[vaskalr]

Everybody knows that two body attract each other. Can somebody please tell me what is the source of this force of attraction, i.e.. How this gravitation force is generated.

[Capuchin]

It's an inherent property of mass.

[jiten55]

According to the Theory of Relativity, there is no real attraction, only seems to be so in our part of the universe.

It is not attraction between bodies but the geometry of the universe near us which makes it seem that bodies attract each other according to Newton's Law of Gravitation.

[vaskalr]

According to the Theory of Relativity, there is no real attraction, only seems to be so in our part of the universe.

It is not attraction between bodies but the geometry of the universe near us which makes it seem that bodies attract each other according to Newton's Law of Gravitation.

I had thoroughly gone through theory of relativity, both special and general one. In both of these nowhere what you had said is described neither in methamatical form nor in anology form then on what basis can you give such a comment please elaborate your point. Please also specify which theory you are mentioning: special or general.

[vaskalr]

it's an inherent property of mass.

"a phenomena remains an inherent property as long as one is ignorant about its true cause" theis was said by RICHARD FYNMANN

[Capuchin]

"a phenomena remains an inherent property as long as one is ignorant about its true cause" theis was said by RICHARD FYNMANN

My point exactly.

[jiten55]

General Theory of Relativity.

See "Mathematical Theory of Relativity" by A.S. Eddington, the Chapter on Einsten's Law of Gravitation, which has nothing to do with "Attraction".

In this chapter, Eddington also derive's Newton's Law from Einstein's Law.

See also: Einstein's Theory

For those not familiar with Tensors or Reimannian Geometry, Bertrand Russell's "ABC of Relativity" is excellent. This book also explains that there is no "attraction", only Geometry.

Einstein's law of gravitation has nothing to do with mutual attraction of bodies. It is purely Geometry, based on Reimannian Geometry.

It is purely based on the geometry of Space-Time.

Presence of mass changes the geometry of Space-Time nearby. This causes bodies to move in a certain way. (A rough example: Bodies move down a hill because of slope)

Newton's Law of gravitation is true approximately near our part of the universe - but there is no "attraction". It is a just a very convenient way of computing motion of bodies near our part of the universe.

That does not make Newton's Law invalid, as long as we remember that in Newton's law motion can be computed (in most cases) in our part of the universe "as if" there was such attraction!

Problem was that Newton's law did not work in certain cases and this led to Einstein's Theory. Bending of light near the Sun was one of the problems. Another was anomalous perihelion precession of the planet Mercury.

[Capuchin]

According to the Theory of Relativity, there is no real attraction, only seems to be so in our part of the universe.

This is the part that I didn't quite follow. What do you mean by "our part of the universe"?

[jiten55]

FURTHER:

See Gravitation - Wikipedia, the free encyclopedia

"In general relativity, the effects of gravitation are ascribed to spacetime curvature instead of a force. .....

To deal with this difficulty, Einstein proposed that spacetime is curved by matter, and that free-falling objects are moving along locally straight paths in curved spacetime. (This type of path is called a geodesic.) More specifically, Einstein discovered the field equations of general relativity, which relate the presence of matter and the curvature of spacetime and are named after him. The Einstein field equations are a set of 10 simultaneous, non-linear, differential equations. The solutions of the field equations are the components of the metric tensor of spacetime. A metric tensor describes a geometry of spacetime. The geodesic paths for a spacetime are calculated from the metric tensor."

[jiten55]

By "our part of the universe" I mean the curvature and geometry of Space-Time around us.

The configuration or Space-Time geometry (which gets modified by presence of matter)
In our part of the universe enables us to use Newton's Law as a convenience.

Presence of matter makes the Space-Time curved. Curvature depends upon how matter is distributed. This curvature is not 3-dimensional but 4-dimensional.

[jiten55]

I wonder if Newton believed there was actual Attraction between bodies.

Is it possible that all he meant in his Law of gravitation was that:

To calculate motion of bodies we may assume that there is the following force of attraction between bodies (for purpose of calculation), or that the following Law is true empirically

[vaskalr]

General Theory of Relativity.

See "Mathematical Theory of Relativity" by A.S. Eddington, the Chapter on Einsten's Law of Gravitation, which has nothing to do with "Attraction".

In this chapter, Eddington also derive's Newton's Law from Einstein's Law.

See also: Einstein's Theory

For those not familiar with Tensors or Reimannian Geometry, Bertrand Russell's "ABC of Relativity" is excellent. This book also explains that there is no "attraction", only Geometry.

Einstein's law of gravitation has nothing to do with mutual attraction of bodies. It is purely Geometry, based on Reimannian Geometry.

It is purely based on the geometry of Space-Time.

Presence of mass changes the geometry of Space-Time nearby. This causes bodies to move in a certain way. (A rough example: Bodies move down a hill because of slope)

Newton's Law of gravitation is true approximately near our part of the universe - but there is no "attraction". It is a just a very convenient way of computing motion of bodies near our part of the universe.

That does not make Newton's Law invalid, as long as we remember that in Newton's law motion can be computed (in most cases) in our part of the universe "as if" there was such attraction!

Problem was that Newton's law did not work in certain cases and this led to Einstein's Theory. Bending of light near the Sun was one of the problems. Another was anomalous perihelion precession of the planet Mercury.

Thanks jiten, I will surely go through the books you have mentioned.

[jiten55]

Eddington was a very great Astronomer and conducted one of the first definitive Astronomical observations that confirmed the Theroy of Relativity.

He was also one of the first great exponents of Relativity.

He wrote Mathematical Theory of Relativity in the Fifties, which is therefore far less technical than the current text books. Currently, Tensors are out of fashion but the new tools make the subject very much harder and much less accessible. The latter may have made the proofs more elegant.

Furthermore, in the time of Eddington and earlier, writers on Mathematics tried much harder than now to make their subject easy on the student. It seems to me that they were not miserly but generous on the time they took to write their books.

With Eddington, you feel that you are sitting in his class as a student while he explains the subject!

None of the Mathematical books on the subject of General Relativity is easy-reading, but his books put the least demand of prior Mathematical knowledge on the student.

He was a also great writer, teacher, and Philosopher.

To better understand his Mathematical Theory of Relativity, you will need to understand Tensors, for which purpose "Reimannian Geometry and Tensor Analysis" by Weatherburn is the best and easiest I have found. You need only to read the first few chapters.

However. It is probabely not really necessary to read any book on Tensors, Eddington does not assume prior knowledge.

You should be able to find his book, which remains a classic, in any university library. Unfortunately it is out of print.