- 06 Aug '10 01:50Einstein's general theory of relativity is the best explanation of gravity we have. The question unanswered is why collective matter warps space/time. Answering that question will add to Einstein's theory and solve the mystery of gravity completely. Anything less than that is an incomplete theory worth little more than garbage.
- 06 Aug '10 02:37 / 1 edit

So Einstein's theory is little more than garbage? Better tell that to the GPS scientists who depend on Einstein's solutions to the changes in space-time with the depth of a gravity well and velocity. It works pretty darn good right there. It also has withstood every experimental test trying to falsify it. I'll take it till something better comes along.*Originally posted by Metal Brain***Einstein's general theory of relativity is the best explanation of gravity we have. The question unanswered is why collective matter warps space/time. Answering that question will add to Einstein's theory and solve the mystery of gravity completely. Anything less than that is an incomplete theory worth little more than garbage.**

You might also tell that to all the particle physicists at Brookhaven and Cern so maybe there can be a better way to get those particles moving at 99.999999999 c to be controlled. - 06 Aug '10 04:02

I didn't interprete MetalBrain's words that Einsteins theories are "little more than garbage".*Originally posted by sonhouse***So Einstein's theory is little more than garbage? Better tell that to the GPS scientists who depend on Einstein's solutions to the changes in space-time with the depth of a gravity well and velocity. It works pretty darn good right there. It also has withstood every experimental test trying to falsify it. I'll take it till something better comes along.**

...[text shortened]... e there can be a better way to get those particles moving at 99.999999999 c to be controlled.

There are a lot of crackpot theories, some religious, some delusional, some both, that explains gravity in a faulty way. Noone has described gravity better than Einstein. But Einsteins theories doesn't described it all. There lack details. - 06 Aug '10 21:45

Fabian is correct. I did not imply Einstein was anything but a remarkable man. His General Theory of Relativity is the best explanation of gravity we have, but it needs added explanation to satisfy those of us with an intellectual curiosity as to why collective matter warps space/time. Nobody has done that thus far, so Einstein is still the man!*Originally posted by sonhouse***So Einstein's theory is little more than garbage? Better tell that to the GPS scientists who depend on Einstein's solutions to the changes in space-time with the depth of a gravity well and velocity. It works pretty darn good right there. It also has withstood every experimental test trying to falsify it. I'll take it till something better comes along.**

...[text shortened]... e there can be a better way to get those particles moving at 99.999999999 c to be controlled. - 06 Aug '10 23:18

Ok, I take it back But big Al does explain gravity, as warps or bends in spacetime. To him it is not a force so much as the geometry of space. like a ball bearing on a sheet of paper, if you bend the paper, say by pushing it together, the ball moves.*Originally posted by Metal Brain***Fabian is correct. I did not imply Einstein was anything but a remarkable man. His General Theory of Relativity is the best explanation of gravity we have, but it needs added explanation to satisfy those of us with an intellectual curiosity as to why collective matter warps space/time. Nobody has done that thus far, so Einstein is still the man!**

That is not a very accurate analog but just a way of describing Einsteins view. There have been many attempts to plug in a particle that mediates gravity like photons mediate electomagnetic radiation and such but nothing has been found so far. If they find a valid gravity mediating particle, there would be a big hint gravity is more than just the geometry of space.

Till then, Big Al's equations work just fine - 07 Aug '10 14:01

This is what the paper attempts to do: explain how gravity is mediated in a microscopic sense. Einstein himself postulated that "gravity waves" are responsible for this, but according to the article in the OP it's an entropic force.*Originally posted by sonhouse***Ok, I take it back But big Al does explain gravity, as warps or bends in spacetime. To him it is not a force so much as the geometry of space. like a ball bearing on a sheet of paper, if you bend the paper, say by pushing it together, the ball moves.**

That is not a very accurate analog but just a way of describing Einsteins view. There have been many a ...[text shortened]... ity is more than just the geometry of space.

Till then, Big Al's equations work just fine - 07 Aug '10 16:21

If gravity is a result of space-time geometry there would be no mediators, unless there were two versions of gravity, two ways to achieve gravitation, one by space-time bends and the other by particles. So far only the geometric version has passed the test of time.*Originally posted by KazetNagorra***This is what the paper attempts to do: explain how gravity is mediated in a microscopic sense. Einstein himself postulated that "gravity waves" are responsible for this, but according to the article in the OP it's an entropic force.**

I'm sure there will be a spate of experiments and theory if particles are actually found. - 07 Aug '10 16:41

Are you referring to the hypothetical graviton?*Originally posted by sonhouse***Ok, I take it back But big Al does explain gravity, as warps or bends in spacetime. To him it is not a force so much as the geometry of space. like a ball bearing on a sheet of paper, if you bend the paper, say by pushing it together, the ball moves.**

That is not a very accurate analog but just a way of describing Einsteins view. There have been many a ...[text shortened]... ity is more than just the geometry of space.

Till then, Big Al's equations work just fine - 08 Aug '10 00:34 / 2 edits

Yes, and another one called the gravitino. I imagine there are more in the cookbook but nothing detected as of yet.*Originally posted by Metal Brain***Are you referring to the hypothetical graviton?**

Here is a bit from Wiki about the graviton:

In physics, the graviton is a hypothetical elementary particle that mediates the force of gravitation in the framework of quantum field theory. If it exists, the graviton must be massless (because the gravitational force has unlimited range) and must have a spin of 2.

This is because the source of gravitation is the stress-energy tensor, which is a second-rank tensor, compared to electromagnetism, the source of which is the four-current, which is a first-rank tensor.

Additionally, it can be shown that any massless spin-2 field would be indistinguishable from gravitation, because a massless spin-2 field must couple to the stress-energy tensor in the same way that the gravitational field does.

[4] This result suggests that if a massless spin-2 particle is discovered, it must be the graviton, so that the only experimental verification needed for the graviton may simply be the discovery of a massless spin-2 particle.[5]

And a quickie from wiki on the gravitino:

The gravitino, symbol G͂, is the supersymmetric partner of the graviton, as predicted by theories combining general relativity and supersymmetry; i.e. supergravity theories. If it exists it is a fermion of spin 3/2 and therefore obeys the Rarita-Schwinger equation.

The gravitino field is conventionally written as ψμα with μ = 0,1,2,3 a four-vector index and α = 1,2 a spinor index. For μ = 0 one would get negative norm modes, as with every massless particle of spin 1 or higher.

These modes are unphysical, and for consistency there must be a gauge symmetry which cancels these modes: \delta\psi_{\mu\alpha} = \partial_\mu\epsilon_\alpha where \epsilon_\alpha(x)\, is a spinor function of spacetime. This gauge symmetry is a local supersymmetry transformation, and the resulting theory is supergravity.

Thus the gravitino is the fermion mediating supergravity interactions, just as the photon is mediating electromagnetism, and the graviton is presumably mediating gravitation. Whenever supersymmetry is broken in supergravity theories, it acquires a mass which is directly the supersymmetry breaking scale.

As a proposed solution to the fine tuning problem of the Standard Model, and in order to allow grand unification, the supersymmetry breaking scale needs to be pushed down to the TeV range.

Therefore the gravitino mass needs to be of this order (unless we have intermediate scale SUSY breaking), much lower than Planck scale, which is the natural scale for gravitation interactions. This difference in energy scales is known as the hierarchy problem.