Current Affairs for UPSC: 3 October 2025

Exploring Gravitational Waves: From Earth to the Moon and Beyond

Hello everyone, and welcome once again to our page.

In this week’s Science Editorial, we dive deep into a fascinating scientific development — the detection of gravitational waves and the future experiments that aim to expand our understanding of the universe. If you have studied this topic before, this will serve as a thorough revision. And if not, you’re in for an exciting journey through space-time.

Understanding the Cosmic Symphony

Think of the universe like a grand orchestra. When you listen to a song, you hear different instruments playing together — the piano, guitar, drums, and vocals. Their blend creates a melody. Similarly, the universe is constantly “playing” through a mix of signals: electromagnetic waves, X-rays, gamma rays, gravitational waves, and more. These different frequencies together form the music of the cosmos.

Among these cosmic notes, scientists focus on a particularly special “beat” — gravitational waves. These are ripples in the fabric of space-time, produced when massive celestial objects like black holes or neutron stars move, collide, or merge. Imagine two black holes spiraling around each other; their movement distorts space-time itself, creating waves that travel across the universe. When these waves reach Earth, they cause minuscule stretching and squeezing — so tiny that it’s on the scale of a single proton.

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Einstein’s Prediction and LIGO’s Achievement

The concept of gravitational waves was first introduced by Albert Einstein in his General Theory of Relativity. For decades, it remained a theoretical idea. Even Einstein himself doubted whether these waves could ever be detected experimentally. But in 2015, humanity achieved a remarkable feat: gravitational waves were observed for the first time through the LIGO project in the USA.

LIGO (Laser Interferometer Gravitational-Wave Observatory) consists of two long, perpendicular arms — each 4 km in length. A laser beam is split between the two arms, reflected by mirrors, and then recombined. Normally, the beams cancel each other out. But if a gravitational wave passes through, it slightly alters the length of the arms, disrupting the interference pattern. This allows LIGO to detect frequency ranges between 10 to 1000 Hz.

To enhance accuracy, several sister facilities were built — in Japan, Germany, Italy, and even LIGO India (under construction in Hingoli district, Maharashtra, expected by 2030). However, ground-based detectors like LIGO have limitations. They can only pick up waves up to certain distances (around 7 billion light-years) and frequencies.

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Beyond Earth: The LISA Mission

To bridge these gaps, scientists turned to space. The LISA mission (Laser Interferometer Space Antenna), a joint project by the European Space Agency (ESA) and NASA, aims to detect gravitational waves at lower frequencies (0.1 to 0.001 Hz) that ground-based detectors cannot catch.

LISA involves placing three satellites in a triangular formation, about 1–3 million km apart, orbiting the Sun alongside Earth. By using laser interferometry between these satellites, scientists can study gravitational waves in a new frequency spectrum — providing insights into cosmic events billions of years old.

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The Lunar Leap: Project LILA

Despite the advancements of LIGO and LISA, there’s still a frequency gap between 0.1 and 10 Hz. To cover this, scientists are now planning a lunar-based detector, named LILA (Laser Interferometer Lunar Antenna).

LILA will consist of two stages:

LILA Pioneer, a smaller 3–5 km interferometer to test technology.

LILA Horizon, a full-scale 40 km triangular array on the Moon’s surface.

By placing detectors on the Moon, researchers can avoid Earth’s seismic noise and achieve unprecedented sensitivity. LILA aims to study mid-frequency gravitational waves, bridging the gap between LIGO and LISA.

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Detecting Gravitational Waves Through Pulsars

At even lower frequencies — the decihertz and nanohertz ranges — scientists rely on Pulsar Timing Arrays. Pulsars are rapidly rotating neutron stars that emit precise beams of radiation. By observing the timing variations between pulsars and Earth, researchers can detect incredibly subtle gravitational waves affecting vast cosmic distances.

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A Complete Spectrum of Cosmic Detection

With these four methods — LIGO (ground-based), LISA (space-based), LILA (Moon-based), and Pulsar Timing Arrays (natural detectors) — scientists are building a comprehensive framework to study gravitational waves across all frequency ranges. This multi-layered detection network will unlock mysteries about the birth of the universe, the formation of black holes, the nature of neutron stars, and cosmic events from the earliest epochs.

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A Parallel Development: Detecting Pathogens Early

Interestingly, in a completely different field, India’s ICMR (Indian Council of Medical Research) has taken significant steps in pre-diagnosing harmful pathogens — viruses, bacteria, and other microorganisms that can harm humans. Just as gravitational wave detectors identify invisible ripples in space-time, these medical advancements aim to detect disease-causing agents early, helping to prevent outbreaks and protect public health.

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Conclusion

From observing cosmic ripples billions of light-years away to detecting invisible pathogens within our bodies, science is constantly pushing the boundaries of the unseen. Projects like LIGO, LISA, and LILA represent humanity’s quest to listen to the universe’s grand symphony in its entirety. As technology evolves, our understanding of space-time, matter, and life itself grows ever deeper.

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