Einstein's Theory of Relativity
Principle of Relativity (First Postulate): The laws of physics are the same for all inertial reference frames.
Principle of Constancy of the Speed of Light (Second Postulate): Light always propagates through a vacuum (i.e. empty space or "free space") at a definite velocity, c, which is independent of the state of motion of the emitting body.
Actually, the paper presents a more formal, mathematical formulation of the postulates. The phrasing of the postulates are slightly different from textbook to textbook because of translation issues, from mathematical German to comprehensible English.
The second postulate is often mistakenly written to include that the speed of light in a vacuum is c in all frames of reference. This is actually a derived result of the two postulates, rather than part of the second postulate itself.
The first postulate is pretty much common sense. The second postulate, however, was the revolution. Einstein had already introduced the photon theory of light in his paper on the photoelectric effect (which rendered the ether unnecessary). The second postulate, therefore, was a consequence of massless photons moving at the velocity c in a vacuum. The ether no longer had a special role as an "absolute" inertial frame of reference, so it was not only unnecessary but qualitatively useless under special relativity.
As for the paper itself, the goal was to reconcile Maxwell's equations for electricity and magnetism with the motion of electrons near the speed of light. The result of Einstein's paper was to introduce new coordinate transformations, called Lorentz transformations, between inertial frames of reference. At slow speeds, these transformations were essentially identical to the classical model, but at high speeds, near the speed of light, they produced radically different results.
Effects of Special Relativity
Special relativity yields several consequences from applying Lorentz transformations at high velocities (near the speed of light). Among them are:
* Time dilation (including the popular "twin paradox")
* Length contraction
* Velocity transformation
* Relativistic velocity addition
* Relativistic doppler effect
* Simultaneity & clock synchronization
* Relativistic momentum
* Relativistic kinetic energy
* Relativistic mass
* Relativistic total energy
In addition, simple algebraic manipulations of the above concepts yield two significant results that deserve individual mention.
Mass-Energy Relationship
Einstein was able to show that mass and energy were related, through the famous formula E=mc2. This relationship was proven most dramatically to the world when nuclear bombs released the energy of mass in Hiroshima and Nagasaki at the end of World War II.
Speed of Light
No object with mass can accelerate to precisely the speed of light. A massless object, like a photon, can move at the speed of light. (A photon doesn't actually accelerate, though, since it always moves exactly at the speed of light.)
But for a physical object, the speed of light is a limit. The kinetic energy at the speed of light goes to infinity, so it can never be reached by acceleration.
Some have pointed out that an object could in theory move at greater than the speed of light, so long as it did not accelerate to reach that speed. So far no physical entities have ever displayed that property, however.
Adopting Special Relativity
In 1908, Max Planck applied the term "theory of relativity" to describe these concepts, because of the key role relativity played in them. At the time, of course, the term applied only to special relativity, because there was not yet any general relativity.
Einstein's relativity was not immediately embraced by physicists as a whole, because it seemed so theoretical and counterintuitive. When he received his 1921 Nobel Prize, it was specifically for his solution to the photoelectric effect and for his "contributions to Theoretical Physics." Relativity was still too controversial to be specifically referenced.
Over time, however, the predictions of special relativity have been shown to be true. For example, clocks flown around the world have been shown to slow down by the duration predicted by the theory.
Principle of Constancy of the Speed of Light (Second Postulate): Light always propagates through a vacuum (i.e. empty space or "free space") at a definite velocity, c, which is independent of the state of motion of the emitting body.
Actually, the paper presents a more formal, mathematical formulation of the postulates. The phrasing of the postulates are slightly different from textbook to textbook because of translation issues, from mathematical German to comprehensible English.
The second postulate is often mistakenly written to include that the speed of light in a vacuum is c in all frames of reference. This is actually a derived result of the two postulates, rather than part of the second postulate itself.
The first postulate is pretty much common sense. The second postulate, however, was the revolution. Einstein had already introduced the photon theory of light in his paper on the photoelectric effect (which rendered the ether unnecessary). The second postulate, therefore, was a consequence of massless photons moving at the velocity c in a vacuum. The ether no longer had a special role as an "absolute" inertial frame of reference, so it was not only unnecessary but qualitatively useless under special relativity.
As for the paper itself, the goal was to reconcile Maxwell's equations for electricity and magnetism with the motion of electrons near the speed of light. The result of Einstein's paper was to introduce new coordinate transformations, called Lorentz transformations, between inertial frames of reference. At slow speeds, these transformations were essentially identical to the classical model, but at high speeds, near the speed of light, they produced radically different results.
