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Field theory (view source)

Revision as of 02:17, November 16, 2009

7 bytes removed ,  02:17, November 16, 2009
fixed reference to "action at a distance"; Newtonian gravity does not entail a force field
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==History==
 
==History==
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A "field theory" is based upon the principle of "action-at-a-distance" - that is, the idea that one object can influence another without touching it.  The earliest mathematical field theory is the classical theory of [[gravity]], first described by [[Isaac Newton]].  He described the force on a particle as related to the product of the particles mass <math>m_1 \ </math> and its distance from another mass, <math>\frac{m_2}{r^2} \ </math>.  This is called a field theory because regardless of the first particle, the second gives rise to a "field" everywhere in space which would affect any particle at any position.
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A "field theory" describes a force on a particle in terms of its position, or location in a "field".  An example of a field theory is [[James Maxwell]]s theory of [[electromagnetism]].  Subsequent field theories are the [[theory of relativity]], and modern quantum field theory.
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Later field theories include [[James Maxwell]]s theory of [[electromagnetism]], the [[general theory of relativity]], and modern quantum field theory.
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[[Isaac Newton]]'s (classical) theory of [[gravity]] is also considered a field theory, but it is based on "[[action at a distance]]" and does not have a force field.  To the extent that a field theory has come to imply the existence of a force field, Newtonian gravity would not be one.
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'''Classical''' field theories, like Newtons, do not include the effects of [[special relativity]].  Modern field theories tend to include special relativity in their formulation.
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Newton described the force on a particle as related to the product of the particles mass <math>m_1 \ </math> and its distance from another mass, <math>\frac{m_2}{r^2} \ </math>.  This is called a field theory because regardless of the first particle, the second gives rise to a "field" everywhere in space which would affect any particle at any position.
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[[Category:physics]]
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