Humans have been studying the stars by looking at light for centuries. But many phenomena in the universe, such as black holes, do not give off any light at all and therefore cannot be seen by telescopes. Gravitational waves are “ripples” in space and time created by massive objects colliding. “The search to detect the gravitational waves has been, in many respects, like adding sound to a silent movie, a way to hear the universe's most violent explosions and learn about gravity in a way that wasn’t possible before. The concept of LIGO dates back to the 1960s and 70s. Researchers such as Rainer Weiss and Kip Thorne believed they could use a laser to detect the very slight expansion of space itself. Many believed it to be impossible, as the expansion was so slight, thousands times smaller (~10⁻²¹) than an individual atom. It took a long time, dedication, resources provided by the government, and large construction projects to finally develop such technology. In 2015, their dedication finally paid off as they detected a sign of the collision of two black holes a billion light-years away. LIGO is not an individual facility but a huge collaborative project. Though there are only two major universities operating the labs – Caltech and MIT – there are currently over 1,000 scientists from across the globe working together in what is known as the LIGO Scientific Collaboration (LSC). Their work is in collaboration with other observatories in Europe (Virgo) and Japan (KAGRA) in sharing data and thoughts with them. The result is that the whole scientific community across the whole world can confirm their findings when there is a new discovery. LIGO has two identical stations in the United States. One is in Hanford, in the state of Washington, and the other is in Livingston, Louisiana. The two stations are 1,800 miles apart. This was a key part of the design: if something were to vibrate in Louisiana, such as during a small earthquake or a truck driving by, it would not vibrate in Washington at exactly the same time. But a gravitational wave in space is so large that it reaches both stations nearly at the same time. With this in mind, scientists know that they are receiving a signal from space and not just local noise.
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