Early and modern theories

In differentiation, heavier materials moved downward and lighter materials upward. In exams, link it with formation of core and crust.

The modern theory uses condensation and accretion to form protoplanets. For exams, remember this sequence.

Gases released from early Earth helped form the atmosphere. In exams, connect outgassing with the early atmosphere.

The governing concept is accretion during the formation of the Solar System. In the early solar nebula, dust and rock particles collided and stuck together, gradually producing kilometre-sized planetesimals. Continued collisions and gravitational attraction caused many planetesimals to combine into larger bodies called protoplanets. With further accretion and differentiation, these protoplanets developed into planets. Therefore option C correctly states the relationship and the direction of growth: small planetesimals join to form larger protoplanets. Option A reverses the sequence, B incorrectly says they become stars, and D ignores their central role in planetary formation.

The tidal theory assumes matter was pulled from the Sun due to a nearby star. In exams, remember passing star and solar matter together.

The Big Bang theory relates to the origin and expansion of the universe. In exams, treat it as a larger-scale theory than Earth formation.

More matter collected at the cloud center and contraction formed the Sun. In exams, remember center and gravity together.

Older planet-origin theories could not explain all physical details satisfactorily. In exams, recognize scientific limitations too.

Laplace is associated with the nebular hypothesis. In exams, memorize scientist-theory pairs separately.

The modern theory matches observations and processes like gravity, condensation, and accretion. In exams, prefer evidence-based explanations.

A disk-like gas-dust structure is a key clue for the modern solar nebula theory. In exams, connect the word disk with this theory.

Continuous expansion of the universe is a major idea in the Big Bang theory. In exams, remember Big Bang when you see expansion.

Collisions and joining made planetesimals and protoplanets grow larger. In exams, see collisions not only as destruction but also as a formation process.

The tidal theory has several orbital and physical problems. In exams, study both evidence and limitations of every theory.

The contracting nebula was thought to rotate faster. In exams, study contraction and rotation together.

The Big Bang works at the universe scale, while the solar nebula theory works at the solar system scale. In exams, clearly mention the scale difference.

The flat disk of gas and dust is called a protoplanetary disk. In exams, link it with planet formation.

Cooling formed a solid crust and later conditions for water condensation. In exams, remember cooling and crust formation together.

Red shift is space-based evidence of galaxies moving away. In exams, connect it with the cosmological part of physical geography.

Both theories give importance to a nearby star or its influence. In exams, identify external influence in older theories.

Gravity gathers matter and helps in planet formation. In exams, treat gravity as the main force behind accretion.

The solar nebula theory relates to the formation of the solar system. In exams, identifying the scale of a theory is important.

Heavy elements sinking and lighter elements remaining above is differentiation. In exams, use it to understand core and mantle formation.

The recession of distant galaxies shows the expansion of the universe. In exams, understand not static as expanding.

This sequence shows accretion-based modern planet formation. In exams, the order from particles to planets is often asked.