Principle of relativity: Encyclopedia II - Principle of relativity - Special relativity

Principle of relativity - Special relativity

If one assumes that both the Maxwell equations are valid, and that Galilean transformation is the appropriate transformation, then it should be possible to measure velocity absolutely. Poincaré and Einstein noticed that if one assumes that the Lorentz transformations are the appropriate transformations for transforming between inertial reference frames, then that constitutes a principle of relativity that is compatible with the Maxwell equations.

Special relativity restored a principle of relativity in physics. The Maxwell equations referred to ether-theories, in which the nature of electrostatic and magnetic forces depend on the velocity of an object. Special relativity brought back the interpretation that in all inertial reference frames the same physics is observed. Thus there is no phenomenon that would allow an observer to pinpoint a zero point of velocity.

The assumption that the Lorentz transformations are the appropriate transformations has vast implications. The intuitive assumption that clock time is universal has to be relinquished.

Adapted from the Wikipedia article "Special relativity", under the G.N U Free Docmentation License. Please also see http://en.wikipedia.org/wiki