What theories explain the origin of the world?

Answer 1

The world - including all of observable reality - as it is today is explained by several theoretical models:

- M-theory provides candidate explanations for explaining the origin of the universe.
- The Big Bang theory explains the large scale structure of the cosmos as it is today.
- The Kant nebular hypothesis describes the formation of stars and planets.
- Plate tectonics describes the development of large scale geological features of Earth.
- Abiogenesis provides candidate explanations for the origin of life on Earth.
- Evolutionary theory explains the development of the diversity of life today.

There are various models which I've not included, not because they're not relevant, but because they're basically either part of or fundamental to the above models or tributaries to them: quantum mechanics, atomic theory, relativity theory, etc.

Answer 2

The three major theories are The Big Bang Theory which refers to the creation of the universe from a massive explosion approximately 15 billion years ago, The Big Bounce theory which suggests that there was something before the Big Bang that went through a Big Crunch (which is when a universe compacts itself into a tiny ball because of gravity) and then exploded into the current universe, and the religious theory of Intelligent Design which suggests that a divine entity created the universe.