The last theory of Albert Einstein is associated with gravitational waves and it seemed to be the most impossible parameter to detect so far! However, a team of scientists announced on Thursday that they had heard and recorded the sound of two black holes colliding a billion light-years away.
David Reitze, the American laser physicist and LIGO executive director at California Institute of Technology made the announcement, “We have detected gravitational waves. We did it.” At highly anticipated press conference in Washington.
The gravitational waves, ripples in fabric of space-time was first anticipated by Einstein hundred years ago but never observed directly until now. They are not light but a brand new communication medium that travel unimpeded through gas, dust and interstellar space. A gravitational wave, which expands and contracts all matter as it passes through, will cause a phase shift in the light that will be seen as the returning beams merge.
The waves were detected on September 14, 2015, scientists said. Since then, scientists have been evaluating their findings to make sure they were accurate. Indian scientists have contributed significantly in designing the algorithms that were used to analyze the signals recorded by the detectors and be sure that it was indeed from a gravitational wave.
Furthermore, the scientists not only detected the ripples but also were able to confirm the actual source of the waves. These ripples are product of enormous collision between two massive black holes. Reitze stated, one black hole had the mass of 29 suns; the other was equivalent of 36 suns.
Black holes are objects of extreme density, with such a strong gravitational attraction that even light cannot escape from their grasp. Black holes are incredibly massive but it cover only a small region it’s due to the relationship between mass and gravity.
How big is this discovery?
Discovering gravitational waves would be a huge deal for physics, cosmology and mankind’s understanding of black holes and the universe at a larger scale. As famed physicist Stephen Hawking noted in Nature, “These amazing observations are the confirmation of a lot of theoretical work, including Einstein’s general theory of relativity, which predicts gravitational waves.”  Apart from the fact of affirming a big piece of Einstein’s theory of general relativity, gravitational waves can be utilized to probe some of the most mysterious phenomena in the cosmos. Moreover, these waves can be used as fingerprints of the most energetic events in the universe because black holes, neutron stars and other object that do not emit light which makes it  extremely difficult to study from our vantage point. These fingerprints can help scientists understand how the force of gravity operates under extreme conditions.
All the previous predictions of Albert Einstein has been tested and verified such as; force of gravity is an illusion instead mass wraps the fabric of 4-D spacetime leading to gravitational motion, gravitational of light that is known as gravitational lensing, slowing of time in gravitational field and dragging of spacetime by spinning of masses. However, only the last prediction, gravitational waves has never been observed directly, but now!
Simply put, gravitational waves are vibrations in the fabric of the universe- light-speed ripples in spacetime itself, caused by such violent events as exploding stars and black hole mergers. The atoms that make up everything from the stars in the sky to the human beings on Earth are shaking a tiny bit, all the time. Group of scientists in Louisiana and Washington where two of the most sensitive detectors have been waiting and listening has claimed they have detected gravitational waves.
What devices are used to detect gravitational waves?
In Washington, LIGO Hanford Observatory the laser interferometer gravitational wave observatory has detectors that has L-shape antenna with arms 2.5 miles (4km) long. Inside the ends of each arm mirrors of ultra-pure glass are isolated from the noise, heat and vibrations of outside world. A beam of leaser light measures the separation of the mirrors, the beam is split and send towards the mirrors at the end of each arm. If the arms are precisely the same length, the returning beams cancel each other out and LIGO detectors sees no light but a passing gravitational wave that stretch one arm and squeeze the other. The resulting discrepancies’ are as tiny as a fraction of the width of proton but enough to misalign the beams and light up the detector in rhythmic pattern.
A schematic drawing of a Laser Interferometer Gravitational Wave Observatory (LIGO)
On 14th of September 2015, LIGO detected flickering light and turned it into a sound wave, a chirp. It was the eco of the merge of those two black holes, a cosmic cataclysm that took place billion years ago.
The Future Hearing a gravitational wave has opened a new eye of Astronomy, for the first time humans have ears and eyes on the universe. In January 2016, the LISA Pathfinder space craft has arrived at its destination, a spot in space a million miles away from earth. A place where gravity of earth cancel each other, a quiet place to attempt the impossible. The mission keeps two cubes of golden platinum in perfect free fall and perfectly still position. The mission is a test and a ground work for a future mission “A LISA”. Laser Interferometer Space Antenna (LISA) Pathfinder is testing certain technologies required for future LISA-like space missions that cannot be proven on Earth due to our planet’s gravity. The mission aims to, demonstrate that a test mass can be put in a pure gravitational free-fall, demonstrate laser interferometry with a free-falling mirror and  assess the reliability of micro-Newton thrusters, lasers and optics in a space environment.
The LISA Pathfinder is in Halo orbit about the Lagrangian point it’s 1.5 million kilometers away from Earth. Three space craft a million kilometers apart linked with lasers waiting for gravitational waves.