In one hand, you hold an aluminum tube 12″ long. In your other hand, you have a small, polished metal cylinder. You drop the cylinder into the tube (Figure A), and — it disappears.
Where did it go? Nowhere! It’s inside the tube, but instead of falling freely, it’s moving slowly. After 5 seconds, it finally emerges at the bottom. It has just defied the force of gravity (partially, at least).
To see this yourself, you’ll need a cylindrical neodymium magnet measuring ½” high and 11/16″ diameter. This is the smallest, cheapest option to generate a good result. I suggest you buy it from KJ Magnetics, which stocks the unusual 11/16″ size. You also need 12″ of round aluminum tubing with ¾” internal diameter (often abbreviated as ID). Many online sources such as Speedy Metals will sell you this for just a couple of dollars.
If you peek into the end of the tube after inserting the magnet, you’ll see it mysteriously drifting down, as if it’s falling through water. Aluminum is not magnetic, so why should this happen? When I demonstrated the phenomenon at the 2017 Maker Faire Bay Area, no one in the audience could figure it out.
To explain it, I suggest you make yourself a coil of wire that’s just a fraction larger than the magnet. I described this experiment in my book Make: Electronics, but the version here is quicker and easier to build, and much cheaper, because I figured out a way to use a smaller magnet. The secret is to wind a coil that’s a tighter fit.