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UPSC » Daily News Analysis ‘Gravitational Waves: From Earth to the Moon’ : 30 September

Daily News Analysis ‘Gravitational Waves: From Earth to the Moon’ : 30 September

Table of Content

What are Gravitational Waves?

  • Gravitational waves are ripples in the fabric of spacetime caused by massive cosmic events like merging black holes or colliding neutron stars.
  • They travel at the speed of light, but are extremely weak when they reach Earth.
  • First directly detected in 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) from two colliding black holes 1.3 billion light-years away.

How Do We Detect Them?

  • Special instruments called interferometers use laser beams and mirrors to measure tiny distortions in spacetime.
  • Example: LIGO in the United States (US) has two L-shaped detectors, each with 4-kilometre-long arms.
  • Albert Einstein predicted it in his General Theory of Relativity (1916), which was confirmed a century later.

Limitations on Earth:

  • Ground-based detectors such as LIGO (US), Virgo (Italy), KAGRA (Japan), and GEO600 (Germany) detect waves only in the 100–1,000 Hertz frequency range.
  • Lower-frequency gravitational waves cannot be detected due to Earth’s seismic noise and vibrations.

Moon-Based Detector: LILA

  • The Laser Interferometer Lunar Antenna (LILA) is planned for the lunar surface by Vanderbilt Lunar Labs (US).
  • Advantages:
    • Very low seismic noise.
    • Natural vacuum conditions.
    • Permanently shadowed polar regions are ideal for observation.
  • Two phases:
    • LILA Pioneer (this decade) using lunar landers like Chandrayaan and US private landers (Blue Origin, Intuitive Machines).
    • LILA Horizon (future phase) requires astronauts to deploy.

Global Projects:

  • Laser Interferometer Space Antenna (LISA): European Space Agency (ESA) mission in the 2030s, using three satellites to detect low-frequency gravitational waves.
  • DECi-hertz Interferometer Gravitational Wave Observatory (DECIGO): Japan-led mission targeting the decihertz range.
  • TianGo: A United States-led initiative for space-based detection.
  • Lunar Gravitational-wave Antenna (LGWA): Another proposed lunar-based detector.
  • Square Kilometre Array (SKA): World’s largest radio telescope (Australia & South Africa) scanning nanohertz frequencies.

India’s Contribution:

  • Indian Initiative in Gravitational-wave Observations (IndIGO) has a roadmap to build LIGO-India in Hingoli district, Maharashtra, by 2030.
  • It will be part of the global LIGO network and boost India’s capacity in gravitational wave astronomy.

Why It Matters?

  • Opens a new window to study black holes, neutron stars, and the early universe.
  • The decihertz frequency range can help detect intermediate-mass black holes, which may be the building blocks of supermassive black holes.
  • Monitoring pulsars can potentially turn the entire Milky Way galaxy into a natural gravitational wave detector.

Why in News?

    • Scientists are planning to set up the Laser Interferometer Lunar Antenna (LILA) on the moon’s surface to detect low-frequency gravitational waves that Earth-based detectors cannot capture.