By Dr. Mercola
In 1916, Albert Einstein predicted the existence of gravitational waves in his general theory of relativity.
Gravitational waves are "ripples in the fabric of space-time caused by some of the most violent and energetic processes in the Universe," according to the Laser Interferometer Gravitational-Wave Observatory (LIGO).1
LIGO is the world's largest gravitational wave observatory, with detectors in Livingston, Louisiana and Hanford, Washington. In September 2015, nearly 100 years after Einstein's prediction, the discovery of a lifetime was made: both of LIGO's detectors observed gravitational waves, a historical first.
The source of the waves was a collision between two black holes that took place 1.3 billion years ago. The "violent astrophysical event" was virtually beyond comprehension in scale, as each black hole is said to have had a mass that was more than 25 times greater than that of the sun.2
The discovery was kept largely quiet for five months, while physicists worked tirelessly to confirm their astounding finding. In February 2016, the announcement was made public and published in the journal Physical Review Letters:3
"A century after the fundamental predictions of Einstein and Schwarzschild [who published work that further the discovery of black holes], we report the first direct detection of gravitational waves and the first direct observation of a binary black hole system merging to form a single black hole."
Advanced LIGO Gets the Job Done
The first-generation LIGO experiment operated for nearly a decade with no results. Detecting gravitational waves is no easy feat, and the original technology just wasn't sensitive enough. As reported by Gizmodo:4
"Gravitational waves are minuscule — the atomic jitters that pass through our world when two black holes bash together in a distant galaxy are on the order of a billionth of a billionth the diameter of an atom.
LIGO detects them by proxy, using high powered lasers to measure tiny changes in the distance between two objects positioned thousands of miles apart.
A million things can screw this up, including a rumbling freight train, a tremor in the Earth, and the inconvenient reality that all objects with a temperature above absolute zero are vibrating all the time."
Upgrades over the last five years led to an advanced LIGO system that began operating in September 2015, just days before the first waves were detected.
It has new-and-improved lasers and is better able to separate potential gravitational waves from background "noise." It also allows a larger volume of the universe to be probed.
When the first waves were detected, researchers could hardly believe their luck and quickly set to work confirming that the signal was real (and it was!). Gizmodo continued:5
"According to Einstein's theory of relativity, when a pair of black holes orbit on another, they lose energy slowly, causing them to creep gradually closer.
In the final minutes of their merger, they speed up considerably, until finally, moving at about half the speed of light, they bash together, forming a larger black hole. A tremendous burst of energy is released, propagating through space as gravitational waves.
The two black holes behind the all the hubbub are 29 and 36 times the mass of the Sun, respectively. During the peak of their cosmic collision, LIGO researchers estimate that their power output was 50 times that of the entire visible universe.
'The description of this observation is beautifully described in the Einstein theory of general relativity formulated 100 years ago and comprises the first test of the theory in strong gravitation,' said Rainer Weiss, who first proposed LIGO as a means of detecting gravitational waves in the 1980s.
'It would have been wonderful to watch Einstein's face had we been able to tell him.'"
Why Detect Gravitational Waves?
The physics world is abuzz with this new discovery. Scott Hughes, Ph.D., an astrophysicist at MIT, told Gizmodo:6
"Seeing the data that the public just saw hit me like at ton of bricks … Imagine twenty three years of your career suddenly coming to fruition. It's hard to express the way everything seemed to just fall into place."
The finding is expected to set the course for a "new era of observational astrophysics," so it's easy to understand why physicists are excited.7 But there's reason for everyone to share in on this excitement. The detection of gravitational waves is only the beginning.
Electromagnetic radiation has historically been the only tool to observe and understand the goings-on of the universe. Gravitational waves offer an entirely new method for observation, as they carry "information about cosmic objects and events that is not carried by electromagnetic radiation," LIGO noted.8
Writing in the journal Physics, Emanuele Berti, Ph.D. of the Department of Physics and Astronomy at the University of Mississippi, explained it this way:9
"With Advanced LIGO's result, we are entering the dawn of the age of gravitational wave astronomy: with this new tool, it is as though we are able to hear, when before we could only see.
It is very significant that the first 'sound' picked up by Advanced LIGO came from the merger of two black holes.
These are objects we can't see with electromagnetic radiation. The implications of gravitational-wave astronomy for astrophysics in the near future are dazzling."
Part of what makes gravitational waves such a perfect "window" into the universe is the fact that they don't interact with matter, so they travel through the universe unimpeded. LIGO explained:10
"They will carry information about their origins that is free of the distortion or alteration suffered by electromagnetic radiation as it travels through millions of light years of intergalactic space. With this completely new way of examining astrophysical objects and phenomena, gravitational waves will truly open a new window on the Universe …
… [P]roviding astronomers and other scientists with their first glimpses of previously unseen and unseeable wonders, and greatly adding to our understanding of the nature of space and time itself."
Third LIGO Interferometer to Be Built in India
Following the momentous announcement, the Indian Cabinet approved funding to build a third LIGO detector in India. The addition of a third detector is expected to help scientists better pinpoint gravitational waves. It may be activated by the end of 2023.
While researchers are anticipating several sources and types of gravitational waves to appear, they're also anticipating new discoveries that have yet to be anticipated. LIGO Laboratory Executive Director David Reitze, Ph.D. said in a press release:11
"Any time you turn on some new type of telescope or microscope, you discover things you couldn't anticipate. So while there will be certain sources of gravitational waves that we expect to see, the really exciting part is what we did not predict and what we did not expect to see."
In case you were wondering how gravitational waves are detected by LIGO, it involves the use of laser interferometers. As the press release explained it:12
"At each observatory, the two-and-a-half-mile (4-km) long L-shaped interferometer uses laser light split into two beams that travel back and forth down the arms (four-foot diameter tubes kept under a near-perfect vacuum). The beams are used to monitor the distance between mirrors precisely positioned at the ends of the arms.
According to Einstein's theory, the distance between the mirrors will change by an infinitesimal amount when a gravitational wave passes by the detector. A change in the lengths of the arms smaller than one-ten-thousandth the diameter of a proton (10-19 meter) can be detected.
According to David Reitze, executive director of LIGO and a Caltech research professor, the degree of precision achieved by Advanced LIGO is analogous to being able to measure the distance between our solar system and the sun's nearest neighbor Alpha Centauri — about 4.4 light-years away — accurately to within a few microns, a tiny fraction of the diameter of a human hair."
Discoveries About the Nature of Gravity Could Be Around the Corner
The gravitational waves from black holes are expected to shed new light on the universe as we know it, including, perhaps, telling us about the nature of gravity itself. "Does gravity really behave as predicted by Einstein in the vicinity of black holes, where the fields are very strong? Can dark energy and the acceleration of the Universe be explained if we modify Einstein's gravity? We are only just beginning to answer these questions," Berti pondered.13
One thing’s for certain – if you’re a physics buff, things are really going to get interesting in the next few decades. You can also check out my own foray into zero gravity in the video at the top of this article.