Gravitational waves stretch space by a fraction smaller than an atom. Detecting that from three spacecraft flying a million kilometres apart was the whole point of eLISA.
🏛️ Must Know
What eLISA Is Actually For
- Detecting Gravitational Waves The purpose of the evolved Laser Interferometer Space Antenna, eLISA, is to detect gravitational waves.
- Not About Neutrinos or Missiles It is not designed to detect neutrinos, nor to test the effectiveness of missile defence systems. Those are entirely different fields.
- Not About Solar Flares eLISA also isn’t built to study how solar flares affect communication systems, another unrelated space-science topic.
Good to Know
📘 Good to Know
How eLISA Was Designed to Catch Gravitational Waves
- Three Spacecraft in Formation eLISA’s design uses three spacecraft flying in a triangular formation. Laser beams roughly a million kilometres long connect them.
- Measuring Tiny Distance Changes A passing gravitational wave would stretch and squeeze the distance between the spacecraft. That change is smaller than an atom, but the lasers can detect it.
- A Scaled-Down LISA eLISA was proposed as a lower-cost version of the original LISA mission. It shortened the arm length from 5 million km to about 1 million km.
📝 Previous Year Questions
UPSC CSP 2017 — What eLISA Is Actually For
- UPSC 2017 eLISA’s purpose is to detect gravitational waves, not neutrinos, missile-defence effectiveness, or solar-flare effects on communications. See UPSC CSP 2017 GS Paper I, Q87. View this question.
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Great to Know
🌟 Great to Know
Why Space-Based Detection Was Even Needed
- Ground Detectors Have Limits Earth-based detectors like LIGO can’t sense the lowest-frequency gravitational waves. Ground vibrations and arm-length limits get in the way.
- LISA Is Now Confirmed The full-scale LISA mission, which eLISA fed into, is a European Space Agency mission planned for launch around 2035.
- Connects to Other PYQ Facts This same gravitational-wave detection theme also underlies UPSC questions on LIGO and the 2015 first-ever detection of gravitational waves.
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