Here's how a Washington-state observatory detected gravitational waves

The stunning announcement that scientists have finally detected gravitational waves, the ripples in the fabric of space-time that Einstein predicted a century ago, shined a light on a research facility located on the Hanford Nuclear Reservation in the Tri-Cities.

For decades researchers have searched for the waves but have been unable to prove their existence. That all changed when two observatories — one  in Livingston, Louisiana and one in the Hanford Observatory — each found evidence of the waves when they followed a sequence of events after two black holes merged.

So what does the discovery mean?

The discovery of the waves, believed to be caused by violent collisions in the universe, also offers evidence that black holes do exist.  According to a story from The Associated Press, scientists worldwide see the announcement as a life-changing event.

The Hanford observatory says that according to general relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes. "During the final fraction of a second, the two black holes collide into each other at nearly one-half the speed of light and form a single more massive black hole, converting a portion of the combined black holes' mass to energy, according to Einstein's formula E=mc2. This energy is emitted as a final strong burst of gravitational waves. It is these gravitational waves that LIGO has observed," the news release said.

The gravitational waves were detected last September 14 by both twin Laser Interferometer Gravitational-wave Observatory (LIGO) detectors, located in Livingston, Louisiana, and at Hanford, near Richland, Washington.

Each LIGO has two giant perpendicular arms more than 2 miles long. A laser beam is split and travels both arms, bouncing off mirrors to return to the arms' intersection. Gravitational waves stretch the arms to create an incredibly tiny mismatch — smaller than a subatomic particle — in the beams' locations. That mismatch is what LIGO detects.

The research also included contributions from scientists at Washington State University.

"We have quite a few researchers on the ground floor at the Large Interferometer Gravitational Wave Observatory (LIGO) at Hanford," Will Ferguson, a spokesman for WSU in Pullman, said after the news was announced Thursday.

Here's a timeline of events 

• In 1979, the National Science Foundation decided to give money to the California Institute of Technology and the Massachusetts Institute of Technology to come up with a way to detect the waves.
• Twenty years later, they started building two LIGO detectors in Hanford, Washington, and Livingston, Louisiana, and they were turned on in 2001. But after years with no luck, scientists realized they had to build a much more sensitive system, which was turned on last September.
• At LIGO Hanford Observatory, scientists, engineers and technicians worked along with local contractors from 2008 until 2015 to build the Advanced LIGO detector, guided by more than 15,000 drawings covering over a million named parts.
• As Initial LIGO was observing between 2009-2010, truckloads of parts were arriving daily, from our colleagues and contractors around the world, to be prepared and assembled into larger detector sub-units with rigorous testing at each step.
• By October 2010, the Initial LIGO detector was shut down and disassembled, so that the Advanced LIGO sub-units could be installed into the vacuum system for final integration and testing of the new detector.
• This process was completed at the end of March 2015.
• in the early morning hours of September 14 in the Pacific Northwest, Nature declared it was time as the gravitational wave, known as GW150914, arrived at Earth. It took 3 minutes for an online analysis code to identify the event. Shortly thereafter, our rapid response team initiated the vetting process for this event.
• Read more about this process on LIGO's website.

An explanation of why this is a life-changing event:

The news confirmed a major prediction of Albert Einstein's 1915 general theory of relativity and opened an unprecedented new window into the cosmos. Arriving at Earth from a cataclysmic event in the distant universe, gravitational waves carry information about their dramatic origins and about the nature of gravity that cannot otherwise be obtained.

Detecting gravitational waves is so difficult that when Einstein first theorized about them, he figured scientists would never be able to hear them.

In 1979, the National Science Foundation decided to give money to the California Institute of Technology and the Massachusetts Institute of Technology to come up with a way to detect the waves.

More: Gravitational waves: What they are and why was Einstein right

Twenty years later, they started building the two LIGO detectors, and they were turned on in 2001.

After years with no luck, scientists realized they had to build a more advanced system, which was turned on last September.

Cox Media Group