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

A stamp can travel around the world while staying in a corner because it is affixed to a corner of an envelope or postcard. When a letter is mailed, it can reach international destinations while the stamp itself is confined to the corner of the mailed item. This riddle effectively uses the imagery of stamps being placed on envelopes to convey movement, despite their constant position, challenging one's conventional understanding of space and motion.