Early and modern theories

Kant linked the origin of the Sun and planets with a gaseous nebula. In exams, identify similarities between old and modern ideas.

Laplace proposed rings separating from a contracting and rotating nebula. In exams, remember contraction, rotation, and ring together.

The planetesimal hypothesis explains planets forming from small solid planetesimals. In exams, accumulation of solid bodies is the key clue.

It is difficult to assume that hot matter drawn from the Sun could easily condense into stable planets. In exams, mention the physical limitation of the theory.

Bodies formed in a flat rotating disk move nearly in the same plane. In exams, connect orbital plane with the protoplanetary disk.

Near the Sun, temperature was high, so light gases could not remain easily. In exams, treat inner planets as rocky and dense.

Outer regions were colder, so gas and ice could remain in larger amounts. In exams, remember outer planets as gas giants.

The Big Bang works at the universe scale, while the solar nebula works at the solar system scale. In exams, identify the scale first.

Red shift indicated galaxies moving away and expansion of the universe. In exams, take it as evidence against a static universe.

This radiation gives strong support to the Big Bang theory. In exams, identify it as cosmological evidence.

The steady state theory assumed new matter formed during expansion to keep average density constant. In exams, remember the link between expansion and continuous creation.

Expansion made the early hot universe cool gradually. In exams, write expansion and temperature decrease together.

In accretion, joining of particles and planetesimals is the basis of planetary growth. In exams, connect collisions with growth too.

Planetesimals combine to form protoplanets, and a protoplanet may become a planet. In exams, remember size and developmental order.

In differentiation, heavy materials settled downward and lighter materials stayed above. In exams, connect core, mantle, and crust with density.

Impacts and radioactive heat kept early Earth in a molten state. In exams, link heat sources with differentiation.

Free oxygen in the atmosphere increased later due to biological activity. In exams, keep early and present atmospheres separate.

Water vapour released by outgassing cooled and turned into water. In exams, study atmosphere and hydrosphere development together.

In the molten state, materials could separate according to density. In exams, remember molten Earth and differentiation together.

The giant impact idea links Moon's origin with the active early Earth. In exams, treat it as a modern explanation.

The tidal theory has difficulties related to a passing star and condensation of ejected matter. In exams, match the correct limitation with the correct theory.

Background radiation is a signal of the early hot universe. In exams, understand it as strong evidence against the steady state theory.

This sequence shows the accretion process from smaller to larger bodies. In exams, identify the process from the sequence.

Bodies formed from the same rotating cloud show similar direction of motion. In exams, connect common source and angular momentum.

The asteroid belt is linked with leftover construction material of the solar system. In exams, study it as a remnant region.