Question 35 from UPSC CSE 2017 - Current
Affairs

Question

What is the purpose of 'evolved Laser Interferometer Space Antenna (eLISA)' project?

Accepted Answer

Correct Option: B. To detect gravitational waves

Strategy: - Focus on the project name: "Laser Interferometer Space Antenna."
- Identify "Laser Interferometer" as a key scientific instrument.
- Associate this technology with the detection of gravitational waves, similar to the LIGO experiment.
- Distinguish from other detection methods: neutrinos (underground detectors), missile defense (radar), and solar flares (telescopes).

Key Info: ## evolved Laser Interferometer Space Antenna (eLISA) / LISA
- The Laser Interferometer Space Antenna (LISA), formerly known as eLISA, is a space mission concept led by the European Space Agency (ESA) with contributions from NASA.
- Its primary purpose is to detect and accurately measure gravitational waves--ripples in the fabric of spacetime--from astronomical sources.
- The mission will consist of three spacecraft flying in a triangular formation, with each side of the triangle being approximately 2.5 million kilometers long. Lasers will be continuously beamed between the spacecraft.
- A passing gravitational wave will cause minuscule changes in the distance between the spacecraft. The laser interferometer will be sensitive enough to detect these changes, which are smaller than the diameter of an atom.
- Unlike ground-based detectors like LIGO, a space-based observatory like LISA can detect much lower-frequency gravitational waves. These are expected from sources such as the merger of supermassive black holes at the centers of galaxies, which are undetectable from Earth due to seismic and other terrestrial noise.

## Gravitational Waves
- Gravitational waves are disturbances in spacetime, generated by accelerated masses, that propagate as waves outward from their source at the speed of light. They were first predicted by Albert Einstein in 1916 on the basis of his theory of general relativity.
- The first direct observation of gravitational waves was made in September 2015 by the Laser Interferometer Gravitational-Wave Observatory (LIGO) and the Virgo collaboration, from the merger of two black holes. This discovery was awarded the Nobel Prize in Physics in 2017.
- Detecting gravitational waves opens a new window to the universe, allowing for the study of phenomena like black hole mergers, neutron star collisions, and potentially the Big Bang itself, which are invisible through traditional electromagnetic telescopes.

## Other Options Explained
- **Neutrinos:** These are subatomic particles with no electric charge and very little mass. They are detected using large-scale experiments, often located deep underground or underwater to shield from background radiation, such as the IceCube Neutrino Observatory in Antarctica or the Super-Kamiokande in Japan.
- **Missile Defence System:** These systems use a network of radar, satellites, and interceptor missiles to track and destroy incoming ballistic missiles. The technology involved is fundamentally different from laser interferometry for astronomical purposes.
- **Solar Flares:** These are intense bursts of radiation from the Sun's atmosphere. They are studied using a variety of space-based and ground-based telescopes that observe the Sun across the electromagnetic spectrum, such as NASA's Solar Dynamics Observatory (SDO).

Answer

Option A: To detect neutrinos

Answer

Option C: To detect the effectiveness of missile defence system

Answer

Option D: To study the effect of solar flares on our communication systems