ARE WE LISTENING? Physics and Technology of Gravitational Wave Detectors

Gravitational waves are emitted by accelerating mass distributions, analogous to electromagnetic waves emitted by accelerating charges. However, there are unique and important differences in the characteristics of these waves. They are known to be emitted by binary neutron stars and other massive astrophysical systems, but their strength when they reach the earth is tiny because of the thousands and millions of light years that separate us from these sources.  Gravity is very weak compared to electromagnetism and therefore, making or sensing these waves is an extremely difficult task. Indeed, it is so difficult a task that nobody has detected gravitational waves yet in spite of an array of ‘detectors’ operating around the world for almost a decade now. However, continuous improvement of the sensitivity of these detectors is expected to yield the first detection within the next few years and then usher in the new field of gravitational wave astronomy.
	The advanced terrestrial detectors are sophisticated optical interferometers, kilometers in physical size, and thousands of kilometers in effective size. They represent the ultimate in optical instrumentation and sensitivity of metrology, attempting to measure motion that is less than a billionth of the atomic size. I will present an overview of the physical principles of gravitational wave detectors and explain the technologies that go into their construction and operation. I will present a glimpse of the expectations for the future, including plans for developing experimental gravitational wave research and astronomy in India.