Scientists are diving into the deep sea to study one of the universe’s biggest mysteries—quantum gravity.

Using KM3NeT, a vast underwater neutrino telescope, researchers are watching ghost-like particles that may hold the key to uniting the physics of the very large and the very small. By analyzing how neutrinos oscillate—or don’t—during their journey through space, they’re searching for subtle signs of decoherence, a possible effect of quantum gravity.

A tiny particle and a big physics puzzle.