Which one of the following hypothesis/theory explains the origin of the universe?
- (a)Nebular hypothesis
- (b)Binary theory
- (c)Big Bang theory
- (d)Planetesimal hypothesis
Correct — C, the Big Bang theory. The Big Bang theory explains the origin and expansion of the universe from an extremely hot, dense initial state about 13.8 billion years ago. The nebular, binary and planetesimal ideas are hypotheses about the origin of the solar system, not the universe as a whole.
- (a)Nebular hypothesis — The nebular hypothesis (Laplace) explains how the Sun and planets formed from a rotating cloud of gas and dust — the origin of the solar system, not the universe.
- (b)Binary theory — The binary (or twin-star) theory is another solar-system hypothesis, proposing that the planets formed from material associated with a companion star of the Sun.
- (d)Planetesimal hypothesis — The planetesimal hypothesis (Chamberlin–Moulton) again concerns the solar system, describing planets built up from small solid bodies called planetesimals.
Cosmology distinguishes theories about the origin of the universe from those about the origin of the solar system. The Big Bang theory addresses the universe: it began in a hot, dense state and has been expanding ever since, evidence for which includes the cosmic microwave background and the redshift of distant galaxies.
Separate 'universe' from 'solar system'. Three of the options — nebular, binary and planetesimal — are solar-system formation hypotheses; only the Big Bang describes the birth of the whole universe. The trap is that all four sound like grand origin theories.
- The Big Bang theory describes the origin and expansion of the universe.
- It places the origin at about 13.8 billion years ago.
- The cosmic microwave background is key evidence for the Big Bang.
- Nebular, binary and planetesimal hypotheses concern the solar system's origin.
Only the Big Bang explains the universe; the other three explain the solar system.
- Mixing up solar-system origin hypotheses (nebular, planetesimal) with a theory of the whole universe.
- Reading 'nebular' as cosmic because nebulae are in space — it is a solar-system model.
You must pick the theory of the universe's origin from a set that mostly explains the solar system — anchor 'universe' to the Big Bang.
No directly related past PYQ was found.
- practice — not a real PYQ
The cosmic microwave background radiation is cited as evidence for
- (a)the nebular hypothesis
- (b)the Big Bang theory
- (c)continental drift
- (d)the planetesimal hypothesis
Answer(b) the Big Bang theory — the CMB is relic radiation from the early hot universe.
- practice — not a real PYQ
The nebular hypothesis is associated with the origin of the
- (a)universe
- (b)solar system
- (c)galaxies
- (d)Milky Way alone
Answer(b) solar system — it explains the formation of the Sun and planets.