Here's a great piece I saw a while ago and meant to post. Jeff Lieberman has explores two phenomena, the stabilization of unstable systems using feedback, and wireless power transmission. Feedback systems often levitate objects, stabilize inverted pendulums, and the like. Wireless power transmission has been around since Tesla's invention a century ago, although it is still not widely utilized. Jeff wanted to explore these effects together.
Lightbulb uses a special bulb, inside which magnets and circuitry are hidden. Using a magnetic hall effect sensor, an electromagnet, and a [modified] PD feedback system, it floats a lightbulb stably in the air, while power is transmitted wirelessly from the base of the sculpture into the bulb. LEDs in the bulb rectify this AC power and convert it to light. The power transfer functions very similarly to how radio station tuning works and requires a well tuned matched pair of resonant windings, but allows power transmission over through the air.