This video was made way back in 2010, but this week Digg dug it back up (see what we did there?) and we couldn't help but share it with you guys. It's a little slow to get started, but we promise that by the end you'll be totally wowed. To start with, not only does this home-made coil levitate a solid slug of aluminium, it then proceeds to melt it into a soft globby sphere that glows neon pink and finally white hot, before dropping it to the floor like a metallic cow pat.
It may look like witchcraft, but there's a good scientific explanation for all of this. First of all, that homemade coil has been crafted into a solenoid, and is acting as a DIY induction heater. That means it has an electric current flowing through it, and this creates an alternating magnetic field inside the cylinder.
Aluminium obviously isn't magnetic, but when it's dropped inside the cylinder, the alternating magnetic field induces a special kind of electrical current known as eddy currents within the aluminium, and this causes the metal to behave like a diamagnet. These eddy currents create their own little fields, which oppose the magnetic field produced by the copper coil, and therefore cause the aluminium to levitate. It's the same phenomenon that makes this magnet flip in slow motion as it falls through a copper pipe.
And, if you leave the aluminium in the coil long enough, these eddy currents also give rise to something known as Joule heating, which, with enough power, can melt a solid bar of metal, as you can see above. "It's like poking a marshmallow," as YouTuber imsmoother exclaims of his floating motel sphere.
It's all super impressive, and you can actually build your own induction heater at home, using these instructions. Aluminium can generally be levitated with an electrical input of around 1.6 to 2.5 kilowatts. But if you want to amp up the power, you can also find out how to make a 10-kilowatt coil that can levitate molten copper and steel.
Before you run away and do that, here's some more levitation prettiness to inspire you. You're welcome.