UPSC Prelims 2017 Q87: Science & Technology – Space Technology & Astronomy
What is the purpose of ‘evolved Laser Interferometer Space Antenna (eLISA)’ project?
- (a) To detect neutrinos
- (b) To detect gravitational waves
- (c) To detect the effectiveness of missile defence system
- (d) To study the effect of solar flares on our communication systems
Answer: (b) To detect gravitational waves
Explanation
evolved Laser Interferometer Space Antenna (eLISA)
eLISA is a planned European Space Agency mission to detect gravitational waves from space.
| Feature | Detail |
|---|---|
| Design | Three spacecraft flying in a triangle, linked by laser beams |
| Method | Laser interferometry: a passing wave changes the distance between spacecraft very slightly |
| Test mission | LISA Pathfinder, launched in December 2015 |
| Why in space | Much longer arms than ground detectors, so it can catch low-frequency waves |
Detectors compared:
| Detector | Detects | Where |
|---|---|---|
| eLISA (LISA) | Gravitational waves | Space |
| LIGO | Gravitational waves (first detection in 2015) | Ground, United States |
| IceCube, INO | Neutrinos | Antarctica; India (proposed) |
The bank earlier stored (a) as the key; the official key is (b).
Answer: (b) To detect gravitational waves.
Why each option is right or wrong
- (a) Incorrect. Neutrinos are detected by observatories such as IceCube, not by eLISA.
- (b) CORRECT. The purpose of the eLISA project is to detect gravitational waves from space.
- (c) Incorrect. eLISA is a science mission, not a test of any missile defence system.
- (d) Incorrect. Solar flares and their effect on communication systems are studied by solar missions.
Key point
eLISA: European Space Agency's space-based laser interferometer of three spacecraft to detect gravitational waves; LISA Pathfinder tested it in 2015.
Remember
eLISA = gravitational waves from space.
Common mistakes
- Confusing gravitational wave detectors with neutrino observatories.
- Reading 'Laser' and 'Antenna' as a missile defence or communication project.
- Thinking only LIGO on the ground can detect gravitational waves.
Exam tip
Laser Interferometer = gravitational waves, whether in LIGO or in eLISA.
Sources
- eLISA Consortium — The Gravitational Universe (white paper submitted to the European Space Agency, 2013)
- LIGO Scientific Collaboration — Observation of Gravitational Waves (February 2016)