What can travel around the world while staying in a corner?

The correct answer is a stamp because a stamp can be affixed to a piece of mail that is sent around the world. While the stamp itself physically remains in the corner of the envelope or postcard, it facilitates the journey of that mail globally. This riddle plays on the concept of physical placement; "in a corner" refers to where the stamp is placed on the envelope, while its purpose allows it to "travel" around the world as the mail is delivered.

In this context, a globe, although it can represent the entire world, does not itself travel anywhere. A shadow also doesn't travel in the same sense; it is a projection based on a light source and the object casting it. A postcard, while it can travel globally, does not fit the specific framing of remaining in the corner as stamps do. Thus, the nature of a stamp meets both criteria of the riddle: it remains in a corner and enables global travel.