levitating

Levitation is the act of suspending an object in a position above a surface or within a medium without physical contact. In physics, levitation occurs when an external force balances gravity, enabling stable or quasi-stable suspension. Methods vary by interaction type and include magnetic, acoustic, optical, electrostatic, and buoyant approaches.

Magnetic levitation relies on magnetic forces to counteract weight. Diamagnetic levitation uses materials that generate a weak repulsive response to magnetic fields, while superconducting levitation exploits the Meissner effect and magnetic flux pinning to stabilize objects. Active magnetic levitation uses controlled electromagnets with feedback to maintain position. Because Earnshaw's theorem forbids static stability of a simple arrangement of magnets, real-world magnetic levitation typically relies on one of these stabilization mechanisms.

Acoustic levitation uses standing ultrasonic waves to trap small objects at pressure nodes in air. Optical levitation employs focused laser beams (optical tweezers) to exert gradient forces that hold microscopic particles or droplets. Electrostatic levitation uses electric fields to suspend charged bodies, often coupled with high-temperature measurements. Aerodynamic or gas-jet levitation uses a fast air stream to support an object, while buoyant levitation involves an object remaining suspended in a fluid due to buoyancy.

Applications include maglev transportation, containerless processing of materials, and scientific manipulation of microscopic particles. A notable historical example is the 1997 levitation of a frog using a strong magnetic field, demonstrated by Andre Geim and Michael Berry to illustrate diamagnetic levitation. Such demonstrations and technologies illustrate the variety of mechanisms by which gravity can be countered without physical contact.