45 thoughts on “Magnets are magic”

  1. I trust that the last little trick where the guy/gal snaps down on the full column of magnets and they all jump back to the original array is just sped-up reverse motion photography (or video).

    Otherwise the laws of entropy are in a bit of trouble.

    1. No, the laws of entropy aren’t broken, because the owner of the finger is inputting energy into the system at that point.

      I think, energy-wise, it’s possible for there to be two metastable states and the finger is causing a switch between them. (I said ‘possible’, I’d love the flip-back at the end to be genuine and not video trickery but I wouldn’t bet on it yet. Maybe later comments will illumine this).

      cr

      1. Sadly, stepping through it frame by frame confirms that the flip-back at the end is just the initial sequence speeded-up and reversed. 8-(

        (Downloaded with youtube-dl and viewed with Avidemux)

        Wish they hadn’t done that, it detracts from the extraordinariness of the original effect. That point where the green piece leaps into the air is particularly dramatic.

        cr

  3. I wonder if it was a chore to set it up in the first place. Wouldn’t the magnets keep shifting around as more and more were added to the field?

    1. Yes, this would be very hard to set up.

      Much harder than a chain of dominoes.

      They would need some way of holding them in place while placing the rest. I’m guessing a clear sheet of plexiglass (or similar) then using a thin stick to move them around.

      1. Nah… they just turn off the magnets remotely with the iPhone app.

        What, you don’t have that app? Come on, get with it!

        1. Probably the same way BMC (British Motor Corporation) used to assemble gearboxes.

          “Hold the gear in one hand, press the three spring-loaded detent balls into their radial holes with the other three hands, and with the remaining hand slide the synchro sleeve over the gear thus trapping the balls in their correct location”. Do this inside a cardboard box as otherwise, should any balls escape, they and their springs will rocket off into the darkest recesses of the workshop never to be seen again.

          The magnets just remind me of that, all that potential energy just looking for the slightest excuse to descend into chaos.

          cr

    2. I’m guessing that they arranged the round inner magnets first and then added the “corral” of black magnets to add magnetic pressure to the whole thing till it was almost ready to destabilize on it’s own.

  4. NOT the Butterfly Effect.

    Not even remotely.

    The initial arrangement of magnets is highly unstable, and collapses to a highly stable (low potential energy) state once perturbed.

    Although the exact order in which the pieces come together will be quasi random and dependent on slight differences in starting positions, this is not an example of a chaotic system.

    This is a system that starts in a highly ordered, but highly unstable, configuration, and collapses to a highly ordered and highly stable configuration.

    It truly is *magic*, however. 🙂

    1. Doesn’t the existence of the Butterfly Effect imply that the system is also unstable?

      Still looks to me that it’s a difference of degree, not of kind, and your commentary doesn’t show, IMO, why they’re different.

      1. The problem is a mishmash of related things.

        – The butterfly effect is mostly associated with chaotic systems.

        – The article Jerry links to cover exponential divergence (a sign of chaos), but also goes into nonlinear systems (which magnets aren’t as such, but collapses are) and for good measure describes Lorentz coinage of an older idea (unquantified large effects from small causes).

        YMMV, and I think most people have stopped using the term due to the misunderstandings.

      2. In a word, no.

        The butterfly effect refers to a system such that the tiniest deviations in initial conditions lead to radically different outcomes. *Any* uncertainty in measurement of the starting state means you cannot predict what it will do in the long run. Though you may know the range or space of possible future states, they become unpredictable in a short time if there is, in effect, even an infinitesimal uncertainty in the initial conditions.

        An unstable system is one which may be perfectly balanced and static, but the slightest nudge will set it off. Simple case is a ball balanced at the exact top of a smooth dome. The magnets here are basically the same, just with many more degrees of freedom. In this case, the more accurate your measurements of the starting conditions (and the “nudge”), the more accurately you can predict the future states.

        Furthermore, overall this is a stable system that happens to be in a balanced unstable initial state. It is stable in the sense that it has (many) stable, minimum energy states to collapse to, once nudged — this is analogous to numerous holes surrounding the dome on which the ball is balanced. It will fall to the bottom of one of the holes and then stay put.

        1. I think there’s a further difference between ‘unstable’ and ‘butterfly effect’.

          I think ‘unstable’ implies there’s stored energy available to drive the system to a new state once an initial threshold (which may be arbitrarily low) is overcome. In fact for the ball-and-dome the threshold is near zero.

          Whereas ‘butterfly effect’ can manifest itself in a system that requires continuous energy input to run – such as the weather.

          (I could be wrong on this).

          cr

          1. Technically no, although it may be a quibble. If there is a threshold to be overcome, then the system is in a local energy minimum.

            In the strictest (idealized) sense, unstable basically means there is no minimum “nudge” required.

            As a practical matter, real systems at least have a bit of friction or something to overcome, so there is a minimum nudge.

            But if you imagine the ball on top of the smooth dome, but the dome has a *slight* depression right at the top that the ball sits in, this would not be considered unstable. Might call it “in a stable high energy state with a low threshhold”.

    1. I don’t see a pattern to it.
      I was thinking that it might be interesting to repeat the experiment to have (say) a ring of blue around the impact site ; then a ring of red ; then a ring of green, then …
      On the “butterfly effect” comment above, one might expect there to be some predictability in the sequence of magnets in the final stack. Using numbers to represent the “ring” of the disc’s original position w.r.t the impact site (ring 0), one would expect a pattern like :
      4344333232212121112212232122332333423434
      BR Hmm, not a good representation. But I’m hypothesising that you’d see the closer-to-the-impact magnets going onto the stack before the further, on average.

    1. You must be attracted to them.

      They have that magnetic personality, but sometimes they can be repulsive.

  7. If you use glue to cover a ball with magnets, all with their north poles facing outward, and line the inside of a bowl with magnets, all with their north poles facing inward, would the ball float inside the bowl? If not, why not?

    1. I don’t know, but for a start, try the thought experiment of imagining what the magnetic lines of force would look like. How do they connect the south poles of the magnets on the ball to their north poles?

    2. Sure it would. This is basically how maglev trains work (except they use electromagnets rather than permanent magnets).

        1. But (looking at your link) not necessarily with a ball.

          Probably because no-one’s bothered.

          I think you’d have to use a goldfish bowl – for access. And it would be quite fiddly to do and hard to get a good clear photograph of.

          cr

          1. Oh, I misread Needtob’s initial comment. I though he had a ball floating inside another ball, not just a bowl. Ignore everything I just said. 🙁

            cr

      1. Insane Clown Posse? I just watched their video
        http://www.youtube.com/watch?v=_-agl0pOQfs

        Nice video. (Shame about the song).

        Srsly, it’s the first time I’ve ever watched a rap … err, song? … right through.

        I only knew of them before from that excellent website Lowering the Bar, which documents innumerable legal stupidities including the FBI classifying the Juggalos (ICP’s fan club) as a terrorist organisation. Which immediately gives ICP some cred in my eyes.

        cr

          1. 🙂

            As it happened, the phrase genuinely sprang to mind. But the moment I thought it, the entire NRA and their armament couldn’t have stopped me writing it down.

            I’m so pleased someone got the NTNON reference.

            cr

      1. On that subject (slightly OT but I hope I’ll be forgiven) I just got, from ‘Fox Breaking’, “Bill O’Reilly shows what you must do to protect your family from this terrorist threat”.
        G*d knows why I got spammed with that. It got deleted even faster and with less regret than the Russian women who just want to f&#k me.

        cr

  10. … a cool chain reaction.

    “The Italian navigator has just landed in the new world.”

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