Generally, "world" is not capitalized when referring to Earth.
For example:
* "The world is a beautiful place."
* "We need to take care of our planet, the world."
However, there are a few exceptions:
* When "world" is used in a formal or literary sense, it can be capitalized. For example: "The World is a Stage."
* In some cases, "world" may be capitalized for emphasis or to highlight its importance. For example: "The World needs to come together to solve this problem."
Ultimately, the capitalization of "world" is a matter of style and context. If you are unsure, it is always best to err on the side of not capitalizing it.