Dark matter is thought to make up some five sixths of all matter in the universe. Yet incredibly sophisticated projects ranging from the most powerful atom smasher ever built to vats of chilly liquid xenon have failed to find a trace of it. But now some scientists are hoping atomic clocks, the most precise timekeepers ever made, could be used to help explain this elusive phenomenon.

Many physicists believe dark matter is an invisible substance whose predicted gravitational effects on known matter would help explain a variety of cosmic mysteries, such as why galaxies can spin as fast as they do without flying apart. Despite its apparently colossal importance to the very structure of the universe, however, no one knows anything for certain about what it might be composed of or where it came from.