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Levitation (from Latin levitas "lightness")[1] 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 (or other object) without any physical aid. The illusion can be produced by clever mechanics, lighting arrangements and other means.
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Physics
For levitation on Earth, 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. The stable levitation can be naturally achieved by, for example magnetic or aerodynamic forces.
Though any electromagnetic force could be used to counteract gravity, diamagnetic materials are most commonly used. In this case the returning force appears from the interaction with the screening currents. For example, a superconducting sample, which can be considered either as a perfect diamagnet or an ideally hard superconductor, easily levitates an ambient external magnetic field. In very strong magnetic field, by means of diamagnetic levitation even small live animals have been levitated.
By means of aerodynamic forces, the effect of levitation can also be achieved using the upthrust of air, with the levitating object having the same average density as air.
Acoustic levitation uses sound waves to provide a levitating force.
Scientists have discovered a way of levitating ultra small objects by manipulating the so-called Casimir force, which normally causes objects to stick together due to forces predicted by quantum field theory. This is, however, only possible for micro-objects.[2][3]
Animal levitation
Scientists have levitated frogs, grasshoppers, and mice. The mice acted confused at first, but adjusted to the levitation after about four hours.[4]
Further reading
- Schiller, Christoph (2007). Motion Mountain: The Free Physics Textbook. http://www.motionmountain.net/. esp. the section on levitation in the chapter on electromagnetism.
- Charles P. Strehlow, M. C. Sullivan (2008). A Classroom Demonstration of Levitation.... http://arxiv.org/abs/0803.3090..
- [1] Public Response to frog levitation.
References
- ^ Levitate, "to rise by virtue of lightness," from Latin levitas "lightness," patterned in English on gravitate: Online Etymology Dictionary
- ^ Scientists reveal secret of levitation, Yahoo! News
- ^ Levitation in Miniature, Null Hypothesis
- ^ NASA Levitates a Mouse With Magnetic Fields, Popular Science, September 9, 2009
See also
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Look up levitation in Wiktionary, the free dictionary. |
- Types of physical levitation:
- Anti-gravity
- Flying Saints
- Illusions
- Laputa
- Balducci levitation
- Sooperman
- King levitation
- Party Levitation
- Levitation (paranormal)
- Weightlessness
- Shoko Asahara
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