This is the 1231st most frequent Turkish word.
dünyanın
"Of the world"
The word 'dünyanın' is used in possessive form ('of the world') indicating the origin belonging within a superlative construction.
Dünyanın en güzel şehirlerinden biri İstanbul'dur.
Istanbul is one of the most beautiful cities in the world.
Here, 'dünyanın' indicates possession ('of the world') referring to several parts belonging to the world.
Dünyanın birçok yerini gezdim.
I have traveled to many parts of the world.
In this sentence, 'dünyanın' is again used in possessive form ('of the world') combined with the infinitive verb 'değişmesi' to show causality.