[tdsoap7 (OP)]

I understand the theory of relativity and that space is, indeed, curved but i want to know what characteristic of matter(atoms) actually causes space(nothingness) to become warped resulting in gravity.

[graham.d]

It is really energy (more strictly the stress-energy-momentum tensor) that causes space to curve. But this is being pedantic. You are asking what is in the nature of this stuff, be it matter, energy etc.) that causes space to curve and so results in gravity. The answer is that nobody knows. It is just something that appears as a property of the universe that has been observed. It is no more and no less mysterious that the Newtonion view that matter has the property of attracting other matter via a gravitational field.

As Feynman once commented that physics is like peeling an onion only to find more layers to peel inside. More insight may come if and when there are good theories of quantum gravity which will require a widely accepted theory of how to combine QM with GR. There will always be more layers to peel though.

[Pmb]

When someone asks a "How?" question they are normally looking for a desdcription and when they as "Why?" they are looking for a mechanism. As graham.d explained above, nobody knows the mechanism. The desccription is given by Einstein's field equations.

The source of gravity is mass, which, as Einstein described it in his 1016 GR paper, is fullly described by the stress-energy-momentum tensor. Think of the EM analogy where charge is the source of the EM field. What is charge in one frame is current in another. Charge and current form a 4-vector and that 4-vector appears in the tensor form of Maxwell's equations. A similar thing happens in GR. What is mass in one frame is momentum and stress in another. The mass, momentum and current form a second rank 4-tensor which appears in Eisntein's field equations.