Introduction to LIGO & Gravitational Waves

Using Multiple Detectors


Aerial view of the LIGO detector in Livingston, LA. [Image: LIGO]

LIGO Livingston Observatory, LA
Multiple interferometers are needed to confidently detect and locate the sources of gravitational waves (except continuous signals), since directional observations cannot be made with a single detector like LIGO, which is sensitive to large portions of the sky at once.  Gravitational waves have a finite speed and are expected to travel at the speed of light.  This will induce a detection delay (up to about 10 milliseconds) between the two LIGO detectors.  Using this delay and the delay between LIGO and its international partners will help pinpoint the sky location of the gravitational wave source.  Multiple detectors also help sort out candidate gravitational wave events that are caused by local sources, like trees falling in the woods or even a technician dropping a hammer on site.  These events are clearly not gravitational waves but they might look like a gravitational wave in the collected data.  If a candidate gravitational wave is observed at one detector but not the other within the light travel time between detectors, the candidate event is discarded.

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