Principle of relativity
Special relativity |
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In
For example, in the framework of special relativity the
Several principles of relativity have been successfully applied throughout
Basic concepts
Certain principles of relativity have been widely assumed in most scientific disciplines. One of the most widespread is the belief that any
Any principle of relativity prescribes a
Special principle of relativity
According to the first postulate of the special theory of relativity:[3]
Special principle of relativity: If a system of coordinates K is chosen so that, in relation to it, physical laws hold good in their simplest form, the same laws hold good in relation to any other system of coordinates K' moving in uniform translation relatively to K.
— Albert Einstein: The Foundation of the General Theory of Relativity, Part A, §1
This postulate defines an inertial frame of reference.
The special principle of relativity states that physical laws should be the same in every
The principle requires physical laws to be the same for any body moving at constant velocity as they are for a body at rest. A consequence is that an observer in an inertial reference frame cannot determine an absolute speed or direction of travel in space, and may only speak of speed or direction relative to some other object.
The principle does not extend to
In Newtonian mechanics
The special principle of relativity was first explicitly enunciated by Galileo Galilei in 1632 in his Dialogue Concerning the Two Chief World Systems, using the metaphor of Galileo's ship.
Newtonian mechanics added to the special principle several other concepts, including laws of motion, gravitation, and an assertion of an
In special relativity
Joseph Larmor and Hendrik Lorentz discovered that Maxwell's equations, used in the theory of electromagnetism, were invariant only by a certain change of time and length units. This left some confusion among physicists, many of whom thought that a luminiferous aether was incompatible with the relativity principle, in the way it was defined by Henri Poincaré:
The principle of relativity, according to which the laws of physical phenomena should be the same, whether for an observer fixed, or for an observer carried along in a uniform movement of translation; so that we have not and could not have any means of discerning whether or not we are carried along in such a motion.
— Henri Poincaré, 1904[5]
In their 1905 papers on
The strength of special relativity lies in its use of simple, basic principles, including the
It is possible to derive the form of the Lorentz transformations from the principle of relativity alone. Using only the isotropy of space and the symmetry implied by the principle of special relativity, one can show that the space-time transformations between inertial frames are either Galilean or Lorentzian. Whether the transformation is actually Galilean or Lorentzian must be determined with physical experiments. It is not possible to conclude that the speed of light c is invariant by mathematical logic alone. In the Lorentzian case, one can then obtain relativistic interval conservation and the constancy of the speed of light.[6]
General principle of relativity
The general principle of relativity states:[7]
All systems of reference are equivalent with respect to the formulation of the fundamental laws of physics.
— C. Møller The Theory of Relativity, p. 220
That is, physical laws are the same in all reference frames—inertial or non-inertial. An accelerated charged particle might emit synchrotron radiation, though a particle at rest does not. If we consider now the same accelerated charged particle in its non-inertial rest frame, it emits radiation at rest.
Physics in non-inertial reference frames was historically treated by a
The problems involved are not always so trivial. Special relativity predicts that an observer in an inertial reference frame does not see objects he would describe as moving faster than the speed of light. However, in the non-inertial reference frame of Earth, treating a spot on the Earth as a fixed point, the stars are observed to move in the sky, circling once about the Earth per day. Since the stars are light years away, this observation means that, in the non-inertial reference frame of the Earth, anybody who looks at the stars is seeing objects which appear, to them, to be moving faster than the speed of light.
Since non-inertial reference frames do not abide by the special principle of relativity, such situations are not self-contradictory.
General relativity
General relativity was developed by Einstein in the years 1907 - 1915. General relativity postulates that the
. Einstein based this new theory on the general principle of relativity, and he named the theory after the underlying principle.See also
- Background independence
- Conjugate diameters
- Cosmic microwave background radiation
- Equivalence principle
- Galilean relativity
- General relativity including Introduction to general relativity
- Invariant
- List of important publications in physics: Relativity
- Newton's Laws
- Preferred frame
- Principle of covariance
- Principle of uniformity
- Special relativity
Notes and references
- ISBN 0-486-60081-5.)
{{cite book}}
: CS1 maint: multiple names: authors list (link - ^ Poincaré, Henri (1904–1906). . Congress of arts and science, universal exposition, St. Louis, 1904. Vol. 1. Boston and New York: Houghton, Mifflin and Company. pp. 604–622.
- ^ Yaakov Friedman, Physical Applications of Homogeneous Balls, Progress in Mathematical Physics 40 Birkhäuser, Boston, 2004, pages 1-21.
- ISBN 0-19-560539-X.
Further reading
See the special relativity references and the general relativity references.
External links
- Wikibooks: Special Relativity
- Living Reviews in Relativity — An open access, peer-referred, solely online physics journal publishing invited reviews covering all areas of relativity research.
- MathPages - Reflections on Relativity — A complete online course on Relativity.
- Special Relativity Simulator
- A Relativity Tutorial at Caltech — A basic introduction to concepts of Special and General Relativity, as well as astrophysics.
- Relativity Gravity and Cosmology — A short course offered at MIT.
- Relativity in film clips and animations from the University of New South Wales.
- Animation clip visualizing the effects of special relativity on fast moving objects.
- Relativity Calculator - Learn Special Relativity Mathematics The mathematics of special relativity presented in as simple and comprehensive manner possible within philosophical and historical contexts.