Levitation
From Wikipedia, the free encyclopedia
Levitation (from Latin levare, to raise)[citation needed] is the process by which an object is suspended against gravity, in a stable position, without physical contact.
It is also a conjuring trick, apparently raising a human being without any physical aid. The illusion can be produced by clever mechanics, lighting arrangements and other means.
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[edit] Physics
For levitation on earth, a force is required directed vertically upwards and equal to the object's weight. This can be achieved by, for example, magnetic, electrostatic (i.e. electrically charged objects) or aerodynamic forces. By means of diamagnetic levitation even small live animals have been levitated.
Scientists have discovered a way of levitating ultra small objects by manipulating the so-called Casimir force, which normally causes objects to stick together by quantum force. This practice however, is only possible for micro-objects.[1][2]
Aerodynamic levitation is seen in air hockey where jets of gas from the table push upwards against the puck. Levitating objects may also force air downwards e.g. VTOL aircraft and hovercraft. The use of an airfoil allows a fixed-wing aircraft or rotary-wing aircraft, such as a Helicopter, to fly by Bernoulli's principle. A sphere can be stably levitated in a stream of air without any type of control system, if conditions are right. This was merchandised as a toy, circa 1960.
The effect of levitation can also be achieved using the upthrust of air, with the levitating object having the same average density as air. The heavier parts are compensated with one or more tanks of Helium or other gas (or vacuum) having less density than air.
[edit] Further reading
- Schiller, Christoph (2007). Motion Mountain: The Free Physics Textbook. esp. the section on levitation in the chapter on electromagnetism.
