Diamagnetic levitation: Flying frogs and floating magnets (invited)
Contrary to our intuition, apparently nonmagnetic substances can be levitated in a magnetic field and can stabilize free levitation of a permanent magnet. Most substances are weakly diamagnetic and the tiny forces associated with this property make the two types of levitation possible. Living things mostly consist of diamagnetic molecules ~such as water and proteins! and components ~such as bones! and therefore can be levitated and can experience low gravity. In this way, frogs have been able to fly in the throat of a high field magnet. Stable levitation of one magnet by another with no energy input is usually prohibited by Earnshaw’s Theorem. However, the introduction of diamagnetic material at special locations can stabilize such levitation. A magnet can even be stably suspended between ~diamagnetic! fingertips.