Seeing Gravitons in Colliding Gravitational Waves

If gravity and quantum mechanics are to be unified, gravitational waves—usually studied as a classical phenomenon using general relativity—must comprise hypothesized particles called gravitons. In theory, gravitons can interact with each other to produce photons, but these interactions were thought to be vanishingly rare and impossible to detect. In new theoretical work, Raymond Sawyer of the University of California, Santa Barbara, finds that in certain cases, colliding gravitational waves could produce enough radio frequency photons to yield a detectable signal.