For second time, LIGO detects gravitational waves
For the second time, scientists have directly detected gravitational waves — ripples through the fabric of space-time, created by extreme, cataclysmic events in the distant universe. The team has determined that the incredibly faint ripple that eventually reached Earth was produced by two black holes colliding at half the speed of light, 1.4 billion light years away. The scientists detected the gravitational waves using the twin Laser Interferometer Gravitational-wave Observatory (LIGO) interferometers, located in Livingston, Louisiana, and Hanford, Washington. On Dec. 26, 2015, at 3:38 UTC, both detectors, situated more than 3,000 kilometers apart, picked up a very faint signal amid the surrounding noise. While LIGO’s first detection, reported on Feb. 11, produced a clear peak, or “chirp,” in the data, this second signal was far subtler, generating a shallower waveform — essentially a faint squeak — that was almost buried in the data. Using advanced data analysis techniques, the team determined...