If gravity arises from the curvature of spacetime, why is there a need for gravitons? If gravity arises from the curvature of space time, why is there a need for gravitons? If someone could explain this to me I would be very thankful. I dont understand why.
 A: Caution: This is going to enter into speculative domain.
One of modern physics most outstanding achievements is the theory called Quantum Electrodynamics which explains electromagnetic forces very well. QED brought along the idea of photon as a messenger of EM forces. 
Later, people were able to apply the same idea (of messenger particles) and came up with Quantum Chromodynamics and Quantum Flavourdynamics to explain strong and weak forces respectively. The success of all these theories has led people to explore an alternate theory for gravity which may perhaps be able to reconcile gravity with quantum mechanics.
The reason why we are looking for an alternate theory of gravity is because our current best theory (due to Einstein) does not agree very well with quantum mechanics. One reason why gravitons appeal to some theorists is because there is a rather nice symmetry (if we can call it that) if every "force" in nature can be assigned a messenger particle with some measurable parameters (charge etc.). Only gravity stands out right now. But who knows --may be all we will find is that it is special or perhaps our notions for the other three forces are wrong.
That having been said, all our current theories for the four forces have been amply confirmed by experiments and thus stand on very strong foundations.
