Here’s the explanation!

by Matthew Cobb

Here’s the explanation of the Mephisto illusion I posted earlier today… Cunning, eh?

19 Comments

  1. Damien
    Posted October 26, 2017 at 1:36 pm | Permalink

    Does he really give the explanation ?

    If so I didn’t understand it.

    • Janet
      Posted October 26, 2017 at 1:44 pm | Permalink

      I don’t either!

      • infiniteimprobabilit
        Posted October 26, 2017 at 7:27 pm | Permalink

        The two spirals are opposite-handed – one’s left-handed, one’s tight-handed – and fixed together.

        Everybody instinctively assumed the spirals were both the same chirality.

        cr

  2. sshort
    Posted October 26, 2017 at 1:49 pm | Permalink

    Ah… chirality strikes again! I didn’t notice that before. I don’t have the math to explain how this works for the illusion, but it must be rather central.

    • sshort
      Posted October 26, 2017 at 1:51 pm | Permalink

      Is it something like phase-shifting?

  3. busterggi
    Posted October 26, 2017 at 1:56 pm | Permalink

    You mean it wasn’t magic?

    • sshort
      Posted October 26, 2017 at 4:34 pm | Permalink

      ha! what i mean is, he said they are wound differently. one right-handed and one left. I suspect that contributes to the illusion in a way two similar-handed coils would not. any topologists around here?

      • infiniteimprobabilit
        Posted October 26, 2017 at 7:29 pm | Permalink

        Don’t need much topology. They’re opposite-handed. So as they both rotate the same way, they seem to be ‘screwing’ in different directions.

        cr

  4. Frank Bath
    Posted October 26, 2017 at 3:26 pm | Permalink

    I think he has to turning it in the back of his hand. So a conjuring trick. Otherwise I’m stumped.

  5. Diane G.
    Posted October 26, 2017 at 6:19 pm | Permalink

    Sigh! I mean, sub.

  6. mordacious1
    Posted October 26, 2017 at 7:04 pm | Permalink

    So klar wie Schlamm…

  7. b
    Posted October 26, 2017 at 7:05 pm | Permalink

    i think that the twist is held between the fingers and thumb in such a way that when pulling apart a force is induced that rotates the whole thing

    • bascule
      Posted October 26, 2017 at 7:06 pm | Permalink

      so much for autofill in firefox!

      bascule

  8. infiniteimprobabilit
    Posted October 26, 2017 at 7:34 pm | Permalink

    They’re fixed together but opposite-handed.

    So as they both rotate the same way, they seem to be ‘screwing’ in opposite directions.

    NOBODY in the last post thought of that (I didn’t). Everybody assumed without even thinking about it that both spirals were the same chirality (e.g. both ‘right-handed’).

    In fact the guy says it at 6 seconds in to this video and I still missed it till I saw the big welded-together sample at the end.

    Once you realise what it is, it’s blindingly obvious to anyone familiar with screw threads, at least.

    What a diabolically cunning trick.

    cr

  9. Michael Fisher
    Posted October 26, 2017 at 10:08 pm | Permalink

    THIS is a video demonstration of the principle behind the Mephisto Spiral that everybody will understand:

    • Diane G.
      Posted October 26, 2017 at 11:06 pm | Permalink

      That is much clearer, thanks.

  10. Melanie
    Posted October 26, 2017 at 10:19 pm | Permalink

    I feel so stupid. Tell me if this is it: It’s his hands that are moving back and forth – not the spiral?

    • Posted October 27, 2017 at 1:09 am | Permalink

      yeah, the hand just slides along the coil, it doesn’t grip and pull, which is what people naturally assume.

      The operator should take care to obscure the ens of the coils, as soon as observers focus on them the game is up.

  11. Charles Minus
    Posted October 27, 2017 at 12:27 am | Permalink

    Can we give it up for Time Rowett, the presenter here? His Grand Illusions channel on YouTube is responsible for millions of hours of lost production hours due to his charming presentation of clever toys and gimmicks.


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