- Einstein gives two postulates of the Special theory of relativity. Which are given in the list below: The laws of physics are the same in all inertial frames of reference. The speed of light in free space has the same value in all inertial frames of reference in all directions.
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The physical theory given by classical mechanics, and Newtonian gravity is consistent with Galilean relativity, but not special relativity. Conversely, Maxwell's equations are not consistent with Galilean relativity unless one postulates the existence of a physical aether.
- Theory of Relativity
- Postulates of The Theory of Relativity
- Importance of Special Theory of Relativity
The theory of relativity is concerned with the way in which the observers who are in a state of relative motion describe the physical phenomenon. The theory of relativity is given by Albert Einstein in 1905 which states that there is no absolute state that exists in the universe, all states are relative. The theory of relativity is concerned with the way in which the observers who are in a state of relative motion describe the physical phenomenon. The special theory of relativity has an undeserved reputation as a difficult subject. It is not mathematically complicated; most of its details can be understood using techniques well known to readers of this text. Perhaps the most challenging aspect of special relativity is its insistence that we replace some of our ideas about space and time, which we have acquired years of common sense experiences with new ideas. The kinematics developed by Galileo and mechanics developed by Newton, which forms the basis of what we call classical physic...
A scientific theory usually begins with general statements called postulates, which attempt to provide a basis for the theory. From these postulates, we can obtain a set of mathematical laws in the form of equations that relate to physical variables. For about two centuries, the mechanics of Galileo and Newton withstood all experimental tests. In this case, the postulates concern the absolute nature of space and time. Based on his thought experiment about catching a light beam, Einstein realized the need to replace the Galilean laws of relative motion. In his paper, entitled On the Electrodynamics of moving bodies, Einstein offered two postulates that form the basis of his Special theory of relativity. 1st postulate The laws of physics are the same in all initial frames of reference. 2nd postulate The speed of light in free space has the same value in all initial frames of reference in all directions. The 1st postulate is the generalization of the fact that all physical laws are the...Relativity affects every aspect of physics; we have concentrated on mechanics, and later in this text, we consider the effect of relativity on electromagnetism.Indeed, we must carefully reexamine every subfield of physics from the perspective of the special theory, verifying that each is consistent with the two postulates. We must also note that relativit...It is a theory that is of great aesthetic value, providing us with a view more satisfying than that of classical physics about the validity of different perspectives and symmetries.It is also a theory of great practical value, providing engineers with the proper guidance to construct large particle accelerators and providing those concerned about maintaining standards with th...
The special theory of relativity or special relativity is a physical theory which states the relationship between space and time. This is often termed as STR theory. This is theory is based on two postulates – Laws of Physics are invariant
- Einstein’s First Postulate
- Einstein’s Second Postulate
- Section Summary
The first postulate upon which Einstein based the theory of special relativity relates to reference frames. All velocities are measured relative to some frame of reference. For example, a car’s motion is measured relative to its starting point or the road it is moving over, a projectile’s motion is measured relative to the surface it was launched from, and a planet’s orbit is measured relative to the star it is orbiting around. The simplest frames of reference are those that are not accelerated and are not rotating. Newton’s first law, the law of inertia, holds exactly in such a frame. The laws of physics seem to be simplest in inertial frames. For example, when you are in a plane flying at a constant altitude and speed, physics seems to work exactly the same as if you were standing on the surface of the Earth. However, in a plane that is taking off, matters are somewhat more complicated. In these cases, the net force on an object, F, is not equal to the product of mass and accelera...
The second postulate upon which Einstein based his theory of special relativity deals with the speed of light. Late in the 19th century, the major tenets of classical physics were well established. Two of the most important were the laws of electricity and magnetism and Newton’s laws. In particular, the laws of electricity and magnetism predict that light travels at c = 3.00 × 108m/s in a vacuum, but they do not specify the frame of reference in which light has this speed. There was a contradiction between this prediction and Newton’s laws, in which velocities add like simple vectors. If the latter were true, then two observers moving at different speeds would see light traveling at different speeds. Imagine what a light wave would look like to a person traveling along with it at a speed c. If such a motion were possible then the wave would be stationary relative to the observer. It would have electric and magnetic fields that varied in strength at various distances from the observe...Relativity is the study of how different observers measure the same event.Modern relativity is divided into two parts. Special relativity deals with observers who are in uniform (unaccelerated) motion, whereas general relativity includes accelerated relative motion and g...An inertial frame of reference is a reference frame in which a body at rest remains at rest and a body in motion moves at a constant speed in a straight line unless acted on by an outside force.Modern relativity is based on Einstein’s two postulates. The first postulate of special relativity is the idea that the laws of physics are the same and can be stated in their simplest form in all...
relativity:the study of how different observers measure the same event special relativity:the theory that, in an inertial frame of reference, the motion of an object is relative to the frame from which it is viewed or measured inertial frame of reference:a reference frame in which a body at rest remains at rest and a body in motion moves at a constant speed in a straight line unless acted on by an outside force first postulate of special relativity:the idea that the laws of physics are the same and can be stated in their simplest form in all inertial frames of reference second postulate of special relativity: the idea that the speed of light cis a constant, independent of the source Michelson-Morley experiment:an investigation performed in 1887 that proved that the speed of light in a vacuum is the same in all frames of reference from which it is viewed
- Origins of Special Relativity
- Special Relativity
- Towards General Relativity
- General Relativity
- Applications of Relativity
Rest and Motion
Prior to special relativity, the prevalent theory that explained motion was that of Newton. Newton’s three laws of motionwere believed to be sufficient to explain all forms of motion, in terms of forces and acceleration. It was also hugely successful when it came to experimental evidence at that time, as the results obtained were quite in agreement with the theory. Inside the mathematical framework of Newton’s laws of motion was the Galilean transformation, which was basically a mathematical...
