## One Hundred Years of Gravitational Waves

We all are familiar with the force of gravity. But, where do the gravitational waves fit in the picture?

On September 14, 2015 at 5:51 am ET, Laser Interferometer Gravitational-wave Observatory (LIGO), detected the gravitational waves for the first time. This discovery confirmed one of the major predictions of Einstein’s general theory of relativity, which will definitely pave the way for a new era of observational astrophysics.

The general theory of relativity, published a hundred years ago, describes spacetime as a single dynamic entity and predicts the bizarre phenomena, like black holes and gravitational waves. In other words, Einstein discarded Newtonian notion of the independent nature of space and time and argued that space is not a mere canvas upon which all the events unfold by the mysterious force of gravity, as envisioned by Newton.

The general theory of relativity also predicts that a strong gravitational field, similar to that of the sun, “warps” spacetime and even light is deflected by gravity. In 1919, the British astrophysicist Arthur Eddington measured the bending of star light around the sun during a solar eclipse as predicted by the general theory of relativity — it was a clear vindication of the validity of this theory. There have been other verifications of general theory of relativity since the days of Eddington.

In fact, the seemingly abstract concept of warping of spacetime produces noticeable effects, such as time dilation that has been measured precisely. The general theory of relativity predicts that the warping spacetime will be larger in stronger gravitational fields. Apparently, clocks on the ground (closer to earth) will run more slowly than the clocks, say, aboard the GPS satellites orbiting the earth.

Einstein’s equations calculate this time difference to be about 38 —> Read More