Levitation is the process by which an object is suspended by a physical force

Force

In physics, a force is any influence that causes an object to undergo a change in speed, a change in direction, or a change in shape. In other words, a force is that which can cause an object with mass to change its velocity , i.e., to accelerate, or which can cause a flexible object to deform...

 against gravity, in a stable position without solid physical contact. A number of different techniques have been developed to levitate matter, including the aerodynamic

Aerodynamic levitation

Aerodynamic levitation is the use of gas pressure to levitate materials so that they are no longer in physical contact with any container. In scientific experiments this removes contamination and nucleation issues associated with physical contact with a container.-Overview:The term aerodynamic...

, magnetic

Magnetic levitation

Magnetic levitation, maglev, or magnetic suspension is a method by which an object is suspended with no support other than magnetic fields...

, acoustic

Acoustic levitation

Acoustic levitation is a method for suspending matter in a medium by using acoustic radiation pressure from intense sound waves in the medium. Acoustic levitation is possible because of the non-linear effects of intense sound waves....

, electromagnetic, electrostatic

Electrostatic levitation

Electrostatic levitation is the process of using an electric field to levitate a charged object and counteract the effects of gravity. It was used, for instance, in Robert Millikan's oil drop experiment and is used to suspend the gyroscopes in Gravity Probe B during launch.Due to Earnshaw's...

, gas film, and optical

Optical levitation

Optical levitation is a method developed by Arthur Ashkin whereby a material is levitated against the downward force of gravity by an upward force stemming from photon momentum transfer...

 levitation methods.
For levitation on Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, first, a force is required directed vertically upwards and equal to the gravitational force, second, for any small displacement of the levitating object, a returning force should appear to stabilize it.