UPSC Prelims 2012 Q19: Science & Technology – Space Technology & Astronomy
Which of the following is/are cited by the scientists as evidence/evidences for the continued
expansion of universe?
1. Detection of microwaves in space
2. Observation of redshift phenomenon in space
3. Movement of asteroids in space
4. Occurrence of supernova explosions in space
- (a) 1 and 2
- (b) 2 only
- (c) 1, 3 and 4
- (d) None of the above can be cited as evidence
Answer: (a) 1 and 2
Explanation
Evidence for the continued expansion of the universe
| Observation | Evidence of expansion? | Fact |
|---|---|---|
| 1. Detection of microwaves in space | Yes | The Cosmic Microwave Background is the left-over glow of the Big Bang, found by Penzias and Wilson in 1965 |
| 2. Observation of redshift phenomenon in space | Yes | Light from distant galaxies is shifted to red: they are moving away (Hubble, 1929) |
| 3. Movement of asteroids in space | No | Asteroids orbit the Sun; nothing to do with expansion |
| 4. Occurrence of supernova explosions in space | No | The explosions themselves are not the evidence cited here |
Key ideas:
| Idea | Detail |
|---|---|
| Hubble's law | The farther a galaxy, the faster it recedes |
| Redshift | Stretching of light waves from a receding source (Doppler effect) |
| Accelerating expansion | Found in 1998; put down to dark energy |
Answer: (a) 1 and 2.
Why each option is right or wrong
- (a) CORRECT. Microwave background and redshift are the cited evidence of expansion.
- (b) Incorrect. The microwaves in space are also evidence.
- (c) Incorrect. Asteroids and supernova explosions are not the cited evidence.
- (d) Incorrect. Two of the observations are valid evidence.
Key point
Expanding universe: redshift of galaxies (Hubble, 1929) and cosmic microwave background (Penzias and Wilson, 1965); expansion is accelerating (dark energy).
Remember
Expansion: redshift + microwave background.
Common mistakes
- Not linking microwaves to the Big Bang's afterglow.
- Confusing redshift (moving away) with blueshift (moving closer).
- Counting asteroid motion, which is local to the solar system.
Exam tip
Red means receding. Redshift and the microwave glow are the two classic proofs.
Sources
- NCERT Class XI — Fundamentals of Physical Geography, Ch 2 (The Origin and Evolution of the Earth)
- Arno A. Penzias and Robert W. Wilson — "A Measurement of Excess Antenna Temperature at 4080 Mc/s", The Astrophysical Journal, vol. 142 (1965)