Introduction to LIGO & Gravitational Waves
Using Multiple Detectors
Aerial view of the LIGO detector in Livingston,
LA. [Image: LIGO]
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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.
