Gravitational wave astronomy will open an entire new window on our Universe. Gravitational waves are ripples in the fabric of space and time produced by violent events in the distant universe, for example by the collision of two black holes or by the cores of supernova explosions. Gravitational waves are emitted by accelerating masses much in the same way as radio waves are produced by accelerating charges – for example, such as electrons in antennas. These ripples in the space-time fabric travel to Earth, bringing with them information about their violent origins and about the nature of gravity that cannot be obtained by other astronomical tools.
Albert Einstein predicted the existence of these gravitational waves in 1916 in his general theory of relativity, but only since the 1990s has technology become powerful enough to permit detecting them and harnessing them for science. Although they have not yet been detected directly, the influence of gravitational waves on a binary pulsar system (two neutron stars orbiting each other) has been measured accurately and is in excellent agreement with the predictions. In 1993 R. A. Hulse and J. H. Taylor received the Nobel Prize in physics for that indirect proof. Scientists therefore have great confidence that gravitational waves exist. But a direct detection will confirm Einstein’s vision of the waves, and allow a fascinating and unique view of cataclysms in the cosmos.
The first direct detection
For the first time, scientists have observed ripples in the fabric of spacetime called gravitational waves, confirming Einstein’s prediction and opening an unprecedented new window onto the cosmos.
The gravitational waves were detected on September 14, 2015 at 9:51 UTC by both of the twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and Hanford, Washington, USA.
Gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained. The detected gravitational waves were produced during the final fraction of a second of the merger of two black holes to produce a single, more massive spinning black hole. This collision of two black holes had been predicted but never observed.