Earth, formed 4.5 billion years ago, is the third planet from the Sun and the only known world that supports life. It has a layered structure: **crust**, **mantle**, and **core**, with the core generating a protective **magnetic field**. The atmosphere, rich in **nitrogen and oxygen**, regulates temperature and shields life from harmful radiation. 

About **71%** of Earth is covered in water, which is essential for life. **Tectonic plates** shape the landscape and cause geological activity like earthquakes. Earth’s **23.5° tilt** gives rise to the seasons, while its rotation creates day and night.