The most widely accepted theory for the formation of the Moon is the Giant Impact Hypothesis. According to this hypothesis, around 4.5 billion years ago, a Mars-sized object, often referred to as Theia, collided with the early Earth. The impact was incredibly powerful and ejected a large amount of debris into space. This debris eventually coalesced to form the Moon.
The Giant Impact Hypothesis suggests that the Moon formed from the materials of both Theia and the early Earth. The collision resulted in the ejection of a significant amount of material, which eventually condensed and formed a satellite around the Earth. Over time, this satellite cooled and solidified, becoming the Moon we see today.
As for why other planets in our solar system don't have moons like ours, it's important to note that several other planets do have moons, but their characteristics may differ. The number and size of moons can vary depending on the planet's mass, formation, and gravitational interactions with other celestial bodies.
In the case of Earth, the Moon is relatively large compared to our planet's size. It's thought that the collision with Theia provided the necessary conditions for the formation of a sizable moon. Other factors, such as the Earth's position in the solar system and the gravitational interactions between celestial bodies, also play a role in determining the presence and characteristics of moons.
Each planet has its own unique formation history, and the specific conditions during their formation can influence whether or not they have moons and what properties those moons possess. So, while Earth's Moon is a result of a specific set of circumstances, other planets can have their own moon systems, each shaped by their own unique processes and histories.