Why does the Earth have only one moon?

The reason Earth has only one natural satellite which is the moon, is believed to be linked to a hypothesis known as the 'giant impact hypothesis' or 'Big Splash'.

Early in the history of the solar system, about 4.5 billion years ago, a Mars-sized celestial body, often referred to as Theia, collided with the young Earth.

The impact was so powerful that it resulted in the ejection of a significant amount of debris from both Theia and Earth into space.

Over time, the debris in orbit around Earth began to accrete and form what we now know as the Moon.

The material that formed the Moon eventually coalesced into a single celestial body, creating the Moon as Earth's only natural satellite.

The Moon's composition is similar to Earth's outer layers, and it lacks a significant iron core, further supporting the idea of formed from material ejected during a massive impact