`We are enriching our knowledge of the cosmos'
We now have a different channel to understand the universe. Gravitational waves (GWs) are not electromagnetic (EM) waves, so we cannot "see" them though our eyes or with telescopes. But this is the first time ever we have seen black holes of this mass (about 30 times heavier than the sun), and we have seen them collide.
We were "blind" to certain aspects of the universe, but now we will be able to study them as LIGO detects more such events. It is also the only way we can test Einstein's general theory of relativity in the "strong gravity" regime. Detection of GWs was one of the final remaining evidence of Einstein's theory of relativity. These waves generate a "strain"—a fractional change in length of anything that they travel through. Measuring this small change in length required one of the most sensitive instruments ever built with the best lasers, vacuum and other technical apparatus.
During the early stages of LIGO, we demonstrated technology, learnt lessons and adapted them to the next generation of instruments. After LIGO's first run, we implemented several tweaks at all levels—from hardware upgrades to better signal processing—to make detections possible.
The detection of GWs is a long-awaited confirmation of Einstein's predictions. However, it does not deal with, say, the quantum nature of matter. This discovery improves our understanding of gravity, but does not give us a grand unified theory just yet.
Further data from the GW detectors will tell us more about black holes, certain types of binary neutron stars and neutron star binaries. This will further our understanding about the formation and death of stars, and enrich our knowledge of our cosmic neighbourhood.
(As told to DownToEarth) VARUN BHALERAO Inter-University Centre for Astronomy and Astrophysics (IUCAA), Pune. He is working with the LIGO project