On January 12, scientists began a gradual shutdown of the Advanced LIGO experiment, marking the end of a four-month search for gravitational waves, ripples of energy that course through the cosmic fabric of space and time. Now the question is whether persistent rumors that the experiment has detected the long-sought waves are accurate. A discovery would confirm one of general relativity’s most extraordinary predictions and provide an unprecedented glimpse of cataclysmic events such as black hole mergers.
Pairs of tightly orbiting massive objects such as black holes or the dense cores of dead stars should trigger subtle but detectable waves through spacetime that spread in all directions. Advanced LIGO hunts for these cosmic ripples at sites in Hanford, Wash., and Livingston, La., by measuring the precise lengths of perpendicular 4-kilometer-long laser beams. A passing gravitational wave should slightly stretch one beam while compressing the other.
Lately scientists’ excitement has grown thanks to well-publicized rumors about a discovery — some specific (detection of a black hole merger), some not so much. The Advanced LIGO team isn’t commenting on the speculation. “We just finished taking data,” says chief detector scientist Peter Fritschel. “It takes time to analyze.”
After five years upgrading instruments, scientists began the first Advanced LIGO survey in September 2015 and achieved up to four times the sensitivity of the previous best data, Fritschel says. By identifying length differences much smaller than the size of a proton, the experiment could in theory have spotted gravitational waves from merging black holes up to a few billion light-years away.
As we wait to learn whether the rumors have merit, check out Science News’s past articles on gravitational waves.