For the second time in human history, scientists have detected gravitational waves passing through Earth. These waves, created by the violent spiraling collision of two black holes, are the warping and distortion of the fabric of space itself. This finding is a confirmation of the game-changing discovery of gravitational waves, and one that could lead to many more.

A team of more than 1,000 physicists working with the Advanced LIGO detectors in Livingston, Louisiana, and Hanford, Washington announced this second gravitational wave discovery today. The wave in this study was originally detected in the United States late on Christmas night in 2015, though it hails from a black hole merger 1.4 billion years ago. The black holes that collided to create it are far smaller than those behind the first gravitational wave detection earlier this year, yet they bent the fabric of space itself with roughly as much energy as is contained in the entire mass of our Sun. The details of the detection are outlined today in the science journal Physical Review Letters.

"That first detection showed we could hear the cosmos in a completely new way. With this second detection we're really diving into a new era."

New Window to the Universe

"That first gravitational wave detection showed that we could hear the cosmos in a completely new way," says Vicky Kalogera, a physicist with the research team at Northwestern University. "But with this second detection we're really diving into a new era. An era in which we can sample and compare the enormous wealth of these gravitational wave sources across the cosmos; spying the full picture of what nature has created around us."

With this second detection, scientists also can begin to forecast how often measurable gravitational waves pass through Earth. "This really is a brand-new window into the universe, like when Galileo first turned his telescope towards the sky," Kalogera says.

This content is imported from YouTube. You may be able to find the same content in another format, or you may be able to find more information, at their web site.

"It's a promising start to mapping the populations of black holes in our universe," agrees Gabriela González, an astronomer at Louisiana State University who is part of the team.

As far as black holes go, the two that caused today's wave were fairly small. One contained about as much mass as eight suns; the other, 14. Comparatively, the black holes behind the first signal were 36 and 29 times bigger than our Sun. That's important, because scientists were able to listen in longer as these smaller black holes pirouetted about one another. They twirled for about a full second, "spinning in 55 cycles right before they collided with each other. That's compared to only about 10 cycles for the first signal," says Sarah Caudill, a physicist with the research team who's from the University of Wisconsin-Milwaukee.

Ripples in Space

What exactly are gravitational waves? Like an ocean wave is a slosh of water, a gravitational wave is likewise the movement of a medium. But with gravitational waves, it's space itself that's moving and warping. Imagine that the world around you covered with 3D grid lines. A passing gravitational wave causes those physical coordinates to stretch, making space itself longer or shorter in different directions. Crazy, right?

According to Einstein's 1915 general theory of relativity, gravitational waves are caused by virtually any matter, from a black hole to a bumblebee, moving about. Any accelerating matter warps the physical coordinates of space around it, sending out these waves at light speed. Here's the catch: Space is so extraordinarily stiff that it takes a huge mass moving at an astonishing speed to produce a wave big enough for us to measure.

"This really is a brand-new window into the universe, like when Galileo first turned his telescope towards the sky."

The Advanced LIGO detectors use a straightforward setup to catch gravitational waves passing through Earth. Simply put, the detectors send lasers in different directions at exactly equal lengths and see whether either laser traveled farther than the other. If the lasers don't match up, you can infer that space itself shrunk or stretched while the laser was moving. Each detector tests for this possible stretching with an endless number of laser bursts, and compares any possible findings with the other instrument located across the country.

But gravitational waves are so achingly faint that to measure the slight stretch or compression of space, your observatory has to be incredibly still and as quiet as you can imagine. Never mind the constant hum of seismic jitters the Earth produces all the time; just a pine-cone falling miles away from the observatory would mess up a reading. That's how faint these waves are. To adjust for this outside noise, in Advanced LIGO the lasers travel through an insulated vacuum. The entire L-shaped device is underground and suspended in a noise-canceling setup made of seven individually nested supports.

Still Other Theories

These gravitational waves are expected to be a major boon to astrophysics and cosmology, says Chiara Mingarelli, a gravitational wave expert at the California Institute of Technology, who was not involved in today's finding.

"One of the interesting things that we can do with these waves is to test Einstein's theory of general relativity. So far thats the most successful theory that describes gravity, but there are still other theories that make the same predictions, but only differ during this strong gravitational regime." Mingarelli also notes that by taking a census of all the various sizes of gravitational wave creating events, we can start to understand why certain cosmological events may happen more frequently than others. Scientists at the Advanced LIGO detectors hope to soon record the crash of other massive objects besides black holes, like neutron stars.

Oddly enough, the researchers working with Advanced LIGO also announced a possible third "candidate" gravitational wave, which was measured back in early October. But the measurement was a bit fuzzy. The signal-to-noise ratio was fairly high during the event, and so the scientists only have 95 percent confidence the event wasn't an instrumental fluke. That may sound pretty damn sure to you or I, but it's not high enough here. Cosmologists require at least 99.99994 percent statistical confidence to confirm a gravitational wave.

Waves Crashing Onward

Advanced LIGO has been upgraded since the detection of this wave on Christmas Day. It will power up for its second run in September of this year. According to Dave Reitze, the Executive Director of LIGO Laboratory, the upgrades will roughly double the number of gravitational waves that the instruments can detect. With further upgrades planned in 2018 (all of which are basically noise-canceling improvements), by 2019 we could see an influx of more than 100 gravitational wave detections per year, says Reitze.

There's an even more immediate and exciting technological breakthrough around the corner. Later this year, Europe's own Advanced LIGO-style detector will get up running. It's called Advanced VIRGO, and it will have an enormous impact on the information we're able to garner from gravitational waves.

According to Caudill at the University of Wisconsin-Milwaukee, this third detector will allow physicists to "triangulate where the gravitational waves are originating from," she says, pinpointing them in the sky. That's a big problem the scientists are currently facing. "With only two detectors, we're a bit blind. We could only constrain the location of this most recent detection to about 850 square degrees in the sky," says Caudill. That's basically most of the nighs sky. For reference, the moon takes up only about "half of a square degree in the sky," she says.

Knowing the origin of these gravitational waves is more than a cool factoid. "Eventually we want to follow up with partner observations, to scour for a counterpart signal in, for example, optical or gamma rays," she says. "That would tell us much more about the special process in nature that shape and drive these things."

This content is created and maintained by a third party, and imported onto this page to help users provide their email addresses. You may be able to find more information about this and similar content at piano.io