LIGO Hanford Observatory

Assembled from 19 blocks · 1 evidence · 16 related

1. Story
2. One of the two American laser interferometers whose simultaneous response constitutes a gravitational-wave detection, situated on the Hanford Site in eastern Washington State. Each arm is four kilometres long and holds a laser beam in an ultra-high vacuum; a passing gravitational wave changes the relative arm lengths by a fraction of the diameter of a proton, and the instrument reads that as a shift in the interference pattern where the beams recombine. A single such instrument cannot claim a detection, because seismic, thermal and human disturbances produce transients constantly; what makes a signal credible is a matching waveform appearing at a second, distant detector within the light travel time between them. In the 14 September 2015 event the signal reached Livingston first and Hanford about seven milliseconds later, which is both a consistency check and the crudest possible measurement of where the source was.
3. Knowledge
4. LIGO Hanford Observatory
5. GW150914 - two black holes merge and the signal reaches Earth
6. Connections
7. GW150914 - two black holes merge and the signal reaches Earth
8. GW150914 - two black holes merge and the signal reaches Earth
9. The detection is announced and published
10. LIGO Hanford Observatory
11. LIGO Livingston Observatory
12. The no-hair result
13. Stellar-mass black hole
14. Gravitational waves
15. LIGO Hanford Observatory
16. LIGO Livingston Observatory
17. The event horizon
18. Evidence
19. The first direct detection of gravitational waves, from the merger of two black holes on 14 September 2015. V55 VERIFICATION BASIS: not consulted in session; WebFetch to www.ligo.org and every other host was refused by the egress proxy. Volume and article number are from recall of a canonical citation; component masses and distance quoted in this pack are recalled central values with uncertainties omitted.