Why in the News?

Scientists are planning the Laser Interferometer Lunar Antenna (LILA) Project on the Moon to bypass seismic noise, atmosphere, and frequency limits faced by Earth-based detectors like Laser Interferometer Gravitational-wave Observatory (LIGO).

What are Gravitational Waves?

• Overview: Gravitational waves are ripples in the spacetime continuum created when massive objects such as black holes or neutron stars collide.
• Speed & Effect: They travel at the speed of light, subtly stretching and compressing spacetime. On small scales, effects are extremely weak (e.g., Earth–Moon distance altered by less than an atom’s diameter).
• Prediction: Proposed by Albert Einstein (1916) in his General Theory of Relativity.
• First Detection: In 2015, LIGO recorded the first gravitational waves from two colliding black holes 1.3 billion light-years away, confirming their existence.

Detection on Earth and Challenges:

• Ground Observatories: LIGO (USA), Virgo (Italy), KAGRA (Japan), GEO600 (Germany) use laser interferometers to detect minuscule delays in light caused by waves.
• Working of LIGO: Two L-shaped detectors (Louisiana, Washington), each with 4 km arms; differences in reflections signal gravitational waves.
• Detection Range: Sensitive to events up to 7 billion light years away; frequency range ~100–1,000 Hz.
• Challenges: Seismic noise, atmosphere, and human activity mask weaker signals.
• Future Space Missions:
  • LISA (Laser Interferometer Space Antenna, 2030s): Three satellites in triangular formation, sensitive to 0.1 millihertz–0.1 hertz.
  • SKA (Square Kilometre Array, Australia & South Africa): Monitors pulsars for nanohertz waves.
  • Decihertz Gap: Frequencies 0.1–10 Hz remain unexplored, which LILA aims to study.

About Laser Interferometer Lunar Antenna (LILA) Project

• Overview: Proposed by Vanderbilt Lunar Labs, USA, to build a gravitational-wave detector on the Moon.
• Ideal Conditions: The Moon’s polar shadow zones provide ultra-low seismic activity, natural vacuum, and no atmospheric or radio interference.
• Focus: Sub-hertz gravitational waves, vital for studying intermediate-mass black holes and the early universe.
• Phases:
  • LILA Pioneer: Can be deployed within this decade using American lunar landers (Blue Origin, Intuitive Machines) and possibly India’s Chandrayaan programme.
  • LILA Horizon: Advanced phase requiring astronauts for setup.
• Cosmic Symphony Analogy:
  • SKA: Captures low-frequency “bass notes.”
  • LIGO (and future LIGO-India): Detects high-pitched bursts from stellar collisions.
  • LILA: Covers missing middle frequencies, completing the “cosmic raag.”
• Historical Note: Since Apollo, retro-reflectors on the Moon track Earth–Moon distance. Some scientists suggest the Earth–Moon system itself acts as a natural detector.

Significance:

• Scientific Advancement: Opens the decihertz frontier, inaccessible so far.
• Global Collaboration: Complements LIGO-India (IndIGO project), operational by 2030.
• Research Potential: Helps study intermediate-mass black holes, cosmic mergers, and universe origins.
• Lunar Astronomy: Marks the start of using the Moon as a laboratory for space science.
• Holistic Coverage: With LISA, SKA, and Earth detectors, LILA would map the entire gravitational-wave spectrum, giving a complete picture of the universe.

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