Relativity theory was first studied by Albert Einstein. The general theory of relativity was published in 1915. It is the current description of gravitation in modern physics. It unifies special theory of relativity and Newton’s law of gravitation. It describes gravity as a geometrical property of space and time or space - time. The speed of light in a vacuum is constant and an absolute physical boundary for motion. This does not have much effect on person’s day to day life since we travel much lower speed than light. For objects traveling near light speed, however, the theory of relativity states that objects will move slower and shorten in length from the point of view of an observer on Earth. Einstein also derived the famous equation, E = mc2, which reveals the equivalence of mass and energy.
THEORY OF RELATIVITY
Theory of relativity is of two types. Special Theory of Relativity and General Theory of Relativity.
Special Theory of Relativity
The first is the Special Theory of Relativity, which essentially deals with the question of whether rest and motion are relative or absolute, and with the consequences of Einstein’s conjecture that they are relative.
General Theory of Relativity
The second is the General Theory of Relativity, which primarily applies to particles as they accelerate, particularly due to gravitation, and acts as a radical revision of Newton’s theory, predicting important new results for fast-moving and/or very massive bodies. The General Theory of Relativity correctly reproduces all validated predictions of Newton’s theory, but expands on our understanding of some of the key principles. Newtonian physics had previously hypothesized that gravity operated through empty space, but the theory lacked explanatory power as far as how the distance and mass of a given object could be transmitted through space. General relativity irons out this paradox, for it shows that objects continue to move in a straight line in space-time, but we observe the motion as acceleration because of the curved nature of space-time.
The development of general relativity began with the equivalence principle, under which the state of accelerated motion and being at rest in a gravitational field are physically identical. The upshot of this is that free fall is inertial motion; an object in free fall is falling because that is how objects move when there is no force being exerted on them, instead of this being due to the force of gravity as in the case in classical mechanics. This is incompatible with classical mechanics and special relativity because in those theories inertially moving objects can not accelerate with respect to each other, but objects in free fall do so. To resolve this difficulty Einstein first propose that space – time is curved. Some of the consequences of general relativity are:
i) Time goes slower in higher gravitational fields. This is called gravitational time dilation.
ii) Orbits precess in a way unexpected in Newton’s theory of gravity.
iii) Rays of light bend in the presence of a gravitational field.
iv) Frame – dragging in which, a rotating mass “ drags along” the space time around it.
v) The Universe is expanding, and the far parts of it are moving away from us faster than the speed of light.
The general theory of relativity is constructed so that its results are approximately the same as those of Newton's theories as long as the velocities of all bodies interacting with each other gravitationally are small compared with the speed of light--i.e., as long as the gravitational fields involved are weak. The latter requirement may be stated roughly in terms of the escape velocity. A gravitational field is considered strong if the escape velocity approaches the speed of light, weak if it is much smaller. All gravitational fields encountered in the solar system are weak in this sense.
Notice that at low speeds and weak gravitational fields, general and special relativity reduce to Newtonian physics, i.e. everyday experience.
THEORY OF RELATIVITY
Theory of relativity is of two types. Special Theory of Relativity and General Theory of Relativity.
Special Theory of Relativity
The first is the Special Theory of Relativity, which essentially deals with the question of whether rest and motion are relative or absolute, and with the consequences of Einstein’s conjecture that they are relative.
General Theory of Relativity
The second is the General Theory of Relativity, which primarily applies to particles as they accelerate, particularly due to gravitation, and acts as a radical revision of Newton’s theory, predicting important new results for fast-moving and/or very massive bodies. The General Theory of Relativity correctly reproduces all validated predictions of Newton’s theory, but expands on our understanding of some of the key principles. Newtonian physics had previously hypothesized that gravity operated through empty space, but the theory lacked explanatory power as far as how the distance and mass of a given object could be transmitted through space. General relativity irons out this paradox, for it shows that objects continue to move in a straight line in space-time, but we observe the motion as acceleration because of the curved nature of space-time.
