1. Photon: This is the fundamental particle responsible for the electromagnetic force, which governs interactions between charged particles. It is the carrier of light, and is responsible for all electromagnetic phenomena, from radio waves to gamma rays.
2. Gluon: This is the force carrier of the strong nuclear force, which binds quarks together to form protons and neutrons. It is responsible for the strong interaction, which holds the nucleus of an atom together.
3. Graviton: This is the hypothetical particle that mediates the force of gravity. While it hasn't been directly observed yet, it is a crucial part of the Standard Model and is believed to be responsible for the gravitational attraction between objects.
It's important to note that the idea of "massless" is a bit of a simplification. All particles have a certain amount of energy, and according to Einstein's famous equation E=mc², energy and mass are equivalent. So, even though these particles are considered massless, they still have energy and momentum, which can interact with other particles.
