Question

why are gravitons considered hypothetical?

Answer 1

They are the mediating field particle of the gravitaional field in particle physics. The other three mediating field particles (gluons for the strong force, photons for the electromagnetic force, W and Z bosons for the weak force) have been detected. Gravitons, however, while necessary (as the exchange particle or mediating particle) to describe the gravitational force (in particle physics)m have not been detected and are therfore hypothetical or only theoretical (to date).

Answer 2

Wow, thanks for the great answer.

Answer 3

@Mally: it hasn't been detected yet, cause gravity is soo much weaker than the other 3 fundamental forces. If you consider the strong force with the strength 1, the strenght of the 4 fundamental interactions is:\[StrongForce: 1\]\[EM - Force: 10^{-2}\]\[Weak Force: 10^{-15}\]\[Gravitation: 10^{-41}\]