A new tool to study Universe: Gravitational Waves

Jyoti Kapil

University of Delhi

Gravitational waves have been detected directly for the first time ever in history, produced by the collision of two massive black holes almost 1.3 billion years ago; confirming the predictions made by Albert Einstein about the existence of these waves. Till now we have had only indirect evidence of their existence; but they were finally detected by the Laser Interferometer Gravitational waves Observatory (LIGO) in United States, revolutionizing the world of astronomical exploration. Albert Einstein first predicted the existence of gravitational waves in his paper on “General theory of Relativity” in 1916. He unified the concept of space and time into a single 4-dimensional space-time continuum. He proposed that gravity was not an instantaneous force as proposed by Newton; it was an effect produced due to the warping of space-time fabric by the presence of heavy objects like stars and planets. And any object with mass accelerating on the surface of this fabric produces ripples in the space-time fabric, stretching and compressing it and travelling as “gravitational waves”. These waves travel with the speed of light and unlike light or any electromagnetic wave can travel through matter unaffected; making it possible to explore those regions of space which are opaque to light or electromagnetic waves. The laser Interferometer used in LIGO is world’s largest and most sensitive equipment, capable of detecting a change in length of the order of 10,000 times smaller than the size of a proton. The interference pattern produced in the interferometer is dependent on the distance travelled by the laser beam, so any change in the path length of the laser beam in one arm of the interferometer relative to the other arm causes the interference pattern to change; the basic principle used for detection of signals from gravitational waves.