INTRODUCTION TO GENERAL RELATIVITY
General relativity was devloped by Albert Einstein a century ago. Accoring to general relativity, the observed gravitational attraction between masses depend on space and time also.
Newton’s law of universal gravitation was accepted before Einstein’s theory of relativity. In Newton’s model, gravity is the result of an attractive force between massive objects. Newton’s theory of gravitation was also extremely successful at describing motion, But Einstein’s description was a much better improvement to Newton’s law of gravity. Einstein’s description accounted for several effects which were unexplained by Newton’s law of gravitation, Minute anomalies in the orbits of Mercury and other planets are considered in Einstein’s general theory of relativity. This theory of relativity also predicts the novel effects of gravity like gravitational waves, gravitational lensing and and an effect of graivty on time known as gravitational time dilation.
Einstein’s theory of general relativity is four dimensional :
Einstein’s theory can be described as four dimensional with time also as one of the coordinate. Normally till Einstein devleoped general theory of relativity noone considered time as a factgor affecting the position. But in Einstein’s theory he first took time also as a fourth coordinate and found out that time will appear slower due to some effects.
E=mc^2 equivalence of mass and energy
Equivalance theory of mass and energy:
Though the concept of relativity was in vogue before Einstein’s time, It became popular and approved after Einstein’s theory only.
The main theory in this is that the speed of light in a vacuum is constant and an absolute physical boundar for motion. We common people never realise this because normally the speed we travel is negligible compared to speed of light. For objects travelling near light speed, the theory of relativity states that objects will move slower and shorten in length from the point of view of observer on earth. We should make it clear that time dilation and length short is only apparent and not real. In other words, there is no change in actual time or length. It seems apparent relative to the place from where we are seeing. This is the very important point in General theory of relativity.
First point is it applies when travelling in a very high speed almost equal to that of light. Hence we should not compare this theory in normal life with negligible speeds and come to conclusion there is no apparent change in time of length.
Second point is there is no actual or real change in time or length, It is apparent from the view of observer because of relativity.
The famous equation of Einstein E =mc2 which reveals the equivalence of mass and energy.
Theory of relativity – Fundamental points
The theory of relativity consists of two main points.
1. The first is the Special theory of relativity. It deals with the question of whether rest and motion are relative or absolute. According to Einstein’s special theory of relative, the relationship between rest and motion are relative and not absolute. 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 and not absolute.
2. The second is the General Theory of Relatitivy, which primarily applies to particles when they accelerate, mainly due to gravitation. The theory of Einstein acts as a radical revision of Newton’s theory for fast moving and/or very massive bodies. In other words, we can say that this is an expansion of Newton’s theory on understanding some of the key principles involved. Newton’s theory of gravity operated through empty space, but did not explain as far as how the distance and mass of a given object could be transmitted through space. Einstein’s general theory of relativity second part provides explanation for this.
The second part of the theory of relativity states that objects continue to move in straight line in space time, but we observe the motion as acceleration because nature of space time is curved.
ACCURACY OF Einstein’s theory of relativity:
Einstein’s general theory of relativity have been confirmed to be accurate to a very high degree over a period of time. Also the data has been proved to corroborate many other important key predictions.
How it was proved in 1919?
Total solar eclipse which was inaccessible due to brightness of sun was analysed by astrronomers straight near the edge of the sun. This was possible because the light of stars is indeed deflected by the sun as the light passes near the sun on its way to earth. It also predicted the rate at which two neutron stars orbiting one another will move toward each other. Thus the general theory of relativity was proved to be the best confirmed principles in all of physics.
general theory of relativity – amazing results
How really amazing General theory of relativity is:
Here the fourth dimension coordinate that is time is linked or related to matter and space. A continuum is created by dimensions of matter, time and space. Time itself cannot exist without matter and space. So we can infer that the uncaused first cause must exist outside of the four dimensions of space and time, and possess eternal, personal, and intelligent qualities in order to possess the capabilities of intentionally space, matter — and indeed even time itself — into being. This is really amazing to persons having average brains and limitations like us.
The existence of time implies eternity (with beginning and end) and the existance of space implies infinity. Hence the theory itself is a combination of infinity and eternity. To understand this, we have to take so much pain. Really we have to wonder how Einstein, an ordinary human being, by birth, thought and found all these things accurately. The nobel prize awarded to him was very less compared to the volume of theory he proved.
The article we discussed is only introduction to general theory of relativity. Full applications and concepts will be very useful and interesting. The general theory of relativity thus is a theory which expands Newton’s previous findings about gravitation without contradicting his findings. Also here time, space and matter are considered to provide a continuum. Also when speed nearly equals that of light, time appears to go slower while length appears shorter.
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* (September 24, 2012) Leonard Susskind gives a broad introduction to general relativity, touching upon the equivalence principle.
This series is the fourth installment of a six-quarter series that explore the foundations of modern physics. In this quarter, Leonard Susskind focuses on Einstein’s General Theory of Relativity.
Stanford Continuing Studies Program:
Stanford University Channel on YouTube:
General Relativity Lecture 1