Skeptical Inquirer 30:4

The July/August issue of Skeptical Inquirer has been released, and as usual the SI website has a number of the articles available for free as tasters to the full mag:

See the SI website for a complete rundown of their online articles.

  1. Houdini’s Great Trick
    Re: Houdini’s Imposs. Demo….

    Being a great admirer of HH’s from many years back, had already been familiar with this story, tho’ not sure I had heard of the deconstruction… anyway, I have my doubts about this explanation as well…

    A cork ball with iron core being moved by a magnet behind the slate…

    such a ball “began ROLLING across the surface…”. I do not believe that this ball would have rolled across anything. The force behind the movement is not related to an axial or rotational force or action, but comes from a single direction on the other side of the slate, said force being simultaneously responsible for holding the ball (pinning it) against the slate. I do not see how any spin or rotation could be induced/produced. The ball would have been DRAGGED along, on top of this surface. Under such circumstances the white ink, at at the point of contact with the slate, would have quickly been used up. and since this point is under pressure, the ink on the surrounding area of the ball would have tended to move away from, not toward, the point of contact.

    I don’t see how the writing of much more than a letter or two before the ink ran out would have been possible.

    what do YOU think?

    teehee… ; )

    1. cork ball….cute
      actually it is basic physics…when a force is applied to an object of any shape, when the force becomes critical the shape will fold at the weakest point. In the case of a sphere this is the edge.So it folds. Iron inside the ball being attracted to a magnet would be pulled to the magnet in a direct line of force. The cork folds and momentum is produced as the center of force is moved….it will roll….
      As for ink….well cork is very poorus so it would suck up ink as it stands in the saucer for awhile.

      so…..what do you think?

  2. simple?
    I don’t see it as quite that simple.

    there is the concept of “rolling resistance”. In this case, the rolling resistance of the ball would include some measure of the force of the magnets’ attraction. the element of friction is a critical factor, i.e., how smooth is the cork and the slate? I guess the ball will roll if the work done causing the ball to turn is less than the work of overcoming the friction and the pull of the magnet. the hard part is getting the ball to start rolling in the first place: overcoming “rolling resistance”. would think that the lighter the ball, and the smaller, the more easily it would merely slide along the surface of the slate; however, the size of the ball is not given. remembering my experience (casual) with magnets, I recall that the force of a magnet’s attraction (and practical ability to control an object) is greatly reduced as soon as contact is lost. and of course attractive force is proportional to the inverse square of the distance between the objects, i.e., it diminishes. in our case, the iron core is already separated by the thickness(?) of the slate, then add on the thickness(?) of the cork. if you make the core bigger, the attractive force increases, but so does the weight and the rolling res. and the tendency to be influenced by gravity = fall off the slate.

    so maybe the magnet should be really strong, which again augers agin the rolling of the ball.

    would love to test this experimentally: I figure empirically is the only way to go here, but am energetically-challenged enough to be satisfied with this as a mental puzzle.

    and how hard would it be to write the msg.?! story does not disclose if written in script (really tricky) as the msg would have to be written backwards and from right to left. leave that to Leonardo, please!

    teehee… ; )

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