Early and modern theories

Kant explained the Sun and planets from a rotating gaseous nebula. For exams, connect nebula with a gas cloud.

Laplace proposed rings separating from a contracting nebula. In exams, link the ring idea with Laplace.

This hypothesis says small planetesimals combined to form larger planets. For exams, treat planetesimals as small solid bodies.

The tidal theory suggests a passing star pulled matter from the Sun. In exams, connect tidal force with an external star.

The Big Bang theory connects the universe with an extremely hot and dense beginning. For exams, expansion is its key feature.

Red shift shows that distant galaxies are moving away from us. In exams, write red shift as evidence of universal expansion.

The steady state theory assumes the universe remains almost the same on average over time. In exams, contrast it with the evolutionary idea of the Big Bang.

Both ideas link planet formation to cloud-like material. For exams, understand solar nebula as a source of gas and dust.

These ideas explain planets through accretion of gas and dust around the Sun. In exams, connect this with the modern solar nebula view.

The planetesimal hypothesis emphasizes the accumulation of small solid bodies. For exams, see it as a growth process of solid particles.

In the Big Bang idea, expansion began after an extremely hot and dense initial event. In exams, link it with the origin of the universe, not only Earth.

In accretion, small particles collide and combine to form larger bodies. For exams, it is the growth process of planet formation.

The flat disk of the solar nebula became the region of planet formation. In exams, treat the disk as the birthplace of planets.

Many early theories were attractive but could not fully explain issues like energy and angular momentum. In exams, remember limitations too.

The shift of light from distant galaxies toward red shows that they are moving away. For exams, take it as evidence of expansion.

After the Big Bang, basic particles and light elements formed first, followed by larger bodies. For exams, remember the order from small to large.

A protoplanet is a body growing toward becoming a planet through accretion. In exams, understand it as an early form of a planet.

The modern theory says the Sun and planets formed from the collapse of the same gas-dust cloud. For exams, remember the common source.

The tidal theory assumes that a passing star pulled matter from the Sun by gravity. In exams, a passing star is the clue.

The nebular hypothesis was proposed before modern space science. In exams, study early theories in their historical context.

Cosmic microwave background is considered leftover radiation from the Big Bang. In exams, mention it as major evidence for the Big Bang.

Planets formed in a flat rotating disk orbit nearly in the same plane. In exams, connect the orbital plane with disk structure.

The steady state theory treats the universe as always similar on average. In exams, contrast it with the Big Bang.

In condensation, hot gas cools and changes into particles. For exams, treat it as the beginning of dust and small bodies.

Early Earth was hot and later cooled to form layers. In exams, remember Earth's gradual evolution.