What is a graviton? Where can it be found?

The graviton is a hypothetical particle which is thought to be responsible for transferring the force of gravity. Like a photon it is a massless particle, however it is a spin 2 particle rather than a spin 1 particle (what is spin?). The photon is responsible for communicating all electromagnetic forces, and it has been shown mathematically that a massless spin 2 particle would produce a force exactly equivalent to gravity.

Despite being widely accepted to exist by physicists and astronomers, direct detection of a graviton is unlikely to ever happen. Gravity is an incredibly weak force (compared to the other fundamental forces) which means that the particles that transfer it only interact very weakly with matter. As all experiments ultimately rely on interactions with matter, this means that an experiment sensitive enough to directly detect gravitons is practically impossible. However, we may be able to infer information about gravitons by measuring gravitational waves. There are a number of ongoing experiments hoping to detect both gravitational waves created in the recent past by merging black holes or neutron stars, and experiments aiming to detect the imprint on the Cosmic Microwave Background Radiation of gravitational waves formed the instant after the Big Bang.

This page was last updated on January 31, 2016.