Key Terms & Concepts — UPSC Mains
Gravitational Waves
"Ripples in the fabric of spacetime produced by violent cosmic events such as merging black holes, predicted by Einstein and first detected in 2015"
Gravitational waves are distortions in spacetime that propagate at the speed of light, generated when massive objects accelerate, most dramatically during the merger of black holes or neutron stars. Predicted by Albert Einstein in 1916 from his General Theory of Relativity, they were directly detected for the first time on 14 September 2015 by the LIGO observatories in the United States. Their detection opened the field of gravitational-wave astronomy, letting scientists observe cosmic events that emit no light. India is building LIGO-India, which broke ground in April 2026, to join the global detector network.
Relevant for GS3 (frontier physics and astronomy, big science, international collaboration). Gravitational-wave astronomy enables multi-messenger observation of the universe and tests fundamental physics. LIGO-India, which broke ground on 23 April 2026 in Maharashtra, is a landmark for Indian science and a strong Prelims and Mains topic in 2026.
- 1 Predicted by Einstein in 1916 from General Relativity; first directly detected on 14 September 2015 (event GW150914)
- 2 Detected using laser interferometers (LIGO) that measure spacetime stretching smaller than a proton's width
- 3 The 2017 Nobel Prize in Physics honoured the LIGO founders for the first detection
- 4 LIGO-India broke ground on 23 April 2026 at Aundha, Hingoli district, Maharashtra; expected to operate in the early 2030s
- 5 By mid-2026 the global network (LIGO, Virgo, KAGRA) had confirmed more than 200 detections
- 6 Enables multi-messenger astronomy, combining gravitational waves with light and neutrinos
- 7 Sources include merging black holes, neutron stars and, potentially, the early universe
On 23 April 2026 LIGO-India broke ground at Aundha in Maharashtra's Hingoli district, making India a full partner in a global gravitational-wave network that has already confirmed more than 200 detections since the 2015 discovery.
