The first thing that comes to our mind about outer space is that it is pitch black and void, but it is not so. Outer space acts as a fabric of space-time. Imagine space as water, if we touch the water, ripples are created, in the same way, if massive accelerating objects such as neutron star or black holes orbiting each other, would disrupt space-time in such a way that waves of distorted space would radiate from the source, this was shown mathematically in Einstein’s general theory of relativity, which was predicted by him in 1916. So we can say that gravitational waves are distortions or ripples in the fabric of space-time caused by some of the most violent and energetic processes in the universe. Also, these waves would travel at the speed of light through the universe carrying with them information about their cataclysmic as well as invaluable clues to the nature of gravity itself.
After 1916 the proof of their existence didn’t arrive till 1974. In 1974 two astronomers discovered a binary pulsar i.e., two extremely dense and heavy stars in orbit around each other. This was exactly the type of system according to relativity should radiate gravitational waves. They started measuring how the period of the stars’ orbit changed over time. After 8 long years of observations, it was determined that the stars were getting closer to each other, as we know that everybody attracts each other, but the force with which it attracts differs, at precisely the rate predicted by relativity. This system has been monitored for over 40 years and the observed changes in the orbit agree so well with general relativity, there is no doubt that it is emitting gravitational waves. But these confirmations have been indirectly and mathematically and not through physical contact, until 14th September 2015. On this day first observation of gravitational waves was detected by LIGO(Laser Interferometer Gravitational-Wave Observatory)and Virgo collaborations, originating from a pair of black holes and was announced on 11th February 2016.
Amazingly, by the time these waves reach the detectors on earth the amount of space-time movement they will generate is thousands of times smaller than an atomic nucleus!