1. Nebular Hypothesis:

- Proposed in the 18th century by German philosopher Immanuel Kant and further developed by Pierre-Simon Laplace, this theory suggests that the Earth formed from a rotating cloud of gas and dust known as a solar nebula.

- According to this hypothesis, the nebula initially contracted and formed a proto-sun at its center. The remaining material flattened into a rotating disk around the proto-sun, which eventually condensed to form the planets, including the Earth.

2. Collision (Giant Impact) Hypothesis:

- This theory, developed in the 20th century, suggests that the Earth formed through a massive collision between two or more celestial bodies.

- According to this hypothesis, a planet-sized object called Theia collided with Earth during the early stages of solar system formation. The collision ejected a large amount of material into orbit around Earth, which eventually coalesced to form the Moon.

3. Planetesimal Hypothesis:

- Proposed by Soviet astronomer Otto Schmidt in the 1940s, this theory suggests that the Earth formed from the accumulation of smaller bodies called planetesimals.

- According to this hypothesis, the cloud of gas and dust in the early solar system began to condense and form small solid particles known as planetesimals. Through collisions and gravitational attraction, these planetesimals grew in size, eventually forming the Earth and other planets.

Each of these theories has its own evidence and limitations, and the scientific community continues to explore and refine our understanding of how the Earth formed through further research and observations.