Prelims 2012 · archive
MediumWhich of the following is/are cited by the scientists as evidence/evidences for the continued expansion of the 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
Select the correct answer using the codes given below:
Answer & explanation
Answer: (a) 1 and 2
Two observations support an expanding universe. One is the redshift of light from distant galaxies. The other is the cosmic microwave background, the stretched afterglow of the hot early universe. Asteroid movement and the occurrence of supernova explosions do not show that the universe is expanding.
- ✓ 1. The cosmic microwave background was released about 380,000 years after the Big Bang. The expansion of the universe has stretched it into a cold microwave glow of about 2.7 K. Detecting it supports the expanding, cooling universe of the Big Bang model.
- ✓ 2. Light from distant galaxies is shifted towards longer, redder wavelengths. The farther the galaxy, the larger the shift. This is the classic observation (Hubble's law) showing that galaxies are receding from one another as space expands.
- ✗ 3. Asteroids are small bodies in our own solar system. Their movement says nothing about the large-scale expansion of space.
- ✗ 4. A supernova is the explosion of a single star. Its mere occurrence does not show that space is expanding. Astronomers use the measured brightness and redshift of certain supernovae to track the expansion rate, but the item lists only the occurrence of explosions.
Remember · Expanding universe: galaxies' redshift (Hubble's law) plus the cosmic microwave background, the stretched afterglow of the Big Bang. Asteroids and the mere occurrence of supernova explosions are not evidence of expansion.
📘 Read it in NCERT: Class 11 Fundamentals of Physical Geography, Ch 2 (practise this chapter)
Sources
- NCERT Class 11 · Fundamentals of Physical Geography, Chapter 2 “Edwin Hubble, in 1920, provided evidence that the universe is expanding. As time passes, galaxies move further and further apart.”
- NASA Science: Hubble and cosmological redshift ↗ “The universe must be expanding for light traveling across space to stretch to such long, reddish wavelengths.”
- NASA Science: Big Bang and the Evolution of the Universe ↗ “We observe that same light today, stretched by the expansion of the universe to a cold 2.7K glow.”
Question: UPSC Civil Services (Preliminary) 2012, General Studies paper. Explanation: Minimalist IAS, checked 25 Oct 2026 (how we verify). ·