Lunar Gravitational-Wave Detectors to Probe Spacetime’s Faintest Signals

Context:

• Scientists are proposing a moon-based gravitational-wave observatory to detect extremely faint ripples in spacetime that remain inaccessible from Earth.

• The proposed Laser Interferometer Lunar Antenna (LILA) aims to explore the sub-hertz (decihertz) gravitational-wave spectrum, opening a new observational window into the universe.

• This initiative complements existing and planned Earth- and space-based detectors, marking a major leap in gravitational-wave astronomy.

Key Highlights:

What is LILA (Laser Interferometer Lunar Antenna)?

• A proposed gravitational-wave detector to be installed on the Moon.

• Designed to detect sub-hertz / decihertz frequency gravitational waves, which are currently poorly explored.

• LILA Pioneer, the first phase, could be built within this decade using lunar landers from:

  • Blue Origin

  • Intuitive Machines

  • India’s Chandrayaan programme

Why the Moon?

• Permanently shadowed polar regions offer:

  • Extremely low seismic noise

  • Natural vacuum, ideal for laser interferometry

  • Thermal stability, improving detector sensitivity

• Absence of atmospheric and human-made disturbances enhances signal clarity.

Gravitational-Wave Detection Landscape

• LIGO (ground-based):

  • Sensitive to 100–1,000 hertz frequencies.

  • Detected gravitational waves for the first time in 2015.

• LISA (space-based, 2030s):

  • Will observe waves in the 0.1 millihertz to 0.1 hertz range.

• LIGO-India:

  • An advanced observatory under construction in Hingoli district, Maharashtra.

  • Expected completion: 2030.

• Gap Identified:

  • The decihertz band (0.1–10 hertz) lies between LIGO and LISA sensitivity ranges and remains largely unexplored.

Scientific Importance of the Decihertz Band

• Enables study of:

  • Intermediate-mass black holes, thought to be precursors of supermassive black holes.

  • Early inspiral phases of compact binaries.

• Enhances understanding of cosmic evolution and structure formation.

• Proposed parallel detectors:

  • DECIGO (Japan)

  • TianGo (U.S.-led)

  • LGWA (Lunar Gravitational-wave Antenna)

Scientific Principles Involved

• Gravitational Waves:

  • Predicted by Albert Einstein’s General Theory of Relativity.

  • Generated by accelerating massive objects such as black hole mergers.

• Interferometry:

  • Laser beams measure minuscule changes in distance caused by spacetime distortions.

• Pulsars:

  • Monitoring pulsar timing may allow scientists to use the entire Milky Way as a gravitational-wave detector.

UPSC Relevance (GS-wise):

• GS Paper 3 – Science & Technology

  • Prelims:

    • Gravitational waves, interferometers, spacetime, pulsars.

    • LIGO, LISA, Chandrayaan, LIGO-India.

  • Mains:

    • Importance of big science missions in advancing fundamental physics.

    • India’s role in global space and astrophysics research.

    • Technological challenges and strategic significance of lunar exploration.