The development of general relativity began with the equivalence principle, under which the state of accelerated motion and being at rest in a gravitational field are physically identical. The upshot of this is that free fall is inertial motion; an object in free fall is falling because that is how objects move when there is no force being exerted on them, instead of this being due to the force of gravity as in the case in classical mechanics. This is incompatible with classical mechanics and special relativity because in those theories inertially moving objects can not accelerate with respect to each other, but objects in free fall do so. To resolve this difficulty Einstein first propose that space – time is curved. Some of the consequences of general relativity are:
i) Time goes slower in higher gravitational fields. This is called gravitational time dilation.
ii) Orbits precess in a way unexpected in Newton’s theory of gravity.
iii) Rays of light bend in the presence of a gravitational field.
iv) Frame – dragging in which, a rotating mass “ drags along” the space time around it.
v) The Universe is expanding, and the far parts of it are moving away from us faster than the speed of light.
Dragging Space and Time
The results of two studies announced in early November 1997 provide unprecedented support for “frame-dragging,” a concept predicted by physicist Albert Einstein's general theory of relativity. Frame-dragging describes how massive objects actually distort space and time around themselves as they rotate. One of the studies examined frame-dragging around black holes, an example of which is shown here in an artist's conception.
The results of two studies announced in early November 1997 provide unprecedented support for “frame-dragging,” a concept predicted by physicist Albert Einstein's general theory of relativity. Frame-dragging describes how massive objects actually distort space and time around themselves as they rotate. One of the studies examined frame-dragging around black holes, an example of which is shown here in an artist's conception.
General Relativity:
The second part of relativity is the theory of general relativity and lies on two empirical findings that he elevated to the status of basic postulates. The first postulate is the relativity principle: local physics is governed by the theory of special relativity. The second postulate is the equivalence principle: there is no way for an observer to distinguish locally between gravity and acceleration.
The second part of relativity is the theory of general relativity and lies on two empirical findings that he elevated to the status of basic postulates. The first postulate is the relativity principle: local physics is governed by the theory of special relativity. The second postulate is the equivalence principle: there is no way for an observer to distinguish locally between gravity and acceleration.
Einstein discovered that there is a relationship between mass, gravity and space-time. Mass distorts space-time, causing it to curve.
Gravity can be described as motion caused in curved space time.
Gravity can be described as motion caused in curved space time.
Thus, the primary result from general relativity is that gravitation is a purely geometric consequence of the properties of space-time. Special relativity destroyed classical physics view of absolute space and time, general relativity dismantles the idea that space-time is described by Euclidean or plane geometry. In this sense, general relativity is a field theory, relating Newton's law of gravity to the field nature of space-time, which can be curved.
Gravity in general relativity is described in terms of curved space-time. The idea that space-time is distorted by motion, as in special relativity, is extended to gravity by the equivalence principle. Gravity comes from matter, so the presence of matter causes distortions or warps in space-time. Matter tells space-time how to curve, and space-time tells matter how to move (orbits). Gravity in general relativity is described in terms of curved space-time. The idea that space-time is distorted
There were two classical test of general relativity; the first was that light should be deflected by passing close to a massive body. The first opportunity occurred during a total eclipse of the Sun in 1919.
There were two classical test of general relativity; the first was that light should be deflected by passing close to a massive body. The first opportunity occurred during a total eclipse of the Sun in 1919.
Measurements of stellar positions near the darkened solar limb proved Einstein was right. Direct confirmation of gravitational lensing was obtained by the Hubble Space Telescope last year.
The second test is that general relativity predicts a time dilation in a gravitational field, so that, relative to someone outside of the field, clocks (or atomic processes) go slowly. This was confirmed with atomic clocks flying airplanes in the mid-1970.
The second test is that general relativity predicts a time dilation in a gravitational field, so that, relative to someone outside of the field, clocks (or atomic processes) go slowly. This was confirmed with atomic clocks flying airplanes in the mid-1970.
The general theory of relativity is constructed so that its results are approximately the same as those of Newton's theories as long as the velocities of all bodies interacting with each other gravitationally are small compared with the speed of light--i.e., as long as the gravitational fields involved are weak. The latter requirement may be stated roughly in terms of the escape velocity. A gravitational field is considered strong if the escape velocity approaches the speed of light, weak if it is much smaller. All gravitational fields encountered in the solar system are weak in this sense.
Notice that at low speeds and weak gravitational fields, general and special relativity reduce to Newtonian physics, i.e. everyday experience.
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