What is LIGO?
LIGO is a network of two gravitational wave detectors. Its mission is to detect gravitational waves from astrophysical sources such as merging black holes. There are two LIGO detectors: one in Washington State and the other in Louisiana. The LIGO Scientific Collaboration includes members of the GEO observatory in Germany and collaborates with the Virgo Scientific Collaboration in Italy.
What are gravitational waves?
Gravitational waves are a prediction by Einstein in his general theory of relativity. General relativity predicts that massive objects will warp space and time. The warping of space is what we know as gravity! Systems in motion will warp space dynamically, causing ripples in space itself to propagate and carry away energy. These ripples in space, called gravitational waves, are observed by making very precise measurements here on Earth. As a gravitational wave passes through space (including your computer screen!), it squeezes the screen along one direction and stretches it along the other. The squeezing and stretching, which we call “strain” is how an objects length changes relative to its length. In other words, if a meter stick changes by 1 centimeter, the strain would be 0.01 or 1 part in 100. The strain from a typical gravitational wave source is so small that it goes unnoticed, except by the most sensitive detectors. A typical squeezing or stretching here on Earth is only one part in 1,000,000,000,000,000,000,000– that’s one in a billion trillion.