The special theory of relativity (STR) is a theory in physics describing measurements in inertial reference systems with the same value of the speed of light (c) in each of them, regardless of the State of motion of its source and became the speed of light from property of a particular phenomenon in a fundamental characteristic of space-time. It summarizes the principle of relativity of Galileo by the mechanics to all the physical laws, including those of the electrodynamics. The theory is exposed in 1905 by Albert Einstein in " Electrodynamics of the moving bodies" and is based on the earlier contributions of Hendrik Lorentz, Henri Poincaré and others.
The special theory of relativity has a wide range of consequences that are experimentally confirmed, including thenon trivial phenomena, contradicting the classical notion that the duration of time intervals is the same for all observers, such as shortening the lengths, the delay time and the relativity of simultaneity. The predictions of the special theory of relativity coincide largely with Newtonian mechanics in their common area of application, more specifically in experiments in which the velocities are small compared with the speed of light.
Combined with other physical laws, the postulates of special relativity lead to the prediction of equivalence of matter and energy, expressed in the famous formula E = mc^2 - a consequence of this relationship is the impossibility of a particle that has a residual mass to be accelerated to the speed of light.
The theory is called special because it applies the principle of relativity only to a private case of inertial reference systems-reference systems that move with constant speed relative to one another.Later Albert Einstein developed general relativity to apply the principle and to the more general case of accelerating reference systems and to take account of the effects of gravity. General relativity allows the local applicability of the special theory, as well as in relativistic situations where gravity is not a significant factor.
Postulates Albert Einstein highlights two fundamental assertions that seem the most secure among the laws of mechanics and electrodynamics. These are the permanent value of the speed of light and the independence of physical laws (including the continuing value of the speed of light) by choosing the system inertia. In the original statement of the special theory of relativity he formulated these postulates as:
• Principle of relativity: the laws by which the States of physical systems undergo change are not affected, whether these changes of State be referred to one or another system in uniform translational motion relative to one another.
• Principle of invariant speed of light: "...the light is always distributed in empty space with a definite velocity c which is independent of the State of motion of the radiating body”. So the light in vacuum propagates with the velocity c, constant, independent of the direction, in at least one inertia coordinate system, regardless of the State of motion of its source.
Special relativity is displayed not only on these two explicit indivisibility but also several tacit assumptions used in almost all physical theories.
After the initial statement of the special theory of Einstein in 1905 appear a multitude of alternative formulations of its postulates. However the most commonly used form is the one described originally by Einstein. He later makes a mathematical formulation of the principle of relativity, which introduces the concept of simplicity: "If the coordinate system K is chosen so that the physical laws are implemented in its most simple form, the same laws are fulfilled in relation to any other coordinate system K '.
Another formulation of the postulates of the theory is the invariant of physical laws to Lorentz conversions. Einstein wrote: "the universal principle of special relativity is contained in this postulate: the laws of physics are invariant on Lorentz transformations (such as transformation of an inertia system to any other randomly chosen inertia system)." So many modern interpretations of the theory is based on the single postulate of universal Lorentz co-variants or equivalent postulate of Minkowski space.
- Albert Einstein.jpg (7.95 KiB) Viewed 9072 times