Line of force

This article is about "lines of force", as used in the early history and philosophy of electromagnetism. For the modern use of "lines of force" as a way to depict electromagnetic and other vector fields, see Field line.

In the history of physics, a line of force in Michael Faraday's extended sense is synonymous with James Clerk Maxwell's line of induction.[1] According to J.J. Thomson, Faraday usually discusses lines of force as chains of polarized particles in a dielectric, yet sometimes Faraday discusses them as having an existence all their own as in stretching across a vacuum.[2] In addition to lines of force, J.J. Thomson—similar to Maxwell—also calls them tubes of electrostatic inductance, or simply Faraday tubes.[2] From the 20th century perspective, lines of force are energy linkages embedded in a 19th-century field theory that led to more mathematically and experimentally sophisticated concepts and theories, including Maxwell's equations and Albert Einstein's theory of relativity.

Lines of force originated with Michael Faraday, whose theory holds that all of reality is made up of force itself. His theory predicts that electricity, light, and gravity have finite propagation delays. The theories and experimental data of later scientific figures such as Maxwell, Heinrich Hertz, Einstein, and others are in agreement with the ramifications of Faraday's theory. Nevertheless, Faraday's theory remains distinct. Unlike Faraday, Maxwell and others (e.g., J.J. Thomson) thought that light and electricity must propagate through an ether. In Einstein's relativity, there is no ether, yet the physical reality of force is much weaker than in the theories of Faraday.[3][4]

Historian Nancy J. Nersessian in her paper "Faraday's Field Concept" distinguishes between the ideas of Maxwell and Faraday:[5]

The specific features of Faraday's field concept, in its 'favourite' and most complete form, are that force is a substance, that it is the only substance and that all forces are interconvertible through various motions of the lines of force. These features of Faraday's 'favourite notion' were not carried on. Maxwell, in his approach to the problem of finding a mathematical representation for the continuous transmission of electric and magnetic forces, considered these to be states of stress and strain in a mechanical aether. This was part of the quite different network of beliefs and problems with which Maxwell was working.

  1. ^ 1907 Encyclopædia Britannica, page 64
  2. ^ a b Notes on Recent Researches in Electricity and Magnetism, Joseph John Thomson, James Clerk Maxwell, 1883
  3. ^ Fields of Force, William Berkson, 1974
  4. ^ Forces and Fields, Mary B. Hesse, 1961
  5. ^ Faraday Rediscovered: Essays on the Life and Work of Michael Faraday, 1791-1867, David Gooding, Frank A. J. L. James, Stockton Press, 1985, ISBN 0-943818-91-5, ISBN 978-0-943818-91-7, 258 pages, page 183-