The general theory of relativity is much more complex and difficult to understand than the special theory. It proves the force of Gravitation, as proved by Sir Isaac Newton, wrong. According to Newton, gravity was a force between two bodies, which depends on their respective mass and the distance between them.
The basic idea of general relativity can be illustrated with the help of an imaginary experiment as performed by Einstein. Suppose a lift is at rest in space. If a ball is released within the lift, it will float in space and not fall. If the lift accelerates upward, an observer within the lift will see the ball fall to the floor exactly as it would under the pull of gravity. The ball appears to fall because the floor of the lift, as seen from outside the lift, it accelerates upward toward the ball. All the effects we associate with gravity would be seen by the observer in the lift. Einstein called the phenomenon shown in this experiment the Principle of Equivalence. This principle states that it makes no difference whether an object is acted on by a gravitational force or is in an accelerated frame of reference. The result in both cases will be the same. From this principle, Einstein reasoned that matter in space distorts or "curves" the frame of reference of space. The result of this curvature is what we experience as gravity. The Euclidian or flat geometry was unable to explain the curve, so Einstein used geometries called Riemannian geometry to explain the effect.
According to Newton's theory, a planet moves around the sun because of the gravitational force exerted by the sun. According to the theory of general relativity, the planet chooses the shortest possible path throughout the four-dimensional space- time, which is deformed by the presence of the sun. This shortest possible path is called a geodesic. This may be compared to the fact that a ship or an aeroplane crossing the ocean follows the section of a circle, rather than a straight line, in order to travel the shortest route between two points. In the same way, a planet or light ray moves along the "shortest" line in its four-dimensional world.
So far, three things have been discovered in which Einstein's theory of general relativity receives experimental proof as opposed to the theories of Newton. These differences are not great, but are measurable. In the first place, according to Newton's theory, the planet Mercury moves in an ellipse about the sun. According to Einstein's theory, Mercury moves along an ellipse, but at the same time the ellipse rotates very slowly in the direction of the planet's motion. The ellipse will turn about forty-three seconds of an arc per century (a complete rotation contains 360 degrees of an arc and 360 X 60 X 60 seconds of an arc). This effect is rather small, but it has been observed. Mercury is nearest to the sun and the relativistic effect would be still smaller for other planets.
If we take a picture of part of the heavens during an eclipse of the sun and near the eclipsed sun, and then take another picture of the same part of the heavens a little later, the two photographs will not show identical positions for all the stars. This is so because, according to general relativity, a light ray sent by a star and passing near the rim of the sun is deflected from its original path because the sun's gravity curves space. The effect of gravity on light is also the reason why black holes are invisible. The gravitation in a black hole is so strong that light cannot escape from it.
Physicists have known for more than a hundred years that when some elements are heated to incandescence they give off a pattern of spectral lines (coloured lines), which can be examined through a spectroscope. According to the Einstein theory, the wavelength of light emitted from a massive object will become longer because of gravitation. This results in a shift of the spectral lines towards the red end of the spectrum; this type of red shift is called gravitational red shift. If we examine the spectral lines of an element on our earth with the spectral lines given off by the same element on the sun or on a star, the spectral lines of the element on the sun or star should be very slightly shifted toward the red end of the spectrum, compared with the spectral lines of the same element on our earth. Experiment has confirmed this shift. In 1960, two American physicists, R. V. Pound and G. A. Rebka, Jr., detected the red shift resulting from the earth's gravitational field. They measured the effect of altitude on the frequency of gamma rays.
Conclusion- The theory of relativity is a truly wonderful theoretical concept that cleanly defies many of the facts of classical physics.
How ever scientists are still trying to confirm this theory and some success has also been achieved, as some scientists believe that velocity of light is not same even in vacuum or space.
forfurther ref. go to the link below
2006-06-13 08:18:23
·
answer #1
·
answered by know it all 3
·
1⤊
0⤋
Einstein's Theory of General Relativity is basically a new description of gravity. Instead of treating gravity as a force between two objects with mass, gravity is thought of as the warping of the fabric of space-time by an object with mass. Imagine that space is a rubber sheet stretched tight. Place a bowling ball at the center, and it warps the sheet, just like planets and stars do in our universe. Take a small BB and roll it towards the bowling ball, and the BB's path will curve because the sheet is curved - objects in space have their paths curved by massive objects like planets and stars. Even the paths of light rays are bent by massive objects.
To my knowledge general relativity does not have any applications in technology here on Earth, although scientists use it to understand their observations of stars and galaxies. Outside of astrophysics I don't think it is used.
2006-06-13 08:05:16
·
answer #2
·
answered by kris 6
·
0⤊
0⤋
Imagine a stretched bed spread with a bowling ball in the middle. That is a 2-dimensional model of space being distorted my effects of gravity. Einstein postulated that our three observed 3-d space is similarly distorted. Einstein predicted and later proved by experiment that light traveling from a distant star would actually bend around our sun because of the gravitational distortion. General relativity has predicted things like blackholes.
2006-06-13 08:13:40
·
answer #3
·
answered by Toshe 1
·
0⤊
0⤋
The main use I know of of relativity today is in GPS satellites. Because they are at large distances from the Earth's surface and are moving at high velocities, combined with the need for high precision and accuracy, classical mechanics is not good enough. Over time, using classical physics will lead to errors in the clocks aboard the GPS satellites. This will, in turn, cause errors in positioning on Earth. Therefore, GPS satellites correct for their speeds relativistically, although they are far below the speed of light.
2006-06-13 08:08:42
·
answer #4
·
answered by Brad C 2
·
0⤊
0⤋
In 1916 Einstein expanded his Special Theory to include the effect of gravitation on the shape of space and the flow of time.
This theory is referred to as the General Theory of Relativity. It proposes that matter causes space to curve.
Its' uses today? It laid the foundation for all subsequent research into relativity and partly for modern cosmology as well.
2006-06-13 08:08:27
·
answer #5
·
answered by kindred_silverwolf 1
·
0⤊
0⤋
do u mean the einstein theory? it means that the time, speed and space is related in some ways.. when we travel at a high speed, we'll lose some time.. that was why when the astronauts re-entered the Earth, it was proven that they had lost some miliseconds..
and we cannot travel at a higher speed than the speed of sound, cuz time will stop.
2006-06-13 07:56:09
·
answer #6
·
answered by hakunamatata 2
·
0⤊
0⤋
(dealing with gravity) is based on the postulate that the local effects of a graviational field and of acceleration of an inertial system are identical
2006-06-13 07:54:30
·
answer #7
·
answered by Fallon 1
·
0⤊
0⤋
technology has never been my in demand field, as my heart's area is literature! yet your poem calls me in the route of technology when I obviously see how spell binding mild propagation will be! :))
2016-10-14 03:14:56
·
answer #8
·
answered by Anonymous
·
0⤊
0⤋