The theory that suggests the moon and Earth formed at the same time from the dust and gas of the solar nebula is called the co-formation theory.

Here's how it works:

* Solar Nebula: The solar system began as a vast cloud of gas and dust called the solar nebula.

* Accretion: Over millions of years, particles in the nebula clumped together through gravity, forming planetesimals.

* Planetesimals: These planetesimals continued to collide and merge, eventually forming the planets, including Earth and the moon.

* Simultaneous Formation: According to the co-formation theory, Earth and the moon formed at roughly the same time from the same disk of material within the solar nebula.

Key Points of the Co-formation Theory:

* Similar Composition: The Earth and moon share some similarities in their composition, which supports the idea of a common origin.

* Early Solar System Dynamics: The chaotic environment of the early solar system would have made it possible for Earth and the moon to form simultaneously.

Note: While the co-formation theory is a plausible explanation, there are alternative theories like the Giant Impact Hypothesis that suggests the moon formed from a collision between Earth and a Mars-sized object. The exact details of the moon's origin are still debated within the scientific community.