The Origin and Evolution of the Earth

Big Bang Theory

Also called the expanding universe hypothesis, it proposes that all matter in the universe existed in a tiny, extremely hot singularity that exploded and expanded about 13.7 billion years ago.

Nebular Hypothesis

Proposed by Immanuel Kant and revised by Laplace, it suggests that the planets were formed out of a cloud of material associated with a youthful sun, called a nebula.

Planetesimal Hypothesis

A passing star approached the sun, causing cigar-shaped material to separate from the sun, which later condensed into smaller bodies called planetesimals and eventually formed planets.

Differentiation of Earth's Layers

The process during the earth's formation where heavier elements (like iron) sank toward the centre to form the core, while lighter ones rose to the surface to form the crust.

Evolution of Atmosphere and Oceans

The earth's early atmosphere containing hydrogen and helium was stripped away, followed by degassing from the interior releasing water vapour, nitrogen, carbon dioxide, and methane, which later cooled to form oceans.