroni than like the round beads in the RS second video, where the filaments are long and thin.
posted by Pre-Taped Call In Show at 3:42 AM on January 17, 2014 [5 favorites]

I like the way the academics are rather dispassionate about it, rather than exclaiming "THE CHAIN IS FLOATING LIKE MAGIC!"

Although I'm sure they're giggling inside as they get to chuck chains off grand staircases in posh buildings.
posted by milkb0at at 3:43 AM on January 17, 2014 [5 favorites]

Is this what physicists do at Mardi Gras?
posted by BrotherCaine at 4:04 AM on January 17, 2014 [4 favorites]

I will watch videos like this all day.
posted by empath at 4:21 AM on January 17, 2014

arXiv link to full paper: http://arxiv.org/abs/1310.4056
posted by Omission at 4:30 AM on January 17, 2014 [3 favorites]

Thanks Pre-Tapes Call In Show, that's kind of what I thought. From a layperson's perspective, they seemed to gloss over that a bit, although I guess it's aimed at people who have the theoretical knowledge in the first place.
posted by dg at 4:47 AM on January 17, 2014

Incidentally I think the best lay explanation is that the beads ollie like a skateboarder!
posted by Pre-Taped Call In Show at 4:57 AM on January 17, 2014 [4 favorites]

I totally read this as "A video showing a chain of heads behaving in a very peculiar way" and immediately thought 'Is there a normal way for a chain of heads to behave?' I need more sleep.
posted by aclevername at 5:38 AM on January 17, 2014 [2 favorites]

In the spirit of the X Prize, I hereby announce the AAAAAAAAAAAAHHH prize, in which I give a hearty handshake to the first team to construct a rollercoaster based on this phenomenon.
posted by oulipian at 5:41 AM on January 17, 2014 [5 favorites]

I could have sworn I saw a preview for the new season of Mythbusters where they showed (Mefi's Own) Adam Savage performing this.
posted by bondcliff at 5:51 AM on January 17, 2014

Yeah, at 43 seconds into this.
posted by bondcliff at 5:56 AM on January 17, 2014 [1 favorite]

That's just distracting me from asking "and what does the mean for the space elevator?"
posted by hawthorne at 7:56 AM on January 17, 2014 [1 favorite]

This would explain the elaborate anchor windlasses on ships, which control the release of anchor chain through the spurling pipe from the chain locker. If you just let 'er rip, there would be dead people resulting from that chain fountain. ‘Engineers: Keeping People Safe From The Effects Of Physics Since Before We Even Knew What Physics Was’.

(and yeah, I just learned what the bitter end is, too.)
posted by scruss at 8:06 AM on January 17, 2014 [1 favorite]

More importantly the chain would have a shit ton of momentum that would come to an abrupt and damaging stop when the chain ran out if you just let the anchor free fall. A 1" chain weights about 10lbs per foot.
posted by Mitheral at 8:18 AM on January 17, 2014

I'll bite.. What IS "the bitter end", scruss?
posted by bird internet at 8:45 AM on January 17, 2014

A few months ago I was buying some bead chain, and I could not find it in the hardware store. I had to ask for it as they don't put it out on the floor anymore as people steal it. I said that was odd ,and he thought so too. Now I know.
I had a string toy that gives a similar effect String pipe.
I believe the effect is more exaggerated by the heaviness and the limpness of the chain.
posted by boilermonster at 9:45 AM on January 17, 2014

Last fall there was a "fountain" in the Hoog Catharijne shopping center attached to the Utrecht train station that did that same thing as the Popeye String Pipe. It was fascinating to watch.
posted by humboldt32 at 10:05 AM on January 17, 2014

 → “What IS "the bitter end"…?”

The end of the anchor chain (that is, the one that's not attached to the anchor). If your anchor chain is all out and you're still not holding, that's not going to be much fun.
posted by scruss at 11:36 AM on January 17, 2014 [2 favorites]

The Exploratorium has a long bicycle chain loop on a motorized driver (called the lariat chain) that you can play with and see this sort of effect on. Really cool, if you're in the SF Bay Area go check it out!
posted by phliar at 12:47 PM on January 17, 2014

The chain fountain is because each link does an ollie!
posted by lastobelus at 4:17 PM on January 17, 2014

I saw the film but didn't think it was hard to explain. Just gravity acting on a chain with a fixed minimum arc.

um, but this is actually wrong. I'm sure you'd have done well before the renaissance, but these days automatically assuming your naive intuitive understandings of phenomena are correct and not bothering to question them makes you look quite silly.
posted by lastobelus at 4:23 PM on January 17, 2014 [1 favorite]

I was wondering about the original bead chain too - the beads seem like they'd be too short to "kick the table" instead of rotating. Maybe it's actually the little rigid linkers between the beads that do the kicking? Basically, it's sort of inverted: the metal link-rods are the macaroni, and the beads are the "string", the actual flex points that let the chain move. Make sense?
posted by Quietgal at 7:16 PM on January 17, 2014

The question is if an actual linked chain will do the same thing. Not this bead chain or even a bike chain, but a interlinked chain like used for towing or other heavy chain type activities.

I think it would (but it's probably be wicked dangerous due to the amount of kinetic force and the weight of that type of chain in general), given that the main thing needed is that each link in the chain is able to rotate around it's central mass, thus providing the kick as that force is returned by the surface the chain is resting on.

I also wonder if you can get an arch like this by applying a force other than gravity to the chain. We know this works in the given scenario, but what about a force applied in a different manner, say horizontally. Like, turn the whole thing on it's side and yank the chain in the opposite direction of the opening of the container. Would you be able to make the chain arch away from the edge of the container (if the force being applied to pull the chain was constant, or would you have to have the force be accelerating due to the length and thus mass of the chain out of the container is constantly rising).
posted by daq at 12:56 AM on January 20, 2014