Early and modern theories

Kant is related to the nebular hypothesis, not plate tectonics. In exams, practice identifying incorrect pairs.

Radioactive heat contributed to the internal heat of early Earth. In exams, link it with development of Earth's internal structure.

Impacts increased Earth's heat and added material. In exams, consider early Earth an active state.

A popular modern idea says the Moon formed from material ejected by a giant impact. In exams, identify it as the giant impact idea.

Radiometric dating helps measure the age of rocks and meteorites. In exams, connect age determination with radioactive decay.

The asteroid belt is linked with leftover or incomplete planet-forming material. In exams, study it as a remnant region of the solar system.

These three clues point to the modern solar nebula theory. In exams, identify theories through clue words.

Earth's development began with accretion and moved toward layers and outer spheres. In exams, remember the sequence in small stages.

Scientific ideas can be modified based on evidence. In exams, treat science as an evidence-based process.

The old nebular hypothesis could not satisfactorily answer many physical questions. In exams, remember the limitation along with the theory.

The tidal theory says matter pulled from the Sun cooled and formed planets. In exams, remember this sequence.

The steady state theory imagined continuous creation of matter to keep average density the same. In exams, identify the clue of expansion plus new matter.

Planetary orbits are explained through organized distribution of matter in a rotating flat disk. In exams, keep orbit and disk structure together.

Earth’s origin and the origin of life are related but distinct scientific questions. Earth formed about 4.6 billion years ago through the accretion and differentiation of material in the early solar system. Much later, after the planet had suitable conditions such as liquid water and a stable environment, the earliest life emerged through chemical and biological processes; the exact pathway remains an area of scientific study. Option A correctly separates planetary formation from later biochemical evolution. Option B incorrectly treats them as one event, C reverses the broad sequence, and D confuses planetary science with human economic activity.

In molten Earth, materials separated according to density. In exams, remember density and differentiation together.

The early atmosphere had low free oxygen and was dominated by water vapour and other gases. In exams, keep it different from the present atmosphere.

Old collision-based ideas had difficulties of probability and physical explanation. In exams, write rarity as a limitation.

Bodies formed from the same rotating nebula show similarity in motion. In exams, connect angular momentum with original rotation.

The modern theory explains many observations in an integrated way. In exams, consider broad explanation as its strength.

Red shift and background radiation are major supports for the Big Bang. In exams, identify them as cosmological evidence.

In modern accretion, small particles gradually make large planets. In exams, remember the order of size growth.

Earth's layers developed through density-based differentiation. In exams, connect core, mantle, and crust with this process.

The governing concept is the Doppler and cosmological red shift of light. When a distant galaxy is receding, the wavelengths of the light it emits are stretched toward the red end of the spectrum. Astronomers observe that the light from most distant galaxies is red-shifted, and, broadly, more distant galaxies show greater recession speeds. This pattern is evidence that space itself is expanding and supports the Big Bang model. Therefore option A is correct. River erosion, soil-colour change and sea-wave height are Earth-surface or oceanographic observations; they do not measure the large-scale expansion of the universe.

The governing concept is that scientific theories may explain different scales of cosmic development. The Big Bang model describes the origin and early expansion of the universe as a whole, whereas the solar nebula model explains how a rotating cloud of gas and dust eventually produced the Sun and planets within that universe. Therefore, option A correctly separates the cosmic background from the later formation of our planetary system. Option B incorrectly treats two different models as identical. Option C reverses the broad sequence, because the universe predates the solar system, and option D belongs to drainage geography rather than astronomy.