The Origin and Evolution of the Earth

Nebular Hypothesis

Proposed by Immanuel Kant and revised by Laplace, this hypothesis suggests that the planets were formed from a slowly rotating cloud of gas and dust called a nebula.

Big Bang Theory

The most accepted scientific theory regarding the origin of the universe, stating that everything expanded outward from a single extremely hot and dense point approximately 13.7 billion years ago.

Planetesimal Hypothesis

A theory suggesting that a passing star drew out gaseous material from the primitive sun, which condensed into small solid bodies called planetesimals that eventually collided and clumped together to form planets.

Differentiation

The process during the earth's early molten stage where heavier elements like iron sank toward the center to form the core, while lighter elements rose to form the crust and mantle.

Degassing

The process through which gases trapped deep inside the earth's interior were released through volcanic eruptions, forming the primitive atmosphere containing water vapor, nitrogen, carbon dioxide, methane, and ammonia.