Visualisation of the gravitational waves caused by two black holes merging.
Henze/NASA
Scientists just discovered Einstein's ripples in the fabric of spacetime.
A century ago, Albert Einstein's General Theory of Relativity changed human understanding of space and time. From a fixed speed of light to the existence of gravitational waves, the mode era of theoretical physics was bo in 1916.
Today, researchers on the Laser Interferometer Gravitational-Wave Observatory project have announced they have solid evidence for the existence of gravitational waves -- disturbances in the fabric of spacetime.
Beyond proving Einstein's theory, the discovery brings us one step closer to a grand unified theory -- the Holy Grail of physics that provides an all-encompassing explanation for the universe as we know it.
Speaking at a press conference today, a team of LIGO scientists announced that they had observed a gravitational wave, created 1.3 million years ago by a collision between two black holes. These waves were detected on September 14, 2015, when the facility was tued back on after an upgrade.
How do you picture gravitational waves? Think of spacetime like a taut sheet. Rolling a ball across the sheet causes it to curve. As the ball moves, the sheet's curvature moves as well and certain objects moving quickly cause ripples across the sheet.
Einstein's original theory proposed that as mass changes position, it causes a ripple in the universe's gravitational field, a wave travelling at the speed of light outward from the source. Gravitational waves are caused by objects like oddly shaped spinning planets and binary black hole and star systems. Theories also suggest that supeovae, and even the Big Bang itself, are a source of gravitational waves. You can read more about them on Einstein Online.
Animation of gravitational waves produced by a fast binary orbit.
NASA
Now that LIGO has detected these waves, researchers have an entirely new way of studying these objects and events. In the case of black holes, which are very difficult to study since we cannot view them directly, it could blow research wide open. Researchers may be even to peer back to just a split second after the Big Bang, something that is impossible with other methods.
Stop and think about that for a second. We may finally be able to see the beginning of time. The universe. Everything there is.
The LIGO facility uses two 4-kilometer (2.5-mile) long arms in an L shape as "antennas" to track gravitational waves. Each arm contains an interferometer, an array of lasers and mirrors used to detect the minute movements that gravitational waves would cause -- movements 10,000 times smaller than a proton.
But detecting gravitational waves is not easy to do. Gravity is, for something that binds the universe together, surprisingly weak. For almost a decade LIGO facilities failed to detect any gravitational waves. Five years of upgrades led to Advanced LIGO going live in September 2015 and it has identified XX waves in less than six months. The addition of a third facility will allow the team to triangulate the waves to find their source.
Robert Ward, an Australian National University scientist who installed the interferometers (the devices used to track waves), explains how Advanced LIGO works.
"The gravitational waves will affect masses that are free to move under the influence of gravity by changing the distance between them. This is often described at the wave 'stretching and squeezing the space between the masses'. We measure the distance between the two masses by attaching high-quality mirrors to them, and then by bouncing laser beams off those mirrors. We then effectively time how long it takes for the laser beam to retu, and since we know the speed of light, that lets us measure the distance. Of course it's both more and less complicated than that, but that's the basic idea."
Now that the LIGO team has observed these waves, they will open up avenues not just to study obscure objects in greater depth, but also a new means to discover previously unknown objects, much like radio telescopy located objects undetectable by visible light telescopes.
In other words, gravitational wave astronomy will usher in an entirely new era of space discovery.
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