By Udita Shukla
Gravitational waves were first hypothesised (by Einstein) back in 1916, as part of his General Theory of Relativity. The most common analogy is to imagine the space-time continuum as a pool of water which is ruffled by a stone, and subsequently, gives rise to ripples on its surface.
Understanding the gravitational waves
Gravitational waves are ripples in the fabric of space-time. They are created when massive objects move with ever increasing acceleration, and hence, disrupt the apparent stillness and curvature (of spacetime) in their vicinity. This disturbance, then, spreads and travels outward into the universe in the form of ‘waves’ at the speed of light.
Surprisingly, gravitational waves are produced every time the most commonplace of objects move or fiddle around – for example, cars, aeroplanes, humans, etc. However, these are so small in magnitude and wavelength that they have till now escaped the eye of detection. Detection of disturbance in spacetime of such an infinitesimally small magnitude demands unmanageably high rotation speeds of machine components.
Identification of waves by LIGO
Therefore, in order to identify and study these elusive messengers of nature, scientists look for gravitational waves produced in deep ‘corners’ of the cosmos and have set up facilities to capture their transient passage through the earth. LIGO (Laser Interferometer Gravitational-Wave Observatory) is one such experimental observatory, based in the United States.
The first near confirmation of the existence of gravitational waves came from the variation in the arrival times of radio pulses emitted by PSR1913+16 (a pair of neutron stars orbiting each other, 21,000 light years away from earth). The reported difference in times exactly dovetailed with that predicted by general relativity if they were radiating gravitational waves. Finally, the first direct detection occurred in September 2015, by the LIGO team.
The new wave discovery
On August 14, 2017, the scientific community went agog over a fourth gravitational wave as reported by an Italy-based equipment. The discovery is widely expected to fetch the Nobel Prize in Physics, which is slated to be unveiled next week. The ripple is being accorded to the collision of two black holes 1.8 billion light-years away from the earth. The masses of the colliding cosmic objects is estimated to be thirty-one and twenty-five times the mass of the Sun.
According to the international scientists at the Virgo detector, located at the European Gravitational Observatory (EGO) in Cascina, near Pisa, Italy, “The newly produced spinning black hole has about 53 times the mass of our Sun. While this new event is of astrophysical relevance, its detection comes with an additional asset: This is the first significant gravitational wave signal recorded by the Virgo detector.”
Origin of the waves
Specifically, gravitational waves are born when two neutron stars or black holes (some of the most compact and densest astrophysical objects) orbit or violently merge with each other, a dying star explodes into a supernova, or most intriguingly at the birth of the universe itself.
Consequently, these waves allow us a window into the shrouded past and farthest reaches of the cosmos. They carry within them detailed information about the cataclysmic events that generated them – an active and evolving area of cutting-edge research in Physics, Astronomy and Astrophysics.
Two sides of the coin
Astrophysicists have historically depended on the electromagnetic radiation captured from space in order to explore and probe cosmic mysteries. However, the received radiation (from both intra and inter-galactic regions) is often adulterated with the imprints of expanding the universe, interstellar reddening, absorption by intervening dust particles and other miscellaneous factors. Thus, they are unable to unravel a true, complete picture of the source of radiation.
On the other hand, gravitational waves are an entirely different phenomenon which carries details about events and objects that do not emit measurable radiation – for example, black holes emit little or no radiation but the gravitational force emitted by them make them ‘visible’ to us in the dark sea of hidden cosmic signals.
Scientific achievements with discoveries
Additionally, the interaction of gravitational waves with matter is extremely feeble (unlike electromagnetic radiation), and hence, furnish a clear landscape of what’s out there.
The discovery of gravitational waves is easily among the most radical and era-defining scientific achievements of the century, which bears profound implications for our understanding of the origins of the universe, its evolution, working and perhaps, its future. As aptly worded by an MIT researcher, “It is remarkable that humans can put together a story, and test it, for such strange and extreme events that took place billions of years ago and billions of light-years distant from us.”
Featured Image Source: Visual Hunt
Photo credit: NASA Goddard Photo and Video via Visual hunt / CC BY
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