Peer closely enough, and everything begins to look granular. Trees are made largely of quarks. Sunbeams are swarms of photons. Phones run on streams of electrons. Physicists have detected particles of matter, light, and most forces—but no experiment has yet unveiled gravity's grainy side.

Many physicists assume that gravity must come in particles but that these massless “gravitons” interact with familiar particles too weakly to detect. To confirm the existence of gravitons, some theorists suggest searching for them when they gather in hordes surrounding intense gravitational events such as black hole mergers. A recent analysis, published in March in Physical Review Letters, hints that such violent cataclysms just might bring gravitons out of the shadows.

Where there is energy, there is gravity. And photons—massless packets of light energy—can, in exceedingly rare cases, spontaneously transform into gravity particles, according to Douglas Singleton, a physicist at California State University, who was not involved with the new study. The reverse happens, too, he says: gravitons can become photons. The new analysis considers a mechanism by which gravitons could unleash many billions of times more photons than earlier research suggested—making it easier to confirm their existence.

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