Why Do We Consider Gravitons if Gravity Is Space-Time Curvature?

[mandhjh]

If gravity manifests itself as a warpage in space-time, "forcing" bodies to travel in curved paths in the vicinity of more "massive" objects, why is graviton exchange/mediation necessary?? If not necessary, then why is the existence of the graviton particle (which has yet to be discovered) necessary? Newton (a mysterious force acting at a distance) and Einstein can't both be right, can they?

 

[PAllen]

If gravity manifests itself as a warpage in space-time, "forcing" bodies to travel in curved paths in the vicinity of more "massive" objects, why is graviton exchange/mediation necessary?? If not necessary, then why is the existence of the graviton particle (which has yet to be discovered) necessary? Newton (a mysterious force acting at a distance) and Einstein can't both be right, can they?

Newton and Einstein cannot both be right, and experiment rejects Newton, emphatically. General relativity has not been falsified by any clear evidence, so far (no theory can be confirmed with certainty; they can only be 'not falsified').

Gravitons are not predicted by either Newtonian gravity or GR. They are hypothesized for a quantum field treatment of gravity as a 'force' just like electro-weak, and strong. They are also predicted by string/M theory. Thus, the motivation for them is uniting quantum reality with gravity.

Note that almost all physicists believe GR must be wrong, even though not yet falsified. This is due to predicted singularities as well as incompatibility with quantum nature of reality.

Despite fairly strong belief that gravitions are needed for a successor theory to GR, there are strong arguments that they will never be detected in the direct way photons are (e.g. photoelectric effect). The strength of this argument for impossibility of direct detection does not rule out experiments that verify gravitons indirectly.

 

[zhermes]

If gravity manifests itself as a warpage in space-time, "forcing" bodies to travel in curved paths in the vicinity of more "massive" objects, why is graviton exchange/mediation necessary??

Gravitons are not 'necessary', as PAllen says - some theories have suggested their existence. I don't think the existence of gravitons would necessarily conflict with the geometrical interpretation of gravity; gravitons would just be quantized distortions in space-time.