The Speed of Light
By the late 19th century, thanks to the work of Maxwell, Hertz, and others it was accepted that light was an electromagnetic wave that traveled at a measurable, high speed of nearly 300,000 kilometers per second. The four simple mathematical formulas involved in this theory of electromagnetism were called Maxwell’s Equations. They were expected to be universally applicable. Interestingly, when Galilean Transformations (which seem correct by “common sense”) were applied to Maxwell’s Equations,...
The Search for Ether
The ether frame was important because it was the only frame in which Maxwell’s Equations retained their simple form. A direct conclusion, guided by the Galilean transformation, was that the speed of lightis 300,000 km/s only in this frame. In any other frame, the speed of the frame should add up to the speed of light, just like in the case of the person and the train in the previous example. There was however little or no proof for the existence of ether. Its supposed properties were also ver...
With the ether theory discarded, new explanations had to be found for the contradictions between Galilean transformations and Maxwell’s Equations. The step forward was taken by Albert Einstein, who took a radical assumption and declared that Galilean Transformations were wrong. This seemed to go against common sense, which strongly supported Galilean transformations. Yet, Einstein started off on his new theory with just two basic assumptions.
Postulates of Special Relativity
1. All non-accelerating frames are equivalent. 2. The speed of light is the same (300,000 km/s or 3 • 108 m s-1) in all reference frames. While these may not look too drastic, they go directly against the Galilean transformation. While the Galilean Transformation implies that there is only one frame in which the speed of light is 3 • 108 m s-1, Einstein’s postulates say that the speed of light is the same in every frame. If that does not sound unusual, think of the previous example of two peo...
Starting from this remarkable hypothesis, Einstein proceeded to derive many results, many of which seemed to go against common sense. The general theme throughout was that all measurements are relative, and there is no absolute “correctness” of observations. Observations are correct only in whichever reference frame they are made, and do not need to agree with observations in other frames. The fundamental effects of special relativity include length contraction, time dilation, and loss of sim...
As we have seen so far, special relativity deals with non-accelerating frames of reference. With the completion of this theory, Einstein wanted to proceed to a more general theory that described motion of all forms, accelerated or not. Further, he hoped to include gravity in such a framework that could successfully explain all motion.
General relativity is fundamentally a theory of gravity. Unlike Newton’s theory of gravitation, it does not treat gravity as a force, rather as a geometric property of space-time itself. It says that the presence of mass curves space-time in such a fashion that results in what we perceive as the “force” of gravity. A common metaphor for this involves placing a large ball on a stretched rubber sheet. The sheet curves around the ball, and if another ball is placed somewhere on the rubber sheet,...
Some of the earliest experiments to test the validity of general relativity were suggested by Einstein himself. These were: the anomalous orbit of Mercury, deflection of light by the sun, and gravitational redshift of light. Einstein himself managed to explain the long-unsolved mystery of the anomaly in Mercury’s orbit around the sun, by invoking general relativity and the curvature of space-time. The proof for gravitational light deflection was first observed during a solar eclipse in 1919 w...
As a complete theory of motion, relativity is applicable in all physical phenomena. However, its most explicit applications are where it diverges significantly from classical predictions. Prominently, GPS (Global Positioning System) uses both special and general relativity to account for various effects such as time dilation and loss of simultaneity that cannot be explained otherwise. Properties of matter at speeds close to that of light are explained by relativity too. One prominent example is the color and chemical behaviour of gold, which is explained by the relativistic velocity of electrons. Relativity also helps us understand many cosmological phenomena better, such as the origin and expansion of the universe, along with the behaviour of bodies such as black holes and binary systems.
Relativity is a revolutionary scientific theory that reshaped our understanding of the Universe. It changed our views on what was considered basic – facts such as rest, motion, and mass. Possibly in the future, it could become part of a more unified theory in the understanding of the universe: some form of Quantum Gravity or Theory of Everything.
There are two main ideas that make up Einstein's theory of special relativity. 1. The principle of relativity: The laws of physics are the same for any inertial reference frame. 2.
The ad hoc 1904 theories of Lorentz and Poincaré then became a template for Einstein’s 1905 Special Theory, his two fundamental postulates, his Lorentz transformations, his relativistic kinematics and dynamics, and all of the other bizarre mathematical consequences of his Special Theory.
The postulates of special theory of relativity are as follows: i) The laws of physics are the same in all inertial frames of reference. ii) The velocity of light in free space is a constant in all the frames of reference.