A photon and a graviton are both hypothetical elementary particles, but they have different properties and roles in the fundamental forces of nature.
Photon: A photon is the elementary particle associated with the electromagnetic force, which includes phenomena such as light, radio waves, and X-rays. Photons are massless particles that travel at the speed of light and carry electromagnetic energy. They have zero rest mass, zero electric charge, and a spin of 1. Photons mediate the electromagnetic interactions between charged particles, such as electrons and protons, through the exchange of virtual photons.
Graviton: A graviton, on the other hand, is a hypothetical elementary particle that is postulated to be the mediator of the gravitational force. The gravitational force is responsible for the attraction between masses and is described by Einstein's theory of general relativity. Gravitons, if they exist, would be massless particles with zero electric charge and a spin of 2. Unlike photons, which mediate electromagnetic interactions, gravitons would mediate gravitational interactions between objects with mass or energy.
It's important to note that while photons have been experimentally observed and their properties are well understood within the framework of quantum electrodynamics, gravitons have not yet been directly detected. The theoretical framework for describing gravity at the quantum level is still an area of active research, and the existence of gravitons remains a subject of investigation.