Gravitational Waves: From Cataclysm To Detection
Two massive black holes far from our galaxy merged into a single,larger hole in the vast darkness of space.
Einstein believed that something unusual happens when two celestial bodies, such as planets or stars, orbit each other. He felt that this kind of movement might produce ripples in space. These ripples would spread out just like the ripples appear when a stone is dropped in a pond.
Researchers have now discovered rumblings from the cataclysmic collision as ripples in the space time itself. The discovery emerges a century after Albert Einstein predicted the existence of space ripples, better known as The Gravitational Waves.
What Are Gravitational Waves?
As mentioned by Albert Einstein, Gravitational waves are basically ‘ripples’ in space-time generated by some of the universe’s most furious and energetic phenomena. Einstein had predicted the existence of gravitational waves in 1916 in his general theory of relativity.
According to his mathematics and equations, Einstein predicted that massive accelerating objects, such as neutron stars or black holes orbiting each other would disrupt space-time in such a way that ‘waves’ of undulating space-time would radiate in all directions away from the source. These cosmic waves would move at the speed of light, providing information about their origin as well as hints about the nature of gravity.
Cataclysmic events such as collision of black holes, supernovae (massive stars exploding at the end of their life), and collision of neutron stars generate some of the strongest gravitational waves. Other waves are thought to be generated by the rotation of neutron stars that aren’t perfect spheres, as well as the remnants of gravitational radiation created by the Big Bang.
The First Evidence
Though the existence of gravitational waves was predicted in 1916, it wasn’t until 1974, that the first evidence of their existence could be discovered. In that year, two astronomers at Puerto Rico’s Arecibo Radio Observatory discovered a binary pulsar, the kind of system that general relativity predicted should emit gravitational waves.
Astronomers began tracking how the stars’ orbits shifted over time, realizing that the observations could be used to verify Einstein’s audacious prediction. After eight years of observation, they determined that the stars were moving closer to one other, precisely at the pace predicted by general relativity, as if they were radiating gravitational waves.
Since then, many scientists analyzed pulsar radio-emissions (pulsars are neutron stars that emit beams of radio waves) and have discovered similar effects, supporting the presence of gravitational waves. However,these confirmations have always been received in an indirect or mathematical form, rather than direct contact.
The Major Breakthrough
After more than four decades of research and development,in late summer of 2015, the LIGO detectors were finally sensitive enough to detect astrophysical sources. On September 14, 2015, fate once again favoured physicists: nearly as soon as the detectors were turned on, they generated a signal powerful enough to be identified as an unmistakable source.
Scientists discovered gravitational waves for the first time in 2015. They utilized the LIGO(Laser Interferometer Gravitational-Wave Observatory) equipment, which is extremely sensitive. These first gravitational waves were created when two black holes collided sometime around 1.3 billion years ago. However, the waves did not make it to Earth until 2015!
The detection of the first gravitational waves was a very important event in science. Prior to this, almost everything we knew about the universe was by studying light waves. We now had a new way of learning about the universe: studying the waves of gravity.
How Are Gravitational Waves Detected?
A gravitational wave squeezes and stretches space as it passes through Earth. This squeezing and stretching can be detected by LIGO. Each LIGO observatory has two arms each measuring more than 2 miles (4 kilometres) in length. The length of the arms changes slightly when a gravitational wave passes by. To detect these microscopic changes, the observatory utilizes lasers, mirrors, and highly sensitive equipment.
Why Detect Them?
To explore the Universe, scientists have traditionally depended almost entirely on electromagnetic (EM) radiation (visible light, X-rays, radio waves, microwaves,etc.). Some are also attempting to use subatomic particles known as neutrinos. Each of these ‘messengers’ of information offers scientists a unique but complementary perspective about the Universe.
Gravitational waves, on the other hand, are completely unrelated to EM radiation. They differ from light in the same way that hearing differs from vision.
Imagine that you only had vision and no hearing. Simply studying the light from objects would reveal a lot of things to you about the surroundings. Then, one day, someone creates a device known as an ear, which senses vibrations in air or water that you were previously unaware of. This is the way in which Gravitational waves have opened a new ‘window’ to look at our universe.
Since the interaction between gravitational waves and matter is very minimal (unlike electromagnetic radiation, which may be absorbed, reflected, refracted, or bent), they travel through the Universe almost unhindered, enabling us to see the gravitational-wave Universe clearly.
LIGO-India
The Laser Interferometer Gravitational-wave Observatory (LIGO) project operates three gravitational-wave(GW) detectors. LIGO-India is a projected advanced gravitational-wave observatory that will be a part of the global LIGO network and would be located in India. The Indian government has decided to give the project the in-principle approval.
The LIGO-India project is envisioned as an international collaboration between the LIGO Laboratory and three leading institutions in the IndIGO consortium : Institute of Plasma Research (IPR) Gandhinagar, Inter University Centre for Astronomy and Astrophysics (IUCAA) Pune, and Raja Ramanna Centre for Advanced Technology (RRCAT) Indore.
The LIGO lab would provide the complete design as well as all of the essential detector components. Indian scientists would provide the infrastructure for the detector’s installation and commissioning at a suitable location in India.
Gravitational waves, according to researchers, could reveal even more information about our universe. It’s like seeing the universe through fresh eyes- the amount of information that’s going to be there would be incredible. LIGO has lifted a veil of mystery from the Universe, paving the way for fascinating new studies of physics, astronomy, and astrophysics.
The proposed LIGO-India initiative will assist the Indian scientific community to become an important player in the GW astronomy research frontier. LIGO-India, a key effort, would further encourage India’s frontier research and development programmes.