Effects of Special Relativity
Special relativity yields several consequences from applying Lorentz transformations at high velocities (near the speed of light). Among them are:
* Time dilation (including the popular "twin paradox")
* Length contraction
* Velocity transformation
* Relativistic velocity addition
* Relativistic doppler effect
* Simultaneity & clock synchronization
* Relativistic momentum
* Relativistic kinetic energy
* Relativistic mass
* Relativistic total energy
In addition, simple algebraic manipulations of the above concepts yield two significant results that deserve individual mention.
Mass-Energy Relationship
Einstein was able to show that mass and energy were related, through the famous formula E=mc2. This relationship was proven most dramatically to the world when nuclear bombs released the energy of mass in Hiroshima and Nagasaki at the end of World War II.
Speed of Light
No object with mass can accelerate to precisely the speed of light. A massless object, like a photon, can move at the speed of light. (A photon doesn't actually accelerate, though, since it always moves exactly at the speed of light.)
But for a physical object, the speed of light is a limit. The kinetic energy at the speed of light goes to infinity, so it can never be reached by acceleration.
Some have pointed out that an object could in theory move at greater than the speed of light, so long as it did not accelerate to reach that speed. So far no physical entities have ever displayed that property, however.
Adopting Special Relativity
In 1908, Max Planck applied the term "theory of relativity" to describe these concepts, because of the key role relativity played in them. At the time, of course, the term applied only to special relativity, because there was not yet any general relativity.
Einstein's relativity was not immediately embraced by physicists as a whole, because it seemed so theoretical and counterintuitive. When he received his 1921 Nobel Prize, it was specifically for his solution to the photoelectric effect and for his "contributions to Theoretical Physics." Relativity was still too controversial to be specifically referenced.
Over time, however, the predictions of special relativity have been shown to be true. For example, clocks flown around the world have been shown to slow down by the duration predicted by the theory.
What is Relativity?
Classical relativity (defined initially by Galileo Galilei and refined by Sir Isaac Newton) involves a simple transformation between a moving object and an observer in another inertial frame of reference. If you are walking in a moving train, and someone stationary on the ground is watching, your speed relative to the observer will be the sum of your speed relative to the train and the train's speed relative to the observer. You're in one inertial frame of reference, the train itself (and anyone sitting still on it) are in another, and the observer is in still another.
The problem with this is that light was believed, in the majority of the 1800s, to propagate as a wave through a universal substance known as the ether, which would have counted as a separate frame of reference (similar to the train in the above example). The famed Michelson-Morley experiment, however, had failed to detect Earth's motion relative to the ether and no one could explain why. Something was wrong with the classical interpretation of relativity as it applied to light ... and so the field was ripe for a new interpretation when Einstein came along.
The problem with this is that light was believed, in the majority of the 1800s, to propagate as a wave through a universal substance known as the ether, which would have counted as a separate frame of reference (similar to the train in the above example). The famed Michelson-Morley experiment, however, had failed to detect Earth's motion relative to the ether and no one could explain why. Something was wrong with the classical interpretation of relativity as it applied to light ... and so the field was ripe for a new interpretation when Einstein came along.
Einstein Basic Profile's
Nationality: German
Born: March 14, 1879
Death: April 18, 1955
Spouse:
* Mileva Maric (1903 - 1919)
* Elsa Lowenthal (1919 - 1936)
1921 Nobel Prize in Physics "for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect" (from the official Nobel Prize announcement)
Albert Einstein - Early Work:
In 1901, Albert Einstein received his diploma as a teacher of physics and mathematics. Unable to find a teaching position, he went to work for the Swiss Patent Office. He obtained his doctoral degree in 1905, the same year he published four significant papers, introducing the concepts of special relativity and the photon theory of light.
Albert Einstein & Scientific Revolution:
Albert Einstein's work in 1905 shook the world of physics. In his explanation of the photoelectric effect he introduced the photon theory of light. In his paper "On the Electrodynamics of Moving Bodies," he introduced the concepts of special relativity.
Einstein spent the rest of his life and career dealing with the consequences of these concepts, both by developing general relativity and by questioning the field of quantum physics on the principle that it was "spooky action at a distance."
Albert Einstein Moves to America:
In 1933, Albert Einstein renounced his German citizenship and moved to America, where he took a post at the Institute for Advanced Study in Princeton, New Jersey, as a Professor of Theoretical Physics. He gained American citizenship in 1940.
He was offered the first presidency of Israel, but he declined it, though he did help found the Hebrew University of Jerusalem.
Misconceptions About Albert Einstein:
The rumor began circulating even while Albert Einstein was alive that he had failed mathematics courses as a child. While it is true that Einstein began to talk late - at about age 4 according to his own accounts - he never failed in mathematics, nor did he do poorly in school in general. He did fairly well in his mathematics courses throughout his education and briefly considered becoming a mathematician. He recognized early on that his gift was not in pure mathematics, a fact he lamented throughout his career as he sought out more accomplished mathematicians to assist in the formal descriptions of his theories.
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