In theoretical physics, a preferred or privileged frame is usually a special hypothetical frame of reference in which the laws of physics might appear to be identifiably different from those in other frames. Theoretical physics employs mathematical models and abstractions of physics, as opposed to experimental processes, in an attempt to understand nature. ... A hypothesis (= assumption in ancient Greek) is a proposed explanation for a phenomenon. ... A frame of reference is a particular perspective from which the universe is observed. ... A physical law or a law of nature is a scientific generalization based on empirical observations. ...

In theories that apply the principle of relativity to inertial motion, physics is the same in all inertial frames and no single inertial frame is privileged or preferred above any other. Wikisource has original text related to this article: Relativity: The Special and General Theory A principle of relativity is a criterion for judging physical theories, stating that they are inadequate if they do not prescribe the exact same laws of physics in certain similar situations. ... In physics, an inertial frame of reference, or inertial frame for short (also descibed as absolute frame of reference), is a frame of reference in which the observers move without the influence of any accelerating or decelerating force. ...

Preferred frame in aether theory

In theories that presume that light travels at a fixed speed relative to an unmodifiable aetherial medium, the "preferred frame" would be the frame in which this "aether" would be stationary. In 1887, Michelson and Morley tried to identify the state of motion of this hypothetical "preferred frame". To do so, they assumed Galilean Relativity to be satisfied by clocks and rulers, that's to say rulers' lengthes and clocks' periods invariance under any Galilean frame change. Under such an hypothesis, a preferred frame should have been observed. By comparing measurements made in different directions and looking for an effect due to the Earth's orbital speed, their experiment famously produced a null result. This experiment disproved rulers lengthes and clocks periods Galilean invariance hypothesis and confirmed the universal validity of the principle of relativity of motion (the so-called Lorentz invariance). Henceforth, all inertial frames are physically equivalent. More precisely, provided that no phenomenon violates de principle of relativity of motion, there is no means to measure the velocity of an inertial observer with regard to a possible medium of propagation of quantum waves. Look up aether, ether in Wiktionary, the free dictionary. ... 1887 (MDCCCLXXXVII) is a common year starting on Saturday (click on link for calendar) of the Gregorian calendar or a common year starting on Monday of the Julian calendar. ... The Michelson-Morley experiment, one of the most important and famous experiments in the history of physics, was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University, and is considered by some to be the first strong evidence against the theory of... Generally, a null result is a result which is null (nothing): that is, the absence of an observable result. ...

The Aether (ether) in 19th Century Physics

There arose a theory in 19th-century physics that there existed a hypothetical medium named the "Aether" (or ether). Some physicists suggested that the universe was filled with this substance known as "aether" which transmitted electromagnetic waves. It was also postulated that light arose from vibrations of the aether. Aether constituted an absolute reference frame against which speeds could be measured. In other words, the aether was the only fixed or motionless thing in the universe. Electromagnetic radiation or EM radiation is a combination (cross product) of oscillating electric and magnetic fields perpendicular to each other, moving through space as a wave, effectively transporting energy and momentum. ...

This theory arose out of what had seemed necessary to physics for over 2000 years since the Greek philosopher Aristotle (384-322 B.C.) said that the earth was immovable and a fixture from which all other points could be measured. This theory recorded later, by Ptolemy, remained intact in the earth-centered models of the universe until it was overthrown by the theory of Copernicus. Yet, in the Copernican system, though the Sun was now the center of the universe, the Sun itself took the place of the earth as the fixture upon which all measurements could be made. However, things changed in 1785 when William Herschel began to describe the position of the Sun within the Milky Way galaxy. Now the Sun was no longer a fixture in space and it appeared that there was no center to the universe. This was an unreconciliable idea to 19th century physicists who invented the concept of the aether to create a motionless fixture in the universe from which all measurements could be made. However, since electromagnetic waves passed through the aether and planets moved through the aether, the aether was postulated to have some wonderful properties i.e. it was sufficiently elastic that it could support electromagnetic waves, those waves could interact with matter, yet it offered no resistance to bodies passing through it. In fact, it was said that light could not pass from the Sun to the earth without the aether because it needed a medium to carry it just as sound waves travel in a medium. In trying to prove the existence of the Aether, 19th century physicists in their Michelson-Morley experiment accidentally disproved Galilean relativity assumption of rulers lengthes and clocks periods invariance and confirmed the universal validity of the principle of relativity of motion. This experiment stressed the impossibility of measuring the velocity of observers with regard to a possible aether thanks to any means complying with the principle of relativity of motion. It paved the way for Einstein's Special Theory of Relativity whose mathematical formulation relies on the principle of relativity of motion and doesn't require aether hypothesis. Aristotle (Greek: AristotélÄ“s) (384 BC – March 7, 322 BC) was a Greek philosopher, a student of Plato and teacher of Alexander the Great. ... Nicolaus Copernicus (in Latin; Polish Mikołaj Kopernik, German Nikolaus Kopernikus - February 19, 1473 – May 24, 1543) was a Polish astronomer, mathematician and economist who developed a heliocentric (Sun-centered) theory of the solar system in a form detailed enough to make it scientifically useful. ... William Herschel Sir Frederick William Herschel, FRS KH (15 November 1738-25 August 1822) was a German-born British astronomer and composer who became famous for discovering the planet Uranus. ... The Milky Way (a translation of the Latin Via Lactea, in turn derived from the Greek Galaxia Kuklos; or simply the Galaxy) is a barred spiral galaxy in the Local Group, and has special significance to humanity as the location of the solar system, which is located near the Orion... Electromagnetic radiation or EM radiation is a combination (cross product) of oscillating electric and magnetic fields perpendicular to each other, moving through space as a wave, effectively transporting energy and momentum. ... The Michelson-Morley experiment, one of the most important and famous experiments in the history of physics, was performed in 1887 by Albert Michelson and Edward Morley at what is now Case Western Reserve University, and is considered by some to be the first strong evidence against the theory of... Einstein redirects here. ... Special relativity (SR) or the special theory of relativity is the physical theory published in 1905 by Albert Einstein. ...

Inertial frames preferred above noninertial frames

Although there is no preferred inertial frame under Newtonian mechanics or special relativity, the set of all inertial frames as a group may still be said to be "preferred" over noninertial frames in these theories, since the laws of physics derived for inertial motion only work exactly in this special category of frames. It has been suggested that this article or section be merged with Classical mechanics. ... The special theory of relativity was proposed in 1905 by Albert Einstein in his article On the Electrodynamics of Moving Bodies. Some three centuries earlier, Galileos principle of relativity had stated that all uniform motion was relative, and that there was no absolute and well-defined state of rest...

No preferred frames

In theories that comply with Mach's principle, even the preference for inertial frames is removed: observations made by observers in nominally "inertial" and "noninertial" frames may seem superficially biased in favour of the inertial observer, but ultimately, a full description of the physics becomes similarly complex in either case. In theoretical physics, particularly in discussions of gravitation theories, Machs principle is the name given by Einstein to a vague hypothesis first supported by the physicist and philosopher Ernst Mach. ...

References

• Einstein: Relativity, the special and the general theories (1954)