Q30. Why are very large astronomical distances expressed in light-years?
[UPSC CSE Prelims 2021, GS Paper I]
A. Distances between stars never change
B. Gravitation between stars never changes
C. Light travels only in straight lines
D. The speed of light in vacuum is constant
Answer: D. The speed of light in vacuum is constant
Explanation: A light-year is the distance light travels through vacuum in one year, approximately 9.46 trillion kilometres. The constant speed of light provides a convenient physical reference for describing enormous distances between stars and galaxies.
Q29. Which is regarded as India’s first communication satellite?
[RRB NTPC 2020, General Awareness]
A. Rohini
B. Mars Orbiter Mission
C. Aryabhata
D. APPLE
Answer: D. APPLE
Explanation: APPLE, the Ariane Passenger Payload Experiment, was an experimental Indian geostationary communications satellite launched in June 1981. It demonstrated communications technology and helped lay groundwork for the later INSAT operational satellite system.
Q28. What was the significance of observing the merger of two distant giant black holes?
[UPSC CSE Prelims 2019, GS Paper I]
A. Discovery of Higgs bosons
B. Detection of gravitational waves
C. Confirmation of wormhole travel
D. Proof of a naked singularity
Answer: B. Detection of gravitational waves
Explanation: The black-hole merger produced gravitational waves, ripples in spacetime predicted by Einstein’s relativity. The LIGO collaboration made the first direct detection in 2015, opening a new way of observing violent cosmic events.
Q27. About Indian launch vehicles:
1. PSLV is useful for Earth-resource satellites and GSLV for communications;
2. PSLV satellites appear fixed in the sky; 3 GSLV Mk III has four stages.
Which is correct?
[UPSC CSE Prelims 2018, GS Paper I]
A. 1 only
B. 2 and 3 only
C. 1 and 2 only
D. 3 only
Answer: A. 1 only
Explanation: PSLV commonly delivers Earth-observation spacecraft to polar or sun-synchronous orbits, while GSLV places heavier communications payloads into transfer orbits. PSLV satellites do not generally appear stationary, and LVM3, formerly GSLV Mk III, has three principal stages.
Q26. Which scientist was appointed Chairman of ISRO in January 2018?
[RRB Group D, 10 December 2018 (Shift 1)]
A. A. P. J. Abdul Kalam
B. A. S. Kiran Kumar
C. K. Sivan
D. Rakesh Sharma
Answer: C. K. Sivan
Explanation: K. Sivan took charge as ISRO Chairman in January 2018, succeeding A. S. Kiran Kumar. A launch-vehicle specialist, Sivan subsequently led the organisation during important programmes including the Chandrayaan-2 lunar mission and preparation for human spaceflight.
Q25. The terms event horizon, singularity, string theory and Standard Model are associated primarily with what?
[UPSC CSE Prelims 2017, GS Paper I]
A. Understanding the universe
B. Solar and lunar eclipses only
C. Placing satellites in Earth orbit
D. Evolution of living organisms
Answer: A. Understanding the universe
Explanation: Event horizons and singularities arise in black-hole physics; string theory explores fundamental physical interactions; and the Standard Model explains elementary particles. These concepts belong broadly to modern theoretical physics and cosmology.
Q24. What is the objective of the evolved Laser Interferometer Space Antenna (eLISA) project?
[UPSC CSE Prelims 2017, GS Paper I]
A. Detect neutrinos
B. Detect gravitational waves
C. Test missile-defence systems
D. Study solar flare impacts on telecom
Answer: B. Detect gravitational waves
Explanation: eLISA is a proposed space-based gravitational-wave observatory concept involving widely separated spacecraft linked through precise laser measurements. It seeks to detect low-frequency spacetime ripples generated by massive astronomical events.
Q23. For AstroSat, assess
1. only India besides USA and Russia has such an observatory;
2. it weighs 2,000 kg and orbits at 1,650 km.
Which is correct?
[UPSC CSE Prelims 2016, GS Paper I]
A. 1 only
B. 2 only
C. Both 1 and 2
D. Neither 1 nor 2
Answer: D. Neither 1 nor 2
Explanation: AstroSat is an Indian multiband astronomy observatory launched in 2015 into an orbit around 650 km altitude, with launch mass approximately 1,515 kg. Other countries and organisations also operated space observatories, so both assertions are incorrect.
Q22. Mangalyaan:
1. is the Mars Orbiter Mission,
2. made India second after USA to orbit Mars,
3. succeeded on India’s first Mars-orbit attempt.
Which statements are correct?
[UPSC CSE Prelims 2016, GS Paper I]
A. 1 only
B. 2 and 3 only
C. 1 and 3 only
D. 1, 2 and 3
Answer: C. 1 and 3 only
Explanation: Mangalyaan is the Mars Orbiter Mission and successfully entered Mars orbit on its maiden attempt in September 2014. India was not the second country or agency overall to orbit Mars; earlier successes included Soviet, American and European missions.
Q21. Who is known as the father of India’s space programme?
[RRB NTPC 2016, General Awareness]
A. A. P. J. Abdul Kalam
B. Vikram A. Sarabhai
C. K. Kasturirangan
D. Satish Dhawan
Answer: B. Vikram A. Sarabhai
Explanation: Vikram Sarabhai championed space technology for India’s developmental needs, helped found INCOSPAR and shaped ISRO. His leadership established the institutional direction for scientific rockets, satellite communications and remote sensing.
