Five new ways to catch gravitational waves

Scientists are developing ways to spot those ripples in space-time that are invisible to current gravitational-wave-hunting facilities such as LIGO.

1. Ultra-long waves could be detected over many years by measuring the distance between Earth and stars called pulsars.
2. Telescopes are searching for patterns in the cosmic microwave background that would have been imprinted by gravitational waves in the early universe.
3. Observing atoms as they drop down a 1km-tall pipe could reveal waves coming from black hole collisions.
4. Desktop detectors for speculative high-frequency waves could reveal exotic physics right after the Big Bang.
5. A radical idea for spotting gravity waves involves putting a diamond crystal into quantum superposition — something that has never been demonstrated.