There are two LIGO detectors at Louisiana and Washington

Q.  In which of the following place/places are LIGO detector located?

1) Louisiana
2) Washington
3) Arizona

- Published on 15 Feb 16

a. Only 1
b. 1 and 2
c. Only 3
d. Only 2 and 3

ANSWER: 1 and 2
  • The LIGO is the most precise instrument that has ever been built. It consists of two identical L-shaped laser interferometer systems, one at Hanford in Washington and one at Livingston in Louisiana.
  • There are two systems to ensure that detection at both the instruments that are about 3000 km apart with the calculated time delay ensures that the detected signal is not due to any spurious seismic signal or any other local vibration.
  • Each of the arms of the L is a 4 km tunnel in which laser beams bounce back and forth between two highly sensitive suspended mirrors. The laser beams are tuned to be perfectly in opposite phase so that there is total interference when the beams arrive at the intersection of the arms and no light passes through the beam splitter at the intersection into the photo-detector behind.
  • But when a gravitational wave passes through the detector, the space-time gets distorted much like a squeezed ball, oscillating between the two states compressed in one direction and elongated in the other. So the effect of this oscillatory compression of one arm and elongation of the other is that there is no total cancellation of the interfering laser beams and a net signal gets through to the photo detector.

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