In the framework of general relativity, the theory of gravity proposed by Albert Einstein, the force of gravity is not mediated by a particle like the photon in electromagnetism. Instead, gravity is understood as the curvature of spacetime caused by the presence of mass and energy.
According to general relativity, massive objects, such as planets or stars, curve the fabric of spacetime around them. When a smaller object, such as a particle, moves in the vicinity of a massive object, it follows a path determined by the curvature of spacetime. This curvature is what we perceive as the force of gravity.
The concept of a graviton, a hypothetical elementary particle that would mediate the gravitational force, arises in the context of attempting to reconcile general relativity with quantum mechanics. In the framework of quantum field theory, the other fundamental forces (electromagnetic, weak, and strong) are described by the exchange of force-carrying particles (photons, W and Z bosons, gluons). In a similar vein, some theoretical approaches propose the existence of a graviton as the hypothetical mediator of the gravitational force.
However, it's important to note that the graviton is currently purely theoretical and has not been observed or detected experimentally. Moreover, the full realization of a consistent quantum theory of gravity, including the behavior of gravitons, remains an open question in physics.
In summary, within general relativity, gravity is not mediated by a particle, but rather understood as the curvature of spacetime caused by mass and energy. The concept of a graviton arises in attempts to unify gravity with quantum mechanics, but its existence and properties remain speculative.