Worlds Apart means: Greatly separated by differing attitudes, needs, opinions, or temperaments.
Example of use: "They are worlds apart. I can't imagine how they ever decided to get married."
Scholars are not certain of the origin of the idiom “worlds apart”. The term is closely related to the late 13th century Latin distantia, which is an expression of remoteness or a “standing apart”. By the late 14th century, the figurative meaning of remoteness grew to include space between places or things, which is essentially the same meaning as the more modern idiom “worlds apart.”