Early and modern theories

A rare event and weak orbital explanation become limitations of a theory. In exams, connect acceptance of a model with evidence and explanation.

Both ideas were early attempts toward explaining solar system formation from a nebula. In exams, place them in the nebular category.

Laplace's idea was historical, but modern physical explanation is more complex. In exams, separate the old idea from its limitation.

Joining of small bodies resembles the modern process of accretion. In exams, identify the relation between old terms and modern processes.

The tidal theory depends on a rare close passing-star event. In exams, write probability as a limitation of the theory.

This model connects many observations through one process. In exams, treat broad explanation as its strength.

Near the Sun, rocky materials remained, while in colder outer regions gases and ices remained more. In exams, connect temperature, distance, and composition.

Beyond the frost line, accumulation of ices and light gases was easier. In exams, connect it with the composition of outer planets.

Bodies formed from one rotating disk show similarity in motion. In exams, link angular momentum with orbital order.

The Big Bang is a cosmological theory, and Earth formed later through solar system evolution. In exams, write the scale difference.

Red shift is evidence of expansion and background radiation of an early hot state. In exams, connect both with the Big Bang.

The steady state theory assumed formation of new matter during expansion. In exams, remember average density and continuous creation together.

Background radiation is considered a remnant of the early hot universe. In exams, take it as evidence against the steady state theory.

Accretion formed Earth, while differentiation formed its internal layers. In exams, do not mix the two processes.

The governing concept is density differentiation during the early development of Earth. When the young Earth was sufficiently hot and partly molten, materials could separate according to density. Heavy metallic elements, especially iron and nickel, moved downward under gravity toward the centre, while lighter silicate materials remained nearer the outside and contributed to the mantle and crust. Option B is correct because sinking dense matter helped establish the core and Earth’s layered internal structure. Option A is physically and geologically incorrect, C confuses solid planetary materials with surface water, and D mistakes physical separation for a transformation of matter into light.

In the molten state, heavy and light materials could move to different levels. In exams, write melting and differentiation together.

Impacts contributed to Earth's accretion and hot state. In exams, connect impacts with formation processes too.

Heat from radioactive decay helped maintain internal temperature. In exams, connect heat sources with layer formation.

Gas release supplied water vapour and other gases. In exams, connect atmosphere and hydrosphere with outgassing.

Water vapour and carbon dioxide were important in the early atmosphere. In exams, keep it different from the present atmosphere.

This hypothesis connects a giant impact with Moon formation. In exams, consider the early solar system active and impact-rich.

Radiometric dating estimates age based on radioactive decay. In exams, connect age determination with scientific evidence.

Earth first formed by accretion, and then internal and outer spheres developed. In exams, keep the sequence correct.

Weizsäcker tried to explain planet formation through vortex-like motion in the nebula. In exams, connect him with modern planet-origin ideas.

Schmidt emphasized gas and dust instead of matter drawn from the Sun. In exams, identify the difference in source material.